The aim of this study was the utilization of rice hulls (RH) as a clean, cost effective, renewable and abundant agro-waste in bioethanol production by simple and applicable methods; for this purpose Aspergillus niger MA1 was isolated from RH and selected from many other isolates. This isolate produced 15.0, 3.38 and 49.1 U/g RH for CMCase, FPase and β-glucosidase, respectively, by solid state fermentation of RH after 36 h. The cellulases of the fungus showed good thermal and pH stability with maximum activity at 50°C and pH 5. An increase in cellulases productivity by statistical optimization and multi-response of SSF medium was revealed. Addition of 0.25% brej 35 to tap water or saline is very effective in elution of A. niger MA1. Cellulase which was successfully used in saccharification of steam explosion pretreated RH, revealed 16.36 g/L reducing sugars and subsequently fermentation by Saccharomyces cerevisiae which produced 9.42 g/L ethanol after 24 h.
Key words: Rice hulls, bioethanol, cellulases, solid state fermentation, Aspergillus niger MA1, statistical optimization, multi-response.
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