Ethanol production from dilute-acid softwood hydrolysate by co-culture |
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Authors: | Mingyu Qian Shen Tian Xuefeng Li Jing Zhang Yaping Pan Xiushan Yang |
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Institution: | (1) College of Life Science, Capital Normal University, 100037 Beijing, China |
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Abstract: | Dilute-acid softwood hydrolysate, with glucose and xylose as the dominant sugars was fermented to ethanol by co-cultures.
The strains used include Saccharomyces cerevisiae 2.535 (1#), Pachysolen tannophilis ATCC 2.1662 (2#), and recombinant Escherichia coli (3#) constructed in our laboratory carrying both pdc and adhB genes derived from Zymomonas mobilis. Before fermentation, the co-cultures were adapted for five batches. Observation under light microscope showed aggregation
of adapted strains, which could possibly improve their ability to degrade inhibitors. In addition, we tried to detoxify the
dilute-acid softwood hydrolysate with a combined method before fermentation. Our study showed that fermentation of detoxified
hydrolysate by adapted co-culture (1# + 2@) generated an exceptionally high ethanol yield on total sugar of 0.49 g/g, corresponding
to 96.1% of the maximal theoretical value after 48h; fermentation of detoxified hydrolysate by adapted co-culture (1# + 3#)
is faster (24h) and could reach a high ethanol yield (0.45 g/g total sugar). These experiments suggest that both adaptation
and detoxification significantly improve hydrolysate fermentation and ethanol production. |
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Keywords: | Dilute-acid softwood hydrolysate co-cultures strain adaptation batch fermentation ethanol fermentation |
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