Optimisation of Thermostable Laccase Production by Thermoascus aurantiacus MTCC 375 Using Paddy Straw as Substrate and Digested Biogas Slurry (DBS) as Medium in Solid State Fermentation

Optimisation of laccase production by Thermoascus aurantiacus microbial type culture collection (MTCC) 375 using paddy straw as substrate and digested biogas slurry as medium was carried out. Laccase production by a thermophilic mould, Thermoascus aurantiacus MTCC 375, was optimised in solid state fermentation (SSF) by a conventional ‘one variable at a time approach ‘andfurther by response surface methodology. Enzyme activity was strongly affected by three independent variables namely incubation temperature, incubation period and inoculum level. The optimised conditions for maximum laccase (715.0 Ug⁻¹ of paddy straw) production were 45°C temperature, 10⁷ spores ml⁻¹ and 4 days incubation period. The enzyme titre (715.0 Ug⁻¹ of paddy straw) attained in the validation experiment of this study is higher than those reported in the literature. An overall (2.65 fold) increase in laccase production was achieved in SSF due to statistical optimisation compared to that of a conventional ‘one variable at a time approach ’. All these cultural conditions were found to have statistically significant (P < 0.05) effect on enzyme production.