Ethanol production from sugar cane syrup using Zymomonas mobilis

Since Zymomonas mobilis cannot be made available to industry in dried or lyophilized form, cell biomass was compared with liquid culture for rapid initiation of ethanol formation. The latter gave a more constant production rate at 0.5 g l-1 dry weight equivalent. Of twelve different carbon source combinations in the pre-culture, only those containing sucrose at > 10% (w/v) secured and maintained rapid and complete overall sucrose hydrolysis (97-100%). Of all the nutrient combinations tested, the presence of 1-2 g l-1 MgSO4 and 0.5 g l-1 diammonium phosphate gave close to 20% improvement in conversion efficiency. The addition of 0.06-0.125 g l-1 invertase overcomes sucrose hydrolysis problems owing to pre-culture conditions. Sorbitol formation was reduced to 0.1-0.3% (w/v) using a continuous feeding train cultivation technique at 110 ml h-1 [D = 0.18 h-1]. Batch and continuous processes exhibit ethanol production rates of 3 g l-1 h-1 and final sucrose to ethanol conversion efficiencies in excess of 90%

Sugar-cane molasses fermentation by Zymomonas mobilis

Two different quality types of sugar-cane molasses containing a total sugar content of 48%-50% (w/v) and 35%-42% (w/v) were investigated for Zymomonas biothanol production. Molasses concentrations of up to 250 g/l (1:3 dilution) were successfully fermented within 24 h despite a higher salt concentration in the lower grade molasses. Higher molasses concentrations (300 g/l) led to fructose accumulation. The addition of sucrose to a final sugar concentration of 15% (w/v) led to 10% (v/v) ethanol with conversion efficiencies up to 96%. Sorbitol levels were negligible, but increased up to tenfold upon addition of invertase

zymomonas mobilis-science and industrial application

Zymomonas mobilis is undoubtedly one of the most unique bacterium within the microbial world. Known since 1912 under the names Termobacterium mobilis, Pseudomonas linderi, and Zymomonas mobilis, reviews on its uniqueness have been published in 1977 and 1988. The bacterium Zymomonas mobilis not only exhibits an extraordinarily uniqueness in its biochemistry, but also in its growth behavior, energy production, and response to culture conditions, as well as cultivation techniques used. This uniqueness caused great interest in the scientific, biotechnological, and industrial worlds. Its ability to couple and uncouple energy production in favor of product formation, to respond to physical and chemical environment manipulation, as well as its restricted product formation, makes it an ideal microorganism for microbial process development. This review explores the advances made since 1987, together with new developments in the pure scientific and applied commercial areas