CHAPTER 5: Recent Advances in the Production of CLA and Conjugated Vegetable Oils: Microbial and Enzymatic Production of Conjugated Fatty Acids and Related Fatty Acids in Biohydrogenation Metabolism

Lactic acid bacteria produced CLA from linoleic acid. The produced CLA comprised a mixture of cis-9, trans-11-octadecadienoic acid (18:2) and trans-9, trans-11-18:2. Using washed cells of Lactobacillus plantarum AKU 1009a as a catalyst, CLA production from linoleic acid reached 40 mg/ml under the optimized conditions. Similar reactions were observed with C18 fatty acids with cis-9, cis-12 non-conjugated diene system such as α-linolenic acid, γ-linolenic acid, and stearidonic acid. Lactic acid bacteria transformed ricinoleic acid (12-hydroxy-cis-9-octadecenoic acid) to CLA. Castor oil, which is rich in the triacylglycerol form of ricinoleic acid, was also found to act as a substrate with the aid of lipase-catalysed triacylglycerol hydrolysis. Clostridium bifermentans saturated C20 PUFAs of arachidonic acid and EPA into corresponding partially saturated fatty acids with conjugated isomers of arachidonic acid and EPA as intermediates, respectively. The conjugated fatty acid synthesis was found to be a part reaction of biohydrogenation and the complex metabolic pathway was revealed. The enzyme system catalysing the biohydrogenation was found to consist of four enzymes, i.e., hydratase, dehydrogenase, isomerase and enone reductase. These enzymes are useful for the production of unique PUFA species, such as hydroxy, oxo, conjugated and partially saturated fatty acids.