Direct glucose production from lignocellulose using Clostridium thermocellum cultures supplemented with a thermostable β-glucosidase

Table 1 Biological saccharification using glycoside hydrolase family-1 β-glucosidases from C. thermocellum and T. thermosaccharolyticum

	Specific activity (U/mg)	Thermal stability (%)^a	Optimum temperature (°C)^b	Optimum pH^b	Glucose inhibition (mM)^c	Biological saccharification
						Cellobiose concentration (mM)^d	Glucose concentration (mM)^d
CglT (T. brockii)	26.0 ± 0.05	97	60 to 75	6.0 to 7.0	450 ± 10.2	5.9 ± 0.7	425.9 ± 24.7
BglA (C. thermocellum ATCC)	19.4 ± 0.05	10	50 to 60	6.0 to 7.0	400 ± 5.1	22.1 ± 1.3	240.7 ± 18.5
Bgl (T. thermosaccharolyticum NOI-1)	28.8 ± 0.05	10	60 to 70	6.0 to 7.0	650 ± 3.2	36.4 ± 0.7	304.3 ± 18.5

^aThermal stability is indicated as the percentage of remaining β-glucosidase activity after incubation for 24 hours at 60°C; ^brange reported represents where >90% of the maximal activity was maintained; ^cglucose inhibition was calculated as the glucose concentration required to inhibit 50% of initial β-glucosidase activity; ^dbiological saccharification was carried out by culturing C. thermocellum with each β-glucosidase using 100 g/L crystalline cellulose as described in the Methods section. To allow comparison with glucose production, cellobiose concentration was indicated in mM glucose equivalents. Values are the means of triplicate experiments ± SD.

ISSN: 2731-3654