Bacillus sp. JB-99 was studied for the production of extra-cellular thermostable alkaline cellulase-free xylanase in solid-state fermentation. The xylanase tit was highest on rice bran, among a few easily available lignocellulosic solid substrates tested. Maximum production of xylanase (3644 U/g DBB) was observed bran moistened with mineral salt solution (MSS3) at a substrate-to-moisturizing agent ratio of 1:2.0 (w/v) at 50degreesC for 72 h. A 10% (v/w) inoculum was most suitable to attain a high production of xylanase. Yeast extract, beef extract and xylan enhanced enzyme production, while glucose, lactose and fructose strongly repressed the production process. (C) 2004 Published by Elsevier Ltd.