Esterification Of Lipopeptide And Structural Characterization Of The Products

Surfactin, as one of biosurfactants, with its excellent surface activity and biological activity, plays an importrant role in many areas. The two carboxyl groups in surfactin were chemically modified by esterification with different alcohols with the ring structure untouched and the reaction conditions of esterification and separation conditions of products were explored. The main contents of this study are as follows:The surfactin was prepared by fermention of Bacillus subtilis TD7. Three catalysts, hydrochloric acid, DCC/DMAP (N, N'-dicyclohexyl carbodiimide/4-dimethylamiopryidine), EDC/DMAP(1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide/4-dimethylamiopryidine), were used to esterify surfactin. It was shown that the yield was not very high when hydrochloric acid was used as catalyst, the products of esterification would be reduced because of hydrolysis process while reaction time was elongated. Surfactin esterification was complete using both DCC/DMAP and EDC/DMAP catalysts, but some by-products were formed when using DCC/DMAP catalyst, while there was not by-products detected using EDC/DMAP catalyst. At the same time, the results shown that reaction time of 24 hours is sufficient for EDC/DMAP when esterification process was inspected by HPLC. The EDC/DMAP is suitable for esterification of surfactin, which laid foundation for preparing esterified products of surfactin.The separation conditions of esterification products were explored using HPLC, and esterification products, that surfactin reacted with three different alcohols, were detected by LC-MS. The etylene glycol monoethyl ether esterfication products and 1,6-hexanediol esterification products were prepared and purified successfully. Two isoforms of 1,6-hexanediol esterification products were characterised by infrared spectroscopy, and surface tension of surfactin C15 diester were determined. The modified product still has relatively strong surface avtivity.The production water was detected using ESI-MS and molecular fingerprints to explore the diversity and origial of lipopeptide biosurfactants in oil reservoir. It was shown that there is a wealth of lipopeptide and rhamnolipid biosurfactants in production water, which indicates that there are lipopeptide-producing bacteria, and some bacteria could be screened.