Yeast assessment during alcoholic fermentation inoculated with a natural “pied de cuve” or a commercial yeast strain

Abstract

The present study has been carried out in an organic winery established in 2003 in the Denomination of Origin ''Sierras de Málaga'' (Southern Spain) region during the 2007 vintage. The aim of this work was to ascertain the yeast microflora present in the winery and during the vinifications and to obtain a collection of autochthonous S. cerevisiae strains from this area. Yeast populations from three vats containing fermenting musts from different grape varieties were analysed. Two of them were inoculated with a natural ''pied de cuve'' while the third one was sown with a rehydrated commercial yeast strain. A total of 382 yeasts were isolated and identified, initially by restriction analysis of ribosomal DNA and further by sequencing of this region. Non-Saccharomyces yeasts were found in all three musts but they practically disappeared as the fermentations progressed. Analysis of mitochondrial DNA RFLP revealed 13 different restriction patterns of Saccharomyces cerevisiae strains, five of them similar to those of commercial strains used in the winery. Commercial strains were found even in vats inoculated with a ''pied de cuve'' generated by spontaneous fermentation of a must sample. The analysis of samples recovered from different winery surfaces and equipments demonstrated that nonSaccharomyces and both commercial and autochthonous Saccharomyces strains were part of the resident microflora in the winery. Biodiversity of autochthonous S. cerevisiae in fermentation vats was low but two of them were able to compete with the commercial ones and they were isolated even at the end of the fermentation.

Monitoring volatile compounds production throughout fermentation by Saccharomyces and non-Saccharomyces strains using headspace sorptive extraction

“…Both of them were isolated from previous laboratory-scale fermentations with sun-dried Pedro Ximénez grape must and were identified at species level by PCR-RFLP of the 5.8S ribosomal region as described by Guillamón et al (1998). Identification was corroborated by sequencing the D1/D2 variable domains of 26S rRNA gene according to Clavijo et al (2011). In addition, isolates of S. cerevisiae were characterized at strain level by mitochondrial DNA restriction analysis following Querol et al (1992).…”

Microbiological Quality of a Locally Brewed Alcoholic Beverage (Pito) Sold in a Community within the Greater Accra Region, Ghana

“…This observation is not surprising since this fungus is known to be involved in fermentation [14,15,17] and could therefore have been implicated in the fermentation of the pito. Apart from Saccharomyces cerevisiae, the bacterial isolates from the pito samples can be considered microbial contaminants even though the quantities were within the acceptable limits.…”

“…Similar to other openly sold foods and drinks, several factors may make pito prone to microbial contaminations. Potential microbes that can contaminate pito may include bacteria such as E. coli, Salmonella species, Shigella species and Staphylococcus aureus [13], whiles fungal contaminants may include Aspergillus flavus, Aspergillus niger and Saccharomyces cerevisiae [14][15][16]. Meanwhile, Saccharomyces cerevisiae is known to be associated with fermentation [14,15,17].…”

“…Potential microbes that can contaminate pito may include bacteria such as E. coli, Salmonella species, Shigella species and Staphylococcus aureus [13], whiles fungal contaminants may include Aspergillus flavus, Aspergillus niger and Saccharomyces cerevisiae [14][15][16]. Meanwhile, Saccharomyces cerevisiae is known to be associated with fermentation [14,15,17]. A microbiological and physico-chemical analysis of a traditional sorghum beer "Ikigage", collected from the southern province of Rwanda showed the presence of microbes such as aerobic mesophilic bacteria, lactic acid bacteria, E. coli, feacal streptococci, Staphylococcus aureus, yeast, and moulds [18].…”

Effect of the mechanical harvest of drupes on the quality characteristics of green fermented table olives

“…To our knowledge, no study has so far been carried out to evaluate the effects of the mechanical harvesting of drupes on the final characteristics of table olives. Limited information has been published on the rheological characteristics of drupes just after mechanical harvesting, but no data are available on the microbial and chemical features of the product during fermentation.…”