Alcoholysis and reverse hydrolysis reactions in organic one-phase system with a hyperthermophilic beta-glycosidase.
Alcoholysis and reverse hydrolysis reactions were performed enzymatically in one-phase water-saturated 1-heptanol systems. Lactose or glucose was used as substrate to produce heptyl-beta-galactoside and/or heptyl-beta-glucoside, respectively. When alcoholysis of lactose was performed at 37 degrees C with beta-galactosidase from Escherichia coli, the initial rate was 14 nmol/mL min, and the limiting factors were the poor solubility of the substrate in 1-heptanol and low thermal stability of the enzyme. When a hyperthermophilic beta-glycosidase was used at 90 degrees C, the rate was 3.14-fold higher; in this case a higher concentration of soluble lactose in the water-saturated heptanol was available to the enzyme due to the higher temperature. The hyperthermophilic beta-glycosidase was also able to use glucose and galactose as substrates to achieve the reverse hydrolysis reaction. As a consequence, when lactose was used as substrate, heptyl-beta-galactoside was formed by alcoholysis, while the released glucose moiety was used in a secondary reverse hydrolysis reaction to produce heptyl-beta-glucoside. Both reactions followed Michaelis-Menten kinetics behavior. Neither lactose nor heptyl glycosides were hydrolyzed by this enzyme in water-saturated heptanol. However, the conversion was limited by a strong product inhibition and the formation of oligosaccharides, especially at high substrate concentrations, reducing the final glycoside yield.
Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, México D.F. 04510, México.
M
M
García-Garibay
A
A
López-Munguía
E
E
Barzana
D000438:Alcohols / Q000378:metabolism; D001709:Biotechnology / Q000379:methods*; D004926:Escherichia coli / Q000201:enzymology; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D019850:Heptanol / Q000737:chemistry; D006868:Hydrolysis; D009005:Monosaccharides / Q000378:metabolism; D013379:Substrate Specificity; D001616:beta-Galactosidase / Q000737:chemistry / Q000378:metabolism
D000438:Alcohols; D009005:Monosaccharides; D019850:Heptanol; D006026:Glycoside Hydrolases; D001616:beta-Galactosidase