Regulation of hydrogen sulfide liberation in wine-producing Saccharomyces cerevisiae strains by assimilable nitrogen

Abstract

Saccharomyces cerevisiae wine-producing yeast cultures grown under model winemaking conditions could be induced to liberate hydrogen sulfide (H 2 S) by starvation for assimilable nitrogen. The amount of H 2 S produced was dependent on the yeast strain, the sulfur precursor compound, the culture growth rate, and the activity of the sulfite reductase enzyme (EC 1.8.1.2) immediately before nitrogen depletion. Increased H 2 S formation relative to its utilization by metabolism was not a consequence of a de novo synthesis of sulfite reductase. The greatest amount of H 2 S was produced when nitrogen became depleted during the exponential phase of growth or during growth on amino acids capable of supporting short doubling times. Both sulfate and sulfite were able to act as substrates for the generation of H 2 S in the absence of assimilable nitrogen; however, sulfate reduction was tightly regulated, leading to limited H 2 S liberation, whereas sulfite reduction appeared to be uncontrolled. In addition to ammonium, most amino acids were able to suppress the liberation of excess H 2 S when added as sole sources of nitrogen, particularly for one of the strains studied. Cysteine was the most notable exception, inducing the liberation of H 2 S at levels exceeding that of the nitrogen-depleted control. Threonine and proline also proved to be poor substitutes for ammonium. These data suggest that any compound that can efficiently generate sulfide-binding nitrogenous precursors of organic sulfur compounds will prevent the liberation of excess H 2 S.

Isolation of sulfite reductase variants of a commercial wine yeast with significantly reduced hydrogen sulfide production

“…With the third method, the analytical quantification of H 2 S liberated from cultures during fermentation was achieved by a liquid trap-based method, using cadmium hydroxide as trapping agent, as described elsewhere (Jiranek et al, 1995a).…”

“…The production of H 2 S during wine fermentation is a frequently encountered problem in winemaking, and, if it is not treated, the resulting wine will be tainted, leading to a loss in quality and the possibility of being rejected by consumers. Therefore, factors affecting H 2 S production have attracted the attention of numerous researchers over the last few years (Giudici & Kunkee, 1994;Jiranek et al, 1995a;Wang et al, 2003;Linderholm et al, 2008).…”

“…If there is a deficiency of assimilable nitrogen in the grape must, O-acetyl serine or O-acetyl homoserine becomes limiting, and sulfide builds up and is converted to the volatile gas H 2 S, which then diffuses from the yeast cell into the wine (Vos & Gray, 1979). The conversion of H 2 S from sulfide is a pH-driven reaction and it is favored at the low pH of the wine; therefore, a high rate of H 2 S production can be observed in response to yeast nitrogen deficiency during wine fermentation (Jiranek et al, 1995a). Subsequently, many winemakers routinely add a source of nitrogen in the form of diammonium phosphate to the grape juice.…”

Identification of genes affecting glucose catabolism in nitrogen-limited fermentation

“…Fermentations of nitrogen-deficient media by such strains might therefore be expected to become nitrogen-depleted, even though fermentation should progress and complete ahead of the wild type. The usefulness of these strains as a means of effecting fermentation of nitrogen-deficient juices remains high, however, the potential for development of other problems, such as liberation of hydrogen sulfide [37], would need to be assessed under such conditions. As already described, two genes were isolated and deleted from a laboratory and a wine strain derivative to allow more detailed characterisation.…”

Free amino nitrogen concentration correlates to total yeast assimilable nitrogen concentration in apple juice

“…In wine grape fermentations, YAN deficiencies have been demonstrated to slow fermentation rates (often referred to as "sluggish fermentations") or to result in incomplete sugar utilization (often referred to as a "stuck fermentation") (Bisson, 1999;Blateyron & Sablayrolles, 2001;Ingledew & Kunkee, 1985). This is partly attributable to insufficient YAN concentrations resulting in lower yeast biomass (Martínez-Moreno, Morales, Gonzalez, Low YAN concentration also contributes to increased production of hydrogen sulfide, a compound widely associated with unpleasant aromas and decreased consumer acceptance (Jiranek, Langridge, & Henschke, 1995b;Ugliano, Kolouchova, & Henschke, 2011;Vos, Vos, & Gray, 1979). Low YAN concentration has also been associated with production of other undesirable compounds, such as higher alcohols, and with the lack of formation of positive flavor compounds, such as esters and volatile fatty acids (Bell & Henschke, 2005).…”