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The aim of this study was to evaluate the vitality and viability of the probiotic yeast Saccharomyces boulardii after freezing/thawing and the physiological preconditioning effect on these properties. The results indicate that the specific growth rate (0.3/h(-1)) and biomass (2-3 x10(8)cells/ml) of S. boulardii obtained in flasks shaken at 28 degrees C and at 37 degrees C were similar. Batch cultures of the yeast in bioreactors using glucose or sugar-cane molasses as carbon sources, reached yields of 0.28 g biomass/g sugar consumed, after 10h incubation at 28 degrees C; the same results were obtained in fed batch fermentations. On the other hand, in batch cultures, the vitality of cells recovered during the exponential growth phase was greater than the vitality of cells from the stationary phase of growth. Vitality of cells from fed-batch fermentations was similar to that of stationary growing cells from batch fermentations. Survival to freezing at -20 degrees C and subsequent thawing of cells from batch cultures was 0.31% for cells in exponential phase of growth and 11.5% for cells in stationary phase. Pre-treatment of this yeast in media with water activity (a(w)) 0.98 increased the survival to freezing of S. boulardii cells stored at -20 degrees C for 2 months by 10 fold. Exposure of the yeast to media of reduced a(w) and/or freezing/thawing process negatively affected cell vitality. It was concluded that stress conditions studied herein decrease vitality of S. boulardii. Besides, the yeast strain studied presented good tolerance to bile salts even at low pH values.

The white wine Chacolía de Vizcaya/Bizkaiko Txakolina is characteristic from The Basque Country region and regulated under Appellation Contrôlée standards (BOPV 14/6/94). The objective of this study was the identification and selection of autochthonous yeast strains, to improve the conditions used to maintain the typical characteristics of this region wines. Yeasts identified as Saccharomyces bayanus isolated around these fields from 1996 to 1998, were subjected to a selective procedure based on enological characteristics and fermentative behaviour. Three of the selected strains were used to inoculate, at winery scale, two grape juice varieties accepted by the Appellation Contrôlée (Hondarrabi Zuri and Folle Blanche). The inoculated strains on the respective vinifications was followed by restriction fragment length polymorphism of mitochondrial DNA (REAmt) method with AluI enzyme, due to their specificity, short outcome, and technological simplicity compared with other molecular typing methods such as: chromosomal karyotyping analyzed by pulsed field gel electrophoresis, Random Amplified Polymorphic DNA-PCR (RAPD-PCR) and restriction fragment length polymorphism using the infrequently cutting enzyme SfiI (REA infrequent). This study demonstrated that strains with different phenotypic traits could show indistinguishable restriction patterns with REAmt, but could be discriminated using other typing methods such as RAPD-PCR, which although showing low reproducibility could be used as complementary to REAmt. Our results demonstrate that in spite of using autochthonous selected strains, the inoculation of musts with a particular strain do not guarantee its predominance and driving fermentation features. Of all yeast strains studied, strain no. 2 showed the best results in sensory testing and at the implantation process. Therefore, it could be used with commercial purposes for the production of Chacolí de Vizcaya/Bizkaiko Txakolina, especially when using musts from Folle Blanche.

Candida tropicalis was identified as the etiologic agent of a severe contamination detected on an industrial fodder yeast production at the Cuban eastern region. After a detailed diagnostic task on raw material carried out on different factory sections, protocols to identify the contamination source and to isolate the microorganism were proposed. The identification was by comparison of the internal transcribed spacers ITS1 and ITS4 from 5.8S ribosomal DNA nucleotide sequences. In parallel, propagation of production strain, Candida utilis NRRL Y-660, at lab scale (2.5 l) was performed. Similar results to those observed in the factory concerning to its kinetic behavior in aerobic propagation with contaminated molasses, were detected at this level. The identification and primary kinetic characterization led to the implementation of sanitary and technological measures to bring production at its normal operational conditions as well as the application of prophylactic surveillance methodologies to avoid future contaminations.

Rising activity determined as CO2 production of two commercial strains of Saccharomyces cerevisiae could be increased mainly in sweet bread doughs by introducing a "starvation/pulse feeding" schedule of sugar cane molasses during a fed-batch propagation. Such increase was strain dependent. Except for the trehalose intracellular level, other traits related to the yeast industrial performance were unaffected. Applicability of method for baker's yeast industrial production is discussed.

The present work studies the production of pectinases using a strain of Penicillium simplicissimum A3263 and considering the influence of adding Amaranthus cruentus seed meal in a selected medium. We also considered the influence of aeration on enzyme production. Research was oriented towards the production of pectin lyase, the enzyme having the highest commercial value. This work was carried out in Erlenmeyer flasks in rotary shaker to select the medium and in a mechanically stirred fermentor to study aeration. The microorganism was developed as pellets of 1 mm diameter. Enzyme levels were of the order of 8216.21 pectin lyase units and 167.57 polygalacturonase units per gram of fungal biomass, respectively, using a medium containing 40 g/l of amaranth seed meal. As for the influence of aeration, it was determined that the higher values were obtained at 750 rpm corresponding to an oxygen absorption rate of 2691 ml O2/lh for an air flow of 1 l/l.min. The results obtained are considered very important in view of the fact that they exceeded in 550% those obtained by other authors.

The degradation potential of Phanerochaete sordida, Trametes trogii, Coprinus truncorum and Paecilomyces sp. upon yard wastes was evaluated. The species had been inoculated individually or in pairs formed by P. sordida and Paecilomyces sp., T. trogii and Paecilomyces sp., and C. truncorum and Paecilomyces sp. The highest level of endoxilanase activity was produced by P. sordida growing alone, during day 21 (1.09 U/g of dry material), but in P. sordida and Paecilomyces sp. cultures, the detected activity did not overcome 0.27 U/g of dry material during the whole experiment. T. trogii showed maximum activity on day 14 (0.78 U/g of dry material), but in T. trogii and Paecilomyces sp. cultures, the values increased until day 21 (1.07 U/g of dry material). P. sordida endocellulase activity reached its maximum on day 28 (0.08 U/g of dry material), but in P. sordida and Paecilomyces sp. cultures, this activity increased during the whole experiment (0.04 U/g of dry material). The major weight loss was found in P. sordida (27.6%). The possible beneficial effect of co-culture in yard wastes biodegradation is discussed.

Great amounts of agroindustrial wastes rich in polysaccharides, such as pectic substances, are produced worldwide. Some of these wastes are used for the production of pectin. Currently, pectin is extracted at industrial scale by physicochemical means, but lately new biotechnological alternatives have been developed. In this review, the principal characteristics of pectic substances and pectic enzymes are described. The traditional physicochemical method for the pectin extraction is described and the new biotechnological (microbial and enzymatic) methods for pectin extraction are discussed and commented as well.

Xanthan production from Xanthomonas campestris was studied by a mechanically shaken fermentor. Influence of glucose concentration, aeration of culture media, rheology of broths and pH control was evaluated. Different aeration conditions based on variation of stirring rates were assayed. Substrate concentration was determined according to the Miller method, and polymer production was performed by the Cadmus method. The higher xanthan levels (i.e. 2.3%) were obtained at 750 rpm, with 1 v/v. min. In such conditions, viscosity ranges about 7000 cPoise and a low level of dissolved oxygen were detected in the culture medium. Xanthan production was influenced by the glucose concentration and the presence of amaranth within the culture medium. In the processes wherein an automatic control of pH was performed, the polymer concentration did not increase regarding to processes involving regular pH evolution.

Although modern production techniques keep microorganism levels very low in both finished beer and in beer process, there is still concern about early detection and prevention of accidental proliferation of brewery spoilage microorganisms. Traditional microbiological techniques can detect such low levels, but no results are obtained before 3 to 6 days of incubation. That is why rapid or even "instant" techniques are a main objective of research in the brewing industry. In this work, some instrumental techniques (DEFT, MMCF, impedance, pH, immunology and PCR based techniques, bioluminometry) are described and considered from the point of view of their regular use in brewery Microbiological Quality Assurance Laboratories. Real case experiences are brought forward.

Sherry wine presents, during all its wine-making and aging process, a great diversity of yeast and bacteria, as well as in the wine itself; its particular wine-making system, with traditional and legal additions to correct the acidity and to get a final alcoholic content of 15%, originates a selection of accompanying microorganisms. Species of the genera Kloeckera, Candida, Saccharomyces, Pichia, Hansenula and Saccharomycodes, have been isolated during the fermentation process in different proportions. This fact confirms that, besides S. cerevisiae, strains of S. chevalieri and S. fermentati have an important role in the fermentative process, and that the film-forming Saccharomyces have great activity in the fermentation. The biological aging of the Sherry wine, carried out by S. cheresiensis, S. beticus, S. feduchii and S. rouxii, has been studied in "finos" and "manzanillas". Different species and percentages in both wines have been described.

The production of cava (sparkling wine produced according to the rules of the cava appellation, in i.e. Catalonia and La Rioja, Spain) involves several microbial factors such as growth, fermentation and death of yeast cells (Saccharomyces cerevisiae). Ethanol tolerance, flocculation and aroma characteristics of yeast cells as major selection factors for the production of cava are discussed in this review.

Population dynamics of natural and inoculated industrial wine fermentations have been studied by using a simple molecular biology technique based on mitochondrial DNA restriction analysis profile. The predominance of the inoculated strain in the inoculated fermentations is obvious. A genetic transformation system has been developed for an industrial wine yeast strain named T73. By using this technique, different fungal hydrolases in this industrial strain have been expressed. Problems and benefits of the application of recombinant DNA techniques in wine yeast strains are also discussed here.

Microbial flow tracers are presently limited to a strain of Bacillus globigii and a few highly specific bacteriophages. Bacillus subtilis 65-8 produces a black pigment as part of the primary metabolism under minimal nutritional conditions, with glucose as the sole carbon and energy source. This work shows that Bacillus subtilis 65-8 spores are thermostable (55 degrees C during 150 días), halotolerant (they germinate and grow in an enriched medium with up to 12% NaCl), persistent in a system of sand-soil and sewage, even in the presence of added commercial oil derivatives (kerosene, leaded gasoline and unleaded diesel), they are capable to move through porous systems even as the liquids, viscous as they may be, move through. Moreover, spores were resistant to the presence of autochtonous microorganisms in sewage, where we did not detect any other organism with differential characteristics like our strain (black pigment production in minimal medium) which could interfere with the identification of our biological flow tracer. The characteristics of Bacillus subtilis 65-8 make it a suitable biological flow tracer.

The production of xantano from Xanthomonas campestris B-1459 was analyzed. The experiments were performed in shaked flasks at 250 rpm and 2.5 cm eccentricity. Using a base modified medium it was possible to achieve xantano concentration of 35 g/l in 72 h of process. The modified medium contained glucose as carbon source, and yeast extract, meat peptone, malt extract and amaranth meal as growth factors and nitrogen sources, in a KH2PO4/K2HPO4 buffer.

Food industries use a great variety of enzymes as additives. The main percentage of them are produced by species of filamentous fungi. In this review we present the strategies to purify and overproduce this kind of enzymes using recombinant DNA techniques.

The effect of different parameters on the adsorption of metal ions by Rhizopus oligosporus has been studied. The uranium sorption by dried biomass was rapid, reaching in 5 min around 95.% of the binding capacity. The uranium-binding capacity of the culture showed an inverse relation to the growth kinetic. The relationship between sorption and equilibrium concentration was similar to an adsorption isotherm. Using the Langmuir model, a maximum sorption capacity of 0.52 mmoles uranium/g dry biomass and an affinity constant of 101 l/mmol uranium at pH 4.15 were determined. The best capacity of the biomass to bind ions (UO2(2+), Cu2+, Cd2+ and Zn2+) was best at pH 4.5-5.5. By using hydrochloric acid as eluant a 18% uranium removal of the biomass-bound ions was obtained at pH 1.0. The presence of other cations inhibited uranium-binding in the following order: Cu2+ > Cd2+ > Zn2+ > Mg2+ > Ca2+.

The efficiency of xanthan production through surface processes was evaluated. The best porous material was selected first. Thereafter, a comparative study was performed using submerged agitated process vs other without agitation but containing the selected porous material. The culture medium used was white potatoes infusion, buffered with K2HPO4 and supplemented with glucose in diverse concentrations. Besides, to evaluate a different type of surface process, three vegetables were valued: Ipomaea batatus, Solanum tuberosum and Daucus carota, with an without glucose supplement. Larger xanthan production was achieved with immobilization of X. campestris vs the conventional method, when the liquid culture medium was used. The highest yield was obtained when the white potatoes infusion was supplemented with glucose 2.5%, yielding a conversion of this saccharide to xanthan up to 58%. When X. campestris was cultured on fragmented vegetables, the highest xanthan gum yield (5.6g) was obtained with Solanum tuberosum supplemented with glucose. This yield indicators that X. campestris used the glucose added as well as the constitutive polysaccharide of this vegetable.

In this paper the potential activity of Bacillus thuringiensis as insecticide is reviewed. It is presented recent knowledges of its metabolism, production system and the rinetic constants already reported finally the possibilities for production in batches or continuous culture is discussed in order to improve the productivity and economical aspects.