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A multienzymatic complex production was evaluated, as well as endoglucanase and total cellulase characterization, during solid-state fermentation of rice industry wastes with Rhizopus oryzae CCT 7560 (newly isolated microorganism) and Trichoderma reesei QM 9414 (control). R. oryzae produced enzymes with higher activity at 15 h of fermentation (5.1 and 2.3 U g(-1) to endoglucanase and total cellulase), while T. reesei produced them at 55 h (15.3 and 2.8 U g(-1) to endoglucanase and total cellulase). The optimum temperature for total cellulase and endoglucanase was 60 °C. For Trichoderma and Rhizopus, the optimum pH was 5.0 and 6.0 for total cellulase and 6.0 and 5.0 for endoglucanase, respectively. The enzymes produced by Rhizopus presented higher stability at the temperature range evaluated (25-100 °C); the endoglucanase KM value was 20 times lower than the one found for Trichoderma. The characterization of the cellulolytic enzymes from the fungal species native of rice husk revealed that they can be more efficient than the genetically modified enzymes when rice husk and rice bran are used as substrates.

During the fermentative processes with R hizopus oryzae CCT 7560 and T richoderma reesei QM 9414, the effects of rice hull and moisture content on the endoglucanase and total cellulase activities were investigated by response surface methodology, employing a central composite rotatable design. The nutrient solution and bioreactor design were also studied. In tray bioreactors maximum cellulase activity was achieved with 82.5% of rice hull and 17.5% of rice bran, with an initial moisture content of 30% for R hizopus, while 100% of rice hull with an initial moisture content of 50% was used for T richoderma in Erlenmeyer bioreactors. The results obtained for R hizopus were 91% higher for endoglucanase when compared with T richoderma, confirming the potential of the newly isolated R . oryzae CCT 7560 for cellulase production. In addition, this provided an economical and environmentally viable destination for one of the biggest wastes resulting from the rice industry, the rice hull. Practical Applications Most cellulases related in the literature are obtained from fermentative processes employing genetically modified microorganisms during extensive time to achieve maximum activity. The microorganism studied in this work ( R hizopus oryzae CCT 7560) exhibited rapid enzymatic production indicating its use to obtain digestible carbohydrates from agribusiness waste in a quick and safe way. [ABSTRACT FROM AUTHOR]