Effect of Starch Pre-treatment on the Microbial Degradation of Low Density Polyethene Carrier Bags
Effect of Starch Pre-treatment on the Microbial Degradation of Low-Density Polyethene Carrier Bags.
ABSTRACT
In this study, a cassava starch/low-density polyethene (LDPE) blend was compounded and the effect of this starch pretreatment on the rate of degradation of synthetic polyethene carrier bags was tested using bacteria and fungi (as singles and as consortia) isolated from dumpsites.
Weight loss and Fourier Transformed Infra-Red Spectroscopy (FTIR) were used as analytical techniques for measuring biodegradation. Fungi were found to degrade both synthetic LDPE and LDPE/Starch blend resulting in a weight loss of 3.54% to 19.68% while that obtained from bacteria gave a weight loss of 1.0% to 18.5% within 30days.
Mixed cultures comprising of both bacteria and fungi gave better results than the individual organisms and the addition of starch was found to greatly enhance the biodegradation of the low-density polyethene carrier bags.
FTIR analysis showed the appearance of carbonyl groups in the LDPE residues after microbial treatments between wavelengths of 1703.67cm-1 and 1872.83cm-1 indicating likely oxidation of the carbon-carbon double bond (C=C) and various oxidation products formed during the biodegradation.
This study, therefore, shows that microorganisms with the ability to degrade low-density polyethene carrier bags exist in our natural environment. It has also shown that blending LDPE with natural polymers such as starch can greatly enhance the biodegradation of this polymer and that microbial consortia can accelerate the rate of degradation of this polymer.
Therefore finding the right microorganisms and/or their enzymes that can efficiently and completely biodegrade the recalcitrant polyethene into carbon dioxide, water and biomass will go a long way in solving this global threat and studying the synergism between them will give more insight for future efforts towards the biodegradation of these polymers.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Acknowledgements iv
Abstract vi
Table of Contents vii
List of Figures x
List of Tables xi
List of Plates xii
List of Appendices xiii
Chapter 1 Introduction
- Background 1
- History of Polyethene 1
- Classification of Polyethene 2
- Uses of Polyethene 3
- Disposal of Polyethene 4
- Hazards of Polyethene 5
- Degradation of Polyethene 7
- Biodegradation of Polyethene 8
- Microorganisms involved in Polyethene Degradation 9
- Statement of Problem 9
- Justification of Study 11
- Aim and Objectives of Study 12
1 10.1 Aim of study 12
1 10.2 Specific Objectives 13
Chapter 2 Literature Review
- 1 Polyethene Carrier bags 14
- Disposal Methods of Polyethene 14
- Hazards of Polyethene 17 3.1 Environmental Impacts/ Land pollution 18
2 3.2 Impact on livestock and wildlife 18
2 3.3 Impact on human health 19
- Degradation of Polyethene 20
- 2.4.1 Types of Degradation of Polyethene 20
2.4.2 Nondegradability of Polyethene 21
- Degradable Polyethene 22
- Polyolefin with Pro-oxidant 24
2 5.2 Pretreatments 24
- Polymer Blends 26
- Surface Active Agents- Biosurfactants 27
- Genetic Modification of Microorganisms 27
- Starch as an enhancer 28
- 7 Microbial degradations of Polyethene 29
2.7.1 Biodegradation of Polyethene/Starch Blend 32
2.8. Mechanism of Microbial Degradation of Polyethene 33
2.9 Measurement of Biodegradation of Polyethene 36
Chapter 3 Materials and Methods
- Sample Collection 37
- Media Preparation 37
- Isolation of Microorganisms from LDPE Samples 37
- Identification of Microbial Isolates 38
3 4.1 Identification of Bacterial Isolates 38
3 4.2 Identification of Fungal Isolates 42
- Screening of Microbial Isolates for Polyethene degradation ability 46
- Preparation of Polyethene/Starch Blend 47
- Biodegradation of Polyethene Bags using Individual Bacterial and
Fungal Isolates 47
- Biodegradation of Polyethene Bags Using Bacterial and Fungal Consortium 48
- Analytical Techniques for determination of the extent of biodegradation of Polyethene bags by the Bacterial and Fungal Isolates 49
3.8.1.Weight Loss measurement 49
3.8.2 Fourier Transform Infra-Red Spectrometry (FTIR) 50
Chapter 4 Results
- Identity of Bacterial and Fungal Isolates with the ability to degrade Low-Density Polyethene Carrier bags 51
- Polymerase Chain Reaction Amplicons of Bacteria and Fungi 55
4 1.2 Sequencing Profiles of bacteria 56
4 1.3 Sequencing Profiles of Fungi 57
- Screening of Bacterial and Fungal Isolates for the ability to degrade LDPE 57
- Biodegradation of untreated and Starch treated synthetic LDPE 57
- Comparison of Bacterial and Fungal biodegradative ability on untreated
and Starch treated synthetic LDPE Carrier bags 70
- Fourier Transform Infra-Red Spectroscopy (FTIR) Analysis of residual
LDPE Strips after microbial degradation 70
Chapter 5 Discussion, Conclusion and Recommendations
Discussion 80
Conclusion 84
Recommendations 85
References 87
INTRODUCTION
Background
One of the most common items in our modern world is the ubiquitous plastic shopping bag which is made out of polyethene.
Polyethene is a member of a large family of polymers called thermoplastic polymers. It consists of long chains of the monomer ethene with its 2CH2 groups connected by a double bond, (H2C=CH2) (Nanda et al., 2010).
Polyethene, a waxy chemically inert plastic, is one of the simplest and most inexpensive polymers. It contains the chemical elements, Carbon and Hydrogen, (Suseela and Toppo, 2007; Ramesh and Pramila, 2011).
Polyethene is produced by polymerization of ethene gas by allowing the free-roaming ethene gas molecules to bond together to form long chains of polyethene in the presence of a catalyst.
It can be produced through radical polymerization, anionic addition polymerization, ion coordination polymerization or cationic addition polymerization. Each of these methods results in a different type of polyethene.
REFRENCES
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