Calcium Supplementation Abates the Inhibition Effects of Acetic Acid on Saccharomyces cerevisiae.

The toxic level of acetic acid could be released during the pretreatment of lignocellulosic biomass, and an economical method was reported to minimize the acidic stress on the fermentation of Saccharomyces cerevisiae by cation supplementation. A dose-dependent protection of Ca(2+) was monitored, and the optimal concentration of Ca(2+) was 8 mM under 4.5 g/L acetic acid stress. The activities of catalase and superoxide dismutase of yeast cells supplemented with optimal Ca(2+) increased by 18.6 and 27.3 %, respectively, coupling with an obvious decrease of reactive oxygen species content. Cell viability also performed a significant increase from 52.4 % (without Ca(2+) addition) to 73.56 % (with 8 mM Ca(2+) addition). No significant improvements were found in the bioethanol yields by Ca(2+) supplementation; however, the fermentation time was shortened by about 8 h obviously. Our results illustrated that the Ca(2+) supplementation could be an economical method to make the bioethanol production more efficient and cost-effective.