The screening and selection of the culture variables followed by optimization using statistical approaches led to a 23-fold enhancement in thermo-alkali-stable xylanase production by the polyextremophilic Bacillus halodurans TSEV1. The optimization of crucial parameters involved in the extraction of xylanase from the bacterial bran led to a high enzyme recovery. The purified xylanase produced in submerged fermentation (SmF) and solid state fermentation (SSF) was visualized as a single band on SDS-PAGE with a molecular mass of 40 kDa. The SSF-xylanase is optimally active at 78 degrees C and pH 9.0 and stable in the pH range between 7.0 and 12.0 with a T-1/2 of 65 min at 90 degrees C, which is higher than that of SmF-xylanase. The higher activation energy, enthalpy of deactivation (Delta H*), free energy change of deactivation (Delta G*) and T-1/2 of SSF-xylanase than these of SmF xylanase further confirmed higher thermostability of the former than the latter. The combination of commercial cellulase and TSEV1 xylanase was highly effective in deinking of waste paper at alkaline pH and elevated temperatures. (C) 2013 Elsevier Ltd. All rights reserved.