Abstract

BIOSYNTHESIS OF POLYHYDROXYBUTYRATES FROM AZOTOBACTER CHROOCOCCUM USING CHEAPER SUBSTRATES UNDER DIFFERENT OPTIMAL CONDITIONS

Abstract

Polyhdroxybutyrate (PHB) is a biodegradable thermoplastic which can be extracted from a wide range of bacteria. PHB belongs to the class of polyesters collectively called polyhydroxyalkanoates (PHA). PHB have similar properties to polypropylene and are important due to their complete biodegradability and can be used as packaging material in drug delivery systems, since these polymers are immunologically inert. Biodegradable polymer which provides a reserve of carbon and energy accumulates as intracellular granules .Several factors influence the economics of biodegradable polymer production one such factor is cost of the substrate. The high cost of PHB can be decreased by strain development and improving fermentation process by using cheaper carbon source. Low-cost raw materials can be used to reduce significantly the production cost of PHB. Considering the industrial interest and its high production cost, work has been undertaken for the production of PHB by Azotobacter chroococcum isolated from Azotobacter biofertilizer. In this study, six various inexpensive materials were utilized to enhance PHB production. The influence of these additives were directly compared with cultivations on defined medium as well as on the medium supplemented with inexpensive source such as glucose, molasses, whey, wheat bran, starch and sugarcane bagasse under different optimal physical stress conditions. Among the various inexpensive sources tested, high concentration of PHB was obtained from glucose (72%) and molasses (68%) as substrates, the optimal pH was 7.5 (72.5%) as yield with Glucose supplementation. The optimal temperature was 500 C for 30 min (64%) and UV exposure optimum was 10 min (68%). Sudan black staining and gas chromatography confirmed the PHB content in Azotobacter chroococcum.

Keywords: Polyhydroxybutyrate, Biopolymer, Azotobacter chroococcum, Sudan black, Endopolysaccharide.