Abstract
The exogenous application of yeast-derived mannoproteins presents many opportunities for the improvement of wine technological and oenological properties. Their isolation from the cell wall of Saccharomyces cerevisiae has been well studied. However, investigations into the efficiency of extraction methods from non-Saccharomyces yeasts are necessary to explore the heterogeneity in structure and composition that varies between yeast species, which may influence wine properties such as clarity and mouthfeel. In this study, nine yeast strains were screened for cell wall mannoprotein content using fluorescence microscopy techniques. Four species were subsequently exposed to a combination of mechanical and enzymatic extraction methods to optimize mannoprotein yield. Yeast cells subjected to 4 min of ultrasound treatment applied at 80% of the maximum possible amplitude with a 50% duty cycle, followed by an enzymatic treatment of 4000 U lyticase per g dry cells weight, showed the highest mannoprotein-rich yield from all species. Furthermore, preliminary evaluation of the obtained extracts revealed differences in carbohydrate/protein ratios between species and with increased enzyme incubation time. The results obtained in this study form an important step towards further characterization of extraction treatment impact and yeast species effect on the isolated mannoproteins, and their subsequent influence on wine properties.
Highlights
The application of bioactive molecules for the improvement of industrial processes and products such as winemaking and wine is a topic of great interest, especially when these compounds originate from indigenous sources
After the selection of yeast strains and growth stage for subsequent extractions based on fluorescence intensity data, SB62 cells were subjected to various ultrasound and enzymatic conditions as single and combined treatments
Evaluation of the combined use of ultrasound and enzymatic treatment on cells from different yeast species revealed that ultrasound treatment followed by 20 h incubation with β-glucanase yielded the highest concentrations of carbohydrate and protein
Summary
The application of bioactive molecules for the improvement of industrial processes and products such as winemaking and wine is a topic of great interest, especially when these compounds originate from indigenous sources. During the alcoholic fermentation of wine and wine aging, mannoproteins are released by the fermenting yeast Saccharomyces cerevisiae into the wine matrix where they have been shown to positively affect various quality parameters such as protein and tartrate stability, mouthfeel, astringency, color and foaming in sparkling wines [6,7,8,9,10,11,12,13,14]. These desirable attributes have led to the adoption of winemaking practices such as the inoculation of high mannoprotein-producing yeast strains and aging on the lees for the promotion of yeast autolysis and enhanced mannoprotein release [15,16]
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