Medium optimization of production of xylanase by solid state fermentation from Brevibacillus borstelensis – MTCC 9874 isolated from soil sample of eastern Nepal

ABSTRACT

The main aim of this study was to optimize production medium in solid state fermentation for production of xylanase using Brevibacillus borstelensis MTCC 9874. The organism was isolated from Morang district of Nepal and it was grown for 96 h in five different mineral salt solutions (MMS) with rice husk and MSS-1 was selected as a medium for further study based on xylanolytic activity measured using DNS method. Plackett Burman design (Minitab 15.1) was done with six variables viz. dipotassium hydrogen phosphate, rice husk, sodium chloride, magnesium sulphate, sodium carbonate and calcium chloride. The result showed that dipotassium hydrogen phosphate and rice husk were significant factors for xylanase production (> 95% confidence levels). Full factorial Centre composite design (CCD) was used to optimize the two significant factors. Response surface and contour plot were used to locate the optimal value of the two factors. There was 279.88% increase in xylanolytic activity after optimization of the medium. Study of effect of temperature on xylanolytic activity showed that maximum xylanolytic activity (6.58±1.1 IU/mL) was found at 60 °C. Optimum pH was found to be 7.6 (Xylanolytic activity = 6.81±2.32 IU/mL). Thermal stability study showed that the enzyme has a good stability at 60 °C (95.62%). Lineweaver – Burk plot showed that the enzyme has Vmax and Km values 0.1075 μg/mL .min and 1427.63 μg/mL respectively.