Efficient saccharification of ammonia soaked rice straw by combination of Clostridium thermocellum cellulosome and Thermoanaerobacter brockii β-glucosidase

Clostridium thermocellum is known to produce the cellulosomes with efficient plant cell wall degradation ability. To bring out the maximum cellulolytic ability of the cellulosomes, it is necessary to eliminate the end product inhibition by cellobiose. Combinations of β-glucosidases from thermophilic anaerobic bacteria and Aspergillus niger and C. thermocellum S14 cellulosomes were evaluated for optimization of cellulose degradation. β-Glucosidase (CglT) from Thermoanaerobacter brockii, in combination with cellulosomes, exhibited remarkable saccharification ability for microcrystalline cellulose. When rice straw, soaked in 28% aqueous ammonia for 7 days at 60 °C, was hydrolyzed by an enzyme loading combination of 2 mg cellulosome and 10 units CglT per g glucan, 91% of glucan was hydrolyzed to glucose, indicating roughly1/10 the enzyme load of a Trichoderma reesei cellulase (Celluclast 1.5L) and Novozyme-188 combination is enough for the combination of C. thermocellum S14 cellulosomes and CglT to achieve the same level of saccharification of rice straw.