Efficient production of aggregation prone 4-α-glucanotransferase by combined use of molecular chaperones and chemical chaperones in Escherichia coli.

In this study, a combined optimization strategy, based on co-expression of molecular chaperones and supplementation of osmolytes, was used to reduce the formation of inclusion bodies and enhance the expression of the soluble form of 4-α-glucanotransferase. The 4-α-glucanotransferase yield was enhanced by co-expression with pGro7 and supplementation of trimetlylamine oxide. Subsequently, the effects of process conditions (temperature, inducer concentration, and arabinose concentration) on cell growth and 4-α-glucanotransferase production were also investigated in shake flasks. In addition, a modified high-cell-density fermentation approach was proposed and applied in 3-L fermentor supplied with l-arabinose and trimetlylamine oxide, which achieved a dry cell weight of 65.92 g·L. Through this cultivation approach at 28 °C, the activity of 4-α-glucanotransferase reached 332.5 U·g dry cell weight, which was 24.6-fold greater than the initial activity in shake flask cultivation. This combined strategy is expected to provide an efficient and economical approach to overproduction of aggregation prone proteins on a large scale.