Yeast extract mediated autoinduction of lacUV5 promoter: an insight

We report a simple and cost-effective autoinducible media component responsible for the autoinduction of proteins in Escherichia coli under lacUV5 promoter system. Yeast extract (YE) at high concentration was found to stimulate the expression of T7 RNA polymerase in BL21(DE3) cells while such an effect was not seen in BL21A1 cells. A systematic study on the effect of varying concentrations of YE indicated several folds higher expression of genes viz., human granulocyte colony stimulating factor (rhGCSF), human interferon alpha 2b (rhIFN-alpha2b) and Staphylokinase (rSAK) in BL21(DE3) cells in the absence of any specific inducer like IPTG or additional lactose. Additional investigations on the inducible component of the YE revealed the presence of significant amount of endogenous lactose as the contributory factor for the observed autoinduction phenomenon. This paper highlights the easy scalability of the use of the present media component for large-scale production in biotechnology industry.