Isolation and characterization of Saccharomyces cerevisiae mutants with increased cell wall chitin using fluorescence-activated cell sorting.

Yeast cell wall chitin has been shown to bind grape pathogenesis-related chitinases that are the primary cause of protein haze in wines, suggesting that yeast cell walls may be applied for haze protection. Here, we present a high-throughput screen to identify yeast strains with high cell wall chitin using a reiterative enrichment strategy and fluorescence-activated cell sorting of cells labelled with either GFP-tagged chitinase or Calcofluor white. To assess the validity of the strategy, we first used a pooled deletion strain library of Saccharomyces cerevisiae.

Enforced Mutualism Leads to Improved Cooperative Behavior between and .

and are responsible for alcoholic and malolactic fermentation, respectively. Successful completion of both fermentations is essential for many styles of wine, and an understanding of how these species interact with each other, as well as the development of compatible pairings of these species, will help to manage the process. However, targeted improvements of species interactions are difficult to perform, in part because of the chemical and biological complexity of natural grape juice.

Modifying Saccharomyces cerevisiae Adhesion Properties Regulates Yeast Ecosystem Dynamics.

Physical contact between yeast species, in addition to better-understood and reported metabolic interactions, has recently been proposed to significantly impact the relative fitness of these species in cocultures. Such data have been generated by using membrane bioreactors, which physically separate two yeast species. However, doubts persist about the degree that the various membrane systems allow for continuous and complete metabolic contact, including the exchange of proteins.

Exploring the phenotypic space of non-Saccharomyces wine yeast biodiversity.

Tremendous microbial diversity exists in vineyards, and the potential to harness this diversity for novel mixed or pure starter cultures for wine fermentation has received significant attention in recent years. However, most studies are limited to a small subset of strains and species. Here we present data from a systematic screen of 91 yeast isolates from South African grape must and vineyard samples for oenologically relevant traits.

Co-Flocculation of Yeast Species, a New Mechanism to Govern Population Dynamics in Microbial Ecosystems.

Flocculation has primarily been studied as an important technological property of Saccharomyces cerevisiae yeast strains in fermentation processes such as brewing and winemaking. These studies have led to the identification of a group of closely related genes, referred to as the FLO gene family, which controls the flocculation phenotype. All naturally occurring S.

Identifying and assessing the impact of wine acid-related genes in yeast.

Saccharomyces cerevisiae strains used for winemaking show a wide range of fermentation phenotypes, and the genetic background of individual strains contributes significantly to the organoleptic properties of wine. This strain-dependent impact extends to the organic acid composition of the wine, an important quality parameter. However, little is known about the genes which may impact on organic acids during grape must fermentation.

Transcriptional regulation and the diversification of metabolism in wine yeast strains.

Transcription factors and their binding sites have been proposed as primary targets of evolutionary adaptation because changes to single transcription factors can lead to far-reaching changes in gene expression patterns. Nevertheless, there is very little concrete evidence for such evolutionary changes. Industrial wine yeast strains, of the species Saccharomyces cerevisiae, are a geno- and phenotypically diverse group of organisms that have adapted to the ecological niches of industrial winemaking environments and have been selected to produce specific styles of wine.

The impact of co-inoculation with Oenococcus oeni on the trancriptome of Saccharomyces cerevisiae and on the flavour-active metabolite profiles during fermentation in synthetic must.

Co-inoculation of commercial yeast strains with a bacterial starter culture at the beginning of fermentation of certain varietal grape juices is rapidly becoming a preferred option in the global wine industry, and frequently replaces the previously dominant sequential inoculation strategy where bacterial strains, responsible for malolactic fermentation, are inoculated after alcoholic fermentation has been completed. However, while several studies have highlighted potential advantages of co-inoculation, such studies have mainly focused on broad fermentation properties of the mixed cultures, and no data exist regarding the impact of this strategy on many oenologically relevant attributes of specific wine yeast strains such as aroma production. Here we investigate the impact of co-inoculation on a commercial yeast strain during alcoholic fermentation by comparing the transcriptome of this strain in yeast-only and in co-inoculated fermentations of synthetic must.

The effect of scale on gene expression: commercial versus laboratory wine fermentations.

Molecular and cellular processes that are responsible for industrially relevant phenotypes of fermenting microorganisms are a central focus of biotechnological research. Such research intends to generate insights and solutions for fermentation-based industries with regards to issues such as improving product yield or the quality of the final fermentation product. For logistical reasons, and to ensure data reproducibility, such research is mostly carried out in defined or synthetic media and in small-scale fermentation vessels.

Comparative transcriptomic and proteomic profiling of industrial wine yeast strains.

The geno- and phenotypic diversity of commercial Saccharomyces cerevisiae wine yeast strains provides an opportunity to apply the system-wide approaches that are reasonably well established for laboratory strains to generate insight into the functioning of complex cellular networks in industrial environments. We have previously analyzed the transcriptomes of five industrial wine yeast strains at three time points during alcoholic fermentation. Here, we extend the comparative approach to include an isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis of two of the previously analyzed wine yeast strains at the same three time points during fermentation in synthetic wine must.

Comparing the transcriptomes of wine yeast strains: toward understanding the interaction between environment and transcriptome during fermentation.

System-wide "omics" approaches have been widely applied to study a limited number of laboratory strains of Saccharomyces cerevisiae. More recently, industrial S. cerevisiae strains have become the target of such analyses, mainly to improve our understanding of biotechnologically relevant phenotypes that cannot be adequately studied in laboratory strains.

Comparative transcriptomic approach to investigate differences in wine yeast physiology and metabolism during fermentation.

Commercial wine yeast strains of the species Saccharomyces cerevisiae have been selected to satisfy many different, and sometimes highly specific, oenological requirements. As a consequence, more than 200 different strains with significantly diverging phenotypic traits are produced globally. This genetic resource has been rather neglected by the scientific community because industrial strains are less easily manipulated than the limited number of laboratory strains that have been successfully employed to investigate fundamental aspects of cellular biology.

A sparse PLS for variable selection when integrating omics data.

Recent biotechnology advances allow for multiple types of omics data, such as transcriptomic, proteomic or metabolomic data sets to be integrated. The problem of feature selection has been addressed several times in the context of classification, but needs to be handled in a specific manner when integrating data. In this study, we focus on the integration of two-block data that are measured on the same samples.

Linking gene regulation and the exo-metabolome: a comparative transcriptomics approach to identify genes that impact on the production of volatile aroma compounds in yeast.

Background: 'Omics' tools provide novel opportunities for system-wide analysis of complex cellular functions. Secondary metabolism is an example of a complex network of biochemical pathways, which, although well mapped from a biochemical point of view, is not well understood with regards to its physiological roles and genetic and biochemical regulation. Many of the metabolites produced by this network such as higher alcohols and esters are significant aroma impact compounds in fermentation products, and different yeast strains are known to produce highly divergent aroma profiles.

Downregulation of neutral invertase activity in sugarcane cell suspension cultures leads to a reduction in respiration and growth and an increase in sucrose accumulation.

Suspension cultures were used as a model system to investigate sucrose metabolism in four sugarcane (Saccharum spp. interspecific hybrids) cell lines transformed with antisense neutral invertase (NI) constructs. Throughout a 14-day growth cycle two cell lines in which the antisense sequence was under the control of a tandem CaMV-35S: maize ubiquitin promoter showed a strong reduction in NI activity, as well as reduced hexose and increased sucrose concentrations in comparison to the control line.