Improving the expression of Human Epidermal Growth Factor in Saccharomyces cerevisiae by manipulating culture conditions

Human Epidermal Growth Factor (hEGF) is a protein molecule with potent mitogenic activity, increasing the rate of wound and ulcer healing in different tissues of the human body. In recent years, the Center for Genetic Engineering and Biotechnology (CIGB) has carried out projects at the developmental stages for the application of hEGF in novel therapies. It is now necessary to increase production capacity within the same facility, to meet the increasing demand of this product.The aim of this work was to increase hEGF expression levels by optimizing the culture conditions. The culture media, pH and temperature dependency of hEGF expression and degradation rate were studied. An increase of 1.8 times of the hEGF expression level was achieved by adding to the medium 50 mg/L of histidine and leucine. A factorial design experiment was applied to optimize the yeast extract and bacteriological peptone concentration in the culture media. The statistical analysis of response surface predicted that using 18 g/L of yeast extract and 25 g/L of bacteriological peptone improved the hEGF expression level up to 3.5 mg/g. This is the highest expression level reported for hEGF in yeast up to now. Furthermore, the form in which the hEGF degradation rate was reduced to less than 10% in fermenters when the culture was made on the optimized medium at pH 6.5 and 25 °C, is discussed.