A Review on:

Studies on Bio-degradation of synthetic polymer Nylon 6 by Pseudomonas aeruginosa NCIM

Introduction From last three decades uncontrolled use of the plastics for

packaging (e.g. fast food), transportation, industry and agriculturein rural as well as urban areas, has elevated serious issue of plasticwaste disposal and its pollution.

Light-weight, inertness, durability, strongness and low cost are themain advantages of plastic while it has disadvantages such as, it isrecalcitrant to biodegradation and difficult to degrade naturally.

The global use of plastic is growing at a rate of 12% per year andaround 0.15 billion tones of synthetic polymers are producedworldwide every year.

Accumulation rate of plastic waste in the environment is 25million tons/year

Use of plastics

Plastic’s adverse effects on our environment

1}Plastic pollute beaches &oceans Since the 1940s, plastic use has increased dramatically, resulting

in a huge quantity of nearly indestructible, lightweight materialfloating in the oceans and eventually deposited onbeaches worldwide

2} Plastic bags litter the landscape

Once they are used, most plastic bags go into landfill, or rubbish tips. Each year more and more plastic bags are ending up littering the environment. if they are burned, they infuse the air with toxicfumes.

3} Plastic bags kill animals

About 100,000 animals such as dolphins, turtles whales,penguins are killed every year due to plastic bags. Many animalsingest plastic bags, mistaking them for food, and therefore die.

4}Plastic’s effect on human life

Some of the constituents of plastic such as benzene are known to cause cancer. Plastic resins themselves are flammable and have contributed considerably to several accidents worldwide.

Methods for available for degradation

Any physical or chemical change in polymer are due to environmental factors such

as light, heat, moisture, chemical conditions and biological activity is termed as

degradation of plastic.

Degradation of plastic

1. 2. 3.(Bio-degradation)

PROCESS A.Burying plastics samples in soil or placin g it in a lake or river

Burying plastic sample in acompost or sea water placed in a controlled condition(pH,humidity,Te-mperature)

Defined media inoculated withmixed microbial population(e.g. from waste water) orindividual microbial strains orenzymes which may have beenespecially screened for aparticular polymer

Advantages Most easy&Widely used Practically most suitableBetter analytical tools available than would be used for field test.

1.Faster rate of degradation than natural condition2.Preferred for many systematic many investigation.

Disadv. A)Environment conditions can not be well controlled.B)Analytical oppurtunities to monitor the degradation process are limited

Lacks reproducibility due to variable microbial population

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Bio-degradation of Nylon -6

Nylon 6 is a polymer obtained by ring – opening polymerization of ε caprolactam

Formation of Nylon 6 from ε caprolactam

Due to its strong intermolecular cohesive force caused by hydrogen bonds

between molecular chains of nylon, the rate of degradation is less compared to

polyesters.

Biodegradation of polymers is seen as one of the solution for current plastic

waste management problems.

Nylon 6 monomer is metabolized by numerous microorganisms, including the

bacterial general pseudomonas aeruginosa , Trametes versicolor and many

other

N2

Objective

To Measure the thickness of nylon sheet

To Reduce the thickness of nylon sheet

To Measure adequate method for degradation of polymer

To Increase flexibility and elasticity

Methodology….Step 1. Materials Commercial grade Nylon 6 was provided by Sigma Aldrich(American

multinational company). The material is in the form of pellet. All chemicalsand solvents used in all experiment were AR grade. A thin sheet of nylon 6was prepared from nylon 6 pellets by melting and pressing the pellets ofNylon 6.

Step 2. Selection of Microorganism The bacterium selected in the study was a Pseudomonas aeruginosa NCIM

2242, Trametes versicolor NCIM 1086 that is well known for itsbiodegradation activity. The bacterial strain of above bacteria was obtainedfrom the National Collection of Industrial Microorganisms (NCIM) NCL, pune,Maharashtra, India.

Pseudomonas aeruginosa NCIM 2242 Trametes versicolor NCIM 1086

Methodology….

Step 3: Sterilization of the sample

The nylon sheets were dipped in absolute alcohol for a few hours.

Washed with distilled water and later dried.

No physical or chemical changes were observed in the sample sterilization

treatment.

Step 4: Submerged cultivation procedure

A nylon sheet was exposed to submerged cultivation process Microbial

degradation was performed in Erlenmeyer flasks in shaker condition.

Flask containing small sheet of nylon 6 and 100 ml of the liquid glucose –

salt medium at a pH 6.25. The medium contained per liter of deionised water,

10 gm of glucose, 1 g KH2PO4, 0.5 gm of MgSO4 7H2O and 0.5 gm of (NH4)2

SO4 and 0.1 gm of CaCl2.

Aliquots (100 ml) of medium were poured into 500 ml Erlenmeyer flask and

sterilized in an autoclave for 20 min at 121 oC and 1.2 atm, after cooling the medium

was inoculated with 5 ml of the fungi spore suspension obtained by suspending

spores from one agar slant tube in 20 ml sterile water. The fermentation broth was

incubated on a rotary shaker at 30 oC and 90 rpm. Nylon 6 was the sole source of

nitrogen in the medium. Degradation was left to proceed for a period up to 90 days.

Results &discussion ….

Degradation of Nylon 6 sheets in submerged cultivation using Trametes

versicolor NCIM 1086 and psedonomas aerigunossa was carried out for 15,

30, 45, 60 ,75 and 90 days. Parallel to samples inoculated with the fungus

(biotic sample) blank experiment was carried out with Nylon 6 sheets placed

equally composed media without the fungus (a biotic sample).

1)Morphological Study:

Degradation of sheets of Nylon 6 was observed my measuring thickness of

sheets and weight reduction of sheets as it is treated with selected fungi. Thecolor of sheets becomes brownish and surface morphology become roughwhen sheets are exposed to fungi.

Day Control condition

Trametes versicolor condition

Pseudomonas aeruginosa condition

0 day 0.013 0.013 0.013

15 day 0.013 0.012 0.011

30 day 0.012 0.012 0.009

45 day 0.01 0.011 0.008

60 day 0.009 0.008 0.008

75 day 0.008 0.007 0.006

2)Decrease in weight

Table 1. decrease in weight of nylon(gm) sheet under different condition

The amount of degradation was determined by studying weight loss of

sheets. Weight of sample nylon sheets maximum reduced from 0.013 gm

to 0.006 gm in under the Pseudomonas aeruginosa compare to the

another condition.

Table 2. decrease in Thickness (mm) of nylon sheet under different

condition

Day Control condition

Trametes versicolor condition

pseudomonas aeruginosa condition

0 day 0.117 0.117 0.117

15 day 0.116 0.111 0.111

30 day 0.114 0.099 0.094

45 day 0.114 0.092 0.089

60 day 0.107 0.081 0.075

75 day 0.105 0.074 0.035

4)Decrease in Thickness

The amount of degradation was determined by studying weight loss ofsheets. thickness of sample nylon sheets maximum reduced from 0.017mmto 0.035 mm in under the Pseudomonas aeruginosa compare to theanother condition

4)FTIR Study A FTIR Spectra of Nylon 6 Untreated

FTIR Spectra of Nylon 6 pseudomonas aeruginosa NCIM 1086 The functional groups of Nylon 6 mediated with selected bacteria

Pseudomonas aeruginosa NCIM 2242 was determined by using FT-IRspectroscopy (at Room Temp.) The strength of characteristic bands of C (O) NHoccurring around 3300, 1640, 1550 and 1018 cm-1 decreased after six months.Formation of new groups like CH3, CONH2, CHO and COOH, may be formeddue to hydrolysis and oxidation

FTIR Spectra of Nylon 6 Trametes versicolor NCIM 1086 treated 90 dayssamples (the strength of Characteristic bands of C (O) NH occurring around3300, 1640 and 1550 cm-1 decreased after 90 days)Also shows formation ofnew groups as CH3(2022), CHO(2700)).

Conclusion

Fungus Trametes versicolor NCIM 1086, Pseudomonas aeruginosa NCIM

2242 mediated biodegradation of nylon 6. FTIR spectra for the polymer

nylon 6 indicate formation of new groups such as CH3, CHO and COOH.

This group may be formed due to process of hydrolysis and oxidation. This

may be caused due to cleavage of C-C bond in CH2-CH2 adjacent to

Nitrogen atom. Also the C=N stretching get weaker here. Degradation of

polymer was also confirmed by weight loss of nylon sheets and decrease in

thickness of nylon sheet. Therefore, the data indicates the maximum

potential for degrading recalcitrant polymer such as nylon 6 by

Pseudomonas aeruginosa aeruginosa NCIM 2242.

References

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