Ruminant bacteria, conjugated linoleic

Conjugated linoleic acid (CLA) is a generic name for a mixture of positional and geometric isomers of linoleic acid (9c, 12c-octadecadienoic acid, 08 2) with conjugated double bonds at 7 and 9, 8 and 10, 9 and 11,10 and 12,11 and 13, or 12 and 14 positions. This fatty acid, carried out by rumen bacteria in the ruminal process, arises along a stepped pathway and ends with the full saturation of linoleic acid into stearic acid. These naturally occurring groups of dienoic derivatives of linoleic acid (LA) are incorporated into the fat in beef and the milk of ruminants before the saturation process has been completed. Food products from ruminants, particularly... 

Conjugated linoleic acid (CLA) is naturally present in milk, dairy products, and the meat of ruminants (1). Ruminants are the major dietary source of this fatty acid because of the unique abihty of rumen bacteria to convert linoleic acid into cis-9,trans- CLA (c9,tll-CLA) (1). This reaction is part of a process that takes place in the rumen it is called biohydrogenation and it converts linoleic acid [or, less efficiently, other 18-carbon polyunsaturated fatty acids (PUFA) with double bonds located at 9 and 12 positions] to stearic acid (1). During this process, vaccenic acid (tl 1-18 1) is formed. This acid can be converted to CLA in all organisms that possess A9-desaturase (2). 

McKain, N., Shingfleld, K. J., Wallace, R. J. (2010). Metabohsm of conjugated linoleic acids and 18 1 fatty acids by ruminal bacteria products and mechanisms. Microbiology, 156, 579-588. 

CLA refers to a mixture of positional and geometric isomers of linoleic acid (cis-9, cis-12 octadecadienoic acid) with a conjugated double bond system. The structure of two CLA isomers is contrasted with linoleic and vaccenic acids in Figure 3.1. The presence of CLA isomers in ruminant fat is related to the biohydrogenation of polyunsaturated fatty acids (PUFAs) in the rumen. Ruminant fats are relatively more saturated than most plant oils and this is also a consequence of biohydrogenation of dietary PUFAs by rumen bacteria. Increases in saturated fatty acids are considered undesirable, but consumption of CLA has been shown to be associated with many health benefits, and food products derived from ruminants are the major dietary source of CLA for humans. The interest in health benefits of CLA has its genesis in the research by Pariza and associates who first demonstrated that... 

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