I Lieviti in enologia

L'articolo, dopo un breve excursus storico, presenta l'utilizzo dei lieviti per la produzione dei vini, descrivendo i processi di fermentazione

Produzione di anidride solforosa da parte dei lieviti nel corso della fermentazione alcolica

SO2 production by yeast during alcoholic fermentation. Determinations were made of SO2 produced during must fermentation by 29 strains of Saccharomyces cerevisiae. After 2 days of fermentation, only 4 reached a 50 - 70 mg/l SO2 production; on the 4th day only 2; and on the 7th day only 1. All proved to belong to the low SO2 producer category

L'Invecchiamento biologico del Cannonau di Oliena

Accelerated ageing trials were carried out on « Cannonau di Oliena» under production conditions. Yeast «Flor» strains of the species Saccharomyces prostoserdovii were used as ageing agents. Results showed that wines produced using these yeasts were superior to those produced normally specially when Sacch. Prostoserdovii was added to the musts as «pied de cuve», thus reducing maturing times considerably

Prove di tossicità da S C P nell'ovino: nota 7.: rilievi sul comportamento della microflora ruminale

During chronic and acute toxicity trials on ovines, fed with an alkanegrown SCP, observations were also made on the behaviour of the ruminaI microflora. The different diet supplied to both experimental and control groups of animals, did not seem to have affected the total count and the total numbers of Starch digesters, Cellulose digesters and Proteolytic bacteria. During the chronic toxicity test, 194 strains of yeast were identified belonging to the following species: Candida boidinii, Candida slooffii, Candida tropicalis, Cryptococcus albidus var. albidus, Cryptococcus albidus var. diffluens, Cryptococcus dimennae, Cryptococcus kuetzingii, Rhodotorula glutinis var. dairenensis, Rhodotorula glutinis var. glutinis, Rhodotorula graminis, Rhodotorula pallida, Rhodotorula rubra, Torulopsis versatilis, Trichosporon cutaneum, Debaryomyces hansenii, Debaryomyces phaffi, Debaryomyces tamarii, Saccharomyces vafer . The yeast species that were isolated were not so different from those discovered by other authors in similar researches, carried cut, however, in animals fed differently. A marked diffusion of the genus Debaryomyces was to be observed, together with a notable lipolytic and caseinolytic activity in most of the strains isolated. At first the introduction of SCP in the diet at concentrations of 15% and 40% seemed to favour the multiplication of the yeasts in the rumen fluid, but their numbers diminished towards the end of both test in all groups under observation. The type of protein given, does not seem to have affected even the species of yeasts that are usually lodged in the animals rumen. Screening of the isolated strains is now in course for the SCP production on glucose, lactose, xylose, starch, fruit and citrus pulps, and other conventional substrata

I Lieviti del tubo digerente dell'<i>Apis inellifica ligustica</i> Spinola

The results of microbiological surveis of apis mellifica lingustica Spinola intestinal tacts are givenhere. From 100 samples 54 yeast strains were isolated. The yeast specie identified are: H. anomala var. schneggii, C. guilliermondii var. guilliermondii, T. apicola, T. candida, T. glabrata, T. haemulonii. The yeast species isolated were not so different from those discovered by other authors in similar environments

Aerobic and anaerobic spore-forming bacteria in Sardinian honey.

Apart from an ubiquitous microflora, this investigation into 52 samples of honey revealed some undesirable spore-forming bacteria, Bacillus alvei and B. larvae which are bee pathogens. Bacillus cereus can cause spoilage and food poisoning. It is, therefore, considered essential that every country includes microbiological standards in its Food Safety Regulations for honey, so that the consumer is guaranteed as to the wholesomeness as well as the quality of the product

Diversity of salt response among yeasts

Forty-two yeast strains from 27 species belonging to seven genera, selected for their ability to grow in 10% NaCl, have been analysed for their resistance to salt concentrations up to 5 M, by calculating the Minimum Inhibitory Concentrations (MIC). Using eight different NaCl concentrations from 0 to 5M, results show that halotolerance (MIC) ranges from 1.7 to 3.8 M NaCl, with an avera ge around 2.5 M and confirm that the most halotolerant strains belong to the speciesDebaryomyces hansenii. Since a real halophily could not be found in these isolates, and is generally questioned to be present among the yeast, the effects of NaCl has been measured as salt enhancement effect on growth (MSE), which is defined as the rate between the growth at a given NaCl concentration and theowth in the medium without addition of salt. The implications of these findings in food microbial ecology and technology are discussed

Occurrence of wine yeasts on grapes subjected to different pesticide treatments

As a contribution to the study and preservation of indigenous wine yeast populations, we initiated a programme of isolation and characterization of yeast strains from grapes of the Italian region of Marche. During the 1996 vintage, grape samples were collected from three groups of vineyards differing in the pesticide treatments given. Of the 279 yeasts isolated, thirty-nine were assigned to the species Saccharomyces cerevisiae. The majority of the isolates and all thirty-nine S. cerevisiae came from vineyards which had not been treated with systemic pesticides, indicating that these pesticides may exert a negative effect on the biodiversity of the grape microflora, and in particular on the occurrence of S. cerevisiae on grapes. The thirty-nine S. cerevisiae isolated were subjected to microfermentation mals, in which ten of them showed promising fermentative capabilities

Incidence de la température et du pH sur la production d'acide malique par <em>Saccharomyces cerevisiae</em>

Dans ce travail on étudie la formation d'acide malique par deux souches différentes de Saccharomyces cerevisiae cultivées sur substrat synthétique en conditions anaérobies, en fonction de différentes valeurs de température et pH. Les deux souches produisent environ 1 g/I d'acide malique à 25°C et à pH 4,2. L'opportunité d'utiliser ces souches pour la fermentation des moûts des régions chaudes est discutée

Vanadate and copper induce overlapping oxidative stress responses in the vanadate-tolerant yeast <i>Hansenula polymorpha</i>

The mechanisms by which vanadate exerts a toxic effect on living organisms are not completely understood. This is principally due to the variety of intracellular targets of the metal and to the changes in the chemical form and oxidation states that vanadate can undergo, both in the external environment and intracellularly. In order to further elucidate the reasons for vanadate toxicity, and assuming that common detoxification mechanisms can be evoked by a general heavy metal response, we have compared some aspects of the cellular responses to vanadate and copper in the yeast Hansenula polymorpha. By means of 2D electrophoresis we show the existence of common determinants in the responses to vanadate- and copper-induced stresses. Moreover, we demonstrate that both metals induce significant increases in antioxidant enzyme levels, and that there are significant overlaps in the heavy metal and oxidative stress responses. Interestingly, vanadate induces an increase in catalase activity that is much higher than that seen with copper and, unlike copper, does not cause lipid peroxidation of cellular membranes. This suggests that H. polymorpha cells activate a further specific detoxification pathway against vanadate-induced oxidative insults