During vinification microbial activities can spoil wine quality. As the wine-related lactic acid bacterium Pediococcus parvulus is able to produce slimes consisting of a -1,3-glucan, must and wine filtration can be difficult or impossible. In addition, the metabolic activities of several wild-type yeasts can also negatively affect wine quality. Therefore, there is a need for measures to degrade the exopolysaccharide from Pediococcus parvulus and to inhibit the growth of certain yeasts. We examined an extracellular -1,3-glucanase from Delftia tsuruhatensis strain MV01 with regard to its ability to hydrolyze both polymers, the -1,3-glucan from Pediococcus and that from yeast cell walls. The 29-kDa glycolytic enzyme was purified to homogeneity. It exhibited an optimal activity at 50°C and pH 4.0. The sequencing of the N terminus revealed significant similarities to -1,3-glucanases from different bacteria. In addition, the investigations indicated that this hydrolytic enzyme is still active under wine-relevant parameters such as elevated ethanol, sulfite, and phenol concentrations as well as at low pH values. Therefore, the characterized enzyme seems to be a useful tool to prevent slime production and undesirable yeast growth during vinification.
Beside yeasts, lactic acid bacteria (LAB) are the most abundant microbes in must during vinification. Whereas Oenococcos oeni is commercially used as a starter culture for the biological acid reduction in wines, other species are responsible for different types of wine spoilage. Members of the genera Pediococcus, Weissella, Leuconostoc, and Lactobacillus are producers of exopolysaccharide slimes, biogenic amines, acetic acid, and other off-flavors. In order to control microbial growth, different procedures such as heating of must and addition of sulfite or lysozyme from egg white are generally applied. Yet, because of health risks, the application of sulfite should be reduced and lysozyme is not effective against all LAB. In this study, we describe exoenzymes from a Streptomyces sp. strain B578 lysing nearly all wine-relevant strains of LAB and Gram-negative acetic acid bacteria. The lytic enzymes were active under wine-making conditions, such as the presence of sulfite and ethanol, low temperatures, and low pH values. The analysis of the exoenzyme composition revealed a synergistic action of different cell wall hydrolases. In conclusion, the lytic cocktail of Streptomyces sp. B578 is a promising tool for the control of wine-spoiling bacteria.
The genus Saccharomyces comprises very closely related species. This high degree of relationship makes a simple identification and differentiation of strains difficult since these species are hardly discriminable by their morphological and physiological features. A sequence analysis of ribosomal DNA and the corresponding internal transcribed spacers can only rarely be successfully applied. In this study, we proved the applicability of a novel DNA fingerprinting method, the SAPD-PCR (specifically amplified polymorphic DNA) and of MALDI-TOF-MS (matrix-assisted laser desorption ionization time-of-flight mass spectrometry) fingerprinting with the MALDI Biotyper for the differentiation of species belonging to the genus Saccharomyces. It was possible with SAPD-PCR to create specific banding patterns for all Saccharomyces species. Different strains of the same species produced nearly the same banding patterns. Specific and reproducible reference spectra could be generated for each of the strains with the MALDI Biotyper. Therefore, SAPD-PCR and MALDI-TOF-MS can be fast and reliable tools to identify these related Saccharomyces species which are applied in many biotechnological processes.
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