Target-site directed rational high-throughput screening system for high sophorolipids production by Candida bombicola

In this study we have established a rational and high performance high-throughput screening system to select for a sophorolipids (SLs) high-producing strain of Candida bombicola. Introduction of mutagen combination, relaxation culture and multi-stress significantly improved both mutation and positive mutation rates. A high-performing strain, Ncbio 5, was selected out of 6212 mutants. Final SLs titer, productivity and yield of this strain in 5 L bioreactors were 26.9%, 27.0% and 35.0% higher than in the original strain, respectively. The improved fermentation performance in Ncbio 5 is contributed by the longer production period, higher SLs productivity and more efficient oil utilization. The strategy adopted herein to optimize the high-throughput screening system should be readily extendable to other similar systems.