| Summary: | 碩士 === 東海大學 === 化學工程學系 === 95 === Mucor rouxii BCRC 30546 is an oleaginous fungus with an ability of producing considerable quantities of polyunsaturated fatty acid (PUFAs). One of PUFAs, γ-linolenic acid (GLA) is an essential fatty acid and could not be synthesized by human. Lipids from oleaginous fungi have unusual fatty acid compositions, which are of commercial potential. In this research, the influence of various cultivation conditions was investigated, including medium composition, culture time, temperature, pH, dissolved oxygen tension, agitation rate and external polytron on the growth of the mycelia, lipid accumulation and the production of the γ-linolenic acid.
The experimental results showed that in the shake flask cultures, the optimal medium compositions were determined to be carbon source 30 g/L, nitrogen source 5 g/L, pH 5.5, temperature 30℃. Moreover, the C/N ratio, sunflower oil addition and different levels of dissolving oxygen were found to have a great influence on biomass concentration and metabolism. In a 5 L fermentor, although the two stages control of the temperature caused the reduction of biomass concentration and also the total GLA concentration, but the GLA content could be improved to 42%. The result was attributed to the fact that a lower temperature is beneficial to the production of PUFAs. In the fed batch culture not only raised 12.5% of cellular lipid content but also maintained the biomass concentration about 8 g/L, and steady accumulation of the lipid content. If two cultivation methods were employed simultaneously, not only could increase the GLA content effectively to 67%, but max GLA concentration rose from 0.285 g/L to 0.443 g/L, and had the improvement of near 55%. An external polytron combined could prevent the aggregation of the mycelium effectively and led to the increase of biomass concentration from 7.65 g/L to 9.11 g/L. In addition, the synthesis of fatty acids and oil accumulation were also enhanced obviously.
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