Study On Strain Isolation, Fermentation Strategy Optimization And Fermentation Kinetics For 2-keto-D-gluconic Acid Production

A strain capable of producing 2-keto-D-gluconic acid (2-KDG) was isolated from soil in this wok. The phylogenetic analysis based on 16S rDNA suggested the isolate was assigned to genus Serratia and named Serratia sp. BK-98. Medium loading volume, fermentation time and initial pH value were found to be most significant factors affecting 2-KDG production using Plackett-Burman (PB) design and their values were optimized to be 6.6 mL in a 100 mL Erlenmeyer flask of medium loading volume,57.9 h of fermentation time and 5.0 of initial pH respectively with response surface methodology (RSM) based on central composite design (CCD). Under the optimized fermentation conditions,2-KDG production in a 100 mL Erlenmeyer flask and in a 100 L fermenter reached 187.8 g/L and 192.2 g/L respectively,142.6% and 148.3% increase respectively as compared with the pre-optimized conditions. A close agreement with the predicted value of 191.4 g/L indicates that the proposed relationship model between the impact factors and 2-KDG production is very practical.Based on the optimization of culture conditions for producing 2-KDG by Serratia sp. BK-98 in a Erlenmeyer flask, the factors of dissolved oxygen (DO) and pH affecting 2-KDG batch fermentation in a 100 L fermenter were further optimized to be 30% and 6.0. Under the DO-stat and pH-stat batch culture conditions,2-KDG production reached 211.2 g/L. The kinetics of DO-stat and pH-stat batch fermentation were also been investigated and the models for biomass, substrate consumption and product were established respectively based on Logitstic equation, Leudeking-Piret equation and Modified Leudeking-Piret equation. Curve fittings for the above models by using experimental data were performed by non-linear least squares method with the software Origin 8.0. With the evaluated models parameters, the results showed that the calculated values of the models and experimental data are in a good agreement and the models are of importance for guiding the 2-KDG fermentation production.