Effect of Culture Variables on Mycelial Arachidonic acid Production by Mortierella alpina

Abstract

Effect of culture conditions on biomass, lipid, and arachidonic acid production was investigated in the oleaginous fungus Mortierella alpina CBS 528.72 under shake flask conditions. Several factors have been found to affect the biomass buildup and lipogenesis in this fungus, complicated by the fact that different strains demonstrate varying optimization conditions. Growth, lipid accumulation, and arachidonic acid production in the strain investigated were influenced by media, pH, temperature, carbon source, nitrogen source, etc. The results indicated that the most effective medium for growth and arachidonic acid production was glucose yeast extract medium. The optimum pH and temperature were found to be 6.5 and 28°C, respectively. On the same weight basis, glucose was the most efficient carbon source for biomass and lipid production in this fungal strain which yielded 6.8 g/L dry biomass and 40.2% (w/w) total lipid after 7 days of cultivation. Maximum arachidonic acid (ARA) production of 40.41% achieved in rhamnose-containing media was not concomitant with higher biomass and lipid yields. Efficacy of organic carbon sources, viz, yeast extract and peptone over inorganic sources like sodium nitrate, ammonium sulfate, ammonium chloride, etc, was established in the present study. M. alpina CBS 528.72 grown in peptone acquired the highest lipid content (42.0% (w/w)). However, the ARA content (28.74%) proved to be significantly less than that grown in yeast extract (35.28%). Furthermore, it was found that the biomass and ARA production declined drastically in a medium with vegetable oils as the sole carbon source but triggered the lipogenic pathway leading to higher accumulation of total lipids. Under the ideal conditions mentioned above, the maximum biomass, total lipid, and arachidonic acid production were 6.8 g/L, 41.6%, and 35.28% total fatty acid, respectively, in shake flask system.

Optimization of Physiological Growth Conditions for Maximal Gamma‐linolenic Acid Production by Cunninghamella blakesleeana‐JSK2

“…3).The optimum temperature for lipid accumulation (26 %) and GLA production (21 %) was 28°C. While the results of this study are in agreement with previously published results [22], it indicates that in fungi, the optimal temperature for growth may not necessarily be optimal for lipid production. Such parameters should be taken into account during the development of the bioprocess for large scale production.…”

“…also, lipid production/accumulation was significantly reduced under sub-optimal pH conditions (such as, pH 4 and pH 8). It is possible that interactions between media components and pH reduce the ability of the strain to utilize the available nutrients in the medium [22].…”

Enhanced arachidonic acid production using a bioreactor culture of Mortierella alpina with a combined organic nitrogen source

“…On the basis of several previous reports (Nisha and Venkateswaran 2011) and our experimental results, it is considered that the suitable substrate concentration as the nitrogen source in the medium is 10 g L −1…”

“…Based on the literature (Lu et al 2011;Nisha and Venkateswaran 2011), four types of organic nitrogen sources (YE, peptone, soybean meal, and CSL) were first tested individually in the flask culture at a concentration of 10 g L −1 to determine the optimal single nitrogen source. Then, the chosen optimal single nitrogen source was studied in the bioreactor culture to investigate its scaleup effect on ARA production.…”

“…Replacement of sodium nitrate by corn steep liquor (CSL) significantly improved ARA production by M. alpina ATCC 32222 (Higashiyama et al 2004). Nisha and Venkateswaran (2011) also studied the influence of various nitrogen sources on both the biomass and the production of ARA by M. alpina. They showed that yeast extract (YE) produced the maximum biomass (6.8 g L −1…”