Impact of Botrytis cinerea Contamination on the Characteristics and Foamability of Yeast Macromolecules Released during the Alcoholic Fermentation of a Model Grape Juice

Development of simple, scalable protease production from Botrytis cinerea

Abstract

Heat haze-forming proteins are stable during winemaking and are typically removed via adsorption to bentonite. Proteolytic degradation is an alternative method to prevent wine-haze and offers the opportunity to reduce the environmental impacts and labor cost of the process. Herein, we describe the development of a production system for Botrytis cinerea proteases for the enzymatic degradation of heat haze-forming proteins. The effect of culture medium on the secretion of glucan by B. cinerea was investigated and methods to inactivate B. cinerea laccase in liquid culture medium were assessed. Protease production by B. cinerea was scaled up from 50 mL in shake flasks to 1 L in bioreactors, resulting in an increase in protease yield from 0.30 to 3.04 g L⁻¹. Glucan secretion by B. cinerea was minimal in culture medium containing lactose as a carbon source and either lactic or sulfuric acid for pH control. B. cinerea laccases were inactivated by reducing the pH of culture supernatant to 1.5 for 1 h. B. cinerea proteases were concentrated and partially purified using ammonium sulfate precipitation. SWATH-MS identified aspartic acid protease BcAP8 amongst the precipitated proteins. These results demonstrate a simple, affordable, and scalable process to produce proteases from B. cinerea as a replacement for bentonite in winemaking.

Key points

• Isolates of B. cinerea that produce proteases with potential for reducing wine heat-haze forming proteins were identified.

• Media and fermentation optimization increased protease yield tenfold and reduced glucan secretion.

• Low pH treatment inactivated laccases but not proteases.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-11817-1.

Acacia gums new fractions and sparkling base wines: How their biochemical and structural properties impact foamability?

Foam is the first attribute observed when sparkling wine is served. Bentonite is essentially used to flocculate particles in sparkling base wines but can impair their foamability. Gums from Acacia senegal and Acacia seyal improved the foamability of different bentonite-treated base wines. Our main goal was to see how the supplementation with new fractions separated from Acacia gums by Ion Exchange Chromatography affected foamability of sparkling base wines, deepening the relation between foam behavior and characteristics of wine and gums. High molar mass fractions increased the maximal foam height and the foam height during the stability period in, respectively, 11 out and 8 out of 16 cases (69% and 50%, respectively). The properties of the supplementing gums fractions obtained by IEC and, although to a minor extent, the wine characteristics, affected positively and/or negatively the foam behavior. Wine foamability also depended on the relationship between wine and gums fractions properties.

Influence of fermentation conditions on the secretion of seripauperin 5 (PAU5) by industrial sparkling wine strains of Saccharomyces cerevisiae

The yeast mannoprotein seripauperin 5 (PAU5) from Saccharomyces cerevisiae is a negative gushing biomarker in sparkling wine with a direct gushing-reducing effect. The knowledge about the influence of the yeast strain and the fermentation conditions on the PAU5 content in the final product could reduce the gushing potential of sparkling wines and avoid economic losses for sparkling wine producers. The potential of 30 different commercially used (sparkling) wine S. cerevisiae strains to produce PAU5 was analyzed by RP-HPLC. The experiments revealed great differences between strains and identified three high-PAU5-producing yeast strains. The influence of different fermentation conditions was analyzed in two selected strains. Cultivation conditions of elevated temperature and lower inoculation density, as well as cultivation under diffuse daylight significantly enhanced PAU5 production by the tested S. cerevisiae strains as compared to standard conditions. However, cultivation as agitated cultures and co-cultivation with Metchnikowia pulcherrima or Torulaspora delbrueckii led to a reduction of PAU5 production as compared to standard conditions.