Conversion of Mutton Fat to Cocoa Butter Equivalent by Increasing the Unsaturated Fatty Acids at the Sn-2 Position of Triacylglycerol Through Fermentation by &lt;i&gt;Yarrowia Lipolytica&lt;/i&gt;

Dan Xiong,Nianchu Tang,Aydin Berenjian,Huaiyuan Zhang,Yifang Xie,Yuanda Song

doi:10.3844/ajbbsp.2015.57.65

Abstract

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.

Highlights

Animal fats are acquirable in large quantities from the meat-packing industry (Santos et al, 2013)
Fatty acids of mutton fats were mainly composed of C16, C18 and a small amount of C14 and C17
C18:1 existed at the Sn-2 position of the mutton fat TAGs, is only about 50% (Table 1B), which is significantly lower than that of Cocoa Butter (CB) of which C18:1 content at Sn-2 position reaches up to 87%

Summary

Introduction

Animal fats are acquirable in large quantities from the meat-packing industry (Santos et al, 2013). A main application of edible fats is as a food cooking medium, but fats have recently lost most of the market share to vegetable oils due to the fact that animal fat contains too much SFAs, which may cause health problems (Santos et al, 2013). With respect to this scenario, it is crucial to seek new applications for animal fat to enhance its value. The unsaturation degree of fatty acids at the Sn-2 position of mutton fat and CB is about 60 and 90% (w/w) respectively. Lipase-catalyzed transesterification reaction is excluded owing to the absence of lipase with Sn-2specificity towards triglycerides (Pfeffer et al, 2006)

Methods

Results

Conclusion