Incidence of osmophilic yeasts and Zygosaccharomyces rouxii during the production of concentrate grape juices.

Zygosaccharomyces rouxii is the main spoilage yeast of grape juice concentrates. Detection and identification of Z. rouxii during the production of grape juice concentrate is critical to prevent spoilage in the final product. In this work, three grape juice concentrate processing plants were assessed by identifying osmophilic yeasts in juices and surfaces during different stages of a complete production line. Subsequently, molecular typing of Z. rouxii isolates was done to determine the strain distribution of this spoilage yeast. Osmotolerant yeast species, other than Z. rouxii, were mainly recovered from processing plant environments. Z. rouxii was only isolated from surface samples with grape juice remains. Z. rouxii was largely isolated from grape juice samples with some degree of concentration. Storage of grape juice pre-concentrate and concentrate allowed an increase in the Z. rouxii population. A widely distributed dominant molecular Z. rouxii pattern was found in samples from all three processing plants, suggesting resident microbes inside the plant.

Novel yeast isolated from broilers' feedstuff, gut and faeces as aflatoxin B1 adsorbents.

AIMS: To isolate and characterize native yeast strains from broilers' environment as feedstuff, faeces and gut, and to evaluate their binding capacity for aflatoxin B1 (AFB1 ). METHODS AND RESULTS: A total of nine yeast strains were isolated: three from feedstuff identified as Pichia kudriavzevii (2) and Clavispora lusitaniae (1), two from gut identified as Candida tropicalis and four from faeces identified as Cl. lusitaniae (3) and Cyberlindnera fabianii (1). AFB1 binding percentages varied among yeast strains and with AFB1 concentrations. To carry out adsorption studies, one strain from each genus and each origin was selected as follows: Cl. lusitaniae and P. kudriavzevii from feedstuff, Cl. lusitaniae and Cy. fabianii from faeces and Ca. tropicalis from gut. The most appropriate concentrations for cells and toxin were 107 cells per ml and 100 ng ml-1 of AFB1 respectively. All the tested yeast strains showed similar adsorption capacities independently of the origin. The adsorption isotherm studies in all yeasts assayed showed behaviour of L type or Langmuir and a varied affinity for the toxin. The stability of the AFB1 -yeast complex demonstrated the irreversibility of the binding process. CONCLUSION: Yeast strains tested in this study constitute potential AFB1 adsorbents and they possess the advantage to be native from the avian environment. SIGNIFICANCE AND IMPACT OF THE STUDY: This study makes a contribution to using native yeasts from broilers' environment for controlling chronic aflatoxicosis in avian production.

Effects of pH and sugar concentration in Zygosaccharomyces rouxii growth and time for spoilage in concentrated grape juice at isothermal and non-isothermal conditions.

The effect of pH (1.7-3.2) and sugar concentration (64-68 °Brix) on the growth of Zygosaccharomyces rouxii MC9 using response surface methodology was studied. Experiments were carried out in concentrated grape juice inoculated with Z. rouxii at isothermal conditions (23 °C) for 60 days. pH was the variable with the highest effect on growth parameters (potential maximum growth rate and lag phase duration), although the effect of sugar concentration were also significant. In a second experiment, the time for spoilage by this microorganism in concentrated grape juice was evaluated at isothermal (23 °C) and non-isothermal conditions, in an effort to reproduce standard storage and overseas shipping temperature conditions, respectively. Results show that pH was again the environmental factor with the highest impact on delaying the spoilage of the product. Thereby, a pH value below 2.0 was enough to increase the shelf life of the product for more than 60 days in both isothermal and non-isothermal conditions. The information obtained in the present work could be used by producers and buyers to predict the growth and time for spoilage of Z. rouxii in concentrated grape juice.

In situ detection of apoptotic cells by TUNEL in the gill epithelium of the developing brown trout (Salmo trutta).

Apoptosis is a form of naturally occurring cell death during development and it is characterised by extensive DNA fragmentation. Apoptosis is easily detected in the gill epithelium of brown trout embryos in ultrathin sections (Rojo et al. 1997). Here we provide the first biochemical evidence for apoptosis in the gill epithelium of brown trout embryos, using in situ end-labelling of DNA breaks (Gavrieli et al. 1992). Embryos at d 57 of development as well as those at hatching, were processed to analyse the distribution of apoptotic cells in the gills. The extent of apoptosis revealed by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labelling method technique is considerably greater than apoptosis detected by nuclear morphology. This method revealed that apoptosis was frequent at hatching, although it was also present during embryonic development. The presence and distribution of stained nuclei were different depending on the developmental stage. In embryos of 57 d, apoptotic flattened nuclei were dispersed in the gill epithelium, whereas at hatching, they were mainly grouped in the tips of the filaments and in the gill arches. TUNEL also revealed a distinct pattern of nuclear staining: at hatching, the intense staining covered the entire cell, but in embryos it was restricted to the nucleus. These results show the functional relevance of apoptosis at hatching, when apoptosis seems to be the unique process by which cell numbers in the gill epithelium are adjusted, in order to prepare for the new extrinsic conditions affecting the free-living life of alevins.

A histochemical study of the distribution of lectin binding sites in the developing branchial area of the trout Salmo trutta.

A histochemical study of the branchial area of brown trout embryos from 35 to 71 d of incubation is reported. A battery of 6 different horseradish peroxidase-labelled lectins, the PAS reaction and Alcian blue staining were used to study the distribution of carbohydrate residues in glycoconjugates along the pharyngeal and branchial epithelia. Con A and WGA reacted at every site of the branchial region thus showing the ubiquitous presence of alpha-D-mannose and N-acetyl-D-glucosamine. WGA, DBA and SBA were good markers for the hatching gland cells (HGCs) and mucous cells. Other lectins, such as PNA and UEA I, reacted only for a short time at some sites during the considered period of incubation. From 35 d until posthatching stages, a manifest strong reaction was noted both in the dorsal epithelium of branchial arches and the HGCs as shown by SBA reactivity. This may be significant with regard to the controversial origin of HGCs, which is thought to be endodermal.