The invention discloses a method for preparing acid
sophorolipid, and belongs to the technical field of biological
fermentation. According to the method, candida is used as a
fermentation strain, a composite
carbon source culture medium containing a water-soluble
carbon source and an oil-soluble
carbon source is adopted, and the content of
residual oil is monitored in real time in the
fermentation process; when the
residual oil content exceeds a threshold value of 5g / L, the emulsifying agent of 0.1 g / L-0. 5g / L is supplemented, and the stirring rotating speed is increased by 20-50rpm, so that the emulsification of an
oil phase and the utilization of the thalli on the oil-soluble carbon source are promoted. By accurately controlling the
residual oil content in the fermentation process, the proportion of the acidic
sophorolipid and the carbon source conversion rate are remarkably increased, the proportion of the acidic
sophorolipid is increased to 60% from 30% of a traditional process, the carbon source conversion rate is increased to 65% from 40%, the problems that the increasing means of the proportion of the acidic sophorolipid is single, and the carbon source is wasted are effectively solved, and the method is suitable for industrial production. The method has the advantages of simple process, low cost,
environmental protection and the like.