In order to verify the fermentation performance of our engineered yeast comparing to the wild, we also measured their ethanol yield during the fermentation time to see the potential application in the ethanol industry. After roughly comparing to the wild, we notice that the WXA/pXylanBD yeast showed a relatively outstanding ethanol production capacity among the samples and the initial data is given in the following table (Table 1).
Therefore, we decided to build a model to analyze the relationship between the ethanol yield and the fermentation time.
After several trails, we chose to use the quartic polynomial equation to build the model and draw the fitting curve of the yielded ethanol of WXA/pXylanBD yeast as well as the wild control, WXA yeast during the fermentation.
The quatic polynomial equation:
According to the model results (figure 1), the fitting degree equals 1 thus we could rely on this model to predict the ethanol production situation of WXA/pXylanBD yeast during the fermentation.
Based on the fitting curves (Fig. 5), WXA/pXylanBD shows obviously higher ethanol yield capacity before 7.2 hours than the wild and its optimal fermentation time would be 2.5 hours so as to reach its maximum ethanol yield. To sum up, our engineered yeast WXA/pXylanBD possesses high potential to be applied in the ethanol production industry which could decease the fermentation time in addition to its well enzyme activity to make use of wheat B-starch. Of course, we also notice that the ethanol yield seems to decline after 2.5 hours which might be the measurement error caused by the evaporation of high concentration of ethanol or the influences of the ethanol on the growth of our WXA/pXylanBD yeast.