Vol. 9(1): 1-22, January 2021

DOI: https://doi.org/10.23960/jsl191-22

Jurnal Sylva Lestari

P-ISSN: 2339-0913
E-ISSN: 2549-5747

Journal homepage: https://jurnal.fp.unila.ac.id/index.php/JHT

Review Article

Lignin as an Active Biomaterial: A Review
Nissa Nurfajrin Solihat1,*, Fahriya Puspita Sari1, Faizatul Falah1, Maya Ismayati1, Muhammad Adly
Rahandi Lubis1, Widya Fatriasari1, Eko Budi Santoso2, Wasrin Syafii2
1

Research Center for Biomaterials, Indonesian Institute of Sciences (LIPI). Jl. Raya Bogor Km. 46 Cibinong, Bogor, 16911, Jawa
Barat, Indonesia
2
Department of Forest Products, Faculty of Forestry and Environment, IPB University. Kampus IPB Darmaga, Bogor, 16680,
Jawa Barat, Indonesia
*
Corresponding author. E-mail address: nissa.nurfajrin.solihat@lipi.go.id
ARTICLE HISTORY:
Received: 14 October 2020
Peer review completed: 2 November 2020
Received in revised form: 24 November 2020
Accepted: 19 January 2021

KEYWORDS:
Active packaging
Antimicrobial agent
Bio-surfactant
Lignin
Supercapacitor

© 2021 The Author(s). Published by
Department of Forestry, Faculty of
Agriculture, University of Lampung in
collaboration with Indonesia Network for
Agroforestry Education (INAFE).
This is an open access article under the
CC BY-NC license:
https://creativecommons.org/licenses/bync/4.0/.

ABSTRACT
Lignin is the second most naturally abundant biopolymer in the cell wall
of lignocellulosic compound (15-35%) after cellulose. Lignin can be
generated in massive amounts as by-products in biorefineries and pulp and
paper industries through differing processes. Most lignin is utilized as
generating energy and has always been treated as waste. Due to the high
amount of phenolic compounds in lignin, it is considered as a potential
material for various polymers, building blocks, and biomaterials
production. Even though lignin can be utilized in the form of isolated lignin
directly, the modification of lignin can increase the wide range of lignin
applications. Lignin-based copolymers and modified lignin show better
miscibility with another polymeric matrix, outstanding to the enhanced
performance of such lignin-based polymer composites. This article
summarizes the properly updated information of lignin’s potential
applications, such as bio-surfactant, active packaging, antimicrobial agent,
and supercapacitor.

1. Introduction
Environmental issues and lacking fossil fuels have been intriguing scientists to find
biopolymer-based material in many applications (Thakur et al. 2014). The advantages of
biopolymer include sustainable material, environmentally safe waste processing, and
biodegradability. The polymer has been used in human applications, from household to aerospace.
Global demand for the natural-based polymer is estimated in 2020 from 10.5 billion USD to 27.9
billion USD in 2025. This growth is mainly forced by the growing demand of various end-use
industries such as packaging, agriculture, consumer goods, automotive, and transportation (MNM
2020). Therefore, the isolation of polymer from nature is futuristic to be applied in industry.
In nature, lignin is the second abundant biopolymer after cellulose in biomass. Lignin has a
complicated cross-linked structure and is usually formed with ester linkage with hemicellulose.
Lignin contains some active functional groups such as hydroxyl, methoxy, carbonyl, carboxyl, and
benzene, where coniferyl alcohol (G), p-coumaryl alcohol (H), and sinapyl alcohol (S) are
precursors in lignin molecules (Fig. 1).

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Fig. 1. Precursors of basic units in lignin (Chio et al. 2019).
More than 50% linkage in lignin is dominated by aryl ether linkage (β-O-4’), which is the
easiest linkage to be cleaved during lignin conversion and depolymerization. The others relevant
linkage relatively more challenging to degrade are biphenyl (5-5’), resinol (β-β), diphenyl ether
(4-O-5’), phenylcoumaran (β-5’), and diphenylmethane (β-1), the linkages are shown in Fig. 2
(Moreno and Sipponen 2020). The different sources of lignin, the different number of linkages,
and precursors present in lignin. Lignin with abundant in S precursor is more recalcitrant and more
stable in thermal due to the presence of two methoxyl groups (Nakagawa-Izumi et al. 2017). A
previous study investigated the positive linearity of S/G ratio and β-aryl ether content and lignin
molecular weight, showing lignin with a high S/G ratio was more susceptible to carbohydrate
solubilization (Yoo et al. 2017). However, aromatic and hydroxyl group in all kinds of lignin play
a critical role which is potentially converted into high-demand products such as bio-surfactant,
microbial agent, active packaging, and supercapacitor.

Fig. 2. Various linkages between precursors in lignin: β-O-4’(aryl ether); β-β’(resinol), 5-5’
(biphenyl), β-5’ (phenylcoumaran), 4-O-5’(diphenyl ether) and β-1’ (diphenylmethane) (Chan et
al. 2013).
Surfactant is the most developed type of lignin-based chemical. However, chemical
modification of lignin is needed to improve lignin’s performance. For instance, major chemical
modifications of lignin as a bio-surfactant are sulfonation, amination, methylation, and
etherification (Huang et al. 2019). In addition, increasing health awareness increased the demand
for antimicrobial products, estimated to reach USD 16 million in 2020 (Sriroth and
Sunthornvarabhas 2018). The potential of lignin as an antimicrobial agent has been studied for
decades, yet there are some critical roles such as lignin source, structure of lignin, type of bacteria,
and concentration of lignin (Espinoza-Acosta et al. 2016). The demand for bio-polymer gained
due to the high demand for natural based-packaging (MNM 2020). In the utilization of lignin as
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active packaging, the essential points are lignin’s capability to be a radical scavenger and
antioxidant agent. Finally, as the supercapacitor, some highlighted points are the activation
through chemical and physical treatment to develop active pore of the lignin-derived activated
carbon or supercapacitor. In a few years, several research articles to utilize lignin for those products
have been published. However, its summary is still inadequate. Hence, the main focus of this
article is to summarize the feasibility of lignin as indispensable material to prepare bio-surfactant,
antimicrobial agent, active packaging, and supercapacitor.
2. Lignin Sources
Lignin can be classified as native and technical lignin. Native lignin is the original lignin
structure in lignocellulose without any modification. While, technical lignin, known as modified
lignin, is extracted from biomass or isolated from the industrial by-product. Typical technical
lignin can be categorized as kraft lignin, hydrolysis lignin, organosolv lignin, and pyrolytic lignin
(Chio et al. 2019). It can be directly used as raw material for the production of end-product due to
the present active site of the aliphatic and aromatic hydroxyl group. Depolymerization is an
important step to expose more reactive sites to convert lignin into further products.
Kraft process is the popular method that is applied in pulp and paper production. In this
process, biomass is delignified by sodium hydroxide and sodium hydrosulfide liquor under various
temperatures and cooking times. Kraft pulping of bagasse sorghum at 170ºC for 2.5 h was effective
in removing lignin and providing high cellulose content. After the treatment, the ether bond of
cellulose and lignin cleavage and the biomass were washed to remove residual lignin in the pulp.
This process was followed by obtaining black liquor as a by-product pulping process rich in lignin
content (Fatriasari et al. 2015). Kraft lignin can be isolated by dropping acid into black liquor, and
it will be precipitated in the bottom of the solution. The acidification process in isolation lignin
from black liquor is effective in recovering ion sodium and sulfur in the solution that can be reused
in further kraft pulping (Hermiati et al. 2017).
Bio-ethanol production is a promising application of biomass utilization. Cellulose and
lignin are two major chemical components in biomass that had complex linkage. In bioethanol
production, cellulose in biomass is a sugar monomer to convert into bioethanol during enzymatic
hydrolysis, yet lignin cannot react with the enzyme and became hydrolysis lignin. The hydrolysis
lignin contains lignin and other components such as untreated cellulose and oligosaccharides.
Typically, hydrolysis lignin structure is similar to native lignin, and it has unique characteristics:
low phenolic ratio and sulfur-free. However, it has a higher hydroxyl group content and thus results
in higher reactivity compared to kraft lignin (Chio et al. 2019). Hydrolysis lignin is usually utilized
as a biorefinery concept.
Organosolv lignin is sulfur-free lignin that was solubilized by organic solvent during the
pulping process. Recent studies reported various organic solvents such as alcohol, acetic acid,
organic acid, organic peracid, ketone, and ester to solubilize lignin in different biomass: corn,
wheat, and pinewood (Chan et al. 2013; Zhang et al. 2016; Zhao et al. 2009). Compared to other
extraction methods, the organosolv process obtained high lignin purity and remained a high
cellulose residue. Consequently, it is considered ideal lignin to process lignin-based products.
Pyrolysis is a general method for lignin conversion to highly viscous bio-oil. After the
pyrolysis step, water was added to the bio-oil and resulted in a fraction of water-insoluble. This
fraction is known as pyrolytic lignin (PL). For the purification, PL was dissolved in an organic
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solvent to remove ash and other inorganic compounds. PL can usually be used as a natural resource
for carbon fiber production (Chio et al. 2019).
3. Potential Application of Lignin
3.1. Bio-Surfactant
Surface active agents (surfactants) are chemicals that have two properties: hydrophilic head
interacting with polar compound and hydrophobic tail interacting with a non-polar compound that
commonly is produced from petroleum-based and chemically synthesized. Surfactants changed
the interface’s surface tension between two phases and usually act as emulsifier, dispersant,
cosmetics, and detergent properties. Mostly it is used in agriculture, detergent industry, pesticide,
food industry, oil mining for bioremediation, and healthcare (Fakruddin 2012). The global market
of surfactant is expected to reach USD 1.85 billion by 2024 (Wood 2019). Due to the high demand
for surfactant in the industrial area, researchers seek environmentally friendly and sustainable
materials to produce surfactant due to lessening harmful environmental effects and depletion of
petroleum, called bio-surfactant. It has some advantages compared to oil-based surfactants, such
as easy to degrade in nature, sustainable material, low toxicity, reduced surface tension to 25 m
N/M on the water surface, biocompatible, and digestible in the industrial application (Fakruddin
2012). It was reported that oil-based chemicals in surfactant could be substituted with bio-based
ones such as lignin (Norgren and Edlund 2014).
3.1.1. Classification of lignin bio-surfactant
As the second abundant polymer in lignocellulose material after cellulose, lignin application
has been reviewed in many reports (Duval and Lawoko 2014; Norgren and Edlund 2014; Uraki et
al. 2001). Classification of lignin-based bio-surfactants can be divided based on charge group in
the molecule, such as cationic, anionic, amphoteric, and nonionic. Lignin cationic bio-surfactant
is generally lignin amine and its derivatives where it was produced by the reaction of free hydrogen
atoms in lignin with aldehyde and amine (Huang et al. 2019). The anionic surfactant is mainly
produced through sulfonation as a result of substitution hydroxyl, hydrogen, and methoxy on the
benzene ring or side chain as present in Fig. 3a (Zhang et al. 2017a). Amphoteric surfactant is a
compound that has both charges positive and negative in one molecule. It can be obtained as a
result of the expanding pH application range of lignin surfactant if sulfonic acid is reacted into the
lignin amine. The negative charge is from the hydroxyl group and the positive charge from the
amine group. The reaction process from lignin to amphoteric surfactant shows in Fig. 3b (Cai et
al. 2017). On the contrary, nonionic surfactant does not have a charge in the molecule. Lignin
nonionic surfactant does not contain either sulfonic or amino acid group, which cannot ionize in a
polar solvent. Due to the milder properties of nonionic surfactant than other types of surfactant, it
is generally used in beauty and personal care production. The synthesis route of nonionic surfactant
shows in Fig. 3c (Qing et al. 2009). Type of reaction to synthesize four classes surfactant presents
in Table 1.

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Table 1. Type of reaction to produce lignin bio-surfactant
Classification of lignin
Type of reaction
bio-surfactant
Cationic
Phenolation, Mannich reactions, ketone-amine
condensation
Anionic
High-temperature sulfonation,
sulfomethylation, oxidation sulfonation,
oxidation nitration
Amphoteric surfactant Amination of lignosulfonate
Nonionic surfactant

Hydroxyl ammonium reaction, etherification,
epoxidation

Reference
(Liu et al. 2016; Liu et al.
2013; Zhou et al. 2015)
(Huang et al. 2018; Huang et
al. 2019; Konduri and Fatehi,
2018)
(Cai et al. 2017; Lou et al.
2019; Tian et al. 2014)
(Chen et al. 2016; Huang et al.
2019)

a.

b.

c.

Fig. 3. Synthetic routes of (a) the sulfonation of lignin (Zhang et al. 2017b), (b) lignin
amphoteric bio-surfactant (Cai et al. 2017), (c) diethanolamine-based lignin nonionic surfactant
(Qing et al. 2009).
3.1.2. Influencing factors of surfactant performance
Some factors that affected surfactant performance are hydrophilic-lipophilic balance (HLB),
the chain length, head group structure, and charge density. HLB is a common indicator in
surfactant to measure partitioning tendency between oil and water. A surfactant with HLB between
4 and 6 can be used as water in an oil emulsifier, and HLB in the range of 8-18 is suitable to be
used as oil in a water emulsifier (Kinyanjui et al. 2003). As the application, HLB ranged from 1.5

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– 3 usually applied as an antifoaming agent, 6 – 8 as a wetting agent, 13 – 15 as detergent, and 15
– 18 as solubilizer (Yamashita and Sakamoto 2016). The chemical structure of surfactant impacted
HLB value, where adding more of the alkyl chain from 8 to 20 carbon atoms or number of
lipophilic groups was reduced interface tension (Jiao et al. 2007). In addition, another researcher
reported that the sulfonated surfactant with a long chain length (10-Acetoxy-9-hexoxy-2-sulfooctadecanoic acid methyl ester) reduced the interfacial tension of the core flood test (Mushtaq et
al. 2014).
The type of surfactant head group is another impact factor in surfactant performance. Xu et
al. (2013) reported four anionic surfactants with the same number of alkyl chain and different head
group: sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDSn), sodium dodecyldi(oxyethylene) ether sulfate (AES), and sodium dodecylbenzene sulfonate (SDBS). AES was the
highest capability to reduce interfacial tension due to the polarity of the head group. The order is
as follows: AES > SDBS > SDS > SDSn. The polarity of surfactant was enhanced by the presence
of oxygen, benzene ring, and oxyethyl group, which increased interaction between the head group
and a water molecule (Xu et al. 2013). On the other hand, increasing the charge density of
surfactant could decrease media viscosity because of the increasing electrostatic repulsion between
the surfactant and negatively charged functional group (Alwadani and Fatehi 2018).
3.1.3. Chemical reaction to produce lignin-based bio-surfactant
The complex structure of lignin is a challenge in synthesizing lignin-based bio-surfactant.
Hence, scheme of converting reaction plays a substantial role in lignin conversion to value-added
product. In the past years, many researchers studied the reaction of lignin conversion to biosurfactant to increase surface activity and feasible to be applied in industry. Lignin is usually mixed
with polyethylene to produce bio-surfactant. For instance, blending kraft-lignin with polyethylene
glycol diglycidyl ethers (PEDGE) successfully enhanced enzymatic hydrolysis for bioethanol
production, and the reducing sugar yield increased about 20% besides of lignin-derivative biosurfactant (Fatriasari et al. 2018; Fatriasari et al. 2020). In another report, acetic lignin was reacted
with PEDGE under atmospheric pressure, which reduced the amphiphilic viscosity to less than 0.3
dl/g and was effectively used as a cellulose stabilizer (Uraki et al., 2001). Polyethylene glycol and
epoxy lignin were reacted with potassium persulfate as the catalyst to produce water-soluble alkali
lignin. The analysis of emulsification and surface activity showed 43.30 nM/m at the critical
micelle concentration. It was applied in the enzymatic hydrolysis of hardwood bleached pulp, and
the result showed an increased glucose yield rate of as much as 18%. Moreover, observation of the
fermentation experiment showed that the product was not toxic for fermentation yeast (Chen et al.
2016). Cai et al. (2017) synthesized lignin amphoteric surfactant (SLQA) by reacting lignin
lignosulfonate with (3-Chloro-2-hydroxypropyl)trimethylammonium Chloride (CHPTAC). The
adding of SLQA in the enzymatic hydrolysis of pretreated eucalyptus and corncob elevated
enzyme digestibility from 36% to 84 and 37% to 90%, respectively. This method was reported
significant in reducing the cost of bioethanol production (Cai et al. 2017). Another report stated
that SLQA had no notable effect on recovering cellulase. Hence, adding dodecyl dimethyl betaine
(BS12) in accordance with SLQA could improve the enzymatic hydrolysis of lignocellulose and
recover cellulase (Lou et al. 2019).

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The reaction of lignin through the sulfite process is one popular reaction to produce
lignosulfonate that have been applied as cement admixture, animal feed, oil well drilling, and
pharmaceutical (Alwadani and Fatehi 2018; Aro and Fatehi 2017; Gargulak and Lebo 1999; Jiao
et al. 2007; Xu and Ferdosian 2017). Alkaline lignin was reacted with sodium
hydroxymethylsulfonate with a ratio in mol/mol 0.1:1.4 at temperatures 110ºC during reaction
intervals (4h) and released 94.9% yield of lignosulfonate (AL-LG). Due to the low surface tension
and zeta potential of AL-LG, its application on cement paste admixture showed effectiveness in
improving the fluidity of cement paste regarding achieving a water-reducing ratio (Huang et al.
2018). Lignosulfonate has a function as binders and lubricants in animal feeds. Magnesium oxide
(MgO) as lubricant blended with lignosulfonate (LS) as a binder as an animal feed composition.
The result indicating MgO+LS was a more effective lubricant than vegetable oil (Winowiski and
Zajakowski 2000). The lignosulfonate was grafted through copolymerization with acrylic
compound and the resulted LS molecular with molecular weight 80,000. After adding acrylic acid,
hydrogen peroxide was added into the sample and was heated for 3-4 hours at 70-80ºC. The
acrylic-lignosulfonate was effective as dispersant seawater drilling fluid (Kelley 1983). Moreover,
grafting of acrylamide onto lignosulfonate with redox H2O2/CaCl2 and potassium persulfate at
30ºC was successfully used in the salty water-based drilling fluids (Abdollahia et al. 2018).
Ultrasound-assisted sulfonation process more effective than conventional heating, such as shorter
time of reaction in lower temperature and higher yield of lignosulfonate (Ma’ruf et al. 2018).
However, sulfonation reaction has some limitations, such as lower surface activity and the number
of guaiacyl or free ortho positions in lignin was limited that condensed lignin and decreased
sulfonation degree (Alwadani and Fatehi 2018; Zhang et al. 2017b).
Modification subsequent reaction of amination, sulfonation, and acetylation resulted in the
higher surface activity of lignin compared to lignosulfonate. Firstly, amination was conducted by
reacting purified lignin and diethylenetriamine, the aminated product (AL) was obtained after oven
drying at 65ºC. Subsequently, AL reacted with sodium sulfite, and the pH was adjusted to 10 by
adding NaOH solution with the temperature at 70ºC. Sulfonated product (SAL) was obtained after
formaldehyde was dropped into the solution. Finally, SAL was reacted with palmitoyl chloride for
3.5 h. The acylated product (ASAL) was obtained after oven drying at 65 ºC. This reaction resulted
in the interfacial tension reached to 5.0 (10-3N·m-1), which indicated a suitable surfactant to
enhance oil recovery compared to lignosulfonate (Zhang et al. 2017b). Anti-photolysis ligninbased dispersant for pesticide suspension concentrate was successfully synthesized through
modification reaction of hindered amine (4-amino-2,2,6,6-tetramethylpiperidine) with sodium
lignosulfonate, called SL-Temp. The obtained SL temp was used as a dispersant to prepare
avermectin, and the result showed that the retention rate of avermectin was higher when it was
added with SL-temp compared to adding lignosulfonate (Peng et al. 2020).
3.2. Antimicrobial agent
Lignin consists of many chemical functional groups, for example, methoxyl and phenolic
hydroxyl group specifically the side-chain structure, which obtained various biological activities
(Espinoza-Acosta et al. 2016). The phenolic fragments as the potency against microorganisms
were granted by the existence of a double bond in the side chain (α and β) and the methyl group
(γ position). Besides the chemical structure, type of bacteria used in the experiment, the sample

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origin, and antimicrobial dosage in the cultivation medium are also influenced factors of the
efficacy of lignin as an antimicrobial agent (Kai et al. 2016).
Antimicrobial activities of lignin against bacteria, yeast, and fungi have been examined using
guiacyl and syringyl model compounds. The result showed that microbial growth and enzymatic
digestion were inhibited by the presence of phenolic monomers in lignin (Jung and Fahey 1983).
The phenolic compounds damage and lysis cell membrane of bacteria (Cazacu et al. 2013). Lignin
from various sources has been tested for antimicrobial activity against Gram-positive and Gramnegative at room temperature (35ºC) and low temperatures (0-7ºC). The results found that the
antimicrobial activity depends on biomass source as follows: softwood organosolv > softwood
kraft > grass organosolv due to the effect of acid-soluble lignin content. Inhibition zones of lignin
samples from different sources were tested quantitatively against E. coli (as Gram-negative) and
S. aureus, L. monocytogenes (as Gram-positive). Gram-negative bacteria were inhibited less than
Gram-positive. The highest antimicrobial efficacy was obtained against L. monocytogenes, yet
there was no activity studied lignin regarding E. coli (Alzagameem et al. 2019). A similar result
was also shown for kraft lignin from black liquor (Klein et al. 2019) and lignin extract as the
residue of converting corn stover to bioethanol, which exhibited antimicrobial activities against L.
monocytogenes and S. aureus (Gram-positive) and C. lipolytica (yeast) but not for E. coli O157:H7
and S. Enteritidis (Gram-negative) or bacteriophage MS2 (Alzagameem et al. 2019; Dong et al.
2011). However, chitosan addition enhanced the activity of antimicrobial against Gram-positive
and Gram-negative.
The concentration of antimicrobial in the cultivation medium was investigated and showed
a critical effect. Kraft lignin as antimicrobial at low concentration (0.25% on nutrition medium)
was examined towards Erwinia carotovora and Xanthomonas vesicatoria and showed a positive
effect. However, the inhibitory effect was not shown against Pseudomonas syringe and Bacillus
polimyxa even at high concentration (2%). On the other hand, Pseudomonas syringe presented
inhibition effect at 2% concentration of spruce hydrolysis lignin (HL), yet only slight activity was
observed at a concentration less than 2% (Cazacu et al. 2013). Minet and colleagues reported
antimicrobial testing good on knit fabrics with 2 wt% of kraft lignin toward E. Coli and S.
epidermis (Minet et al. 2019). Extracted lignin from birch wood (1.06 mg DW) per 1 mL broth
can inhibit the growth of S. aureus of 6.48 CFU/mL after incubation for 24 h at 37ºC (Gabov et
al. 2016). Isolated lignin was isolated at different pH 2-5, and the antimicrobial activity was tested
toward S. aureus and L. monocytogenes. The results showed that antimicrobial activity was
increased as increasing pH of lignin and lignin concentration in the media (Klein et al. 2019).
Lignin as an antimicrobial agent is being used in commodity products like in plastic
production (Klein et al. 2019), textile (Sriroth and Sunthornvarabhas 2018; Sunthornvarabhas et
al. 2017; Sunthornvarabhas et al. 2018), medical materials, pest control, and healthcare products
(Gordobil et al. 2018). Depletion of fossil fuels encouraged researchers to find sustainable material
in plastic production. Klein et al. (2019) described demethylation of lignin as a reaction to produce
lignin-polyurethane. Kraft lignin was acidic precipitated with different pH 2-5 to evaluate the
effect of extraction condition on antimicrobial activity in lignin-based polyurethane (LP).
Subsequently, the obtained lignin in sodium hydroxide was demethylated by adding sodium sulfite
and then was stirred for 1 h at room temperature. The process was stopped by dripping 1% of HCl
to pH 2, and the brown solid was precipitated as demethylated lignin. Unmodified (KL) and
demethylated lignin (DL) were used to prepare lignin-based polyurethane. S. aureus was used as
an antimicrobial organism with an inoculation temperature of 37ºC for 24 h. A significant
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microbial reduction toward S. aureus was observed as increasing pH of DL than other samples.
Demethylation reaction can improve the cross-linking density of the LP and correlated with its
antimicrobial activity (Klein et al. 2019).
Hydroxypropylmethylcellulose-lignin (HPMC-lignin) and HPMC-lignin-chitosan were
studied to evaluate lignin as antimicrobial in film. Lignin powder isolated from black liquor was
diluted in DMSO. Next, the film of HPMC-lignin was formed by stirring HPMC and lignin
solution for 15 min. Besides, HPMC-lignin-chitosan was prepared by adding deacetylated chitosan
in ethanol. The antimicrobial activity of both films was analyzed toward S. aureus and E. coli in
saline solution for 24 h at 35ºC. The HMPC-lignin film had an active antimicrobial test toward S.
aureus but not for E. coli. Conversely, microbial activity toward both S. aureus and E. coli was
positive after chitosan addition (HMPC-lignin-chitosan). Lignin concentration in the film was also
a critical effect on antimicrobial activity where the activity increased as increasing active
functional group such as aliphatic OH, carbonyl CO, and COOH. Antimicrobial activity toward E.
coli in the film only was observed after 30% addition of lignin concentration, while activity against
S. aureus was observed in addition of lignin 5%. However, chitosan in HPMC/lignin film
improved the activity where the concentration of lignin 5% had antimicrobial activity against E.
coli. Chitosan consists of amino and hydroxyl group in its structure, which is known as an
antimicrobial compound toward Gram-positive and Gram-negative bacteria. Furthermore, the
activity was also tested against B. thermosphacta and P. fluorescen bacteria. Both HMPC-lignin
and HMPC-lignin-chitosan showed activity only at lignin concentration of 30% against B.
thermosphacta and 5% against P. fluorescen. Higher resistance of P. fluorescen than E. coli was
observed due to exopolysaccharides production (Alzagameem et al. 2019). Another film of mixing
lignin with PVA/gelatin blends exert highly antibacterial activity, especially against foodborne
contaminants such as Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Pseudomonas
aeruginosa. Hydroxyl group of lignin as a phenolic compound interacted with the bacterial cell
causing cell membrane disruption, the infiltration of cell components, and ultimately bacterial cell
lysis (El-Nemr et al. 2019). Yang et al. (2016a) also reported that polymeric film-based PVA,
chitosan, and lignin nanoparticle could inhibit the bacterial growth of Erwinia carotovora subsp.
carotovora and Xanthomonas arboricola pv. pruni. From those experiments, lignin could be
considered as a promising antimicrobial agent for food packaging. The main effect of antimicrobial
activity in active packaging is controlling spoilage of microbial and pathogen contamination onto
food by inhibiting microbial growth, include inhibit topoisomerase, NADH-cytochrome c
reductase, and ATP synthase, also damage the cytoplasmic membrane (Diblan and Kaya 2017;
Rempe et al. 2017). Further explanation of lignin as food packaging is available in the active
packaging section.
The demand for antimicrobial textile in medical and non-medical rapidly increased where
the coating of antimicrobial agents on the fiber is a simple method. In 2017, Sunthornvarabhas et
al. (2017) coated lignin from sugarcane bagasse on fabric to produce antimicrobial textile. Lignin
was dissolved in DMSO and subsequently was mixed with ethyl alcohol. The solution was
submerged with glass fiber then placed in an oven at 60ºC for 2 h before sterilization under UV
light. The antimicrobial activity of coated-fiber was tested against Staphylococcus epidermidis,
the most bacterial found in human skin. Concentration minimum of bactericidal (MBC) and
inhibitory (MIC) of lignin were tested by broth dilution method. The result presented that
increasing extract amount of lignin decreased in colony formation, which means more activity of
antimicrobial properties (Sunthornvarabhas et al. 2017). Bamboo fiber has been popular in recent
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years in the fashion industry as eco-friendly and antibacterial textile. The antimicrobial activities
in bamboo clothing were investigated against Gram-negative bacterium, Escherichia coli, and the
extract dissolved in dioxane showed strong activities due to the presence of lignin (Afrin et al.
2012). The illustration of antimicrobial textile is shown in Fig. 4.

Fig. 4. Schematic of antimicrobial textile (Riaz and Ashraf 2020; Zhu et al. 2019).
In Thailand, natural antimicrobial extract generously gains attention in the application of
medical and cosmetic. It was predicted that antimicrobial product demand reached USD 16 million
in 2020 (Sriroth and Sunthornvarabhas 2018). Lignin in healthcare products such as cosmetics
plays a role not only as an antimicrobial agent but also as an antioxidant and sun protection factor
(SPF). Recently, Gordobil et al. (2018) evaluated the potency of kraft and organosolv lignin for
healthcare products through measurements of antibacterial activity, antioxidant capacity, and SPF.
Lignin showed similar functional properties as a commercial antioxidant, which suitable for use
in cosmetics, replacing butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT),
which is cytotoxic synthetic antioxidants. In addition, antimicrobial activity towards A. niger,
diverse foodborne, and human pathogenic showed positive inhibition that opened new insight to
be used in food and pharmaceutical products. SPF determination of lignin-based sunscreen was
conducted by in vitro method. The lignin concentration in the product significantly affected SPF
result due to the transmittance of elaborated creams was decreased by higher lignin content.
Moreover, the higher content of methoxyl and carbonyl group improved exposure of ultraviolet
due to the auxochromes. Therefore, it concluded the potency of lignin to eliminate harmful
commercial chemicals in sunscreen products (Gordobil et al. 2018).
Copper (II) sulphate is commonly used in pesticides. However, the environmental issue is
intriguing researchers to find sustainable raw material for reducing copper content. Due to highly
polar and easily washed off of Copper (II) sulphate, it gave serious environmental problems. In
2018, Sinisi et al. (2018) reported a novel product of combining Cu-lignin as antibacterial and
antifungal for pesticide products. Lignin from Pinus taeda was dissolved in water and added
CuSO4, NaOH was added until pH 7, and the precipitate brown solid was filtered and dried for
further analysis. The ratio of lignin/CuSO4 was conducted to find the best condition of pesticide.
The antimicrobial activity was tested against yeast and several microorganisms: Escherichia coli,
Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella enteridis, Erwinia amylorova,
Pseudomonas syringae pv actinidiae, Xanthomonas campestris, Campylobacter jejuni, and
Xanthomonas arboricola pv pruni. In general, Cu-lignin gave good activity towards Gram-positive
and Gram-negative, which potential to be used as an antibacterial agent (Sinisi et al. 2018).

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3.3. Active packaging
The market for food packaging exhibits constant growth. The utilization of renewable
biopolymers aims to reduce the amount of non-renewable raw material. Using lignin as new
materials to substitute certain synthetic and petroleum-based materials in the use of bio-polymers
has increased. Lignin structure contains functional groups that have aromatic and highly crosslinked structure. Therefore, lignin can be compatible with many polymeric matrixes to increase
mechanical properties, fire resistance, and wettability. It has been reported that lignin is effectivity
as food packaging additives (Alzagameem et al. 2019) and a filler in active packaging depends on
polymer matrices, like polyvinyl alcohol (El-Nemr et al. 2019; Yang et al. 2016b), latex
(Johansson et al. 2012, 2014) and PLA (Chaubey et al. 2020; Gordobil et al. 2014; Spiridon et al.
2015; Yang et al. 2016a; Yang et al. 2020), chitosan (Crouvisier-Urion et al. 2019; Yang et al.
2016a), gelatin (Aadil et al. 2016a; El-Nemr et al. 2019), alginate (Aadil et al. 2016b) based
materials.
Lignin has potential as a natural antioxidant additive in food packaging due to its
polyphenolic structure (Domenek et al. 2013; Faustino et al. 2010; Vinardell et al. 2008; Vostrejs
et al. 2020; Yang et al. 2020; Zadeh et al. 2019). The lignin with narrow polydispersity, low
molecular weight, more phenolic hydroxyl groups, and less aliphatic hydroxyl groups showed
high antioxidant activity (Pan et al. 2006). Adding lignin in packaging improves the antioxidant
properties of food and antimicrobial properties (El-Nemr et al. 2019; Li and Peng 2015; Yang et
al. 2016a; Yang et al. 2016b). Natural antioxidants could also be used in active packaging to
protect food that has a sensitivity to light and oxygen. Antioxidant agents such as lignin can be
applied to food packaging by various methods. These agents can migrate to the protected food
through the inner walls of the packaging material. Fig. 5 illustrates the scheme and migration
process in each system.
Several studies have been conducted to compare extracted lignin from different sources such
as alkali (Aadil et al. 2016a), lignosulfonate (Li and Peng, 2015), kraft (Faustino et al. 2010), or
steam explosion lignin (Vinardell et al. 2008). Lignosulfonate and alkali lignin were used in soy
protein isolate (SPI) bio-polymeric film modified enzymatically. The radical scavenging activity
test of the films containing lignosulfonate 6% higher than alkali lignin-based film and had values
of 28, but if only alkali lignin itself had much higher radical scavenging activity than
lignosulfonate (Zadeh et al. 2018). Alkali lignin has higher radical scavenging activity than the
other lignin because it contained free phenolic monomers, particularly p-coumaric and ferulic
acids (Domenek et al. 2013). Alkali lignin in modified film reduced the oxidation rate to 75% in
the ability of UV blocking and the activity of radical scavenging (Zadeh et al. 2018). Lignin
phenolic substructures are contributed to antioxidant activity, and UV-blocking property from low
to high was p-hydroxyphenyl phenolic hydroxyl groups > guaiacyl > syringyl. Syringyl phenolic
units have the highest antioxidant activities and UV-shielding properties because it contains
additional methoxyl groups (Guo et al. 2019).
Lignin isolated from grape seeds was used as an additive material for radical scavenging in
active packaging. Grape seed lignin is effective as an antioxidant agent with a high antioxidant
capacity (1 g of grape seeds lignin equal to 238 mg of Trolox). The lignin was added to the poly
(3-hydroxybutyrate) (PHB) and polyhydroxyalkanoate (PHA) film. It acted not only as an
antioxidant but also as a nucleating agent. Moreover, it increased the stiffness and degree of
crystallinity of the film and contributed to the lower oxygen and carbon dioxide permeability of

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the film (Vostrejs et al. 2020). The antioxidant activity of lignin monomers has significant
differences regarding their initial radical scavenging activity. Coumaric, ferulic, and sinapic acids
as phenolic acids that compose lignin were investigated for their radical activity. Sinapic acid has
the highest radical activity due to di-ortho-methoxyl substitution, ferulic acid has an intermediate
activity, and coumaric acid has no antioxidant activity. The results could confirm that the higher
concentration of syringyl, the higher the antioxidant activity (Crouvisier-Urion et al. 2019).
Biopolymer matrix from Poly(lactide) (PLA)-lignin results in a good dispersion. The compounded
material slightly enhanced the oxygen barrier properties. The physical and mechanical properties
of PLA film with the addition of lignin also showed improvement (Aadil et al. 2016a; Domenek
et al. 2013). The experiment was also found that the formation of free phenolic monomers will
increase antioxidant activity. Antioxidant activities increase along with the increasing severity of
the heat treatment. The antioxidant of lignin was not only potential for active packaging but also
for cosmetic formulation because lignin was considered as non-irritants to the eye and skin
(Vinardell et al. 2008). Another research reported that HPMC-lignin and HPMC-lignin-chitosan
films were studied to evaluate the application of lignin for food packaging additives. The result
showed it has good antioxidant activity and antimicrobial activity (Alzagameem et al. 2019). In
addition, filler of blending of lignin with PVA/gelatin showed good result as active packaging to
inhibit microbes (Yang et al. 2016a). The explanation of antimicrobial activity is described in the
antimicrobial section.

Fig. 5. Schematic representation of the application of antioxidant agents in active packaging and
the migration of antioxidant agents in each system (Gaikwad et al. 2018; Nwakaudu et al. 2015).
The shelf-life of food can be improved by using active packaging. The quality and shelf life
of foods influenced by oxygen in packaging. Oxygen leads to oxidation of the product or
encourages aerobic microorganisms to grow, resulting in food deterioration (Yildirim et al. 2018).
Foods that sensitive to oxygen would be better protected by oxygen scavenging films. This active
film not only extends the shelf life of food but also maintains quality, freshness, and essential
nutrients. Some potential oxygen scavenger from organic-based materials has been developed.
Compared with an inorganic oxygen scavenger, organic materials such as lignin have better
dispersion and compatibility with the polymeric matrix. Polymer-organic matrix is possible to
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produce optically transparent and active barrier films. Johansson et al. (2014) compared lignin
derivatives such as organosolv lignin (LO), hydrolytic lignin (LH), alkali lignin (LA), and
lignosulfonate (LS) as a substrate for laccase-catalyzed scavenging of oxygen in coatings and
films. The oxygen-scavenging capability increased in the order LO < LH < LA < LS. Laccase and
LS in the coated board could decrease oxygen content from 1.0% to 0.3% (Johansson et al. 2012).
3.4. Activated carbon (AC) and supercapacitor
Lignin has potential in the energy and chemical sector due to its chemical structure and
availability. Lignin also reported being an excellent precursor for activated carbon production (Fu
et al. 2013; Gao et al. 2013; Rodríguez-Correa et al. 2017; Saha et al. 2018). Activated carbon is
a well-known material with high adsorptive capacity, high surface area, high reactivity, and good
chemical and mechanical stability. Activated carbon not only used as an adsorbent material but
also as energy storage such as supercapacitor (Hu and Hsieh 2017; Yu et al. 2016; Zeng et al.
2019). Supercapacitors can be classified into three types: hybrid capacitors, pseudocapacitors, and
electric double-layer capacitors. Fig. 6 shows the main classifications of supercapacitors and are
further categorized by electrode material. The electric double-layer capacitor (EDLC) is a type of
storage mechanism commonly used in supercapacitors. Activated carbon (AC), graphene, and
carbon nanotubes are high porous carbon materials widely used as electrode materials in the
industry.

Fig. 6. Types of supercapacitors and classification based on electrode materials (González et al.
2016; Mensah-Darkwa et al. 2019).

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The pyrolysis process of lignin occurs slowly (carbonization) and over a wide temperature
range. The degradation mechanisms and char formation involve initiation, propagation, and
termination reactions. The solid phase structure starts from devolatilization phases (loss of weight)
at temperatures higher than 500°C. The release of CO, CO2, H2, and H2O, as well as condensable
volatiles formed due to radical initiation of weaker C−O bond in the β-O-4 structure. Single- and
multi-phenolic compounds start to form and then polymerized further and condensed. The
formation of char residue and C-C bonds from a combination of carbon-centered radicals is
contributed by the secondary reaction between volatile components. By increasing pyrolysis
temperature, the carbon content also increases. This leads to a solid matrix richer in C and makes
the pore structure of lignin-based activated carbon stronger. The hydrogen and oxygen contents
decreased because the oxygen and hydrogen-containing groups were easily fallen off at higher
pyrolysis temperatures (Faravelli et al. 2010; Ma et al. 2019; Rodríguez-Correa et al. 2017).
Preparation of activated carbon from lignin has been reported by difference activation and
purpose. AC from lignin was activated by KOH activation for Ni (II) adsorption (Gao et al. 2013)
and benzene, toluene, and xylene (Saha et al. 2018), and steam activation for methylene blue
adsorption (Albadarin et al. 2017; Fu et al. 2013). Activated carbon from lignin could be
transformed into magnetic activated carbon (MAC) via hydrothermal carbonization together with
formic acid. The MACs resulted in high specific pore volumes, high specific surface areas (up to
2875 m2/g), and also have CO2 adsorption capacities up to 6.0 mmol/g. Because of remarkably
high ultra-micropore volumes, MAC has the potential for carbon capture and storage and gas
purification processes (Hao and Bjo 2017). Rodríguez-Correa et al. (2017) compared the
carbonization process between hydrothermal and pyrolysis processes on the AC properties.
Activated carbon by pyrolysis has thermal stability better than the hydrothermal process. The
experiment also found that the pyrolysis develops larger microporous areas than the hydrothermal
process. The major reasons can be attributed to the lower amount of carbon and the higher amount
of undecomposed lignin in the activated carbon by the hydrothermal process.
Supercapacitor or electrochemical capacitors has outstanding properties in energy storage
conversion system. It also has a high-power density, fast charge/ discharge rate capability, and
excellent cycle performance. Good performance in energy density and durability are required for
carbon-based material (Borenstein et al. 2017; Faraji and Ani 2015; Poonam et al. 2019). Ligninderived activated carbon could be one of the materials that has a lower price, abundant, and
environmentally friendly.
Zeng et al. (2019) reported that lignin and carbonaceous mudstone was activated with HNO3
has been successfully synthesized. As electrodes for supercapacitors, lignin and carbonaceous
mudstone reveals has outstanding electrochemical behaviors and high specific capacitance (155.6
F g-1), which is three times higher than the untreated carbon electrode. Moreover, this electrode
supercapacitor presents excellent cycle behavior of 5000 cycles. Lignin derived activated carbon
for supercapacitor was also activated by NaOH and KOH. The obtained results exhibited excellent
specific capacitance (226 F g-1), 7.8 W h kg-1 energy density, and 47 kW kg-1 power density as
well as over 92% capacitance retention after 5,000 cycles (Hu and Hsieh, 2017).

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4. Conclusions
Comprehensive evaluation in the structure and chemicals of lignin leads to open appropriate
utilization of lignin to valuable bioproducts. Some lignin utilization for active material such as biosurfactant, antimicrobial agents, active packaging, activated carbon, and supercapacitor make this
abundant material promising low-cost additive for various applications. The polymer-lignin matrix
shows great potential in the future as a promising alternative to petroleum-based materials. The
heterogeneity of lignin in the biomass source and processing continues to support demand in
manufacturing. A more in-depth study is needed to understand the properties of natural lignin
better. Modification of lignin through chemicals, physics, or biology might be required to improve
lignin performance in future applications.
Acknowledgments
The authors are grateful for the support of the Research Center for Biomaterials LIPI and
Integrated Laboratory of Bioproduct (iLAB) for the facilities. The authors received no specific
grant from funding agencies for this work.
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