Evaluation of plant cell wall degrading enzyme production by Clostridium thermocellum B8 in the presence of raw agricultural wastes

• Clostridium thermocellum as a source of industrial enzymes.
• Lignocellulosic biomasses degradation by C. thermocellum.
• Non-cellulossomal enzymes from C. thermocellum.

Plant cell wall represents an important source of fermentable sugars for second generation bioethanol production. However, cellulosic biomass hydrolysis still is a bottleneck to bioethanol production in an efficient and low cost process. Thermophilic bacteria have been studied as a source of cellulolytic enzymes for cellulosic biomass deconstruction, as their enzymes present unique features compatible with current industrial process conditions. The present study was carried out to evaluate the use of different agro-industrial wastes as suitable carbon sources for growth and enzyme secretion by a strain of Clostridium thermocellum isolated from goat rumen. C. thermocellum B8 was able to grow on/degrade microcrystalline cellulose, Sugar cane bagasse/Straw and Cotton waste, and produced different sets of cellulases and hemicellulases in their presence. The enzymatic mixtures produced by C. thermocellum (B8) showed activities over a broad range of temperatures (50–70 °C). Highest values were obtained between 60 and 70 °C, at a pH range from 5 to 7, decreasing at alkaline pH values. In addition, enzymes displayed thermostability, with CMCase and xylanase activities maintaining maximum values over 12 days at 50 °C.