Author(s): T Satyanarayana
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The production of extracellular thermostable cellulase-free xylanase (EC 220.127.116.11) by Bacillus licheniformis A99 was studied in solid-state fermentation (SSF). Wheat bran was found to be the best substrate [16.3 U g−1 dry bacterial bran (DBB)] among a few easily available lignocellulosics tested. The production of xylanase reached a peak in 72 h (16.8 U g−1 DBB). A high level of enzyme (17.1 U g−1 DBB) was produced in wheat bran moistened with tap water at a substrate-to-moistening agent ratio of 1:2.5 (w/v). The optimum temperature for xylanase production was 50°C. An elevated water activity suited the enzyme production most. Maximum enzyme production was recorded in an aerated glass column reactor (19.13 U g−1 DBB). Repression by glucose was not evident in SSF even at 6% while it was seen in submerged fermentation (SmF) at or beyond 2%. Cultivation in large enamel trays yielded a xylanase titer (15–17 U g−1 DBB in 72 h) that was comparable to that in flasks. The enzyme production was 22-fold higher in SSF than that in SmF. This is the first report on xylanase production by a thermophilic bacterial strain in SSF.
This article was published in Enzyme and Microbial Technology
and referenced in Fermentation Technology