Resumen de Lactulose production by a thermostable glycoside hydrolase from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167.
Rebaone Letsididi, Hinawi Am Hassanin, Marwa Yf Koko, Tao Zhang, Bo Jiang, Wanmeng Mu
Background: Lactulose has various uses in the food and pharmaceutical fields. Thermostable enzymes have many advantages for industrial exploitation, including high substrate solubilities as well as reduced risk of process contamination.; Results: Enzymatic synthesis of lactulose employing a transgalactosylation reaction by a recombinant thermostable glycoside hydrolase (GH1) from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167 was investigated. The optimal pH for lactulose production was found to be 4.5, while the optimal temperature was 85 °C, before it dropped moderately to 83% at 90 °C. However, the relative activity for lactulose synthesis dropped sharply to 35% at 95 °C. At optimal reaction conditions of 70% (w/w) initial sugar substrates with molar ratio of lactose to fructose of 1:4, 15 U mL-1 enzyme concentration and 85 °C, the time course reaction produced a maximum lactulose concentration of 108 g L-1 at 4 h, corresponding to a lactulose yield of 14% and 27 g L-1 h-1 productivity with 84% lactose conversion. The transgalactosylation reaction for lactulose synthesis was greatly influenced by the ratio of galactose donor to acceptor.; Conclusion: This novel GH1 may be useful for process applications owing to its high activity in very concentrated substrate reaction media and promising thermostability. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.
