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In recent years, there has been a surge in the production of kombucha—a functional beverage obtained via microbial fermentation of tea. However, fresh, unpasteurized kombucha is sensitive to quality deterioration as a result of, among other factors, oxidation. The addition of hops seems to be promising, due to their antioxidative properties, which may improve the stability of kombucha. However, aiming at retaining the highest antioxidative properties of kombucha, it remains unclear at which stage of the production process hops should be added. The study investigated the effect of hop supplementation during kombucha production on the basic physicochemical, antioxidative, and sensory properties of kombucha. Cascade hops in the concentrations 0.5 and 2 g/L were added at the onset of tea infusion and to the fresh, unpasteurized kombucha. The addition of hops (particularly at the pre-fermentation stage of production) led to a significant decrease in radical formation in the produced kombucha measured by electron spin resonance spectroscopy (ESR), which correlated with the higher DPPH antiradical activity and the elevated bitter α-acid content. From the sensory perspective, the post-fermentation addition of hops to kombucha resulted in a significantly higher rating of the overall quality. This enhancement was directly associated with heightened bitterness, increased presence of fruity and citrusy aromas, and a simultaneous reduction in the intensities of acetic and tea-related attributes. The data presented in this study are relevant for kombucha producers, who want to deliver a sensory-novel product in combination with an improved oxidative stability. Key points: • Hop addition in kombucha production improves the antioxidative activity of the beverage. • Hop α-acids display higher antioxidative properties in kombucha than polyphenols. • Oxidative stability of kombucha fortified with hops depends on the timing of hops addition. • Hop addition enriches the taste and aroma attributes of kombucha. [ABSTRACT FROM AUTHOR]

There is growing interest in low-temperature food processing. In the baking industry, low-temperature fermentation improves the production of natural aroma compounds, which have a positive impact on the sensory profile of the final product. The aim of this study was to develop a yeast–lactic acid bacteria starter culture that effectively ferments wheat dough at a temperature of 15 °C. The microorganisms were selected based on their enzymatic activity and ability to grow at low temperature. The fermentation activity of the yeast and mixed cultures was assessed enzymatically. The biosynthesis of volatile organic compounds was quantified using the HS-GC-MS technique. Samples fermented by S. cerevisiae D3 were characterized by the highest concentration of volatile organic compounds, especially esters. The addition of lactic acid bacteria increased not only the biosynthesis of volatile organic compounds but also the productivity of carbon dioxide during dough fermentation. Based on both dough expansion and the profile of volatile organic compounds, a mixed culture of S. cerevisiae D3 and L. brevis B46 was selected as the most effective starter for low-temperature fermentation. [ABSTRACT FROM AUTHOR]

Numerous studies have demonstrated the efficacy of selenium compounds in preventing and treating lifestyle-related diseases such as cancer and cardiovascular disorders. The formulation of selenium-enriched supplements for humans and animals, particularly those containing selenium yeast, is highly advantageous. These products are rich in organic selenium derivatives, showing significantly higher bioavailability than inorganic forms of selenium. A particularly promising selenium analogue of sulphur-containing compounds is selenobiotin. The literature indicates that Phycomyces blakesleeanus and Escherichia coli strains can synthesise this compound. This research aimed to evaluate the effect of selenium supplementation on the biosynthesis of biotin and selenobiotin in Trichosporon cutaneum and Meyerozyma guilliermondii. The results have the potential to advance biotechnological approaches for the production of selenobiotin for various applications. A method based on affinity chromatography was used to quantify selenobiotin. The results confirmed that both yeast strains could synthesise selenobiotin in addition to biotin. In M. guilliermondii cells, selenobiotin accounted for up to 17.3% of the total biotin vitamer fraction. In comparison, in T. cutaneum cells, it accounted for up to 28.4% of the sum of biotin and its analogues. The highest levels of selenobiotin were observed in cells cultured with selenomethionine. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Despite the significant progress in the research, the problem of finding an efficient method for producing bioethanol from renewable lignocellulosic waste materials remains unresolved. Our investigation aimed to assess the efficacy of ethanol production from sugar beet pulp (SBP) utilising various approaches, including pretreatment variations, enzymatic processes, and microbial hydrolysis. Our research involved using the post-cultivation concentrate of T. viride LOCK 0588 grown in the SBP-based medium as a source of enzymes. The SBP hydrolysis process was carried out for 48 h at 50 °C. The quantity of sugar released, up to 61 g dm−3, through the utilisation of this extract proved to be on par with the outcomes achieved by the application of the commercial Cellic Ctec2 preparation. The final yields of the ethanol production with the use of the coculture of S. cerevisiae (Ethanol Red) and Scheffersomyces stipitis LOCK 0047 strain were in the range 5.1 ± 0.11 kg 100 kg−1 ÷ 5.38 ± 0.11 kg 100 kg−1. These results provide a solid basis for improving larger-scale industrial procedures that involve converting SBP into bioethanol using a cost-efficient approach of microbial hydrolysis with T. viride and a blend of pentose and hexose fermenting yeast. [ABSTRACT FROM AUTHOR]

More than 40 yeast strains were isolated from various types of plant biomass and then evaluated for potential applications in biotechnological processes conducted at low temperature. Adaptation to low temperature was tested by passaging the isolates at decreasing temperatures, from 30 to 15 °C. Only the strains that were able to adapt to the final temperature and reached the stationary growth phase relatively quickly were submitted to further experimentation. These included eight environmental yeast isolates from four types of materials of plant origin: wheat, rye, and cucumber, containing glucose, fructose, sucrose, and starch; yeastfermentable sugars; red beetroot, containing large amounts of glucose and fructose; and fruits (grapes and apples) containing glucose, fructose, and sucrose. The strains were identified and then subjected to a series of experiments to assess their suitability for use in low-temperature biotechnological industrial processes incorporating microbial biomass. The growth dynamics and assimilation profiles of the yeast strains were investigated, as well as their ability to produce volatile compounds. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the suitability of buckwheat grain for agricultural distillate production. The effects of the method of starch liberation on the physicochemical composition of the prepared mashes, fermentation results, the concentration of volatile compounds in the obtained distillates, and their organoleptic features, were investigated. The raw materials used were two cultivars of buckwheat grains, Panda and Kora. Both cultivars were characterized by similar starch content, however Panda cultivar had a significantly higher content of reducing sugars. Fermentation of the Kora cultivar-based mashes resulted in a higher fermentation efficiency (up to approximately 85% of the theoretical yield) compared to the Panda cultivar-based mashes (up to approx. 75%). Of the tested methods of starch liberation, the pressure-thermal treatment was revealed as superior, especially in the case of the Panda cultivar. In the case of the Kora cultivar, both the pressure-thermal method and the pressureless method of starch liberation resulted in a high process efficiency (up to 85% of the theoretical). Supplementation of the buckwheat mashes with (NH4)2HPO4 improved fermentation results. The highest scores in sensory assessment were given to distillates from mashes prepared with the pressure-thermal treatment, which contained relatively low concentrations of undesirable compounds, such as acetaldehyde and methanol, and revealed pleasant organoleptic features. [ABSTRACT FROM AUTHOR]