Optimization of culture conditions for xylanase production by mixed fungal fermentation: Effects on pretreated maize cobs

The use of microorganisms for xylanase production plays important role in the bioconversion of lignocelluloses and also required in huge amount for industrial level application. This necessitates the need to select potent microorganisms for xylanase production, followed by optimization of media components for enhanced production. The effects of altering cultural fermentation conditions on the xylanase production ability in maize cobs were investigated. A consortium of four fungi; Lenzites betulina, Trichoderma reesei, Lachnocladium specie and Aspergillus niger were used to carry out single and mixed solid-state fermentation on NaOH pretreated maize cobs. Optimization of fermentation factors were carried out from ten groups of individual and co-fermented fungal combinations. L. flavidum was found to be the most effective xylanase producer with optimal conditions at pH of 5.5, moisture 75%, inoculum concentration at 5-6 x 103 spores/ml, incubation period of 7-9 days and 1% peptone as the best nitrogen media supplement. Variation to different degrees in the degradation of the maize cobs were observed. A 10% decrease in cellulose was observed with co- cultures of T. reesei and A. niger and a 15% decrease in the hemicellulose fraction. The biotechnological potential of corn cobs has been enhanced by the screening and optimizing the culture conditions.