Study of the bioconversion of volatile fatty acids (VFA) to biodegradable polyhydroxyalkanoate (PHA) material by microorganisms

Abstract

This report serves to elaborate on Final Year Project EN-18 – Study of the bioconversion of volatile fatty acids (VFA) to biodegradable polyhydroxyalkanoate (PHA) material by microorganisms.

PHAs are biopolymers that can be used to produce materials, which can potentially replace petroleum-synthesized plastics. They are formed naturally in PHA-accumulating bacteria and can be biodegraded. Currently, the production of PHA is an expensive process in part due to the high cost of pure carbon substrates. The cost of PHA production can be potentially lowered if a cheaper alternative carbon source is used instead. Volatile fatty acids (VFAs), formed from anaerobic digestion of food waste after the acidogenesis stage, presents a low-cost carbon feedstock for PHA production. Thus, this project is lucrative as food waste can be up-recycled as inexpensive carbon source for lowering the cost of PHA production, and PHA in turn can solve the waste problems caused by existing petroleum-synthesized plastics.

Pure bacterial cultures were isolated from waste activated sludge, and a mixture of primary sludge and waste activated sludge, all taken from Ulu Pandan Water Reclamation Plant. Sludge inoculums from wastewater plant were chosen because they have a high microbial diversity and are known to contain PHA-accumulating bacteria.

There were 24 pure bacterial cultures isolated from the waste activated sludge, while 21 pure bacterial cultures were isolated from the waste activated sludge and primary sludge mixture. Of which, 10 and 13 putative PHA-accumulating bacteria have been identified from the mixture of primary sludge and waste activated sludge, and waste activated sludge, respectively. The identification was done through Polymerase Chain Reaction (PCR) gene detection of a gene encoding for the PHA synthase enzyme known as phaC, using primers specific for phaC gene. Total genomic DNA extractions of the putative PHA-accumulating bacteria were also performed, followed by 16S rRNA genetic identification.

This report has 5 chapters. Chapter 1 presents a brief introduction of the project. Chapter 2 presents a literature review of theory and previous work done on similar experiments. Chapter 3 details the materials and methodologies used in this study while Chapter 4 presents the results and discussion. Chapter 5 concludes with recommendations for future experiments.