Sunday, May 3, 2009
6-17
Cellulose degradation: two potential novel cellulolytic bacteria able to produce thermostable cellulases
Yanna Liang, Zisong Feng, and Jemil Yesuf. Civil and Environmental Engineering, Southern Illinois University, 1230 Lincoln Dr., Carbondale, IL 62901
For the purpose of converting natural cellulose to simple sugars, two aerobic and thermophilic cellulose degraders: Brevibacillus sp. JXL and Anoxybacillus sp. 527 were isolated from swine waste. These two bacteria can grow on crystalline cellulose as sole carbon and energy sources at 57oC. Regarding B. JXL, it has been revealed that: 1) Cellobiose or glucose can induce more than 10 times higher cellulase activities at concentrations of 0.5 or 1% compared to that from cellulose; 2) Glucose is a better inducer compared to cellobiose over longer experimental period; 3) Cellulases have maximal activity at 70oC and at pH 6-8; 4) Cellulases are thermostable with more than 60% of activity retained after incubation at 80oC for 3 hr. Even at denaturing temperature like 100oC, cellulases are still active; and 4) Under SEM, cellulosome-resembling protuberatant structures are abundant when cells are grown with glucose or cellobiose. In terms of A. 527, it has been observed that: 1) the optimal cellulase activities are obtained at pH 6 and 70oC; 2) Under optimized conditions with the presence of Fe3+, Ca2+, and reducing agent, crude enzymes from the culture supernatant have an activity as 10.0 FPU/ml. Hence, these two bacteria possess great potential in the field of cellulose hydrolysis and warrant further investigation.