Studies on GLA Oil Fermentation and Modification

Abstract: Gamma linolenic acid (GLA) is a member of polyunsaturated fatty acids (PUFAs), it can be transformed to PGs and LTs in human bodies, which exert important regulation function in the cardiac and brain blood vessel system, breath system, liver, diabetic neuropathy and genital system.Fermentation conditions were studied in this thesis, pH5.5 was the optimized pH value, inoculum higher than 10~6spore/mL could enhance the GLA yield, and too low level of dissolved oxygen was an important reason of low GLA yield. 500 L culture research was carried out and the fermentation conditions were: agitation speed 300 r/min, aeration 0.75v/v, pH5.5 and dissolved oxygen was higher than 10%. The dried biomass could reach 63g/L, oil yield 24.6g/L and the GLA yield reached 2.45g/L, all the indexes were a lot higher than the vibration culture. 5000L culture was carried out based on the above research, and the yield level was close to the level of 500L culture.Tween-80 and olive oil can promote Mortierella to produce lipases, which could lead to oil decomposition and rising of acid value, while dimethyl silicone oil could not induce the lipases. The lipases could also be induced by the hunger of carbon source and could be deactivated by treatment of temperature higher than 80℃. Deactivation treatment brought no obvious effect on the GLA content, but could preserve the oil in the mycelium effectively and avoid rising of acid value.Mortierella oil was separated by TLC. The main compositions were triacylglycerols, fatty acids, diacylglycerols, monoacylglycerols and phospholipids, the gamma linolenic acid contents in them were 8.1%. 6.2%, 10.3% 14.7 and 23.5% respectively. The oil extraction was performed with 5 solvent systems, which were chlorlform-methanol(2:1), hexane, isopropanol, hexane-isopropanol(2:1) and ethanol-hexane two steps extractions. Hexane extraction method was a simple and mature one, which could give high triacylglycerol content, so it was the suitable extraction method of Mortierella oil. Winterization could enhance the gamma linolenic acid content in the oil.Effects of water content, granularity and compact on the super critical CO_…
Key words: Gamma linolenic acid; Fermentation; Lipase; Extraction; Diacylglycerol

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