Alkaline xylanolytic–cellulolytic multienzyme complex from the novel anaerobic alkalithermophilic bacterium Cellulosibacter alkalithermophilus and its hydrolysis of insoluble polysaccharides under neutral and alkaline conditions

Abstract

The multienzyme complex of the novel anaerobic alkalithermophilic bacterium Cellulosibacter alkalithermophilus was isolated by a corn hull column and Sephacryl S-500 gel filtration chromatography. The isolated multienzyme complex showed a single band upon native-polyacrylamide gel electrophoresis (native-PAGE). The molecular weight of the isolated multienzyme complex was greater than 2000kDa. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS–PAGE) revealed at least 19 proteins bands in the multienzyme complex with predominantly xylanase activity (at least 9 xylanases) and with β-xylosidase, arabinofuranosidase, acetyl esterase, carboxymethylcellulase (CMCase) (at least 5 CMCases), avicelase, cellobiohydrolase, and β-glucosidase activities. The multienzyme complex was active and stable under neutral and alkaline pH ranges at high temperature. Moreover, the multienzyme complex also showed effective hydrolysis of xylan, cellulose, and untreated corn hull and rice straw to monosaccharides, xylose and glucose. These results revealed that C. alkalithermophilus produces an alkali-tolerant thermophilic xylanolytic–cellulolytic multienzyme complex, which has never been reported in the genus Cellulosibacter.