Analysis of the Relationship Between Era and YggG in E.coli by Double-promoter Expression Vector pDH2-YggG-P_(tac)-Era / 中国生物工程杂志

yggG, a Era-binding protein gene, was isolated and cloned from the E.coli genomic DNA library. Previous studies indicated that the product of yggG gene, YggG294(amino acids 1-294), strongly inhibited the growth of host bacteria and caused the death of bacteria cells. To elucidate whether Era is related to the death of bacterial cells expressed YggG294,A double promoter expression vector that can express YggG294 and Era proteins controllably in cells was constructed. Using this vector to express YggG294 and Era protein in the same E.coli cells, then analyzed the relation between YggG294 and Era. The results showed that the ratio of Era proteins to total proteins increased with the increase of induction time in E.coli cells without YggG294 expression and with little YggG294 expression;the ratio of Era proteins to total proteins seemed to be a constant level in E.coli cells overexpressing YggG294;but we could not detect any Era hydrolyzate in E.coli cells overexpressed YggG294 could not be detected. The results also showed that pre-expression of Era protein did not produce any effect on the growth inhibition of E.coli cells caused by YggG294. These results indicate that YggG294 can not hydrolyze Era protein in E.coli cells, and that YggG-Era interaction is not associated with the death of bacteria expressed YggG294. It is thus reasonable to draw a conclusion that Era is not associated with the growth inhibition of E.coli cells caused by YggG294. YggG294 inhibits the growth of bacteria by other way.

High density fed-batch culture of Escherichia coli DH5 alpha/pDH-B2m with DO feed-back control of nutrient feeding / 生物工程学报

Optimization of cultivation condition of recombinant E. coli DH5 alpha/pDH-B2m and the condition suitable for expression of recombinant mature peptide of human bone morphogenetic protein-2 was carried out in 500 mL shaking flasks and then transferred to NBS Bioflo IV, a 20 L DO feed-back fed-batch culture system, to obtain rhBMP-2. The results indicate that keeping dissolved oxygen at 40% and controlling nutrient feeding rate with DO feed back strategy can obtain theoretically 3.59 g recombinant mature peptide of hBMP-2 per liter of broth, the final cell density OD600 reaches 57(22.8 g dry cell weight/L), and the expression of rhBMP-2 amounts to 30% of the total protein in E. coli.