Engineering Complex Carbohydrate Catabolism in Industrial Bacteria

Abstract

Second generation biofuels from the fermentation of lignocellulose have the potential to combat increasing problems between transport fuel use and the environment. However, current lignocellulosic degradation methods are complex and expensive requiring large amounts of energy and costly enzymes. This study aimed to improve current degradation methods, increasing product yield, making bioprocessing economically competitive. Geobacillus thermoglucosidans DSM2542 was engineered to express CelZ, a thermostable cellulase protein from Clostridium stercorarium. Optimal expression of the CelZ gene was confirmed by examining alternative promoters controlling the expression. The stability of pS797 PLdhA::CelZ in host organism Geobacillus thermoglucosidans DSM2542 resulted in PLdhA showing the greatest activity against cellulose. CelZ successfully degraded cellulose at 33oC, 55oC and 65oC. In addition, CelZ exhibited lignocellulosic degradation against un-pretreated Zea mays ssp. Mays L and Sorghum bicolor.