Efficient preparation and isolation of sophorolipids with excellent pH-regulated water solubility via environmentally friendly acid-induced chemical modifications

Sophorolipids (SLs) show great potential application in many fields as an alternative to chemically synthesized surfactants. However, their poor water solubility limits industrial applications in many fields. In this study, a new environmentally friendly strategy based on acid-induced chemical modifications has been developed to prepare and isolate water-soluble SLs from natural SLs that not dissolve or precipitate in fermentation broth. Over 70 % of SLs were obtained as sediments from fermentation broth after chemical modification at a pH of 1 at 120 °C for 5 min. The obtained SLs demonstrated excellent pH-regulated water solubility, superior foaming ability, and comparable surface activities with natural SLs. The involved mechanism of the present process was attributed to the generation of glucolipids with excellent water solubility. The present findings are conducive to preparing water-soluble SLs, addressing the problem that SLs cannot be recovered from fermentation broths via acid-induced precipitation in certain case.