Screening And Indentification Of A Strain Producing L-erythrulose And Studies On Fermentation Process

As a food additive and cosmetic raw material and pharmaceutical precursors, L-erythrulose is a widelyused rare suger with high industrial application value.A strain producing L-erythrulose from erythritol was isolated from rotted vegetables. A series ofmorphological and biochemical characteristics and sequence analysis of16S rRNA reveal that it belongs toGluconobacter kondonii, which named Gluconobacter kondonii HD385. A preliminary study of fermentationshowed that the strain produced64.9g/L of L-erythrulose based on10%erythritol in a medium as carbonsource.Flask fermentation conditions on the HD385growth and the production of L-erythrulose were studied. Onbasis of single factor experiments of temperature, pH, carbon sources, nitrogen sources and so on, theconcentration of erythritol, corn steep liquid and CaCO3had significant effect on fermentation. And theResponse Surface Methodology was used to optimize the fermentation medium and build a mathematical modelof three-factor and the yield of L-erythrulose. Under those optimization conditions:14.47%erythritol,2.07%corn steep liquid and0.39%CaCO3, it was predicted that the highest concentation of L-erythrulose recached109.58g/L. After optimization, the L-erythrulose production increased by70.9%, and the experimental databasically in line with the predicted values.The process of batch fermentation in5L fermentor was uesd to verify the result of optimized flaskfermentation conditions. The optimium conditions of aeration rate and initial erythritol concretration were1vvmand15%, and the concentration of initial concentration of L-erythrulose was130.6g/L after48h batchfermentation. Fed batch fermentation was investigated in this study to enhance the production of L-erythrulose. When the initial concentrations of erythritol andaeration rate were7%and1.0vvm, the yield of L-erythrulosewas166.5g/L and the conversion was96.6%after48h fed-batch fermentation.