5. Conclusion
According to the physiological metabolic state of cells, the fed-batch fermentation process for SLs synthesis can be divided into three stages: a stage that is limited by cell production capacity, a stage that is inhibited by high product concentration, and a stage that is limited by oxygen supply. Based on the detection of process multi-parameters, we established a data-driven feedback feeding model. This was combined with analyses of cellular metabolic mechanisms such that an optimal production state was achieved in the first and second stages,in which there was a 4.9% increase in SLs production. Furthermore, the mechanism-assisted data model was applied to the rational and precise control of residual oil concentration during semi-continuous SLs fermentation. The problem associated with oxygen limitation that was encountered during the third stage was effectively alleviated, thereby further increasing the SLs productivity to 2.30 g/L/h. The mechanism-assisted data modeling method developed in this study could be easily extended to other fermentation processes. We also expect our new process strategy for the production of SLs to be applied on an industrial-scale.