Abstract
Polyhydroxyalkanoates (PHAs) are inclusion bodies accumulated by some microorganisms as reserve material under unbalanced growth condition such as limited oxygen, nitrogen, phosphorous or sulphur and excess carbon source. Saccharomyces cerevisiae strains were screened for Polyhydroxyalkanoates (PHA) producing potential using plate assay technique with Sudan Black B stain. Saccharomyces cerevisiae efficiency for PHA production was analysed utilizing sawdust as carbon source and the production rate was compared with glucose (control). Thus, PHA synthesising enzymes, PHA carbon chain distributions and concentrations were determined using gas chromatography flame ionization detector (GCFID) while microbial growth (biomass yield) during production was determined using Uv-Visible spectrophotometric technique at 600 nm. PHA was extracted from Saccharomyces cerevisiae cells using solvent extraction technique and the extract was further dissolved using acetone derivatisation process. PHA-synthesising enzymes such as Glyceraldehyde-3-phosphate dehydrogenase, Pyruvate dehydrogenase, 3-Ketothiolase, Acetoacetyl-CoA reductase, 3-Ketoacyl reductase and Polyhydroxyalkanoate synthase were extracted from cell-free supernatant obtained from glucose and sawdust media. Saccharomyces cerevisiae cells grown in sawdust medium had the highest PHA yield of 75.12 % while 64.66 % PHA was obtained from cells grown in glucose medium. Consequently, utilization of Saccharomyces cerevisiae in limiting condition using agricultural residue could reduce the cost of industrial production of PHA required for plastic production due to its ability to accumulate the polymer intracellularly.
Highlights
Polyhydroxyalkanoates (PHAs) are naturally occurring storage polyesters produced by a wide range of microorganisms under unbalanced growth conditions (Madison and Huisman, 1999)
Portioning of compounds in sawdust into six categories based on the chemical properties of the compounds was determined through proximate
Plastics produced by the petrochemical industry are not biodegradable and accumulate in the environment resulting to environmental pollution (Juang and Chiou, 2007)
Summary
Polyhydroxyalkanoates (PHAs) are naturally occurring storage polyesters produced by a wide range of microorganisms under unbalanced growth conditions (Madison and Huisman, 1999). PHA serves as a carbon and energy source during starvation and is rapidly oxidized thereby retarding the degradation of cellular components (Rawte and Warinkurve, 2002). PHAs are suitable replacements for petrochemical-produced bulk plastics (polyethylene, polypropylene etc.) based on its mechanical properties which include complete degradation to carbondioxide and water through natural microbiological mineralization. Poly-3-hydroxybutirate (PHB) and its copolymers such as 3-hydroxyvalerate (3HV) and poly (3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) are the most known representatives of PHA family. These polyesters are environmentally friendly polymers which can be used in a wide range of agricultural, industrial, and medical applications. Cost of substrate is a major factor that influences the economics of biodegradable polymer production the aim of the research was to produce biodegradable polymers from inexpensive and renewable carbon sources to improve the production process and lower production cost using Saccharomyces cerevisiae strain
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