Production of Cellulase Enzymes by Rhizomucor miehei Isolates in the Submerged Culture Containing Wheat Bran

Large amounts of inedible materials including agricultural and forest residues are discarded or burnt annually. Bioconversion of these abundant, cheap and renewable materials to valuable biofuels is a significant issue in biotechnology. Enzymatic degradation of lignocellulosic biomass is the most expensive phase in biofuel production process, and cellulases play important roles in this phase. In this study, we aimed to find thermophilic cellulase-producing filamentous fungi which are compatible with the properties of this critical stage (acidic pH and high temperature). Four cellulase producing isolates (from cow manure samples) and Rhizomucor miehei PTCC 5155 (as a reference fungus) were grown in a simple medium containing salt solution, peptone and wheat bran in the submerged culture and investigated for their cellulase activities (at acidic condition (pH 5.5) and 50 °C temperature) during a 12-day period. FUM 4-6 isolate showed the highest levels of endoglucanase (70.95 U/g) and Filter Paperase (17.61 U/g) activities at day 8. Endoglucanase activity of FUM 4-6 isolate was measured approximately twofold levels of reference fungus enzyme activity. FUM 4-14 isolate exhibited the highest activity of exoglucanase (4.64 U/g) at day 8, which statistically was higher than reference fungus enzyme activity (3.32 U/g). Respecting our findings, it seems that Rhizomucor miehei FUM 4-6 isolate could be a suitable candidate for further studies in the field of cellulase enzymes production with the purpose of utilizing in biofuel production.