Rapid identification and differentiation of Saccharomyces cerevisiae, Saccharomyces bayanus and their hybrids by multiplex PCR

AIMS: To develop a multiplex PCR assay for the specific identification and differentiation of Saccharomyces cerevisiae, S. bayanus and their hybrids. METHODS AND RESULTS: Two sets of primers with sequences complementary to the region YBR033w were used. A single amplicon of 1710 bp or 329 bp was obtained with species S. cerevisiae and S. bayanus, respectively, while the presence of both bands was observed in S. pastorianus because of its hybrid nature. Both amplification products were also obtained after amplification from DNA of several laboratory S. cerevisiae x S. bayanus hybrid strains. CONCLUSIONS: Multiplex PCR was optimized for the rapid and reliable identification of S. cerevisiae, S. bayanus and their hybrids. SIGNIFICANCE AND IMPACT OF THE STUDY: The procedure may be used for routine detection of the most common Saccharomyces sensu stricto yeasts involved in industrial fermentation processes, overcoming the problems of conventional techniques.     

Use of Yarrowia lipolytica strains for the treatment of olive mill wastewater

The principal aim of this research was to evaluate the ability of different Yarrowia lipolytica strains, having different origin, to grow in olive mill wastewater (OMW) and reduce its COD level. All the strains were able to grow in undiluted OMW; the comparison between the data obtained in a semi-synthetic medium and in OMW suggests that lipases with different specificity can be produced in relation to the medium composition. Under the adopted conditions, the reduction of the OMW COD values varied from 1.47% and 41.22% of the initial value. Some strains determined a significant reduction of polyphenol content, while other ones caused its apparent increase. Moreover, some Y. lipolytica strains, isolated from chilled foods, produced the highest citric acid concentrations. These results evidenced that some Y. lipolytica strains are good candidates for the reduction of the pollution potential of OMW and for the production of enzymes and metabolites such as lipase and citric acid.     

Production of high levels of acetoin in Saccharomyces cerevisiae wine yeasts is a recessive trait

P. ROMANO, G. SUZZI, R. MORTIMER AND M. POLSINELLI. 1995. A genetic study of acetoin production was performed on wild wine yeast strains of Saccharomyces cerevisiae producing different amounts of the compound. By using differences found in these strains as source of genetic variability, it was found that crosses between high and low acetoin producing strains yielded the low level in the hybrids, indicating the low production as a dominant trait. Tetrad analysis showed that high vs low acetoin production is segregated as a single gene.     

Evolution of microbial populations and biogenic amine production in dry sausages produced in Southern Italy

AIMS: To evaluate the occurrence and evolution of biogenic amines during ripening of fermented sausages and their relationship with physico-chemical and microbiological properties of the product. METHODS AND RESULTS: Salsiccia and Soppressata were obtained from artisanal and industrial plants in Basilicata and pH, aW, microbial counts and biogenic amine content were measured. A high variability in amine content was observed. 2-Phenylethylamine and histamine were rarely found, while the tyramine, putrescine and cadaverine content increased during ripening. No correlation was found between individual biogenic amine content, microbial counts or physico-chemical parameters. CONCLUSION: Starter cultures did not necessarily prevent the production of biogenic amines whose total contents were usually higher in Soppressata, a product with a larger diameter and aW compared with Salsiccia. SIGNIFICANCE AND IMPACT OF THE STUDY: Literature findings on biogenic amine content and the evolution of microbial populations were confirmed. Normal ranges for amine content in Salsiccia and Soppressata are reported.     

Yeast microbiota associated with spontaneous sourdough fermentations in the production of traditional wheat sourdough breads of the Abruzzo region (Italy)

The aims of this study were to describe the yeast community of 20 sourdoughs collected from central Italy and to characterize the sourdoughs based on chemical properties. A polyphasic approach consisting of traditional culture-based tests (spore-forming and physiological tests) and molecular techniques (PCR-RFLP, RAPD-PCR, PCR-DGGE) and chemical analysis (total acidity, acids, and sugar contents), was utilized to describe the yeast population and to investigate the chemical composition of the doughs. PCR-RFLP analysis identified 85% of the isolates as Saccharomyces cerevisiae, with the other dominant species being Candida milleri (11%), Candida krusei (2.5%), and Torulaspora delbrueckii (1%). RAPD-PCR analysis, performed with primers M13 and LA1, highlighted intraspecific polymorphism among the S. cerevisiae strains. The diversity of the sourdoughs from the Abruzzo region is reflected in the chemical composition, yeast species, and strain polymorphism. Our approach using a combination of phenotypic and genotypic methods identified the yeast species in the 20 sourdough samples and provided a complete overview of the yeast populations found in sourdoughs from the Abruzzo region.     

Combination of multiplex PCR and PCR-denaturing gradient gel electrophoresis for monitoring common sourdough-associated Lactobacillus species

A combination of denaturing gradient gel electrophoresis (DGGE) and a previously described multiplex PCR approach was employed to detect sourdough lactobacilli. Primers specific for certain groups of Lactobacillus spp. were used to amplify fragments, which were analyzed by DGGE. DGGE profiles obtained from Lactobacillus type strains acted as standards to analyze lactobacilli from four regional Abruzzo (central Italy) sourdoughs.     

Quest for wine yeasts—An old story revisited

Numerous studies have described the yeast biota of grapes, and grape must in order to understand better the succession of yeasts during fermentation of wine. The origin of the wine yeasts has been rather controversial. By using more elaborate isolation methods, classical genetic analysis and electrophoretic karyotyping of monosporic clones, with this study, credible proof now exists that the vineyard is the primary source for the wine yeasts and that strains found on the grapes can be followed through the fermentation process.     

Studies on isobutyric acid-producing bacteira in silage

The statistical technique of response surface methodology was used to optimize the component concentrations of a Salmonella lysine medium for conductance responses on a Malthus microbial growth analyser. When the original and modified media were compared, conductance changes in pure cultures improved by 135 μS on average, and those from fopds both naturally contaminated and spiked with salmonellas by 220 μS. Salmonellas were successfully isolated from all assays after subculturing conductance broths onto xylose lysine desoxycholate agar and confirming by serology.     

Determination of 2,3-butanediol in high and low acetoin producers of Saccharomyces cerevisiae wine yeasts by automated multiple development (AMD)

P. ROMANO, G. SUZZI, V. BRANDOLINI, E. MENZIANI AND P. DOMIZIO. 1996. High performance thin layer chromatography with automated multiple development was used to determine 2,3-butanediol levels in wine produced by high and low acetoin-forming strains of Saccharomyces cerevisiae . An inverse correlation between acetoin and 2,3-butanediol content was found suggesting a leaky mutation in acetoin reductase of the low 2,3-butanediol producing strains.