Résumé
Acyl carrier protein is an essential component involved in the biosynthesis of DHA(Docosahexaenoic Acid) via PKS(Polyketide synthase) pathway,which takes the growing acyl chain from one enzyme to another.One cDNA clone,with high homology of ACP,was isolated from Schizochytrium sp.FJU-512 cDNA library.The deduced amino acid sequence contained 142 residues with isoelectric point of 5.04 and had the 4'-phosphopantetheine prosthetic(4'-PP) binding site.The target fragment was digested with BamHⅠ/HindⅢand inserted into the expression vector pET-30a resulting in the plasmid pET-30a/acp.The recombinant vector was transformed into E.coli BL21(DE3) and induced by IPTG.SDS-PAGE analysis demonstrated that ACP was effectively expressed.
Résumé
To improve ethanol production in Saccharomyces cerevisiae,an integration plasmid pUPGKAT with PGK promoter(phosphoglycerate kinase promoter),adh1 gene(the coding sequences of alcohol dehydrogenaseⅠ) and CYC1 terminator(Cytochrome c transcription terminator) was constructed.Firstly,a fusion fragment composed of PGK promoter and adh1 gene was generated by over lap extension PCR and ligated into pUG6 resulting in plasmid pUPGKA.Subsequently,CYC1 termi nator was amplified from pSH65 by PCR and ligated to the SpeⅠand SacⅡrestriction site of pUPGKA.To integrate PGK-adh1-CYC1 into S.cerevisiae genome,pUPGKAT was digested by TthⅢⅠand the lin-earized plasmid was used to transform S.cerevisiae YS2-△adh2(adh2 disrupted strain) by lithium acetate method.The yeast mutant YS2-△adh2-adh1 which had the adh1 gene placed under the PGK promoter and harbored the adh2 deletion was constructed.Anaerobic fermentation showed overexpression of adh1 by PGK promoter resulted in a 8.84% higher ethanol production compared to YS2-△adh2.