Esterification of conjugated linoleic acid by yeasts for increasing the value of plant materials

Yeast-catalyzed esterification of free cis-9,trans-11-conjugated linoleic acid (c9,t11-CLA) was studied to develop a bioprocess for incorporation of c9,t11-CIA produced in plant materials into triacylglycerol (TAG). Two Yarrowia lipolytica strains and one Saccharomyces cerevisiae strain, each as growing and stationary phase cultures, were used to define their capacity to accumulate and esterify exogenous c9,t11-CLA in TAG. In both culture types all three strains incorporated c9,t11-CIA into neutral lipids and the highest c9,t11-CIA content in TAG, 58 mg/g dry matter and 0.26 mg/mL was reached in growing cultures of S. cerevisiae B-72021. Instead, Y. lipolytica ATCC 20373 was more efficient in non-growing mode for esterification, the highest values in TAG being 31 mg/g d.m. and 0.16 mg/mL. S. cerevisiae B-72021 was chosen to esterify c9,t11-CLA formed in soy okara by Propionibacterium freudenreichii. In spite of the presence of okara-based free fatty acids, c9,t11-CIA concentration of 23 mg/g total d.m. in TAG was obtained corresponding to 0.23 mg/mL of okara-yeast suspension. Then, 81% of the c9,t11-CIA taken into cells ended in TAG and the proportion of c9,t11-CIA in total TAG was 14%. Thus, combining the yeast-based esterification to natural processing of low value plant side streams can add their health beneficial properties. (C) 2014 Elsevier Ltd. All rights reserved.