HIGH-LEVEL EXPRESSION OF AN ENDOXYLANASE GENE FROM BACILLUS SP. IN BACILLUS-SUBTILIS DB104 FOR THE PRODUCTION OF XYLOBIOSE FROM XYLAN

To produce xylobiose from xylan, high-level expression of an endoxylan ase gene from Bacillus sp. was carried out in Bacillus subtilis DB104. A 1.62-kb SmaI DNA fragment, coding for an endoxylanase of Bacillus s p., was ligated into the Escherichia coli/B. subtilis shuttle vector p JH27 Delta 88, producing pJHKJ4, which was subsequently transformed in to B. subtilis DB104. A maximum endoxylanase activity of 105 U/ml was obtained from the supernatant of B. subtilis DB104 harboring pJHKJ4. T he endoxylanase was purified to homogeneity by ion-exchange chromatogr aphy and the production profile of xylooligosaccharides from xylan by the endoxylanase was examined by HPLC with a carbohydrate analysis col umn. Xylobiose was the major product from xylan at 40 degrees C and it s proportion in the xylan hydrolyzates increased with the reaction tim e; at 12 h, over 60% of the reaction products was xylobiose. These res ults suggest that xylobiose, which has a stimulatory effect on the sel ective growth of the intestinal bacterium Bifidobacterium, can be mass -produced effectively by the endoxylanase of Bacillus sp. cloned in B. subtilis.