Abstract

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Laccases are increasingly being used in the biodegradation and utilization of biomass. This trend has led to increased need for development of efficient production systems. This research was carried out with the aim of optimizing the fermentation conditions of selected and consortia of four fungal species (Lachnocladium flavidum, Aspergillus niger, Trichoderma reesei, and Lenzites betulina) for production of laccase from biodegradation of corn cobs. Maize cobs were prepared, alkaline pretreated and fermented with various lignocellulolytic fungi. Single and mixed-culture solid state fermentation with various fungal species was carried out. Process parameters of pH, incubation time, moisture content and inoculum concentration were optimized and the effects of various carbon and nitrogen supplementation were determined. Changes in the fibre contents were analyzed using standard methods. Lachnocladium flavidum proved to be the most effective lignin degrader with optimal lignolytic activities. Optimal conditions were supported at incubation period of 8-9 days with culture conc. of 8 x 103 spores/ml, pH 6-7, moisture at 65-70%, sucrose and yeast as best supporting carbon and nitrogen sources. Results also show variability in degradation of cellulose, hemicellulose and lignin. Cellulose and hemicellulose were most affected. Mixed culture of T. reesei and A. niger had the most significant reduction in cellulose (10.50±1.20%), T. reesei had the most significant reduction in hemicellulose (15.30±1.30%). Lignin was most significantly reduced by mixed culture of Lach. flavidum/ A. niger (7.20±0.80%)

Keywords: Fungi, lignin, laccase, maize cob, mixed fermentation