A Review: Plastics Waste Biodegradation Using Plastics-Degrading Bacteria

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 148-157

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/JETT/9(1)157

A Review: Plastics Waste Biodegradation Using

Plastics-Degrading Bacteria

Angga Puja Asiandu *, Agus Wahyudi , Septi Widiya Sari

Department of Biology, Gadjah Mada University, Yogyakarta, Indonesia

Department of Biology, Sriwijaya University, Indonesia

Department of Sociology, University of Bengkulu, Indonesia

Received: 25/09/2020

Accepted: 25/10/2020

Published: 20/03/2021

Abstract

Plastic is a synthetic polymer that is widely used in almost every field of life. The massive use of this synthetic polymer has led to the

accumulation of this polymer in the environment thus polluting the environment. The general techniques in preventing plastic waste as

landfill, incineration, recycling are considered less effective as they release some hazardous materials to the environment. Thus, the

appropriate technique is needed to overcome this problem. Biodegradation is an enzymatic degradation involving some microorganisms

including bacteria. This technique can be used to prevent the plastic waste problem. Plastic waste biodegradation occurred through several

steps, including biodeterioration, depolymerization, and assimilation. Within this process, bacteria will secrete many enzymes that will

degrade and convert plastic polymers into microbial biomass and gases. Thus, this process has fewer even no side effect.

Keywords: Bacteria, Biodegradation, Enzymes, Plastics Waste

Plastics are daily lives related products used in almost every

Introduction

field of life in all countries (9). They are widely used because of

their strength and durability. On the other hand, those characters

lead to plastic resistance to degradation. These insoluble

recalcitrant polymers take many years to be naturally degraded

in the environment. This problem encourages plastic waste

pollution that threatens many living things, including humans

Plastics are organic polymers containing molecules

composed of long carbon chains back-bone formed through the

polymerization (1). They are made of carbon and hydrogen, with

nitrogen, sulfur, and other various organic and inorganic

materials derived from fossil fuels (2). Plastics divided into

natural plastics, semi-synthetic plastics, synthetic plastics,

thermoplastics, and thermosetting plastics (3).

(

10).

The uncontrolled plastics uses started several decades ago

The massive plastics production has begun in the 1950s,

which is generally produced for disposable use. Most of the

plastics waste is non-biodegradable which takes thousands of

years to be decomposed or degraded (4). In 2010, China was the

highest plastic waste producer in the world with 8.8 million tons

per year or 27% of the total world plastic waste production.

Meanwhile, Indonesia was the second after China as the highest

plastic waste-producing country in the world with 3.2 million

tons per year or 10% of the total world plastic waste (5, 6, 4). In

Indonesia, approximately 15% of the individually daily wastes

are plastics (7). Based on the European Plastics in 2018, total

world plastic production reaches 335 million tons per year, as

much as 60 million of that amount is obtained in Europe. It is

estimated that the number of plastic productions will be two

times greater in the next 20 years. Meanwhile, plastic bags are

the most common form of plastic widely used in daily lives in

the world. Although plastic products are reusable, they are still

one of the main factors causing environmental pollution (8).

have caused many environmental problems related to the

disposal uses and pollutions of plastics waste. The

decomposition process of plastic polymers takes thousands of

years. People usually burn plastics waste to overcome the

accumulation of plastics waste in the environment yet the

burning of plastics waste leads to air pollution. It releases toxic

compounds, CO , and dioxins, into the air. Those released gases

cause lung diseases and cancer (11). As plastics waste is a

pollutant polluting the land, air, and water ecosystem (12),

threatening various living things (10), therefore the appropriate

processing method of plastic waste is necessarily needed to be

carried out. The application of reuse, reduce, and recycle is now

widely applied to prevent the problem caused by plastics waste.

However, this method is less effective, especially for plastics

waste that has been mixed with other types of waste (8). Also,

landfill plastics waste processing requires large space, and

incineration plastics waste processing can produce toxic gases

into the environment (13). Thus the more effective and

environmentally safe processing plastics waste method is

needed. Biodegradation is considered as a more profitable and

more effective method to prevent this worldwide problem.

Corresponding Author: Angga Puja Asiandu, Department of

Biology, Gadjah Mada University, Yogyakarta, Indonesia.

E-mail: anggahasiandu@gmail.com

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 148-157

Biodegradation involves many kinds of plastics degrading

Plastics Waste Problems

microorganisms

(14,

15)

bacteria, such

The plastics degradation process in the environment takes up

0 to 100 years, even reaching 500 years to be degraded

D.nigrificans, and Pseudomonas alcaligenes (16). They can

produce various enzymes, both intracellular and extracellular,

that can degrade plastic polymers to protect the environment

completely (22). Furthermore, the degradation of plastic bags

and styrofoam containers spend 1000 years (4). It causes

negative impacts on the environment as decreasing soil fertility

that contaminated with plastics waste, contaminating water by

plastic constituents, interfering soil-decomposing organisms, and

accumulating toxic compounds through the food chains. Also,

buried plastic waste blocks waterways cause flooding (22).

Plastics waste in both terrestrial and aquatic environments is

the main problem of ecosystem balance. It will be worse when

the plastics have been transformed into invisible microplastics

that are harder to overcome. The large amount of plastics waste

dominated by plastic bags has caused various respiratory and

digestive system problems for thousands of species. Ingested

plastic waste by animals, mainly aquatic animals such as fish,

leads to bioaccumulation of the toxic compounds contained in

the plastic waste. Then the plastic contaminated fish possibly

consumed by humans resulting in many health problems. It is

estimated that in 2050 as many as 99% of seabirds will be

exposed to plastic waste through ingestion (4).

Plastics waste on the land can be broken down by sunlight

into smaller parts or fragments polluting soil and water. Those

toxic fragments may be involved in food chains threatening

many living things. For instance, polyethylene is gravely

hazardous for many aquatic species as aquatic mammals, sea

turtles, and waterbirds when it is consumed accidentally (11).

Plastics waste burning is not an effective solution to solve

plastics accumulation problems. That process releases toxic

gases into the environment including dioxins, heavy metals,

PCBs, and furans causing various respiratory system diseases

(

14, 15), and to stop plastics polluting the land, air, and water

10).

Type of Plastics

Plastics generally divided into two categories,

thermoplastics and thermosets. Thermoplastics are a group of

plastics that can be melted when heated and hardened when

cooled.

Thermoplastics

are

including

Polyethylene

Terephthalate (PET), Polyethylene (PE), Low-Density

Polyethylene (LDPE), High-Density Polyethylene (HDPE),

Polystyrene (PS), Expanded polystyrene (EPS), Polyvinyl-

chloride (PVC), Polycarbonate, Polypropylene (PP), Polylactic

acid (PLA) and Polyhydroxyalkanoates (PHA). Meanwhile,

thermosets are plastics which their chemical structures can be

changed when heated thus can not be re-melted. Thermoset

plastics are including Polyurethane (PUR), Phenolic resins,

Epoxy resins, Silicone, Vinyl ester, Acrylic resins,

Ureaformaldehyde (UF) resins (4).

Polyethylene terephthalate (PET) is a transparent and thin

plastic that commonly used as a wrapper for various foods and

drinks. Low-density polyethylene (LDPE) is a flexible and

strong heat-resistant plastic usually used as a drink container.

High-density polyethylene (HDPE), made from heat-resistant

petroleum, is commonly used as plastic bags. While Polyvinyl

chloride (PVC) is a synthetic plastic containing many chemical

additives such as heavy metals, dioxins, BPA, and phthalates

resulting in various health problems as bronchitis and cancer.

This plastic is widely used as a wrapper, such as vegetable oil

wrapper. Polypropylene (PP), strong and semi-permanent

plastic, commonly used for medicine packaging. Polystyrene

(23, 18). Furthermore, the plastic burning produces CO into the

air, the gas is related to global warming. It will trap solar heat

that increases the earth's surface temperature (24, 18).

(

PS) is a petroleum-based plastic that contains benzene, a

The accumulated plastics waste on the land is hard to

degrade. It will inhibit the water infiltration into the soil (11),

leads to soil infertility. The plastics waste accumulation on the

land reduces the availability of oxygen in the soil. The amount

of plastics waste in the soil causes the reduction of soil-

decomposing organisms, thus decomposition of organic and

inorganic materials will be decreased that affects the soil fertility

and inhibits plant growth (22).

carcinogenic compound. This plastic widely used as cutleries.

Polycarbonate is a plastic that contains hazardous BPA material,

this plastic is usually used as a reusable bottle (17, 18).

Meanwhile, the most common single-use plastics are LDPE,

HDPE, PET, PS, EPS, and PP (4).

Based on Plastic Europe 2018, In Europe, the highest plastic

demands are LDPE, HDPE, polypropylene, polyvinyl chloride,

polyurethane, polystyrene, and polyethylene terephthalate. The

need for LDPE is 17.5% and HDPE 12.3%. While the need for

polypropylene is 19.3%, polyvinyl chloride 10.2%, polyurethane

Plastics Hazardous Substances

Plastics contain some hazardous substances affecting human

(

.7%, polystyrene 7.4%, and polyethylene terephthalate is 7.4%

19).

In addition to nonbiodegradable synthetic plastics,

health. Dangerous plastic components such as bisphenol A

found in PC and PVC can cause the reproductive system

disorders, mainly the ovaries. Phthalates contained in PS and

PVC lead to testosterone disorders and interfere with sperm

motility. The styrene monomers as those found in polystyrene-

type plastics are carcinogenic. Nonylphenol contained in PVC

causes estrogen disorders. Meanwhile, dioxins, persistent

organic pollutants (POPs), polycyclic aromatic hydrocarbons

biodegradable plastics are now being developed and used.

Biodegradable plastics and polymers are materials that are now

widely used in various industries. The use of biodegradable

plastics is related to environmental problems due to the

recalcitrant characteristic of petroleum-based plastics waste.

Some biodegradable plastics are polylactic acid (PLA) and

polybutylene adipate-co-terephthalate (20, 21). Although PLA is

biodegradable, the polymer still requires a long time to be

degraded in nature. The complete biodegradation process of a

biodegradable polymer in nature takes months or even years

(

PAHs), and polychlorinated biphenyls (PCBs) found in almost

all plastic types resulting in various health problems. Dioxins are

carcinogens interfering with testosterone disorders. POPs can

disrupt the nervous and reproductive systems. PAHs associated

with the reproductive system and development disorders, and

PCBs related to thyroid hormone disorders (25, 18).

(

21).

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 148-157

kinds of acid compounds changing the pH of plastic polymers

leads to chemical plastic deterioration causing changes of the

polymer microstructures. These acids are including nitrous acid,

nitric acid or sulfuric acid, citric, fumaric, gluconic, glutaric,

glyoxylic, oxalic, and oxaloacetic (32). The plastic surface

damages associated with metabolites and extracellular enzymes

released by bacteria (34).

Depolymerization of the plastic constituents is carried out by

depolymerase enzymes. The results of this reaction can be in the

form of oligomers, dimers, and monomers that are simpler than

polymers. They will be further processed according to the

presence of oxygen molecules in metabolism. Aerobic

degradation of those components will produce microbial

General Plastics Waste Management

Plastics waste landfill and incineration are two commonly

used plastic waste management methods. However, these two

methods are considered as the managing plastic waste processes

which have side effects on the environment as they release

various toxic gases into the air, besides landfill also requires a

large space. Plastics recycling activities are also relatively

ineffective in dealing with the abundance of plastic waste (13).

The application of reuse, reduce, and recycle is now widely

promoted in addition to solve plastic waste problems. It is

appropriate for postindustrial plastics, yet it is not effective for

plastics that have been used or consumed by people that are

usually mixed with other organic and inorganic wastes.

Afterward, chemical methods of plastics waste management

systems are influenced by several factors and conditions related

to the polymer constituents of each plastic (8).

biomass, CO

change those components into microbial biomass, CO

and CH or H S (35).

, and H

O. While anaerobic degradation will

, H O,

Extracellular and intracellular depolymerase enzymes

secreted by microbes have important roles in plastic waste

degradation. During the degradation process, the released

enzymes will break down complex polymers into smaller and

simpler chains. These decomposed small molecules will be

easily dissolved in water then absorbed through microbial

semipermeable cell membranes to be used as carbon and energy

sources. Assimilation occurs in microbial cytoplasms in which

the metabolic process occurs to produce energy, biomass, food

reserves, primary and secondary metabolites (29). After

degraded into smaller ones, plastic fragments such as monomers

will enter the cells. These components enter the microbial cell

metabolism system to undergo a subsequent degradation process

to form energy and biomass for microorganisms. Even though

monomers have formed, sometimes they do not fully

assimilated. They will be released outside of the cells and will

be used by other microorganisms that have a suitable

assimilation pathway for those monomers (32).

The next process of biodegradation is mineralization.

Mineralization is the final metabolic process of plastic waste

toxic compounds. This process changes those hazardous

compounds into more environmentally safe compounds (36).

Mineralization is a process of converting biodegradable

materials or biomass into gases, water, salt, minerals, and other

residues. The formed gases include carbon dioxide, methane,

and nitrogen components. The mineralization process will be

ended when all biodegradable compounds have been consumed

by microorganisms and all carbons are converted to carbon

dioxide (37, 38).

Plastics Biodegradation

A plastics waste processing effective method is needed (14,

5) to balance the increasing uses of plastics every year (26). It

is Biodegradation. Biodegradation is an effective, profitable, and

economically valuable plastics waste processing method. The

ability of many microorganisms to break down plastic polymers

is an advantage that can be used in dealing with problems arising

from the increasing accumulation of plastics waste every day.

Some microorganisms produce various kinds of enzymes, both

intracellular and extracellular, catalyze plastic polymers

degradation into safe smaller fragments (14, 15). The utilization

of microbial cells directly to degrade plastic C-C bonds is

considered more effective (27). Biodegradation is a specific

enzymatic process. Certain enzymes break down certain

substrates (28).

The plastic waste biodegradation process occurs through

several stages, including biodeterioration, depolymerization, and

assimilation. Biodeterioration is a cooperation between several

microbes and abiotic factors that breaks down polymers into

smaller ones. This process will be continued with

depolymerization. Depolymerization occurs in which microbes

secrete catalytic compounds in the form of enzymes and free

radicals to form biofilms helping them to break the polymer

chains progressively (29).

Biodeterioration is a process of changing or modifying

plastic polymers carried out by some microorganisms on the

plastic surface. The changes include chemical, physical, and

mechanical changes (30). This process will be accelerated by

biofilms formed by microorganisms on the plastic surface. A

biofilm is a form of living things community. Microbes attach

themselves and colonize the surface of an object to form

biofilms assisted by an extracellular compound produced by

them. In the form of biofilms, microbial cells attach one to

another in a polymer matrix containing polysaccharides and

proteins (13). Extracellular polymeric substances (EPS)

produced by microorganisms help them to break down the

plastic surface (31, 32). EPS consists of polysaccharides,

proteins, and nucleic acids (33).

Plastics Degrading Bacteria

Many plastics degrading bacteria have been widely reported

by researchers as compiled in table 1. Some of PE degrading

bacteria are including D.nigrificans and Pseudomonas

alcaligenes isolated from plastic waste contaminated soil

16), Enterobacter sp. D1 isolated from the guts of Galleria

(

mellonella (39) and P.putida MTCC 2475 isolated from garden

soil. P.putida MTCC 2475 reduced milk cover weight about

63.1

–

73.3% within

month incubation (40). In

the Enterobacter sp. D1 treated solution there was increasing of

alcohol, esters, acidic compounds, ethyl decanoate, and 6-

methyl-5-hepten-2-ol. Alcohol, alkaline, hydrocarbon, esters,

and acid compounds indicate bacterial metabolism in degrading

PE (41, 39). That process involves various oxidoreductase

enzymes (39).

EPS penetrates the plastic surface pores causing enlargement

of the pores. It is enhanced microbes, bacteria, to damage plastic

polymers, to form holes, and to encourage the physical

deterioration of plastic polymers (31, 32). Also, the formation of

biofilms on plastic surfaces encourages the formation of various

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2021, Volume 9, Issue 1, Pages: 148-157

Tabel 1: Plastics Degrading Bacteria

Observation of

Media

Plastic

Types

Incubation

References

Time

Bacteria

Isolate Sources

Garbage Soil

Degradation

32% of PWL

14% of PWL

Bacillus

Culture Broth Medium

Nutrient Broth

1 Month

(42)

(16)

amylolyticus

Bacillus subtilis

Desulfotomaculu

m nigrifans

Enterobacter sp.

Pseudomonas

alcaligenes

Pseudomonas

fluorescens

Pseudomonas

putida

Garbage Soil

Plastic Contaminated

Soil

Isolated from Gut of

Galleria mellonella

Plastic Contaminated

Soil

6.2% of PWL

1.98% of CD

1.98% of OI

A Carbon-Free Source

Agar Solid Medium

1 Days

(39)

(16)

(42)

6.2% of PWL

Nutrient Broth

1 Month

Garbage Soil

22% of PWL

18% of PWL

Culture Broth Medium

Pseudomonas

putida MTCC

Garden Soil

>10% of PWL

Mineral Salt Medium

1 Month

(40)

475

Streptomyces

SSP2

Streptomyces

SSP4

Sterptomyces

SSP14

Actinobacter

ursingii

Soil

8% of PWL

ATCC Medium

Solid MSM

1 Month

3 Days

(12)

(48)

Soil

11% of PWL

Soil

19% of PWL

Soil and Plastic Waste

Color Zone on the Medium

Alcanivorax

borkumensis

Marine Plastic Waste

Sedimentations

Liquid Medium Containing

0.05% Hexadecane

.5% of PWL

80 Days

(50)

Bacillus

carbonipphilus

25% of PWL

Mineral Broth

Mineral Agar

LDPE Contaminated

Soil

2 Months

(45)

(49)

34.55% of PWL

Bacillus

coagulans

Bacillus

licheniformis

KC2-MRL

Bacillus

LDPE Contaminated

Soil

16% of PWL

18.37% of PWL

Mineral Broth

Mineral Agar

Months

Soil

Plastic’s Surface Damage

Mineral Salt Medium

1 Month

2 Months

LDPE Contaminated

Soil

LDPE Contaminated

Soil

LDPE Contaminated

Soil

34.48% of PWL

21% of PWL

36.07% of PWL

14% of PWL

16.40% of PWL

8% of PWL

Mineral Agar

Mineral Broth

Mineral Agar

Mineral Broth

Mineral Agar

Mineral Broth

(45)

megaterium

Bacillus nedei

Bacillus smithii

Bacillus sp. KC3-

MRL

Bacillus

sporothermo-

durans

Soil

Plastic Surface Damage

36.54% of PWL

21% of PWL

Mineral Salt Medium

Mineral Agar

1 Month

(49)

(45)

LDPE

LDPE Contaminated

Soil

2 Months

Mineral Broth

Bacillus

weihenstephanens

Hydrocarbon enriched

soil

32.61% of TPBWL and

35.64% of ThPBWL

C-zopek-Dox Broth

6 Months

(82)

Burkholderia

cepacia

Hydrocarbon Enriched

Soil

31.43% of TPBWL and

36.34% of ThPBWL

C-zopek-Dox Broth

6 Months

(82)

Hydrocarbon Enriched

Soil

23.27% of TPBWL and

23.57% of ThPBWL

Escherichia coli

Pseudomonas

aeruginosa

Pseudomonas

fluorescens

Serratia sp. KCI-

MRL

Stenotropphomon

as sp. KC4-MRL

Streptomyces

coelicoflavus

Landfill Soil

Garbage Soil

Soil

18.75% of PWL

Mineral Salt Broth

45 Days

1 Month

4 weeks

(47)

(42)

(49)

(51)

22% of PWL

Culture Broth Medium

Mineral Salt Medium

Mineralt Salt Agar

Plastic Surface Damage

30% of PWL

Soil

Oil Contaminated Soil

151