Hydrolysis of Edible Oils by Fungal Lipases: An Effective Tool to Produce Bioactive Extracts with Antioxidant and Antimicrobial Potential

Abstract

Hydrolysis of olive, rapeseed, linseed, almond, peanut, grape seed and menhaden oils was performed with commercial lipases of Aspergillus niger, Rhizopus oryzae, Rhizopus niveus, Rhizomucor miehei and Candida rugosa. In chromogenic plate tests, olive, rapeseed, peanut and linseed oils degraded well even after 2 h of incubation, and the R. miehei, A. niger and R. oryzae lipases exhibited the highest overall action against the oils. Gas chromatography analysis of vegetable oils hydrolyzed by R. miehei lipase revealed about 1.1 to 38.4-fold increases in the concentrations of palmitic, stearic, oleic, linoleic and α-linolenic acids after the treatment, depending on the fatty acids and the oil. The major polyunsaturated fatty acids produced by R. miehei lipase treatment from menhaden oil were linoleic, α-linolenic, hexadecanedioic, eicosapentaenoic, docosapentaenoic and docosahexaenoic acids, with yields from 12.02 to 52.85 µg/mL reaction mixture. Folin-Ciocalteu and ferric reducing power assays demonstrated improved antioxidant capacity for most tested oils after the lipase treatment in relation to the concentrations of some fatty acids. Some lipase-treated and untreated samples of oils, at 1.25 mg/mL lipid concentration, inhibited the growth of food-contaminating bacteria. The lipid mixtures obtained can be reliable sources of extractable fatty acids with health benefits.

Keywords: antioxidant and antimicrobial activities; bioactive fatty acids; enzyme-assisted hydrolysis; menhaden fish oil; microbial lipases; vegetable oils.

Figure 1

Concentration of major free fatty acids (µg/mL reaction mixture) determined by GC-MS in enzyme-free and R. miehei lipase treated olive (A), almond (B), peanut (C), rapeseed (D), linseed (E) and grape seed (F) vegetable oil substances. Lipolytic reactions were performed at 40 °C for 24 h. Fatty acids: α-linolenic acid, C18:3; linoleic acid, C18:2; oleic acid, C18:1; stearic acid, C18:0; palmitoleic acid, C16:1; palmitic acid, C16:0. Results presented are averages of concentration values determined in three replicates; error bars represent standard deviations. Asterisks indicate significant differences between the enzyme-free and treated samples according to multiple t-tests performed by GraphPad Prism version 7.00, FDR (Q = 10%), * p < 0.05, ** p < 0.01, *** p < 0.0001.

Figure 2

Comparison of FCR (A) and FRAP activity (B) of enzyme-free and R. miehei lipase-treated olive, almond, peanut, rapeseed, linseed, grape seed and menhaden fish oil samples. Results are means of data of three replicates; error bars represent standard deviations. Asterisks indicate significant difference between the enzyme-free and treated samples according to a multiple t-test performed in GraphPad Prism version 7.00, FDR (Q = 10%), * p < 0.05, ** p < 0.01, *** p < 0.0001.