Biotransformation of fatty acid-rich tree oil hydrolysates to hydroxy fatty acid-rich hydrolysates by hydroxylases and their feasibility as biosurfactants

Abstract

The fatty acid compositions of 10 types of tree oils were analyzed and Camellia japonica (CJ), Tetradium daniellii (TD), and Hovenia dulcis (HD) tree oils were selected to be oleic acid (OA)-, linoleic acid (LA)-, and α-linoleic acid (ALA)-rich tree oils, respectively. Recombinant Escherichia coli expressing 10-hydratase and 7,8-diol synthase converted 31.7 and 15.6 g/L unsaturated fatty acids (UFAs) in OA-rich oil hydrolysates to 21.7 g/L 10-monohydroxy fatty acid (monoHFA) and 13.3 g/L 7,8-diHFA, respectively. The cells expressing 13-hydratase, 13-lipoxygenase, 5,8-diol synthase, and 8,11-diol synthase converted 42.8, 28.5, 10.0, and 20.0 g/L UFAs in LA-rich oil hydrolysates to 28.2 g/L 13-monoHFA, 11.8 g/L 13-monoHFA, 7.2 g/L 5,8-diHFA, and 8.9 g/L 8,11-diHFA, respectively. The cells expressing 8,11-diol synthase converted containing 17.5 g/L UFAs in ALA-rich oil hydrolysate to 7.5 g/L 8,11-diHFA. The average emulsifying activities of diHFArich and monoHFA-rich tree oil hydrolysates were 13.9- and 4.3-fold higher than those of tree oil hydrolysates, respectively. Thus, HFA-rich tree oil hydrolysates derived from tree oils can be applied as biosurfactants, and the fatty acid-rich residue as by-product obtained from the tree refinery process may be recycled into biosurfactants.