Effect of Microwave Irradiation on Xylanase Production from Wheat Bran and Biobleaching of Eucalyptus Kraft Pulp

Microwave irradiation (MWI) was used as pretreatment of wheat bran and eucalyptus kraft pulp to examine its effect on xylanase production by Bacillus halodurans FNP 135 using solid state fermentation and biobleaching with xylanase, respectively. Irradiation of wheat bran under optimized conditions (600 W, 6 min, and 20 % consistency) resulted in 56.8, and 31.7 % increase in xylanase yield and water absorbance of wheat bran and 17.3 % reduction in reducing sugars content. Optimized MWI of kraft pulp at 850 W, 2 min, and 20 % consistency led to 0.9 % increase in brightness, 10 % decrease in kappa number, 7.7 % increase in water absorbance, 4.6 % decrease in tear factor, 0.9 % increase in burst factor, and 7.5 % increase in viscosity. Also, MWI enhanced xylanase-mediated biobleaching by increasing brightness (1.1 %) and decreasing kappa number (14.3 %) and leading to a total of about 20 % reduction in chlorine consumption. MWI is an economical, efficient, and environment-friendly pretreatment of wheat bran and pulp for enhanced enzyme yield and rapid heating, respectively.