The influence of inoculum preparation and cell density on the efficiency of Cr(VI) removal was assessed with two chromate-resistant yeasts, Pichia jadinii M9 and Pichia anomala M10, isolated from textile wastewaters. Batch cultures in yeast nitrogen base (YNB)′ liquid medium (YNB without amino acids and ammonium sulfate plus sucrose and ammonium sulfate) containing 1-mM initial Cr(VI) concentrations revealed that heavy metal removal in both isolates was substantially affected by the inoculation procedure. Inocula with high initial density or pregrown in a nutritionally rich medium (Malt Czapek) were found to be key factors in order to achieve successful Cr(VI) decontamination. In contrast, low-density inocula and/or synthetic media-precultured cells were shown to negatively influence Cr(VI) disappearance, either by increasing the time for complete degradation or by reducing the percentage of heavy metal removed. These results emphasized the relevance of the selection of an appropriate inoculum culture medium and the positive influence of increasing one order of magnitude inoculum cell density in order to achieve successful and rapid Cr(VI) removal. Under these considerations, the selected yeasts, P. jadinii M9 and P. anomala M10, exhibited a remarkable ability to tolerate and completely remove Cr(VI) concentrations up to 1 mM, thus being candidates for potential applications in bioremediation of Cr(VI)-contaminated environments.

Significant losses in harvested melon can be directly attributable to decay fungi. In the present study, the use of UV-C treatment combined with biocontrol yeast, Pichia cecembensis, was evaluated for their ability to control postharvest decay of melon fruits after they were artificially inoculated with Fusarium oxysporum and Alternaria alternata. Natural infection of fruit was also assessed. As a stand-alone treatment, UV-C or P. cecembensis significantly reduced Fusarium rot and Alternaria rot, and also the level of natural infection on melon fruit, relative to the untreated control. The combination of UV-C or P. cecembensis, however, provided a superior level of decay control on artificially inoculated and naturally infected fruit, compared to either treatment alone. None of the treatments impaired fruit quality. Integrating the use of UV-C treatment with biocontrol yeast has potential as an effective method to control postharvest decay of melon.