Enhanced Ethanol Production of Saccharomyces cerevisiae Induced by Cold Plasma at Atmospheric Air Pressure

Abstract

In this study, cold plasma at atmospheric pressure, as a novel approach of bioprocess intensification, was used to induce yeast for the improvement of ethanol production. Response surface methodology (RSM) was used to optimize the discharge-associated parameters of cold plasma for the purpose of maximizing the ethanol yield achieved by cold plasma-treated S. cerevisiae. The resulting yield of ethanol reached to 0.48 g g−1 under optimized parameters of plasma exposure time of 1 min, power voltage of 26 V, and an exposed sample volume of 9 mL, which represented an increase of 33% over control. Compared with non-exposed cells, cells exposed with plasma for 1 min presented a notable increment in cytoplasmic free Ca2+, when these exposed cells showed the significant increase in membrane potential. At the same time, ATP level decreased by about 40%, resulting in about 60% reduction in NADH. Taken together, these data suggested that the mechanism that air cold plasma raised plasma membrane potential, which led to increases in cytosolic Ca2+ concentration. Furthermore, the cofactor metabolism, such as ATP and NADH, was subjected to regulation that was mediated by Ca2+, ultimately improving yeast productivity. This may have a underlying and broad utilization in enhancing bioconversion capability of microbe in the next few years.