Apiculate yeasts of the genus Hanseniaspora/Kloeckera are the main species present on mature grapes and play a significant role at the beginning of fermentation, producing enzymes and aroma compounds that expand the diversity of wine color and flavor. Ten species of the genus Hanseniaspora have been recovered from grapes and are associated in two groups: H. valbyensis, H. guilliermondii, H. uvarum, H. opuntiae, H. thailandica, H. meyeri, and H. clermontiae; and H. vineae, H. osmophila, and H. occidentalis. This review focuses on the application of some strains belonging to this genus in co-fermentation with Saccharomyces cerevisiae that demonstrates their positive contribution to winemaking. Some consistent results have shown more intense flavors and complex, full-bodied wines, compared with wines produced by the use of S. cerevisiae alone. Recent genetic and physiologic studies have improved the knowledge of the Hanseniaspora/Kloeckera species. Significant increases in acetyl esters, benzenoids, and sesquiterpene flavor compounds, and relative decreases in alcohols and acids have been reported, due to different fermentation pathways compared to conventional wine yeasts.

Hanseniaspora is the main genus of the apiculate yeast group that represents approximately 70% of the grape-associated microflora. Hanseniaspora vineae is emerging as a promising species for quality wine production compared to other non-Saccharomyces species. Wines produced by H. vineae with Saccharomyces cerevisiae consistently exhibit more intense fruity flavors and complexity than wines produced by S. cerevisiae alone. In this work, genome sequencing, assembling, and phylogenetic analysis of two strains of H. vineae showed that it is a member of the Saccharomyces complex and it diverged before the whole-genome duplication (WGD) event from this clade. Specific flavor gene duplications and absences were identified in the H. vineae genome compared to 14 fully sequenced industrial S. cerevisiae genomes. The increased formation of 2-phenylethyl acetate and phenylpropanoids such as 2-phenylethyl and benzyl alcohols might be explained by gene duplications of H. vineae aromatic amino acid aminotransferases (ARO8 and ARO9) and phenylpyruvate decarboxylases (ARO10). Transcriptome and aroma profiles under fermentation conditions confirmed these genes were highly expressed at the beginning of stationary phase coupled to the production of their related compounds. The extremely high level of acetate esters produced by H. vineae compared to that by S. cerevisiae is consistent with the identification of six novel proteins with alcohol acetyltransferase (AATase) domains. The absence of the branched-chain amino acid transaminases (BAT2) and acyl coenzyme A (acyl-CoA)/ethanol O-acyltransferases (EEB1) genes correlates with H. vineae's reduced production of branched-chain higher alcohols, fatty acids, and ethyl esters, respectively. Our study provides sustenance for understanding and potentially utilizing genes that determine fermentation aromas.IMPORTANCE The huge diversity of non-Saccharomyces yeasts in grapes is dominated by the apiculate genus Hanseniaspora. Two native strains of Hanseniaspora vineae applied to winemaking because of their high oenological potential in aroma and fermentation performance were selected to obtain high-quality genomes. Here, we present a phylogenetic analysis and the complete transcriptome and aroma metabolome of H. vineae during three fermentation steps. This species produced significantly richer flavor compound diversity than Saccharomyces, including benzenoids, phenylpropanoids, and acetate-derived compounds. The identification of six Downloaded from proteins, different from S. cerevisiae ATF, with diverse acetyltransferase domains in H. vineae offers a relevant source of native genetic variants for this enzymatic activity. The discovery of benzenoid synthesis capacity in H. vineae provides a new eukaryotic model to dilucidate an alternative pathway to that catalyzed by plants' phenylalanine lyases.

BackgroundWe report on the functional screening and identification of an active quorum quenching (QQ) gene in the Komagataeibacter europaeus strain CECT 8546, which is a member of the acetic acid bacteria (AAB).ResultsUsing a previously published screening protocol (Schipper et al., in Appl Environ Microbiol 75:224–233, 2009. doi: 10.1128/AEM.01389-08) for QQ genes, we identified a single gene, designated gqqA, that interfered strongly with bacterial quorum sensing (QS) in various reporter strains. It encodes for a 281-amino acid protein with a molecular mass of 30 kDa. Although the GqqA protein is similar to predicted prephenate dehydratases, it does not complement Escherichia coli mutants of the pheA gene, thus indicating a potentially different function. Recombinant GqqA protein attenuated QS-dependent pyocyanin production and swarming motility in the Pseudomonas aeruginosa strain PAO1. Moreover, GqqA quenched the QS response of the Agrobacterium tumefaciens NTL4 and the Chromobacterium violaceum CV026 reporter strains. Interestingly, the addition of recombinant GqqA protein to growing cultures of the Komagataeibacter europaeus strain CECT 8546 altered the cellulose production phenotype of CECT 8546 and other AAB strains. In the presence of GqqA protein, cells were planktonic, and no visible cellulose biofilms formed. The addition of low levels of N-acylhomoserine lactones maintained the biofilm formation phenotype.ConclusionsOur data provide evidence for an interconnection between QS and AAB cellulose biofilm formation as well as QQ activity of the GqqA protein.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0482-y) contains supplementary material, which is available to authorized users.

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