Study On Production Of Dextran, Mannitol, And Diacetyl By Leuconostoc

Leuconostoc strains are Gram-positive, facultatively anaerobic, heteromorphosis lactic acid bacteria (LAB). Leuconostoc spp. is generally regarded as safe (GRAS) organisms because of their common appearance in naturally fermented foods. Leuconostoc strains can produce several functional carbohydrates such as lactic acid, dextran, oligosaccharides, mannitol, and diacety.The effects of glucose (5 g/l), nitrogen source, Mn²⁺ and Mg²⁺, two salt nutrients (K₂HPO₄, NaAC), various initial culture pH, 0.2% (m/v) CaCO₃, and different fermentation technologies on the production of dextran by Leuconostoc mesenteroides CGMCC1.10327 using 2% (m/v) sucrose as the carbon source in batch culture fermentation were investigated, respectively. The results showed that adding glucose and CaCO₃ had no effect on the yield of dextran. When nitrogen source was reduced from the culture, the yield of dextran was improved. The yield of dextran was reduced when Mn²⁺ and Mg²⁺ were in medium. Two salt nutrients (K₂HPO₄, NaAC) contributed to improve the yield of dextran. The highest yield of mannitol was obtained at initial pH 6.0. The fed-batch fermentation contributed to improve the yield of dextran.The effects of glucose (5 g/l), nitrogen source, Mn²⁺ and Mg²⁺, three salt nutrients (K₂HPO₄, NaAC, and ammonium citrate), Tween-80, various initial culture pH, 0.2% (m/v) CaCO₃, and different fermentation technologies on the production of mannitol by Leuconostoc mesenteroides CGMCC1.10327 using 2% (m/v) sucrose as the carbon source in batch culture fermentation were investigated, respectively. The results showed that glucose and Tween-80 contributed to improve the yield of mannitol. When nitrogen source was reduced from the culture, the yield of mannitol was improved. Mn²⁺ improved the yield of mannitol and the productivitiy of mannitol, but Mg²⁺ reduced the yield of mannitol. Three salt nutrients (K₂HPO₄, NaAC, and ammonium citrate) had significant effects on the production of mannitol. The highest yield of mannitol was obtained at initial pH 6.0. The yield of mannitol was significantly decreased by adding CaCO₃. The fed-batch fermentation contributed to improve the yield of mannitol.The effects of yeast extract, ammonium citrate, various initial culture pH, and inoculation on the production of diacetyl on production of diacetyl by Leuconostoc mesenteroides kimshi004 using 2% (m/v) glucose as the carbon source in batch culture fermentation were investigated, respectively. The results showed that the highest yield of diacetyl was obtained when yeast extract was 3 g/l. The highest yield of diacetyl was obtained when ammonium citrate was 3 g/l. The highest yield of diacetyl was obtained at initial pH 7.0. The yield of diacetyl was the highest when the inoculation was 1% (v/v).The significances of this study are that to produce dextran and mannitol cost-effectively on an industrial scale by fermentation. Studying the production of diacetyl by Leuconostoc is to produce fermentation dairy foods with good flavor and quality for increasing the dairy markets.