| L-erythrulose exists at very low concentrations in nature and therefore can be called a rare sugar. It is widely used as a food additive, cosmetic raw material, pharmaceutical precursors and a starting material for the production of other significant rare sugers such as L-erythrose with high industrial application value.An UV method for the determination of L-erythrulose and a method using ion exclusion chromatography for the determination of erythritol and its metabolites L-erythrulose as products of fermentation were established respectively. In UV method, seliwanoff reagent was used as the chromatic reagent. Several factors including the amount of chromatic reagent, reaction temperature, time and color stability were investigated to optimize the test conditions. The calibration curve was linear in the concentration range of 0.1-1.2 g/L. The average recoveries were 101.5% and 101.9%. The results also showed that the medium composition and cell autolysates in the fermentation broth had no significant influence on this method. With method of using ion exclusion chromatography, erythritol and L-erythrulose were separated by a sulfonated polystyrene divinylbenzene column(Aminex HPX-87C) with a refractive index detector. It is found that the optimal conditions for separation were 60 ℃column temperature and 30% acetonitrile as mobile phase, which were applied to the quantification. The results showed that recoveries were within the range of 97.2%~101.8%and the precision CV ranging from 0.9% to 2.4% in samples.In this work, the feasibility of using erythritol product L-erythrulose by Gluconobacter kondonii HD385 was developed for determining the optimal experimental conditions and kLa. The optimized parameters of fermentation show that the speed of 220 r/min, the reaction temperature of 30℃, the initial pH of 6.0, nitrogen source selected yeast powder. Through the study about the strategy of oxygen transfer coefficient control on the L-erythrulose fermentation, a two-stage oxygen supply control strategy was proposed. Finally, L-erythrulose content and L-erythrulose productivity reached 207.9 g/L and 6.50 g/L/h, respectively.Rearch of bioconversion conditions for the production of L-erythrulose from erythritol with resting cells was developed. The production of L-erythrulose by resting cells of Gluconobacter kondonii was optimized using response surface design. On the basis of single factor test, the Response Surface Methodology(RSM) was designed for the first time, and the mathematical model was set up between various factors and L-erythrulose. The results indicated that the effects of the concentration of resting cells, p H value, the concentration of erythritol, reaction time and temperature on the production of L-erythrulose were significant. Response Surface predicted the optimal production of L-erythrulose were as follows: the concentration of resting cells 1.65%, the concentration of erythritol 97.9 g/L, temperature 30.2℃, pH value 5 and the reaction time 18 h, under these conditions, the yield of L-erythrulose reached 96.1 g/L, and the response surface extremes coincide conversion was 98.2%, production intensity of 5.34 g/L/h, showed optimization program to achieve the desired effect.A separation and extraction route was developed. The fermentation broth subjected to decoloring treatment with activated carbon after deal with ceramic membrane, removed macromolecules such as proteins, nucleic acids and polysaccharides with alcohol precipitation method and exchange resins. Then get boutique L-erythrulose through rotary evaporation. The edulcoration effect was optimum by using 732 cation exchange resin and D315 anion exchange resin for desalination and removing macromolecules decoloring conditions as follows: 0.5% activated carbon, the temperature of 25℃, decoloring 30 min. Rotary evaporation temperature set at 45℃, the boutique L-erythrulose of content is above 78%. |
PDF Full Text Request