Conversion of Mutton Fat to Cocoa Butter Equivalent by Increasing the Unsaturated Fatty Acids at the Sn-2 Position of Triacylglycerol Through Fermentation by Yarrowia Lipolytica
Dan Xiong, Huaiyuan Zhang, Yifang Xie, Nianchu Tang, Aydin Berenjian and Yuanda Song
DOI : 10.3844/ajbbsp.2015.57.65
American Journal of Biochemistry and Biotechnology
Volume 11, Issue 2
Mutton fat has a similar fatty acid profile with Cocoa Butter (CB), except that its degree of unsaturation of Triacylglycerol (TAG) at the Sn-2 position is considerably lower than CB and maybe increased by Sn-2 specific lipase to produce Cocoa Butter Equivalent (CBE), a healthy functional lipid. However, there is no commercially available Sn-2 specific lipase that can be used to convert mutton fat to CBE by improving its Unsaturated Fatty Acids (UFA) at Sn-2 position. Similar to plant, yeast fat contains higher UFAs at the Sn-2 position than animal fat. In this study, we investigated the conversion of mutton fat to CBE by fermentation of oleaginous yeast Yarrowia lipolytica which acts as a âSn-2 specific lipaseâ. The yeast was able to grow on mutton fat as the sole carbon source yielding a dry cell weight of 14.11 g L-1 and 33.1% lipid content after 3 days of cultivation. At optimal fermentation conditions, the degree of unsaturation of TAGs at the Sn-2 position increased from 61.5 (mutton fat) to 89.3% (cellar lipid, 72 h) while the amount of Saturated Fatty Acids (SFA) of the Total Fatty Acids (TFA) was decreased from 58.9 to 34.5%. In addition, the presence of methyl stearate as the co-substrate in the medium improved the ratio of SFAs/TFAs. It was found that fatty acid profile of the yeast fat with 24.60% palmitic acid, 31.34% stearic acid, 34.29% oleic acid, 5.57% linoleic acid and degree of unsaturation at Sn-2 position in TAGs (84.66%) resembled that of CB when the yeast was grown on mutton fat/methyl stearate (with a ratio of 60/40) as carbon source. These results suggest that biotransformation or metabolism could be directed by using mixtures of inexpensive animal fats and saturated fatty acid or methyl as co-substrates, to produce functional lipids with predetermined composition, such as CBE.
© 2015 Dan Xiong, Huaiyuan Zhang, Yifang Xie, Nianchu Tang, Aydin Berenjian and Yuanda Song. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.