Funding
This work was financially supported by the National Key Research
Development Program of China (No.
2019YFA0904803).
Abstract:Sophorolipids (SLs) are regarded as one of the most promising
biosurfactants. They have a low toxicity and are easily degradable
without polluting the environment. However, high production costs are
the main obstacle to extended SLs application. Semi-continuous
fermentation is a promising technology for achieving high SLs
productivity, which is based on in-situ separation. In this
study,
the
sedimentation
mechanism of SLs was analyzed.
The
formation of a hydrophobic mixture of SLs and oil was a key factor in
sedimentation. The hydrophobicity and density of the mixture determined
SLs
sedimentation rate. According to the mechanism,
ultrasonic
enhanced sedimentation technology (UEST) was introduced, by which the
sedimentation rates were increased by 46.9% to 485.4% with different
Oil/SLs ratios. UEST-assisted
real-time rational in-situ separation and semi-continuous
fermentation were performed. We observed that SLs productivity and yield
were 2.15 g/L and 0.58 g/g, whereas the loss ratio of cells, glucose,
and oil was reduced by 68.2%, 16.2%, and 65.5%, respectively.In-situ SLs separation efficiency and rate were increased by
34.5% and 26.4%, respectively. This study provides the foundation and
new horizon for the optimization of the SLs fermentation process.
Keywords: Sophorolipids; Multiphase system; Ultrasonic enhanced
sedimentation; Real-time; In-situ separation