Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Cellulase remains to be one of the most costly expenditures in biomass biorefineries. However, the complicated relationship among heterogeneity of solid substrates, different action-mode cellulase components, and competitive/synergetic actions of cellulases on surface-limited substrate result in great challenges in cellulase engineering [1]. Here we present our efforts in bacterial cellulase engineering. Since cellulase activities on synthetic soluble substrates have no relationship with their activities on natural substrates [2, 3], we developed a simple and high-efficiency transformation system based on Bacillus subtilis that can secrete ample cellulases to media [4]. By applying this new platform, we have succeeded in greatly enhancing the activities of glycoside hydrolase family 5 endoglucanse and family 9 processive endoglucanase on solid cellulosic substrate. We also investigated the cocktails of bacterial family 5 endoglucanase, family 9 endoglucanase and family 48 cellobiohydrolase. A linkage of several cellulase components by a mini-scaffoldin can enhance their performance by ca two-fold. Furthermore, the diasply of mini-cellulosome on the surface of B.subtilis exhibited another several-fold activity enhancements. Our research results suggest that cellulolytic bacteria utilize the cell-associated cellulosome strategy to overcome their relatively low activity cellulase components [5]. Also, we will report our advances in CBP bacillus strains.
1. Zhang et al. Biotechnol. Adv., 2006. 24(5): 452-481.
2. Liu et al. et al. Biotechnol. Bioeng., 2009. 103: 1087-1094.
3. Liu et al. Appl. Environ. Microbiol., 2010. 76(14): 4914-4917.
4. Zhang et al. Microb. Biotechnol., 2011. 4: p. 98-105.
5. You, C., et al.. Appl. Environ. Microbiol., 2012: accepted.