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Effect of furfural concentration on ethanol production usingSaccharomyces cerevisiaein an immobilized cells stirred-tank bioreactor with glucose-based medium and mathematical modeling

2020    Erkan, Selime Benemir; Yatmaz, Ercan; Germec, Mustafa; Turhan, Irfan

The aim of this study was to determine the toleration limit of furfural concentration (0.1-10 g/L) in the medium for ethanol fermentation using immobilized cells ofSaccharomyces cerevisiaein the bioreactor with glucose-based media and to model the fermentation. Results showed that the highest ethanol yield and production were 47.62% and 36.40 g/L when 0.5 and 2 g/L of furfural were added in the medium, respectively. In contrast, the lowest yield and production were 5.40% and 0.57 in 10 g/L of furfural. Thus, the furfural has been found to adversely affect the ethanol yield even the yeast was immobilized. Nevertheless, the yeast can grow up to a furfural concentration of 6 g/L. Regarding modeling, the experimental ethanol production, sugar consumption, and biomass production data of the fermentation performed by adding 2 g/L of furfural were successfully predicted by MGM, MMF, and Weibull model. Practical applications In the pretreatment of renewable resources that can be used to produce ethanol, inhibitors are formed, which inhibit the microbial growth and the product formation. Detoxification methods are commonly used to remove the inhibitors. In this study, the immobilization technique was used to protect the yeast growth and thus product formation from inhibition. Yeast cells were covered with Ca-alginate by immobilization. Cells protected with alginate exposed less to inhibition. Protected cells remained more active in this way. Based on the results, this technique was successful since the ethanol was produced in the glucose-based medium including furfural. The results also showed that no detoxification was required and that the process saves time and energy.