Study On The Production Of Neokestose, By Xanthophyllomyces Dendrorhous (Phaffia Rhodozyma)

Fructooligosaccharides (FOS) of the 1F type have been most extensively investigated as prebiotic compounds. The production of 6F type oligosaccharides from sucrose has also received some attention but so far production of potential prebiotic oligosaccharides of the 6G series,such as the trisaccharide neokestose, has not been investigated.In this work,the production of neokestose by was investigated, the main contents include : the optimization of shake flask culture conditions of neokestose production ;the optimization of fed-batch culture conditions of neokestose production; studies on the physiological function of neokestose.Neokestose accumulated as the main product in the culture broth of Xanthophyllomyces dendrorhous (Phaffia rhodozyma) growing on sucrose. The results suggest that neokstose is composed of 2-linked and 1,2-linked fructose and 1,6-linked glucose.It's a novel syrup fructooligosaccharide.A series of single-factor test and orthogonal test were carried on to determine the optimum shake flask culture conditions of neokestose production by Xanthophyllomyces dendrorhous 269 : sucrose 110g/L, urea 9g/L, pH 6.5, cell concentration 6g/L,18℃, 24h. Under this condition, the concentration of noekestose could reach 70.9g/L, sucrose conversion ratio reached 0.644. It is increased 1.84 fold,compared with the neokestose growing under YM medium.Cells harvested in the exponential growth phase produced neokestose more efficiently than stationary phase cells,but the diffierence is not significant.Recycling of cells reduced the level of neokestose production.Fed-bacth fermentation was useful for the level of neokestose production.Different ventilation r and different feeding modes were studied.In 10L fermenter, with initial installation of 4L medium ventilation 8L/min, pH 6.5±0.5, a one-stage fed bacth culture was performed after fermented for 24 hours.The final neokestose concentration reached 119.3g/L , sucrose conversion ratio reached 0.662.The effect of neokstose on Escherichia coli and Bifidobacterium in vitro were investigated. Less biomass was produced by E.coli from glucose, FOS as carbon source and than from neokestose, but were not significantly different. And more biomass was produced by the bifidobacteria from glucose, FOS than from neokestose. Bifidobacteria utilized the neokestose to a greater extent,1.4 times than FOS and 2 times than glucose.