Response Surface Methodology for the Evaluation and Comparison of Cellulase Production by Aspergillus nidulans SU04 and Aspergillus nidulans MTCC344 Cultivated on Pretreated Sugarcane Bagasse

S. Anuradha Jabasingh

Abstract
Response surface methodology (RSM) was used to optimize the conditions for the production of endo β-1,4 glucanase – a component of cellulase by Aspergillus nidulans SU04 and Aspergillus nidulans MTCC344 under solid state fermentation, using pretreated bagasse as chief substrate. A four-factor-five-level central composite design was employed for the experimental design. The endo β-1,4 glucanase produced during the bioconversion of cellulose to glucose by these strains were strongly dependent on the NaOH pretreatment given to bagasse before hydrolysis. Maximum cellulase activity was 32.59 U g–1 and 28.96 U g–1 (CMCase) for A. nidulans SU04 and A. nidulans MTCC344 respectively. The optimum conditions for cellulase production are 15 mm bagasse bed height, 60 % moisture content, pH 5 and temperature 40 °C in the solid state fermenter. A. nidulans MTCC344 and A. nidulans SU04 were able to hydrolyze pretreated sugarcane bagasse completely after 15 days and 6 days of incubation with significant endo β-1,4 glucanase activities. The results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM) of bagasse showed structural changes through pretreatment, in favor of enzymatic hydrolysis. A. nidulans SU04 was found to be highly efficient compared to A. nidulans MTCC344 in terms of endoglucanase, exoglucanase and β-glucosidase activities.

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Keywords
Aspergillus nidulans SU04, Aspergillus nidulans MTCC344, CMCase, pretreated bagasse, solid-state fermentation, central composite design, response surface methodology