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[Objective] To construct the γ-aminobutyrate-producing recombinant strains ofEscherichia coli and investigate their fermentation characteristics.[Methods] We constructed two recombinant plasmids pTrc99a-gadB and pTrc99a-gadB-SNO1-SNZ1 and then respectively transformed them into the gene-knockout strainE.coli K12/ΔgabTΔgabPΔpuuE. We investigated and optimized the fermentation process of the recombinant strains for producing γ-aminobutyrate.[Results] The target proteins were highly expressed in the recombinant strains harboring the constructed plasmids. The highest concentration of γ-aminobutyrate was 4.6 g/L in the fermentation broth ofE.coli K12ΔgabTΔgabPΔpuuE/pTrc99a-gadB cultured in the medium containing 10 g/L l-monosodium glutamate and was 21.9 times higher than that in the fermentation broth of the wild type strain. At the l-monosodium glutamate concentration of 20 g/L, the conversion rate of substrate was the highest and the concentration of γ-aminobutyrate reached 8.4 g/L. The concentration of γ-aminobutyrate was slightly lower in the fermentation broth of the recombinant strainE.coli K12ΔgabTΔgabPΔpuuE/pTrc99a-gadB-SNO1-SNZ1, probably due to the excessive consumption of energy. The highest concentration of γ-aminobutyrate was 9.4 g/L whenE.coli K12ΔgabTΔgabPΔpuuE/ pTrc99a-gadB was cultured in 1 L fermentation medium containing 20 g/L l-monosodium glutamate.[Conclusion] We obviously increased the yield of γ-aminobutyrate produced by the recombinant strain. This finding lays a foundation for the industrial production of γ-aminobutyrate.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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