Improved ethanol production from sucrose by a mutant of Zymomonas mobilis lacking sucrases in immobilized cell fermentation

• Published in: Enzyme and microbial technology Vol. 22; no. 3; pp. 179 - 184
• Main Authors: Kannan, T.R., Sangiliyandi, G., Gunasekaran, P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15.02.1998; Elsevier Science
• Subjects: Biological and medical sciences; Biotechnology; Enzyme immobilization; Ethanol; fermentation; Fundamental and applied biological sciences. Psychology; Hydrolysis; immobilization; levan; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; sorbitol; Sugar (sucrose); Zymomonas mobilis; fermentation; immobilization; levan; ethanol; sorbitol; Zymomonas mobilis; Ethanol; Sucrose; Enzyme; Levansucrase; Transferases; Glycosyltransferases; Optimization; Alcoholic fermentation; Glycosidases; Production; Bacteria; Hydrolases; Hexosyltransferases; Mutation; O-Glycosidases; Entrapped microorganism; Sucrose α-glucosidase
• DOI: 10.1016/S0141-0229(97)00158-0
• ISSN: 0141-0229

Ethanol production from sucrose by Zymomonas mobilis LS1A, a mutant strain lacking levansucrase (SacB) and intracellular sucrase (SacA), was studied in an alginate-immobilized cell fermentation. Since this mutant strain does not produce levan from sucrose, the immobilized cells were stable in sucrose fermentations and therefore produced higher amounts of ethanol (73.5 g l −1) than that of its parent strain, B-806 (65.2 g l −1) in an 18-h fermentation with 150 g sucrose l −1. The absence of levansucrase and the decreased sucrose hydrolysis rate of this strain improved ethanol production without the formation of the by-products levan and sorbitol; however, an increase in the initial concentration of sucrose (150 to 250 g l −1) in the fermentation medium favored the formation of sorbitol as a by-product. Coimmobilization of invertase with cells decreased the fermentation time from 18 to 12 h, thereby resulting in increased ethanol productivity from 4.08 g l −1 h −1 to 6.22 g l −1 h −1 and also increased the level of sorbitol. Decreased fermentation time (from 18 to 12 h) and increased ethanol productivity (6.3 g l −1 h −1) without any by-products were also achieved with the use of repeated batch fermentations of sucrose by immobilized cells of this mutant strain.