The effect of yeast growth stages on the absorption of polyphenols

Colloidal stability of beer is one of the most critical challenges facing the brewing industry. In brewing, stabilization agents are widely used to remove colloids such as proteins and polyphenols. However, the removal efficiency of polyphenols depends on the yeast, which adsorbs these compounds on its surface. The adsorption of polyphenols on the yeast surface is associated with the zeta potential of the cell wall, which correlates with the mannan content in them. The purpose of the study was to investigate the role of yeast strains in adsorption of polyphenols (increasing colloidal stability of beer) and the correlation of this property with the mannan content in the cell wall during the fermentation. Two S. cerevisiae strains were used in this study, and the specific growth rate of yeast, the specific rate of change in the polyphenol content and the mannan content were determined. The results of this study showed that the highest mannan content in yeast was after 9 hours (the end of exponential growth phase). Its content was 10.97% by weight of dry matter in the yeast S. cerevisiae Californian Lager (M54), and 13.69% in the yeast S. cerevisiae Belgian Wit (M21). The desorption of polyphenols was observed during the period from 9 to 24 hours of fermentation, where an increase in the content of polyphenols in the medium was observed. Based on these results, it is necessary to remove the yeast at the end of the exponential growth phase to increase the colloidal stability of the beer

Comparison of the yeast Saccharomyces cerevisiae var. boulardii and top-fermenting brewing yeast strains during the fermentation of model nutrient media and beer wort

Received: June 27th, 2022 ; Accepted: September 18th, 2022 ; Published: October 17th, 2022 ; Correspondence: [email protected], the yeast Saccharomyces cerevisiae var. boulardii have attracted the attention of Food Science researchers due to their unique properties, the main among which are probiotics. Thus, research is conducted on the use of this yeast as a starter culture in the technology of yogurt, fermented vegetables, fruit, vegetable juices, as well as beer. This paper is aimed at studying Saccharomyces cerevisiae var. boulardii 's fermentation performance compared to top-fermenting brewing yeast strains during fermentation of model nutrient media and beer wort. Fermentation activity of the studied strains was assessed based on the character of fermentation curves, as well as the values of the maximum substrate assimilation rate and apparent degree of fermentation. Moreover, during the study, beer was produced using the yeast Saccharomyces cerevisiae var. boulardii as a starter culture. According to the obtained results, it can be concluded that Saccharomyces cerevisiae var. boulardii have less fermentation activity compared to brewing strains. In turn, beer produced with Saccharomyces cerevisiae var. boulardiisignificantly differed in physicochemical, microbiological, and organoleptic parameters from the control sample obtained using the 047A brewing strain. Thus, it contained less ethanol and secondary metabolites; however, the concentration of living cells was significantly higher, which indicates a relatively high viability of the yeast Saccharomyces cerevisiae var. boulardii. From an organoleptic point of view, final beer has a positive sensory profile. The aroma of the product had a complex character: it included caramel, spicy, fruity and phenolic notes, as well as smoked and wine elements; while honey was the dominant note of the taste

Synthesis and Antibacterial Activity of Chitin Tetrazole Derivatives

New tetrazole derivatives of natural chitin polymers of high, medium, and low molecular masses with high, medium, and low degrees of substitution were synthesized and tested in vitro for antibacterial activity. The obtained tetrazole derivatives were characterized by pronounced antibacterial activity in vitro against S. aureus and E. coli. The chitin derivative of medium molecular mass with a medium degree of substitution had the highest antibacterial activity among all obtained derivatives. The antibacterial activity of this derivative as measured by bacterial growth inhibition zones was comparable to those of the antibiotics ampicillin and gentamycin. © 2020, Springer Science+Business Media, LLC, part of Springer Nature

Novel non-toxic high efficient antibacterial azido chitosan derivatives with potential application in food coatings

In this work, we developed a simple method for the preparation of N-(3-azido-2-hydroxypropyl)chitosan. We compared the antibacterial activity of N-(3-azido-2-hydroxypropyl)chitosans and previously synthesized N-(2-azidoethyl)chitosans. N-(3-azido-2-hydroxypropyl)chitosans possess higher antibacterial effect which is comparable with that of ampicillin and gentamicin. The effect is due to azido pharmacophore –CH2–CH(OH)–CH2–N3 (for N-(3-azido-2-hydroxypropyl)chitosan) or –CH2–CH2–N3 (for N-(2-azidoethyl)chitosan) introduced in chitosan chain, since the corresponding organic azides NH2–CH2–CH2–N3 and NH2–CH2–CH2–N3 are characterized by high antibacterial activity. However, high antibacterial organic azides NH2–CH2–CH2–N3 and NH2–CH2–CH2–N3 are characterized by high toxicity. Their conjugation to the chitosan chain saves their antibacterial effect, but strongly diminishes their toxicity, and the toxicity of the resulting derivatives is comparable with that of the starting chitosan. These findings are of interest to food science, since novel effective food coatings can be developed on basis of prepared derivatives. © 201

Синтез и антибактериальная активность тетразольных производных хитина

The present study is devoted to the synthesis and study of the antibacterial activity in vitro of new tetrazole derivatives of natural polymer chitin of high, medium and low molecular weights with high, medium and low degree of substitution. The results showed that the obtained tetrazole derivatives are characterized by pronounced antibacterial activity in vitro against both S. aureus and E. coli strains. Among all derivatives, the highest antibacterial activity is demonstrated by a tetrazole derivative of chitin of moderate molecular weight and moderate degree of substitution. The antibacterial activity of this derivative as measured by the zone of inhibition of bacterial growth is comparable to the antibacterial activity of reference antibiotics ampicillin and gentamicin.Настоящее исследование посвящено синтезу и изучению антибактериальной активности in vitro новых тетразольных производных природного полимера хитина высоких, средних и низких молекулярных масс с высокими, средними и низкими степенями замещения. Полученные тетразольные производные характеризуются выраженной антибактериальной активностью in vitro в отношении S. aureus и E. coli. Среди всех полученных производных наибольшей антибактериальной активностью характеризуется производное хитина средней молекулярной массы умеренной степени замещения. Установленная по зоне ингибирования роста бактерий антибактериальная активность данного производного сопоставима с антибактериальной активностью антибиотиков ампициллина и гентамицина