Air cold plasma has been used as a novel method for enhancing microbial fermentation.The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae,so as to provide valuable information for largescale application of plasma in the fermentation industry.Suspensions of S.cerevisiae cells were exposed to air cold plasma for 0,1,2,3,4 and 5 min,and then subjected to various analyses prior to fermentation(0h) and at the 9 and 21 h stages of fermentation.Compared with nonexposed cells,cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca^(2+) concentration as a result of the significant increase in membrane potential prior to fermentation.At the same time,the ATP level in the cell suspension decreased by about 40%,resulting in a reduction of about 60%in NADH prior to culturing.However,the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at0 h.Taken together,the results indicated that exposure of S.cerevisiae to air cold plasma could increase its cytoplasmic free Ca^(2+) concentration by improving the cell membrane potential,consequently leading to changes in ATP and NADH levels.
In this study, a novel approach to measure the absolute cytoplasmic Ca^(2+) concentration([Ca^(2+) ]cyt) using the Ca^(2+) indicator fluo-3 AM was established. The parameters associated with the probe fluo-3 AM were optimized to accurately determine fluorescence intensity from the Ca^(2+) -bound probe. Using three optimized parameters(final concentration of 6 m M probe,incubation time of 135 min, loading probe before plasma treatment), the maximum fluorescence intensity(F_(max)?=?527.8 a.u.) and the minimum fluorescence intensity(F_(min)?=?63.8 a.u.) were obtained in a saturated Ca^(2+) solution or a solution of lacking Ca^(2+) . Correspondingly, the maximum [Ca^(2+) ]cytinduced by cold plasma was 1232.5 n M. Therefore, the Ca^(2+) indicator fluo-3 AM was successfully applied to measure the absolute [Ca^(2+) ]cytin Saccharomyces cerevisiae stimulated by cold plasma at atmospheric air pressure.
