Advances in sophorolipid-producing strain performance improvement and fermentation optimization technology.

Sophorolipids (SLs), currently one of the most promising biosurfactants, are secondary metabolites produced by many non-pathogenic yeasts, among which Candida bombicola ATCC 22214 is the main sophorolipid-producing strain. SLs have gained much attention since they exhibit anti-tumor, anti-bacterial, anti-inflammatory, and other beneficial biological activities. In addition, as biosurfactants, SLs have a low toxicity level and are easily degradable without polluting the environment. However, the production cost of SLs remains high, which hinders the industrialization process of SL production. This paper describes SL structure and the metabolic pathway of SL synthesis firstly. Furthermore, we analyze factors that contribute to the higher production cost of SLs and summarize current research status on the advancement of SL production based on two aspects: (1) the improvement of strain performance and (2) the optimization of fermentation process. Further prospects of lowering the cost of SL production are also discussed in order to achieve larger-scale SL production with a high yield at a low cost. KEY POINTS: • Review of advances in strain performance improvement and fermentation optimization. • High-throughput screening and metabolic engineering for high-performance strains. • Low-cost substrates and semi-continuous strategies for efficient SL production.