Value-added conversion of biodiesel into the versatile biosurfactant sophorolipid using Starmerella bombicola

Abstract

In this study, we tested whether biodiesel could be used as a feedstock for the microbial synthesis of sophorolipid, a high value-added chemical. Sophorolipid was successfully produced from Starmerrella bombicola using biodiesel as a hydrophobic substrate. Fed-batch fermentation was carried out for the high-level production. Compared to flask culture, the sophorolipid production concentration significantly increased from 58.1 ​g/L to 224.2 ​g/L (an approximate increase of 386%) using fed-batch fermentation, which is the highest value ever reported using fatty acid methyl esters and fatty acid ethyl esters as hydrophobic substrates. Different from rapeseed oil-based sophorolipid (ROSL), the biodiesel-based sophorolipid (BDSL) contained a new type of sophorolipid called esterified sophorolipid (approximately 19.8%). The BDSL demonstrated better surface-active properties, lower surface tension (34.2 vs. 35.8 ​mN/m, respectively), and a decreased critical micelle concentration (25.1 vs. 26.3 ​mg/L, respectively) compared to the ROSL. Given these results, the BDSL is expected to be used in various industrial fields where vegetable oil-based sophorolipids, the commercialized forms of sophorolipids, have been used. To our knowledge, this is the first report to describe the conversion of biodiesel for the production of a high value-added chemical.

Keywords

• Sophorolipid
• High-level production
• Biodiesel
• Starmerella bombicola