Rossana Sidari

Wine colour adsorption phenotype: an inheritable quantitative trait loci of yeasts

Aims:  In this work, a population of 88 descendants derived from three wine strains of Saccharomyces cerevisiae was tested for the enological trait ‘wine colour adsorption’ (WCA) to evaluate its inheritability.

Evolution during wine aging of colour and tannin differences induced by wine starters

The ability of threeSaccharomyces cerevisiae strains, with different colour adsorption aptitude, to induce and maintain colour differences in wines obtained from the Calabrian Gaglioppo and Magliocco black grape varieties was studied during one year of aging. The evolution of wine tannin content was also considered. Total polyphenols, colour parameters and total tannin values exhibited, both for Gaglioppo and Magliocco wines, significant (P < 0.05) or highly significant (P < 0.01) differences among strains. It is interesting to note that yeasts appear to exhibit a different adsorption aptitude for anthocyanins and tannins. The strain that gave wine with high values for the colour parameters was not the same as the one that produced wine with high values of tannins. The obtained results suggest that the choice of yeast strain in winemaking affects, in a significant way, the phenolic composition of wines with direct consequences on their colour and tannin content. Moreover, the interaction between grape cultivar and yeast is close and important, because grape variety, due to its phenolic composition, modulates yeast strain adsorption activity.

Wild Saccharomyces cerevisiae strains display biofilm-like morphology in contact with polyphenols from grapes and wine

Polyphenols are a major component of wine grapes, and contribute to color and flavor, but their influence upon yeast growth forms has not been investigated. In this work we have studied the effect of polyphenols on the ability of natural isolates of wine-related Saccharomyces cerevisiae strains to form biofilms attaching to plastic surfaces, to grow as mat colonies, to invade media, and to display filamentous growth. The use of carbon- and nitrogen-rich or deficient media simulated grape juice fermentation conditions. The addition of wine polyphenols to these media affected biofilm formation, and cells exhibited a wide variety of invasiveness and mat formation ability with associated different growth and footprint patterns. Microscopic observation revealed that some strains switched to filamentous phenotypes which were able to invade media. The wide range of phenotypic expression observed could have a role in selection of strains suitable for inoculated wine fermentations and may explain the persistence of yeast strains in vineyard and winery environments.

Methods for Detecting Enterohaemorrhagic Escherichia Coli in Food

Enterohaemorrhagic Escherichia coli (EHEC) serogroup determines worldwide foodborne illnesses and remains one of the major concerns for the population and for the food industry. These strains, indeed, determine gastrointestinal disease varying from diarrhoea to haemorrhagic colitis, haemolytic uraemic syndrome, and thrombotic thrombocytopaenic purpura. Classic detection methods are based on specific enrichment, often coupled with immunomagnetic separation system, specific media, and different immunoassays. Molecular detection methods, based on DNA probes and PCR, are used to detect the virulence genes and the specific genes associated to the serogroups. Most of the research is focused on E. coli O157:H7, for which the validated standard method ISO 16654/2001 is applied. Regarding the methods used for E. coli non-O157, it is interesting to highlight the existence of the draft of the European Committee for Standardization, which in the near future might constitute the first standard for non-O157 EHEC. This paper describes the state-of-the-art laboratory methods and commercial kits for detecting strains of EHEC vehiculated with foods.

Depuration in aerated ponds of citrus processing wastewater with a high concentration of essential oils

Citrus processing wastewater was treated in aerated pilot plants in order to evaluate the following: (a) energy efficiency under different air flow rates and times; and (b) limits of spontaneous microflora in adapting to essential oils. In comparison to permanent air flow, night aeration for 12 hours determined an increase of up to 12% of the monthly removal rate of chemical oxygen demand (COD) and a consequent reduction by 10% of energy consumptions per unit of COD removed from 0.63 to 0.57 kWh/kgCOD. Lowering night aeration from 14 to 7 l/m3/h reduced by only 10% the removal rate of COD; the energy consumption per unit of COD removed (0.32 kWh/kgCOD) was consequently reduced by more than 40%. Dissolved oxygen was maintained at very low level, rarely exceeding 0.2 ppm, with no bad smell. The consequent high oxygen deficit of 98–99% of saturation induced high oxygen transfer efficiency. The microbial population was characterized mainly by aerobic bacteria; only 5–8% of bacteria were strictly anaerobic. In the deep tank layer under the air diffuser a small amount of sludge settled (0.03–0.04 kg of dry matter per kg of COD removed), containing only 3% of total organic matter detected at the end of the depuration process. The fact that the concentration of essential oils could be progressively increased up to 1400 ppm without noticeably slowing down the biological processes demonstrated the remarkable microbial adaptation.

Selected yeasts to enhance phenolic content and quality in red wine from low pigmented grapes

The aim of this work was to enhance—by yeast activity—the quality of red wine produced from black grapes of the Calabrian Gaglioppo variety, used as a model for grapes with reduced synthesis of anthocyanins. Six selected strains of Saccharomyces cerevisiae were used to control winemaking trials. Among the wines, there are significant differences, due to the wine starter used. The following technological parameters were significantly different from strain to strain: total acidity, alcoholic degree, tartaric, malic, lactic, and acetic acid, and free and total SO2; moreover, the following phenolic parameters were significantly different from strain to strain: A420, A520, A620, colour intensity, colour hue, Folin–Ciocalteu index, percentage of DPPH inactivation, total anthocyanins, total polyphenols (A280), total tannins, delphinidin-3-glucoside, cyanidin-3-glucoside, petunidin-3-glucoside, peonidin-3-glucoside, and malvidin-3-glucoside. From a sensory standpoint, significant differences were observed among wine samples during a short bottle aging. Data validate the main role that wine yeast selection plays in enhancing the quality of red wine from low pigmented grape.

Nutrient depletion modifies cell wall adsorption activity of wine yeast

Yeast cell wall is a structure that helps yeasts to manage and respond to many environmental stresses. The mannosylphosphorylation is a modification in response to stress that provides the cell wall with negative charges able to bind compounds present in the environment. Phenotypes related to the cell wall modification such as the filamentous growth in Saccharomyces cerevisiae are affected by nutrient depletion. The present work aimed at describing the effect of carbon and/or nitrogen limitation on the aptitude of S. cerevisiae strains to bind coloured polyphenols. Carbon- and nitrogen-rich or deficient media supplemented with grape polyphenols were used to simulate different grape juice conditions—early, mid, ‘adjusted’ for nitrogen, and late fermentations. In early fermentation condition, the R+G+B values range from 106 (high adsorption, strain Sc1128) to 192 (low adsorption, strain Σ1278b), in mid-fermentation the values range from 111 (high adsorption, strain Sc1321) to 258 (low adsorption, strain Sc2306), in ‘adjusted’ for nitrogen conditions the values range from 105 (high adsorption, strain Sc1321) to 194 (low adsorption, strain Sc2306) while in late fermentation conditions the values range from 101 (high adsorption, strain Sc384) to 293 (low adsorption, strain Sc2306). The effect of nutrient availability is not univocal for all the strains and the different media tested modified the strains behaviour. In all the media the strains show significant differences. Results demonstrate that wine yeasts decrease/increase their parietal adsorption activity according to the nutrient availability. The wide range of strain variability observed could be useful in selecting wine starters.

Study of the inheritability of the yeast trait “interaction with natural antioxidant activity of red wine” in four generations of Saccharomyces cerevisiae and its enhancing by spore clone selection and hybridization

The aim of this research was to study the inheritability of the yeast trait “interaction with natural antioxidant activity of red wine” and to enhance this trait by spore clone selection and hybridization of wine yeasts. This research was carried out using as a model three strains of Saccharomyces cerevisiae (wild types), 24 derived spore clones, three hybrids obtained crossing the derived spore clones and 34 spore clones derived from the three hybrids. Using these yeast strains, micro-winemaking trials were carried out utilizing grape must of the black varieties, Cabernet and Magliocco: the wines showed significant differences, due to the wine starter used, both for Folin–Ciocalteu’s index and for DPPH analysis. Data validate the main role that wine yeast selection plays to enhance red wine content in antioxidant compounds. Data also demonstrate that using spore clone selection and hybridization, it is possible to significantly enhance the natural antioxidant activity of wines, so improving their quality and stability.

A simple and rapid method for separation and isolation of marine algal species from naturally evolved populations

ABSTRACT To improve the study of mixed microalgal populations, three naturally evolved marine microalgal cultures were subjected to a light crushing mechanical treatment using a silicon spatula coupled with zymolyase treatment at four concentrations: 5, 10, 20 and 25 U/ml, for 15, 30, 45 and 60 min before being observed under a microscope. The enzyme concentration of 20 U/ml after 45 min reduces the size of macroscopic microalgal aggregates and improves the microscopic observation of the different microalgal species comprising the population. There was no improvement using the higher enzyme concentration. This paper proposes a new approach to the study of naturally evolved microalgal populations which is useful for distinguishing the morphology of the different species present in the population and allowing for the identification by classical keys, and also to obtain a pure culture from an inoculum of mixed species by using a micromanipulator for cell counting.

Viability of commercial wine yeasts during freezer storage in glycerol-based media.

Glycerol-based medium (BM) with and without the addition of 1 g/L ascorbic acid (Asc) and/or 100 mg/L (±)-catechin (Cat) was tested for the storage of three commercial wine yeasts at −20 °C. The medium supplemented with Asc was also used to store 706 strains to verify the maintenance of the liquid state. A decline in survival throughout the storage period was observed. The media containing Asc maintained viability better than the other three. The BM caused a loss of viability of 7 orders for one strain and of 6 orders for the other two. All three strains exhibited a loss of viability of 4 orders when stored in BM+Asc. Two strains decreased viability by 5 orders while one strain by 4 orders, when stored in BM+Cat. Two strains decreased viability by 6 orders while one strain by 5 orders, when stored in BM+Asc+Cat. Regarding the physical state of the medium tested on 706 yeast strains, three cases were observed: completely liquid (56.5 %), liquid with only the upper part frozen (40.4 %) without involving the yeast biomass settled at the bottom, and completely frozen (3.12 %). It is practicable to prepare a BM that remains liquid at −20 °C enhancing yeast viability when Asc is added as cryoprotectant.