The Optimization And Scale-up Of Sodium Gluconate Fermentation Based On The Multiple Parameter Assocoation By Aspergillus Niger

The batch fermentation by Aspergillus niger is the main method for sodium gluconate production in recent years. In this paper, a set of mathematical model was constructed based on the research results of kinetics of batch fermentation. Then, batch fermentation and continuous fermentation technology for sodium gluconate production were established and optimized by on-line physiological parameter association analysis. Finally, the scale-up of continuous sodium gluconate fermentation based on metabolic similarity was conducted.First, the effects of oxygen supply level and nitrogen source concentration on the growth of Asper. niger during the fermentation were investigated. The results showed that the high oxygen supply and the high nitrogen source concentration are favor for the growth rate of Asper. niger, whereas the oxygen supply did not make influence on the final biomass. Based on the above results, the Logistic equation was used to describe the growth of Asper. niger.In this paper, the association analysis of the relationship of on-line physiological parameters including oxygen uptake rate (OUR), carbon dioxide evolution rate (CER) and respiratory quotient (RQ) to growth and production were carried out, and the mathematical models to describe glucose consumption and sodium gluconate production were constructed. Metabolic flux analysis was further conducted by combining material balance with the conversion rate of extracellular metabolite under different OUR levels. The results demonstrated that much higher yield could be reached under medium oxygen supply level at the growth stable phase. Thus a two-stage OUR control strategy, in which OUR was controlled at high level during the mycelium growth phase, and OUR was adjusted to 55 ± 2.5 mmol/L/h in the stable phase was proposed. With this strategy, the final sodium gluconate yield of the batch fermentation was enhanced and reached 93.7%(mol/mol).Finally, the effect of dilution rate and the nitrogen source concentration in feed medium on the continuous sodium gluconate fermentation were also investigated. The results demonstrated that glucose consumption rate, sodium gluconate production rate and yield reached 19.9 g/L/h,20.8 g/L/h and 90.4% under optimal dilution rate 0.08 h-1. The results demonstrated that glucose consumption rate, sodium gluconate production rate and yield reached 20.9 g/L/h,23.1 g/L/h and 91.2% under optimal nitrogen source 1.0 g/L in feed medium. Based on this, the continuous sodium gluconate bioprocess was optimized, and a satisfied scale-up work for it was conducted.