Production of ethanol from starch by free and immobilized Candida tropicalis in the presence of α-amylase

• Published in: Bioresource technology 2007-10, Vol.98 (14), p.2765-2770
• Main Authors: Jamai, Latifa, Ettayebi, Khalil, Yamani, Jamal El, Ettayebi, Mohamed
• Format: Article
• Language: English
• Subjects: alpha-amylase; alpha-Amylases - metabolism; biofuels; Biological and medical sciences; Biotechnology; Candida tropicalis; Candida tropicalis - metabolism; Cell immobilization; enzymatic hydrolysis; enzyme activity; enzyme substrates; ethanol; Ethanol - metabolism; Ethanol production; Fermentation - physiology; Fundamental and applied biological sciences. Psychology; genetically engineered microorganisms; glucan 1,4-alpha-glucosidase; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; Saccharomyces cerevisiae; starch; Starch - metabolism; Starch fermentation; transgenes
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2006.09.057

Candida tropicalis is a potentially useful organism for the commercial production of ethanol as it is capable of fermenting starch at a low rate. To enhance this carbon source utilization and increase the rate of alcohol production, we pretreated corn soluble starch with α-amylase. Starch liquefaction was sufficient to drive the fermentation and to convert 96% substrate to ethanol. Indeed, in the presence of exogenous α-amylase, 9% (w/v) soluble starch was converted to 43.1 g ethanol/l in 65 h with a productivity of 0.65 g/l h. Thus, bio-ethanol production using free and calcium alginate-immobilized C. tropicalis does not require the saccharification step. Furthermore, fed-batch fermentation by free C. tropicalis cells increased the final concentration to 56 g ethanol/l, reaching published values for Saccharomyces cerevisiae recombinant strains expressing both α-amylase and glucoamylase.