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| Optimization of fermentation process of culturing Schizochytrium to produce DHA using distiller′s grains treatment liquid as nitrogen source |
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| KeyWord:distiller′s grains treatment liquid Schizochytrium DHA fermentation wastewater |
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| Abstract: |
| In order to reduce the cost of producing DHA by fermentation culture of Schizochytrium, the sauce-flavor distiller′s grains were used as the experimental material, and it was simply pretreated as the nitrogen source of the fermentation culture medium of Schizochytrium.Firstly, the free amino acid composition and content of distiller′s grains treatment liquid and tryptone were analyzed. Then, the biomass, oil yield and DHA yield were used as indicators, the production of DHA by Schizochytrium using distiller′s grains treatment liquid, tryptone, yeast extract and beef extract as nitrogen sources was compared, and the fermentation conditions were optimized when distiller′s grains treatment liquid was used as nitrogen source.The fermentation wastewater was recycled for three times. The results showed that the distiller′s grains treatment liquid could be used as a nitrogen source for the growth of Schizochytrium. Compared with yeast extract and beef extract, distiller′s grains treatment liquid had obvious advantages as nitrogen source. The optimal fermentation conditions for using distiller′ s grains treatment liquid as nitrogen source were obtained as follows: mass ratio of distiller′s grains (about 10% of water content) to water 1∶ 9, dosage of distiller′s grains treatment liquid 70%(replacement ratio of water in the basic fermentation culture medium), initial pH 70, and incubation time 108 h.Under these conditions, the biomass, oil yield, and DHA yield of Schizochytrium reached 22.14, 8.88 g/L, and 2.84 g/L, respectively. After three cycles of adding 15.0% (replacement ratio of water in the basic fermentation culture medium) of fermentation wastewater into the distiller′s grains treatment liquid culture medium, the DHA yield of Schizochytrium was 4.27, 3.70, 2.75 g/L respectively. In summary, it is a new method of resource utilization of distiller′s grains to cultivate Schizochytrium to produce DHA by distiller′s grains treatment liquid. |
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