β-Glucan is a cell wall component that is one of the most plentiful cell polysaccharides. Moreover, it has been found to have several beneficial effects on the immune system. In yeast, β-glucan is mainly contained in the yeast cell wall, and thus it is important to produce high levels of cell mass for the mass production of yeast β-glucan. Response surface methodology (RSM) offers a potential means of optimizing process factors and medium components; it has been used to estimate the effects of medium components on cell mass production. In the present study, the optimal concentrations of molasses and corn steep liquor (CSL) in the medium were determined to be 6.4 % (v/v) and 17 % (v/v). The cell mass predicted by statistical analysis was 9.76 g/L after 20 h of cultivation. In a 2.5-L stirred tank reactor (STR), the cell mass produced in a batch culture was 36.5∼ 39.3 g/L. The maximum cell mass in the fed-batch cultures of Saccharomyces cerevisiae JUL3 was 95.7 g/L using 50 % molasses solution and a feed rate of 10 mL/h. The cell mass obtained in the fed-batch culture was 2.4-fold higher than that obtained in the batch culture.