Enzymatic production of isopropyl and 2-ethylhexyl esters using γ-linolenic acid rich fungal oil produced from spent sulphite liquor

• Published in: Biochemical engineering journal 2021-05, Vol.169, p.107956, Article 107956
• Main Authors: Tsouko, Erminta, Papadaki, Aikaterini, Papanikolaou, Seraphim, Danezis, Georgios P., Georgiou, Constantinos A., Freire, Denise M.G., Koutinas, Apostolis
• Format: Article
• Language: English
• Subjects: 2-ethylhexyl esters; Enzyme biocatalysis; Isopropyl esters; Novozym 435 lipase; Oleaginous fungi; Spent sulphite liquor
• ISSN: 1369-703X; 1873-295X
• DOI: 10.1016/j.bej.2021.107956

[Display omitted] •Spent sulphite liquor was valorized for γ-linolenic acid rich fungal oil production.•Enzymatic production of isopropyl and 2-ethylhexyl fungal oil esters.•Glycolipids, sphingolipids and phospholipids reduced enzymatic conversion yield.•Esterification reactions using hydrolysed fungal oil increased conversion yields.•The produced esters showed suitable properties for cosmetic applications. The enzymatic production of isopropyl and 2-ethylhexyl esters was investigated using fungal oil produced via fermentation of nanofiltrated spent sulphite liquor (SSL). Screening of five oleaginous fungi showed that Cunninghmamella echinulata could accumulate lipids with 12 % (w/w) γ-linolenic acid content in shake flask cultures. Ester formation by the commercial lipase Novozym 435 was favored when transesterifications of fungal oil with isopropyl and 2-ethylhexyl alcohols were performed at 60 °C, 1:3 microbial oil to alcohol molar ratio and 10 % biocatalyst concentration. Transesterifications of individual neutral lipids (NL), glycolipids and sphingolipids (GL + SL) and phospholipids (PL), with isopropanol and 2-ethyl-hexanol showed that the presence of GL + SL and PL in fungal oil hindered ester production. Transesterification of the NL fraction alone with isopropanol and 2-ethylhexanol led to the highest conversion yield of 80.2 % and 73.8 %, respectively. Conversion yields to isopropyl and 2-ethylhexyl esters reached up to 90 % and 80 % (w/w), respectively, when hydrolyzed fungal oil was used. The biocatalyst showed good stability in 5 repeated enzymatic reactions. The physicochemical properties and the ICP-MS analysis of esters demonstrated their potential utilization in cosmetic formulations. This study showed a perspective of valorizing SSL towards the production of value-added fatty acid esters for chemical, cosmetic and pharmaceutical applications.