Studies On Mannitol Preparation Using Microorganism Transformation Method

Mannitol has extensive uses, especially in pharmaceutical and food industry. So far producing mannitol mainly was adopted by natural abstraction and catalytic hydrogenation methods. Microorganism transformation for producing mannitol has many advantages, such as high reaction selectivity, mild reaction conditions, less creating sorbitol and high yield.Lactobacillus sp. biotransformation to produce mannitol was mainly investigated in this paper. Determination of fructose and mannitol's content in broth by spectrophotometry were studied, the content of fructose was determined at 560nm and the content of mannitol was determined at 412nm, adopt this method had rapid and accuate characters. Under the same conditions, three species were compared using fructose as substract for biotranformation to mannitol. Lactobacillus buchneri AS 1.13 has high rate of mannitol production. By using screened AS 1.13, the effect of different kinds of carbon sources, the ratio of fructose to glucose in carbon source, carbon source concentration, nitrogen sourceconcentration, the concentration of inorganic metal ion, the concentration of buffer agent on bacterium species growth and mannitol's transformation were optimized. The results showed that the fermentate culture composition is : carbon source concentration of 225g/L in which the fructose to glucose ratio is 2:1, the concentrations of the four kinds nitro sources, piptone, meat extract, yeast extract, and NH4-citrate, are 5 g/L , 5 g/L , 2.5 g/L , 1 g/L respectively, the concentrations of MgSO4. 7H2O and MnSO4. 4H2O are 0.55 g/L and 0.28 g/L, the buffer agent concentrations of Na-acetate and K2HPO4 are 7.5 g/L and 3.0 g/L. The process conditions of biotranformation to mannitol are studied through Lactobacillus buchneri AS 1.13 and optimal fermantate culture. The inoculation volume, initial fermentate culture pH value, fermentation time, the rotate speed of shaker and fermentation temperature which effects on biotransformation were explored. The optimal process conditions are concluded as: the rotate speed of 200rpm, the inoculation volume of 15%, initial pH value of 6.8, and the fermentate system temperature of 40"C. The mannitol's production rate to total quantity of fructose added is 80.87 % at the same time.