Abstract
A Caldicellulosiluptor sp. strain EP2 was isolated from the sugarcane bagasse pile. It was a thermophilic lignocellulose-degrading anaerobic bacterium. The strain EP2 closely related to Caldicellulosiruptor saccharolyticus DSM 8903 with 98.57% sequence similarity base on 16s rRNA gene analysis. Therefore, the strain EP2 was belonged within the genus Caldicellulosiruptor, given namely Caldicellulosiruptor sp. strain EP2. Interestingly, this strain produced xylanase activity 58.54 Unit/mg, which was 5.9-folds higher than C. saccharolyticus DSM 8903 (9.89 Unit/mg) when cultivated on cellulose powder. The end products obtained from the fermentation of cellulose powder by strain EP2 were mainly acetic acid, ethanol and a small amount of propionic acid and butyric acid, while lactic acid was not detected. The genome of the strain EP2 showed a circular chromosome with size 2,849,880 bp, 2,672 protein-coding genes, 47 tRNA and 9 rRNA genes. Likewise, the genome of strain EP2 indicated that encodes a wide range of glycoside hydrolases (GHs), i.e., hemicellulose-, cellulose-, starchdegrading and chitin-degrading enzymes as 28, 13, 6 and 2 genes, respectively, which higher number of GH genes than C. saccharolyticus DSM8903, especially hemicellulolytic enzymes. Moreover, two cellulosebinding proteins were isolated from the crude enzyme preparation by affinity purification on cellulose. It revealed 16 proteins on SDS-PAGE and five xylanases and four CMCases on zymograms. The result indicated that the strain EP2 produced the xylanolytic-cellulolytic enzymes in a term as a multienzyme complex, which gathers together of enzyme subunits
