Giovanni Antonio Farris

Antagonistic activity of Debaryomyces hansenii towards Clostridium tyrobutyricum and Cl. butyricum

A study of the inhibitory action of Debaryomyces hansenii (31 strains) on Clostridium tyrobutyricum (5 strains) and Cl. butyricum (2 strains) on laboratory media showed that Deb. hansenii inhibited the growth of these organisms, and that this effect was due not only to competition for nutrients but also to the production of both extra- and intracellular antimicrobial metabolites. The inhibitory effect varied with strain and occurred whether the yeasts were grown aerobically or under reduced O2 tension.

Fenhexamid residues in grapes and wine

The behaviour of the fungicide, fenhexamid, on grapes, and during wine-making, as well as its effect on the microflora of alcoholic and malolactic fermentation has been studied. After treatment, the residue on grapes decreased rapidly to one-third of the initial level after the first week, while it remained constant during the following two weeks. At harvest, in the wine obtained by vinification without skins, the fungicide residue decreased on average by 49%, while in the wine obtained by vinification with skins, the decrease was on average 62%. The presence of this fungicide on grapes and in the wine did not affect alcoholic and malolactic fermentation, nor did fermentation cause any degradation of the fungicide. A simple and rapid gas chromatograhic method (GC-NPD) for the determination of fenhexamid residues in grapes, must and wine is described.

A genetic study of natural flor strains of Saccharomyces cerevisiae isolated during biological ageing from Sardinian wines.

In this study, three flor strains of Saccharomyces cerevisiae were genetically characterized. They were isolated from biofilms on Sardinian sherry‐like wines produced at family‐run wineries where pure cultures of yeasts were not used. The study aimed to investigate the life cycle of these naturally‐occurring flor strains, using a genetic procedure supplemented by analysis of subsequent meiotic generations. A semi‐homothallic life cycle was found in three strains that could be helpful in a genetic improvement programme.

Probiotic preparation has the capacity to hydrolyze proteins responsible for wheat allergy

This study was aimed at showing the capacity of probiotic VSL#3 to hydrolyze wheat flour allergens. Hydrolysis was investigated either by the use of bakers yeast bread treated with digestive enzymes and VSL#3, an experimental design that mimicked the activity of probiotics during gut colonization, or by the use of VSL#3 as a starter for dough fermentation, an experimental design that mimicked the predigestion of wheat flour proteins during food processing. Albumins, globulins, and gliadins extracted from wheat flour and chemically acidified and started dough and total proteins extracted from breads were analyzed by immunoblotting with pooled sera from patients with an allergy to wheat. Hydrolysis of wheat flour proteins was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2DE). Mass spectrometry matrix-assisted laser desorption and ionization-time of flight was used to identify some immunoglobulin E (IgE)-binding proteins. As shown by immunoblotting with sera from allergic patients, several IgE-binding proteins persisted after treatment of bakers yeast bread by pepsin and pancreatin. The signal of all these IgE-binding proteins disappeared after further treatment by VSL#3. As shown by SDS-PAGE and related immunoblotting and 2DE analyses, when VSL#3 was used as a starter for bread making, it caused a marked degradation of wheat proteins, including some IgE-binding proteins such as the putative transcription factor APFI and wheat alpha-amylase inhibitors. Indeed, the IgE-binding profile of the bread manufactured by VSL#3 was largely different from that of bakers yeast bread. The IgE-binding proteins that persisted in the bread made with VSL#3 were completely degraded by pepsin and pancreatin.

Cellular fatty acid composition in film‐forming strains of two physiological races of Saccharomyces cerevisiae

Eleven strains belonging to two physiological races of Saccharomyces cerevisiae endowed with different abilities of forming films at air‐liquid interfaces were analysed in relation to cell fatty acid composition and cell hydrophobicity. Extensive individual differences in fatty acid profiles were observed both in the film and in the non‐film phase. The ability of the cells to form a floating film seems to be an implicit strain character associated with an elevated unsaturation level and a mean chain length of fatty acid residues, as well as cellular hydrophobicities higher than those shown by non‐film‐forming strains belonging to the same species.

A preliminary investigation into the effect of Saccharomyces cerevisiae on pesticide concentration during fermentation

SummaryThe experiment was set up to investigate whether degradation of residual pesticides during fermentation might be influenced by yeast action. Six products commonly used in viniculture were tested. After fermentation, 2 of the fungicides (Folpet and Metalaxyl) remained unaffected; the fungicide Vinclozolin and 2 of the insecticides (Carbaryl and Tetrachlorvinphos) suffered degradation not attributable to the yeast; the pyrethroid insecticide, Deltametrin, suffered complete degradation attributable to the yeast.

Malic acid production and consumption by selected of Saccharomyces cerevisiae under anaerobic and aerobic conditions

SummaryFermentation tests in clearly defined laboratory conditions were carried out with eight functionally selected strains of Saccharomyces cerevisiae. Analysis of the data showed that there were no significant differences in malic acid production between the strains when the acid was initially present. When it was initially absent, however, significant differences were observed two strains (Nos. 1141 and 1083) showing marked productive superiority. With malic acid as the sole C source, two strains (Nos. 1109 and 1141) showed less acid consumption.

Identification of killer factor in the yeast genus Metschnikowia

SummaryOut of 260Metschnikowia pulcherrima strains isolated from Sardinian grapes and musts, 6 proved to be killer yeasts. Maximal killing effect occurred between 3.6 and 5.2 pH, and with 48h or 72h cultures.

The effect of Saccharomyces cerevisiae on concentration of dicarboxymide and acylanilide fungicides and pyrethroid insecticides during fermentation

SummaryContinuing the investigation into possible yeast influence on ferment degradation of residual pesticides, two dicarboxymide antibotrytic fungicides (Iprodione and Procymidone), three acylanilide antiperonosporic fungicides (Benalaxyl, Furalaxyl and Ofurace) and two pyrethroid insecticides (Permethrin and Fenvalerate) were tested.Only the pyrethroids were degraded completely during fermentation.

Interactions during fermentation between pesticides and oenological yeasts producing H2S and SO2

The degradative action of two strains of Saccharomyces cerevisiae, producers of large quantities of H2S and SO2, on eight sulphur-containing insecticides (chlorpyrifos-methyl, dimethoate, fenitrothion, fenthion, malation, methidation, parathion, and quinalphos) was studied. Moreover, the influence of these compounds on the fermentative activity of the yeasts was investigated. The yeasts adsorbed and degraded the studied insecticides to various extents, but their fermentative activity was not affected. A moderate adsorbtion (approximately 10% of the residue) was observed for chlorpyrifos-methyl, fenitrothion, parathion, and quinalphos. When absorbed, the insecticides were also degraded by about 50%. The degraded pesticides belong to the thiophosphates, while the dithiophosphates showed higher stability. The two yeast strains showed analogous degradative actions.