Production and optimization of thermostable alkaline xylanase by Penicillium oxalicum in solid state fermentation

The objectives of the present study were Isolation, identification and characterization of xylanase producing fungi, optimization of medium composition and cultural conditions for xylanase enzyme production, production using cheaper sources and extraction and partial purification of extra cellular xylanase enzyme from a potential strain. Xylan has a complex structure consisting of β-1, 4-linked xylose residues in the backbone to which short side chains of o-acetyl, α-L-arabinofuranosyl, D-α- glucuronic and phenolic acid residues are attached. A variety of microorganisms are reported to produce endo xylanases, that can degrade β-1,4-xylan in a random fashion, yielding a series of  linear and branched oligosaccharide fragments. Totally 69 strains were isolated from Pitchavaram mangroves. In secondary screening, based on the diameter of the clear zone formation in oat spelt xylan agar plates, Penicillium oxalicumwas selected and optimized for xylanase enzyme production in solid state fermentation using cheaper sources like wheat bran, rice bran, rice straw, sesame oil cake and wood husk. Maximum enzyme activity was observed in wheat bran. (3.89 U/ml) Optimum pH and temperature for xylanase activity were found to be 8 and 45°C at 3% salt concentration. In purification step, 80% ammonium sulphate saturation was found to be suitable giving maximum xylanase activity. The use of wheat bran as a major carbon source is particularly valuable because oat spelt xylan or birch wood xylan are more expensive, Thus the present study proved that the fungal strain P. oxalicum used is highly potential and useful for industrial production.   Key words: Xylanases, solid state fermentation, fungi, optimization, purification.