| This research focused on the bioconversion of unsaturated fatty acids to hydroxy fatty acids, which are platform chemicals of biological and industrial significance. Oleic, linoleic and linolenic acid are liberated in the soap stock of plant oil refineries as free fatty acids and were used as model substrates for bioconversion. The thesis selected microorganisms, and developed methodology for the rapid and enhanced enzymatic transformation of these unsaturated fatty acids to hydroxy fatty acids. The protocols established can be extended to derive value added compounds from the by-products of plant oils.;The first objective was to identify bacteria with the ability to produce hydroxy fatty acids, and to increase the product turnover. GC-MS analyses indicated the transformation of oleic acid to 10-hydroxystearic acid by Pseudomonas aeruginosa, Lactobacillus plantarum, L. sanfranciscensis, L. reuteri, L. sakei, and Bifidobacterium bifidum BB12. Linoleic and linolenic acid were converted to 10-hydroxy-12-octadecenoic acid, 13-hydroxy-9-octadecenoic acid and 10, 13-dihydroxystearic acid by lactobacilli but not by P. aeruginosa. Maximum transformation rate was observed from crude cell extract and the activity of a hydratase enzyme was indicated.;The second objective was to develop a single step method for the production of coriolic acid from linoleic acid with lipoxygenase (Lox). A process for single step formation of coriolic acid was achieved with a 70% or higher yield from free and immobilized Lox using cysteine as reducing agent containing 2 mmol/L and 100 mmol/L initial linoleic acid. Immobilized Lox was re-used 10 times with 64% yield from 2 mmol/L linoleic acid and 3 times with 40% yield from 100 mmol/L linoleic acid. A comparable activity of free Lox was observed in reactions performed at a 5 mL and 1 L scale.;The dissertation provides practical approach for the biotransformation of unsaturated fatty acids to hydroxy fatty acids by using the specific enzymes from bacterial cell extracts or by commercially available enzymes. The nature of products depends upon the substrates, source of enzyme and transformation conditions. The products thus generated hold the potential to be used as bioactive compounds for food, pharmaceutical and industrial purposes. |
