MOLECULAR-CLONING AND CHARACTERIZATION OF AN ENDOXYLANASE GENE OF BACILLUS SP. IN ESCHERICHIA-COLI

A gene encoding an endoxylanase of Bacillus sp. was cloned acid expres sed in Escherichia coli. The entire nucleotide sequence of a 1,620 bp SmaI fragment containing the endoxylanase gene was determined. The end oxylanase gene was 639 bp long and encoded 213 amino acids which showe d up to 96% amino acid homology with other endoxylanases. The encloxyl anase produced by E. coli harboring pKJX4 was purified by ion-exchange chromatography (DE-52 and CM-Si) and its N-terminal sequence was dete rmined to be r-Asp-Tyr-Trp-Gln-Asn-Trp-Thr-Asp-Gly-Gly-Gly-Thr. The en doxylanase expressed in E. coli was identical to that of the riginal B acillus sp, whose molecular weight was approximately 20,400. Most of t he produced endoxylanase was localized in the periplasmic space of E. coli. When the endoxylanase was reacted with 2% oat spelts xylan (w/v) at 40 degrees C for 10 h, the major product was xylobiose which is kn own to be a selective growth stimulant to one of the healthy intestina l microflora, Bifidobacteria. (C) 1998 Elsevier Science Inc.