## 4 Discussion  
The assimilation activities of _S. cerevisiae_ were evaluated through analysis of its growth in media containing wheat bran as the nutrient component (Figure 1 and Table 2). In order to discuss the values relating to growth, the values in this study should be evaluated relative to the data in previous reports. According to a previous report, the \(\mu_{\rm max}\) value was generally 0.34 \(\pm\) 0.01 in 250-mL flasks containing 50 mL of YG+HLMU medium at 30 \({}^{\circ}\)C [38]. In this study, the \(\mu_{\rm max}\) value in 200 \(\mu\)L of YG+HLMU medium at 23 \({}^{\circ}\)C was 0.407 \(\pm\) 0.035; however, the culturing conditions of volume and temperature were different from the previous report [38]. These conditions should be the same to evaluate the growth property, such that BY4741 was cultivated in 50 mL of YG+HLMU medium at 30 \({}^{\circ}\)C, resulting in obtaining the \(\mu_{\rm max}\). The \(\mu_{\rm max}\) value at 30 \({}^{\circ}\)C was increased compared to previously reported data [38] and BY4741 in this study showed the same growth property as BY4741 in another laboratory. The specific growth rate of yeast could be normally depressed 0.6-0.7 times with a decrease in the temperature to 23-24 \({}^{\circ}\)C from 30 \({}^{\circ}\)C [39]; conversely, it could be enhanced by scaling down culturing volumes, with the result that the balanced \(\mu_{\rm max}\) in 200 \(\mu\)L at 23 \({}^{\circ}\)C in this study was slightly increased compared to that in 50 mL at 30 \({}^{\circ}\)C in this study. To evaluate the use of wheat bran as the nutrient, both the values of \(\mu_{\rm max}\) and OD\({}_{600}\) of BY4741 in WG+HLMU medium and YG+HLMU medium were evaluated, showing significant differences, and we can therefore reject the null hypothesis. Thus, although BY4741 could use wheat bran instead of YNB as the nutrient for its growth, the strain grew more vigorously in YG+HLMU medium rather than in WG+HLMU medium. Additionally, the fact that the cell density at 24 h in WG+HLMU medium shown by the OD\({}_{600}\) was 0.83 times lower than that in YG+HLMU medium could reinforce the conclusion that YNB is a better nutrient than the wheat bran for its growth. As per the composition of the wheat bran shown in Table 3, the protein concentration was an adequate supply of nitrogen source for its growth. The ions of Na, Fe, Ca, Cu, and Zn, which are essential metals for growth [32; 33; 34; 35; 36], showed as N.D. in the elemental analysis results; however, the growth of BY4741 was not significantly depressed, meaning that these ions were present at concentrations below the detection limit. On the other hand, although the maximum cell density in W+HLMU medium was 0.43 times lower than that in WG+HLMU medium, growth in W+HLMU medium was shown, strongly suggesting that the wheat bran contained a carbohydrate source. In the case of BY4741 culturing in WG-group media without one of histidine, methionine, or uracil as the essential nutrients, there were no significant differences in cell growth rates (Figure 2a). Compared to WG+HLMU medium, the growth rates in WG-group medium without one of histidine, methionine, or uracil as the essential nutrients were lower than those in WG+HLMU medium; growth was observed in WG-group medium without one of methionine, histidine, or uracil. Therefore, although the essential nutrient forms in the wheat bran were not convenient, the wheat bran contained enough methionine, histidine, and uracil to allow BY4741 to grow. On the other hand, in the case of BY4741 culturing in WG+HMU medium, even on an agarose plate of WG+HMU medium, no cell proliferation was observed. This indicated that the wheat bran did not contain enough leucine to grow. In addition, the result in Figure 2b was that BY4741 and BY4741/PATP425 could be controlled in WG+HMU medium as a selective medium. It was of great significance industrially that the wheat bran, which is significantly cheaper than YNB, could be used as a restricted medium.