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Sugar beet diffusion juice and syrup as media for ethanol and levan production by Zymomonas mobilis

Bekers, M., Linde, R., Danilevich, A., Kaminska, E., Upite, D., Vigants, A., Scherbaka, R.
Food biotechnology 1999 v.13 no.1 pp. 107-119
Zymomonas mobilis, fermentation, sucrose, levan, carbohydrate metabolism, ethanol production, culture media, syrups, nutrient requirements, nitrogen, phosphorus, potassium, magnesium
Sugar beet is an important crop cultivated widely in Europe. Roots contain up to 6-9 t/ha of fermentable sugar. Our laboratory is targeting to investigate the production possibilities of ethanol and levan by Zymomonas mobilis bacteria, using sugar beet juice or their syrup as raw material. The Z. mobilis strain 113 "S", selected in our institute, produces simultaneously with ethanol up to 40-70 g/l fructose polymer levan in sucrose medium. It was established that Z. mobilis can convert sucrose into ethanol and levan in batch fermentation using natural sugar beet diffusion juice, without additives of mineral salts and growth factors. Syrup obtained in sugar industrial production by conventional technology from diffusion juice after evaporation with 65% sucrose can be used also as raw material for medium preparation. Additives of N, P, K, Mg, as well as yeast extract, were shown to stimulate the culture growth and product synthesis on such media. Reuse of liquid fermentation products after separation of levan, and distillation of ethanol, can be applied for medium preparation. The medium osmolality increases in this case. Ethanol, levan and fructose production may have potential in the sugar production industry.