Cellulosome structure of thermophilic cellulolytic and alkaliphilic xylanolytic microorganisms

Bacillus firmus K-1 was the potent producer of extracellular alkaline xylanase having a specific insoluble xylan-binding region. Xylan-binding endoxylanase from Bacillus firmus K-1 was purified by affinity adsorption-desorption on insoluble xylan. Its adsorption to insoluble xylan was greatly dependent on the concentration of buffer, pH, temperature and metal ions. In addition, xylan-binding endoxylanase has the ability to bind to crystalline cellulose amorphous cellulose and lignocellosic substances. An anaerobic thermophilic, Bacteroides sp. P-1 was isolated from a themophilic anaerobic digester. The growth and adherence of cells to insoluble microcrystalline cellulose and the production of avicelase, carboxymethylcellulase or xylanase when grown on avicel, carboxymethylcellulose or xylan as a sole source of carbon, indicated that this Bacteroides sp. P-1 was found to be a cellulosome producing strain. When grown in avicel, the Bacteroides strain produced cellulas, xylanase, ethanol and organic acids, especially acetic acid. the crude extracellular cellulosome-type enzyme from the Bacteroides strain could absorb on microcrystalline cellulose and hydrolyze raw agricultural residues such as rice straw, bagasse, corn hull and corn cob effectively. The isolation and characterization of the extracellular form of cellulosome-type multienzyme complex of thermophilic Bacteroides sp. P-1 is described. Multienzyme complex was isolated from the culture supernatant by an adsorption-desorption affinity chromatography on crystalline cellulose. The isolated multienzyme complex was found to form a complex that exhibited a high molecular weight and was quite stable, requiring strong denaturing condition of dissociation. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate resolved multienzyme complex into at least 12 subunits with the molecular weight range of 49 to 209 kDa. The isolated multienzyme complex showed insoluble cellulose-bonding ability, cellulase and xylanase activities and effected the hydrolysis of crystalline cellulose and lignocellulosic materials in the form of corncob, corn hull, rice straw and sugarcane bagasse.