Anaerobic cellulose degrading bacteria isolated from biogas plants

Abstract: Two cellulose degrading bacteria, named BCISO-4 and DC1-18-4, were isolated from samples retrieved from two large scale biogas-plants. In order to investigate and determine information regarding their growth preferences multiple tests were performed. Growth for the two isolates was tested on the carbon sources: cellobiose, starch, hemicellulose, straw, cellulose, fructose, glucose, ribose, mannose, xylose and sorbitol (0.5w%/v.). Strong growth was documented on cellulose and cellobiose for both organisms and for BCISO-4 weak growth was possible with xylose, starch, sorbitol, glucose, fructose and ribose. For DC1-18-4 weak growth was observed with xylose, straw, glucose and ribose. Growth was also tested on a more complex nutrient medium, reinforced clostridial medium (RCM), no growth was however documented. The major products produced during growth, as analyzed by HPLC, were determined to be acetate and butyrate for both organisms. For BCISO-4 and DC1-18-4 the growth span for temperature and pH was determined to 25-54 ° C and pH 6-10, and 25-51 ° C and pH 6-9, respectively. Enzyme activity for free enzymes as well as cell-bound was tested on glucose and xylose, and all tests indicated activity. Terminal restriction fragment length polymorphism analysis (TRFLP) targeting the cel 5 gene was performed on samples from the biogas-plants to investigate presence of the isolated species, which confirmed their presence. Keywords: anaerobic bacteria, biogas, cellulose, cellobiose, VFA, enzyme activity, TRFLP