Continuous sucrose conversion into fructose and ethanol by immobilized cell reactor of fructose utilization-negative mutant of zymomonas mobilis

ABSTRACT

Continuous sucrose conversion into fructose and ethanol by immobilized cell reactor of fructose utilization-negative mutant of Zymomonas mobilis was investigated. Levan and sorbitol were produced as the major by-products from fructose. Their mass ratios to hydrolyzed sucrose remained almost constant over a wide range of dilution rates and initial sucrose concentrations. Fermentation temperature affected the synthesis of levan and sorbitol whereas feed medium pH exerted a pronounced effect only on sucrose hydrolysis activity. Simultaneous control of fermentation temperature at 36C and feed medium pH at 6.2 resulted in an excellent performance. At residence time of 1.1 h the immobilized cell reactor of fructose utilization-negative mutant produced 57.6 g/L of fructose and 24.8 g/L of ethanol from 130 g/L of sucrose in feed medium