Optimization of microbial oil production conditions with Mortierella isabellina using whey

Research has shown that essential fatty acids are integral to proper nutrition. It has been found that EFA deficiency causes a host of ailments. In addition, research has also shown that ℽ-linolenic acid, (GLA) belongs to omega-6 PUFA seriescan reverse, as well as prevent, some human disorders and diseases. Being effective against rheumatoid arthritis, reducing cardiovascular risk factors, normalizing nerve conduction velocity are just a few of its known benefits. Lately, many food products are also being enriched with GLA, and there is rapid increase in its demand. Conventionally, it is produced from plant sources such as seeds of evening primrose, borage and blackcurrant. However, to meet the increasing demand, extensive research is being carried out for its production from microbial sources. Microbial oil production was carried out with Mortierella isabellina (DSM 1414) in the study. The effects of fermentation parameters such as initial sugar content, initial pH value, shaking speed, different nitrogen sources, temperature, and the ratio of inoculation, on the GLA productions, were investigated. In the first step, "one factor at a time method" was used for the optimization of fermentation conditions. Firstly, effects of pH values of fermentation medium on GLA production were examined and maximum GLA production, 0.55 g/L, was obtained at pH 7. As for nitrogen sources (ammonium nitrate, beef extract, potassium nitrate, soya peptone, yeast extract), yeast extract was determined as the best nitrogen source with 0.70 g/L GLA production. The inoculum size for maximum GLA production (1.08 g/L) was obtained at %9 inoculum size. As the second step, the effects of initial substrat concentration, agitating speed and fermentation temperature on GLA production were investigated using Box-Behnken experimental design which is one of the response surface methods. As a result of the suggested experimental design, models, expressing the effects of independent variables on the response of (GLA) production, were obtained, and the suitability of the models was evaluated by analysis of variation (ANOVA). Optimum values were determined by the obtained data. Accordingly, confirmation of experiments was carried out and 1.15 g/L GLA was obtained with the initial sugar content of 81.87 g/L; a shaking speed of 120 rpm and a fermentation temperature of 22°C. As a result of optimization study, the amount of GLA production was increased by 2.1 times. It is thought that the production of microbial oil, which has an increasing demand in the world market due to its rich content in polyunsaturated fatty acids with proven benefits in terms of nutrition and health, will contribute to the country's economy. It is considered that, by using the whey, a by-product of the manufacturing of cheese, the damage to the environment will be eliminated and added value will also be provided by producing microbial oil, containing GLA, which has high economic value while a waste material is utilized.