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The issue of managing waste bread is a global concern, with significant environmental and the economic implications. The utilisation of waste bread for bioethanol production, employing energy-saving technology, could prevent these consequences and reduce the consumption of traditionally used fossil fuels. The objective of this study was to evaluate the influence of the type of waste bread (wheat and wheat–rye sourdough) and the mash preparation method on the results of alcoholic fermentation and the concentration of selected congeners in the distillates. The highest fermentation efficiency (96% of theoretical) was achieved for both types of bread through the utilisation of the pressureless starch liberation method combined with simultaneous saccharification and fermentation. The separate saccharification of starch resulted in lower process efficiencies (from 85.75 to 88.60% of theoretical). The application of the native starch hydrolysis method (without starch activation) for the fermentation of wheat bread-based mashes exhibited a higher efficiency (87.85% of the theoretical) than that observed for the wheat–rye bread-based mash sample (83.74% of theoretical). All of the obtained spirit distillates exhibited a low concentration of methanol (≤300 mg/L alcohol 100% v/v) and comply with the requirements of the EU regulation for ethyl alcohol of agricultural origin (rectified spirit).

Poland is one of the leading apple-producing countries, both in Europe and around the world. One of the main byproducts of apple processing is pomace, which can account for 20–35% of the harvested apples. Pomace is a potential source of many valuable bioactive components and can also serve as a food ingredient, either directly or indirectly (after bioconversion with fodder yeast). This study aimed to evaluate the possibility of converting polysaccharides contained in apple pomace to yeast biomass. Meyerozyma guilliermondii and Scheffersomyces stipitis yeasts were grown in a medium prepared by pretreatment of the raw material with water or 2% sulphuric acid at 120 °C. Subsequently, enzymatic hydrolysis was performed using a Cellic CTec2 preparation at 30 °C or 50 °C. The resulting hydrolysates were enriched with ammonium salts, and shaken yeast cultures were incubated at 30 °C for 72 h. Based on the results, it can be concluded that acid pretreatment of apple pomace is more effective than water pretreatment under the same time and temperature conditions. The Meyerozyma guilliermondii strain grows in apple pomace hydrolysates more efficiently (16.29 g/L) than Scheffersomyces stipitis cells do (14.63 g/L).

Throughout history, the fermentation of fruit juices has served as a preservation method and has enhanced the retention of bioactive constituents crucial for human well-being. This study examined the possibility of orange and black currant juice fermentation with the probiotic yeast Saccharomyces cerevisiae var. boulardii. Saccharomyces bayanus was used as the reference. The ethanol concentration of the orange juices fermented without added glucose was close to 27 g/L. Adding glucose to the juice increased the alcohol produced by up to 65.58 ± 1.84 g/L (for the orange juice). For the same wort fermented by S. bayanus, the final ethanol concentration was 71.23 ± 1.62 g/L. Regardless of the type of yeast and additives used, the samples retained much of the color of the unfermented juice. The polyphenols content in the fermented samples was close to the initial polyphenols content in the juices. The sensory attributes of the juices fermented by the probiotic yeast did not differ from the samples fermented by S. bayanus. Fermenting fruit juices with probiotic yeasts offers a commercially viable and sensorially appealing method to enhance the product’s value by imparting it with probiotic properties.