Abstract
: The optimum nitrogen concentration for media supplementation and strain dominance are aspects of key importance to the industrial production of ethanol with a view to reducing costs and increasing yields. In this work, these two factors were investigated for four ethanologenic Saccharomyces cerevisiae strains (CLQCA-INT-001, CLQCA-INT-005, CLQCA-10-099, and UCLM 325), selected from the screening of 150 isolates, mostly from Ecuadorian yeast biodiversity. The effect of nitrogen concentration was assessed in terms of cellular growth, glucose consumption and ethanol production, and the yeast strains’ dominance was evaluated in continuous co-fermentation with cellular recycling by mitochondrial DNA analyses. Among the four selected yeast strains under study, CLQCA-INT-005 presented the highest glucose consumption at a nitrogen supplement concentration as low as 0.4 g·L−1, attaining an ethanol yield of up to 96.72% in 24 h. The same yeast strain was found to be highly competitive, showing a dominance of 80% after four cycles of fermentation in co-culture. Thus, CLQCA-INT-005 may be deemed as a very promising candidate to be used both at pilot-plant scale and at industrial scale cellulosic ethanol production.
Highlights
The exploration of new energy resources for the production of renewable energy is currently a priority in many government policies
The effect of nitrogen concentration was assessed in terms of cellular growth, glucose consumption and ethanol production, and the yeast strains’ dominance was evaluated in continuous co-fermentation with cellular recycling by mitochondrial DNA analyses
Among the four selected yeast strains under study, CLQCA-INT-005 presented the highest glucose consumption at a nitrogen supplement concentration as low as 0.4 g·L−1, attaining an ethanol yield of up to 96.72% in 24 h
Summary
The exploration of new energy resources for the production of renewable energy is currently a priority in many government policies. Fermentation is a crucial step in the production of bioethanol and its performance is highly dependent on the yeast strain, the wort composition (carbon and nitrogen availability), temperature, agitation and pH control [4]. High fermentation efficiencies have been reported for both Saccharomyces cerevisiae strains and non-Saccharomyces strains isolated from traditional and industrial fermentations (e.g., from sugarcane ethanol distilleries) [7]. Previous studies provide important information about the behavior of S. cerevisiae strains in co-culture fermentation, evidencing their high dominance in comparison to other non-distilling yeast strains. The advantage of using such dominant yeast strains is their higher fermentation performance, understood in terms of high ethanol yields and reduced risks of contamination with wild yeasts, which has a positive impact on the financial aspects of the industrial bioethanol production [5]
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