Wenjing Li1, Shuhuai Yu1, Tao Zhang1, Bo Jiang1,2, Wanmeng Mu1,2. 1. State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry and Biotechnology, Jiangnan University, Wuxi, Jiangsu, 214122, China. 2. Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
Abstract
BACKGROUND: Raffinose, a functional trisaccharide of α-d-galactopyranosyl-(1 → 6)-α-d-glucopyranosyl-(1 → 2)-β-d-fructofuranoside, is a prebiotic that shows promise for use as a food ingredient. RESULTS: In this study, the production of raffinose from melibiose and sucrose was studied using whole recombinant Escherichia coli cells harboring the levansucrase from Clostridium arbusti SL206. The reaction conditions were optimized for raffinose synthesis. The optimal pH, temperature and washed cell concentration were pH 6.5 (sodium phosphate buffer, 50 mmol L-1 ), 55 °C and 3% (w/v), respectively. High substrate concentrations, which led to low water activity and thus reduced levansucrase hydrolysis activity, strongly favored the production of raffinose through the fructosyl transfer reaction. Additionally, high concentrations of excess acceptor and donor glycosides favored raffinose production. When 30% (w/v) sucrose and 30% (w/v) melibiose were catalyzed using 3% (w/v) whole cells at pH 6.5 (sodium phosphate buffer, 50 mmol L-1 ) and 55 °C, the highest raffinose yield was 222 g L-1 after a 6 h reaction. The conversion ratio from each substrate to raffinose was 50%. CONCLUSION: Raffinose could be effectively produced with melibiose as an acceptor and with sucrose as a fructosyl donor by whole recombinant E. coli cells harboring C. arbusti levansucrase. The yield from E. coli was significantly higher than those of the previously reported Bacillus subtilis levansucrase and fungal α-galactosidases.
BACKGROUND:Raffinose, a functional trisaccharide of α-d-galactopyranosyl-(1 → 6)-α-d-glucopyranosyl-(1 → 2)-β-d-fructofuranoside, is a prebiotic that shows promise for use as a food ingredient. RESULTS: In this study, the production of raffinose from melibiose and sucrose was studied using whole recombinant Escherichia coli cells harboring the levansucrase from Clostridium arbusti SL206. The reaction conditions were optimized for raffinose synthesis. The optimal pH, temperature and washed cell concentration were pH 6.5 (sodium phosphate buffer, 50 mmol L-1 ), 55 °C and 3% (w/v), respectively. High substrate concentrations, which led to low water activity and thus reduced levansucrase hydrolysis activity, strongly favored the production of raffinose through the fructosyl transfer reaction. Additionally, high concentrations of excess acceptor and donorglycosides favored raffinose production. When 30% (w/v) sucrose and 30% (w/v) melibiose were catalyzed using 3% (w/v) whole cells at pH 6.5 (sodium phosphate buffer, 50 mmol L-1 ) and 55 °C, the highest raffinose yield was 222 g L-1 after a 6 h reaction. The conversion ratio from each substrate to raffinose was 50%. CONCLUSION:Raffinose could be effectively produced with melibiose as an acceptor and with sucrose as a fructosyl donor by whole recombinant E. coli cells harboring C. arbusti levansucrase. The yield from E. coli was significantly higher than those of the previously reported Bacillus subtilis levansucrase and fungal α-galactosidases.