Statistical screening and optimization of process variables for xylanase production utilizing alkali-pretreated rice husk

With the objective of the production of xylanase, local raw material (rice husk) and the indigenous isolate, Aspergillus niger ITCC 7678, were studied. Optimization of the cultivation system for enhancing xylanase production was studied via submerged fermentation. Statistical procedures were employed to study the effect of process variables, such as alkali-pretreated rice husk (as carbon source), NaNO₃ (as nitrogen source), KH₂PO₄, KCl, Tween 80 (as surfactant), MgSO₄, FeSO₄·7H₂O, pH, particle size, agitation, and temperature, on xylanase production by A. niger. The effect and significance of the variables was studied using Plackett–Burman (PBD) and central composite statistical design (CCD). It was found that alkali pretreated rice husk (weight/volume), pH, temperature, and NaNO₃ significantly influence xylanase production. So, these four factors were further optimized by CCD, and it was found that maximum xylanase activity of 10.9 IU/ml was observed at (6.5 % w/v) rice husk, pH (5.5), temperature (32.5 °C), and NaNO₃ (0.35 % w/v) concentration. Under optimum conditions, xylanase production was also studied at the bioreactor level and showed 12.8 % enhanced xylanase activity.