Construction and fermentation study of squalene-producing recombinant Escherichia coli
Squalene is a tri terpenoid compound which has been widely used in the food and pharmaceutical industries.Esche-richia coli is considered a highly promising chassis cell for the synthesis of squalene.In order to increase squalene production in E.coli,an orthogonal design was conducted using three genes dxs,idi and ispA in MEP pathway as factors and three induc-ible promoters of different strengths,p3-lac,p6-lac,pl 0-lac as levels to construct nine recombinant strains for fermentation by inducing squalene synthase gene.The relative strength of the three promoters was determined by the expression level of green fluorescent protein.The p3-lac promoter had the strongest relative strength,while the p10-lac promoter had the weakest rela-tive strength.By analyzing the extreme deviation of the fermentation data,it was found that dxs was the most dominant factor affecting squalene yield,followed by ispA and idi.The strain corresponding to the optimal level combination of the three factors was 1063/DE3,which achieved a yield of 450 mg/L.Overall,an E.coli strain with a 681-fold increase in squalene production compared to the original strain has been obtained and a new strategy for increasing squalene production in E.coli has been provided in this study.
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