Dr. Liang’s research group works on projects that are related to renewable energy production from domestic, renewable, and environmentally sustainable resources. One example is converting cellulose to various value-added products.

Recently, a potentially novel aerobic and thermophilic cellulose-degrader, Brevibacillus sp. JXL, was isolated by Dr. Liang from swine waste. B. JXL has been observed to grow on crystalline cellulose as its sole carbon and energy source at 57oC, produce extracellular cellulases, and utilize a broad range of carbohydrates. Crude cellulases have an optimal temperature as 70oC and a broad optimal pH range of 6-8. These cellulases also have high thermotolerance as evidenced by retaining more than 50% of their activities even at 100oC- protein denaturing temperature. One intriguing observation is that B. JXL may produce cellulosome – the extracellular multi-enzyme complex that is a characteristic of anaerobic cellulose-degraders (Fig. 1 and 2). Research on B. JXL will provide significance and impact on: 1) increasing the diversity of thermophilic bacteria that can break down cellulose; 2) advancing the understanding of the rate-limiting step in enzymatic cellulose hydrolysis; and 3) leading to efficient and cost-effective cellulose saccharification.

REU students will be in charge of: 1) analyzing the degradation products from crystalline cellulose using high-performance liquid chromatography (HPLC); 2) isolation and purification of enzymes from the crude enzyme mixture through a series of anion exchange, size exclusion chromatography; 3) evaluate the activity of different cellulase cocktail; and 4) using 2-dimensional gel electrophoresis to obtain the proteomic profile of B. JXL. In addition, the REU students will have the opportunities to learn from and interact with Dr. Liang’s two Ph.D. students and one Master student working on other cutting-edge biofuel-related projects.

Fig. 1. SEM image of B. JXL grown on cellobiose.

 

Fig. 2. SEM image of B. JXL grown on glucose. Compared with cells grown on cellobiose, much denser extracellular structures are present. The protuberant structures on the cell surface resemble cellulosome- the cellulose degrading multi-enzyme machinery.