Abstract
Mortierella alpina (M. alpina) is well known for arachidonic acid (ARA) production. However, low efficiency and unstableness are long existed problems for industrial production of ARA by M. alpina due to the lack of online regulations. The aim of the present work is to develop an online-regulation strategy for efficient and stable ARA production in industry. The strategy was developed in 50 L fermenters and then applied in a 200 m3 fermenter. Results indicated that yeast extract (YE) highly increased cell growth in shake flask, it was then used in bioreactor fermentation by various feeding strategies. Feeding YE to control respiratory quotient (RQ) at 1.1 during 0–48 h and at 1.5 during 48–160 h, dry cell weight, and ARA titer reached 53.1 and 11.49 g/L in 50 L fermenter, which were increased by 79.4 and 36.9% as compared to that without YE feeding, respectively. Then, the online RQ-feedback strategy was applied in 200 m3 bioreactor fermentation and an average ARA titer of 16.82 g/L was obtained from 12 batches, which was 41.0% higher than the control batches. This is the first report on successful application of online RQ-feedback control of YE in ARA production, especially in an industrial scale of 200 m3 fermentation. It could be applied to other industrial production of microbial oil by oleaginous microorganisms.
Highlights
Arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid, is an important component in cell membranes (Barakat et al, 2015)
Mortierella fungi was proved to be an efficient strain for accumulation of ARA-rich oil, various fermentation processes had been developed for the improvement of ARA production by Mortierella fungi (Ji et al, 2014)
The lipid synthesis was rapidly increased in parallel with the cell growth to achieve 14.8 /lipid (%) ARA (g/L) for the first 65 h, after that it was increased much more slowly from 14.8 to 17.89 g/L and stopped
Summary
Arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid, is an important component in cell membranes (Barakat et al, 2015). Mortierella fungi was proved to be an efficient strain for accumulation of ARA-rich oil, various fermentation processes had been developed for the improvement of ARA production by Mortierella fungi (Ji et al, 2014). Online parameters such as pH and dissolved oxygen are important for ARA industrial production because they could be real-time monitored for regulation of the fermentation process. Online parameters such as pH and dissolved oxygen are important for ARA industrial production because they could be real-time monitored for regulation of the fermentation process. Li et al (2015) used a two-stage pH control strategy to Efficient Arachidonic Acid Production get a maximum ARA production of 8.12 g/L, which was 29.3% higher than the natural pH batch in Mortierella alpina. Peng et al (2010a,b) fed 40 g/L of n-hexadecane as an oxygen vector to achieve an ARA titer of 15.9 g/L
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