Abstract
Increasing demand for sustainable resources and products is becoming a necessity. Opportunities for creation of environmentally conscious commodities is available in several sectors of industry, including replacement of polypropylene and polyethylene plastics with biodegradable polymers, such as polyhydroxybutyrate. Brewer’s Spent grains are the major by-product of the brewing industry containing significant amount of carbohydrates that can be utilized as a renewable resource to produce fermentable sugars. In this study, brewer’s spent grains were pretreated using dilute acid, and enzymatically hydrolyzed using commercial Cellulase (20 FPU / g biomass) and/or pectinase enzymes (50 U / g biomass). The overall sugar yield was 54.88 g/L for the acid hydrolysate (liquid fraction after acid pretreatment), 11.04 g/L for the enzymatic hydrolysate (after enzymatic hydrolysis of solid fraction after acid pretreatment), and 58.64 g/L for the combination of acid hydrolysate and enzymatic hydrolysate. The sugars released were mainly composed of glucose and xylose, with 37.20 g/L and 11.13 g/L for the acid hydrolysate, 9.15 g/L and 1.89 g/L for the enzymatic hydrolysate, and 43.58 g/L and 10.28 g/L for the acid and enzymatic hydrolysate, respectively. The PHB producing strain Escherichia coli LSBJ pBBRSTQKAB produced a cell yield and PHB yield of 4.15 g/L and 0.85 g/L for the acid hydrolysate, 2.89 g/L and 1.84 g/L for the enzymatic hydrolysate, and 5.00 g/L and 1.26 g/L for the acid and enzymatic hydrolysate. Results suggest that brewer’s spent grains are a potential alternative feedstock to produce polyhydroxybutyrate.