Development of fed-batch process for high-yielding β-glucosidase displayed on cell surface of industrial yeast Saccharomyces cerevisiae

Abstract Here, we developed a fed-batch process for the cultivation of multistress tolerant Saccharomyces cerevisiae engineered to display β-glucosidase (BGL) on the cell surface. Although cell growth was promoted by increasing the amount of oxygen supplied, increasing the overall volumetric oxygen transfer coefficient rather decreased the specific BGL activity of yeast cells probably because of the high agitation speed used. To suppress the formation of ethanol, the method of feeding glucose was investigated. Namely, the timely addition of glucose and glucose feed rate were found crucial for increasing both cell concentration and specific BGL activity. When the lowest concentration of dissolved oxygen at 9 h was used as an indicator, the lowest glucose feed rate of 1 g/(L·h) provided the maximum BGL activity of 673.6 U/g-dry cell, which is 1.6-fold higher than that in batch cultivation. By employing the fed-batch technique together with the improved gene cassette containing the SED1 promoter and anchoring domain, we found that the cell concentration and specific BGL activity continued to increase, reaching 15.4 g-dry cell/L and 1866.6 U/g-dry cell after 48 h, respectively. The results show the advantage of the fed-batch process for realizing the potential of cell-surface display systems in S. cerevisiae .