A genomic library of
Bacillus lyticus was constructed in lambda GEM 11 vector and screened for the
xylanase gene using Congo red plate assay. A 16-kb fragment containing the
xylanase gene was obtained which was further subcloned using Mbo I partial
digestion in an E. coli pUC 19 vector. A 1.3-kb sub-fragment was obtained which
coded for a xylanase gene of Mr 23,650 Da. This fragment was sequenced and the
homology was checked with known xylanases. The maximum homology was 97%, which
was obtained with an endo xylanase gene from Bacillus species at the DNA level,
while the translated sequence showed only one amino acid change from alanine to
serine at position number 102. Expression was checked in E. coli, using the native
promoter, and an extracellular activity of 5.25 U/mL was obtained. Cloning of
the gene was done in Bacillus subtilis using a shuttle vector pHB 201, which
resulted in increasing the basal level xylanase activity from 14.02 to 22.01
U/mL.
