THE INFLUENCE OF DISSOLVED-OXYGEN TENSION ON THE PRODUCTION OF COCOA BUTTER EQUIVALENTS AND GAMMA-LINOLENIC ACID BY MUCOR-CIRCINELLOIDES

The influence of different dissolved oxygen tension (DOT) values rangi ng from 5 to 35% of saturation on the production of cocoa butter equiv alents and gamma-linolenic acid by Mucor circinelloides f. circinelloi des CBS 108.16 was investigated in nitrogen limited, fed-batch, pH-sta t cultures with acetic acid as carbon source. DOT values of 8% and 10% were optimal for crude oil and neutral lipid production. The lipid co mposition at low and high DOT values differed extensively. The content of gamma-linolenic acid gradually decreased from 12.4% to approximate ly 4.6% of the neutral lipid fraction when the DOT was decreased from 35% to 5%. The stearic acid (18:0) content increased from 15.6% of the neutral lipid fatty acids at a DOT of 35% to approximately 27% at a D OT of 5%. Similarly, a dramatic increase in symmetrical triacylglycero ls occurred when the DOT was decreased from 35% to 5%. The DOT, theref ore, effected major quantitative changes in lipid desaturation and coc oa butter equivalent production, modifying the microbial oil compositi on also in the DOT range where the respiration rate, and therefore pro bably growth, was not limited by the level of dissolved oxygen.