Production of Polyhydroxybutyrate from Crude Glycerol and Spent Coffee Grounds Extract by Bacillus cereus Isolated from Sewage Treatment Plant

Abstract

Production of biodegradable polymer polyhydroxyalkanoates (PHAs) from industrial wastes exhibits several advantages such as recycle of waste and the production of high valuable products. To this end, this study aimed at isolating from the sewage treatment plant a PHA producing bacterium capable of utilizing wastes generated from biodiesel and food industries. A Bacillus cereus strain capable of producing poly(3-hydroxybutyrate) [P(3HB)] was isolated, which was followed by confirmation of P(3HB) accumulation by gaschromatographic analyses. Then, the effects of nutrient limitation on P(3HB) production by B. cereus was first examined. Cells cultured in a minimal medium under the limitation of nitrogen, potassium and sulfur suggested that nitrogen limitation allows the highest P(3HB) accumulation. Next, production of P(3HB) was examined from both waste of biodiesel production (crude glycerol) and waste from food industry (spent coffee grounds). Cells cultured in nitrogen-limited minimal medium supplemented crude glycerol and waste spent coffee grounds extract accumulated P(3HB) to the contents of 2.4% and 1.0% of DCW. This is the first report demonstrating the capability of B. cereus to produce P(3HB) from waste raw materials such as crude glycerol and spent coffee grounds.