Production of Xylanase by Aspergillus flavus FPDN1 on Pearl millet bran: Optimization of Culture Conditions and Application in Bioethanol Production

Abstract

The production of extracellular xylanase by a locally isolated strain of Aspergillus flavus FPDN1 was studied for optimization of cultural conditions and saccharification followed by bioethanol production. Among the various agro residues used pearl millet (bajara) bran was found to be the best for high activity of xylanase with poor cellulase production under solid state fermentation with compared to submerged fermentation. During optimization, influence of different cultural conditions such as substrate concentration, incubation period, moisture level, inoculum size, pH, temperature, effect of carbon sources, orgenic and inorganic nitrogen sources were investigated. The production of the xylanase reached at maximum  with substrate concentration (4g), incubation period (5 day), moisture level (45%), inoculum size (3 x 10⁶ spores/mL), pH (6), temperature (25⁰C), carbon source (xylose), organic nitrogen source (yeast extract) and inorganic nitrogen source [(NH₄)₂SO₄]. Under optimized conditions enhanced xylanase production achieved was 1530 IU/gds/min. The hydrolysis study of birch wood xylan by TLC was yielded xylose and other xylooligosaccharides as an end product. Crude xylanase was further utilized for enzymatic saccharification of pearl millet bran followed by bioethanol production from saccharified sugars. It was further confirmed by GLC analysis.