Monday, April 30, 2007

SSF: A novel strategy for enhanced production of laccase by mutant Aspergillus fumigatus VkJ2-4.5 using banana peel as an ideal solid support

V. Vivekanand, P Dwivedi, N Sabharwal, and R P Singh. Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247 667, India

In the present study banana peel which is available in plenty, enriched with nutrients and is of no use could support the fungal growth, was selected as a novel solid support for microbial anchorage in solid-state fermentation (SSF). The work deals with production of laccase through SSF by using banana peel as solid support. Aspergillus fumigatus VkJ2-4.5 developed in our laboratory by two stage UV mutagenesis of Aspergillus fumigatus VkJ (ITCC 6035) which was isolated from sugarcane industry waste produced high levels of extracellular laccase, manganese peroxidase and xylanase during SSF. Different solid supports: poplar leaves, banana peel, wheat bran, wheat straw and bagasse were evaluated to derive the best suited substrate. Use of banana peel had resulted into maximal activity (6281±229 Ul-1) under derived conditions. Higher levels of laccase production using banana peel may be attributed to rich nutrient composition of banana peel. The conditions derived were: moisture content, 80%; incubation time, 6 days; inoculum, 6% and with 2.5 l min-1 of aeration level. The thermal stability profile revealed that enzyme was stable up to 50% at 550C-600C and at pH from 5.0 to 9.0 for two hours. Laccase activity appeared as a single band on native gel (34±1 kDa) and further analysis had indicated that enzyme may be a monomer. This agricultural waste therefore seems to be significant for the production of value-added products and the bioconversion strategy adopted may be suitable for utilization of other agro-horticultural wastes for generating value added products in an economic manner.