The synthesis of hyperbranched polyglycerol dendron analogues with precisely one focal amino functionality (H 2 N-hbPG) and their use for the synthesis of linear-hyperbranched graftcopolymers in a grafting-to approach is reported. By use of N,Ndibenzyl tris(hydroxylmethyl) aminomethane as a novel initiator for the ring-opening multibranching polymerization of glycidol, dendron analogues with one focal amino functionality of molecular weights ranging from 500 to 15000 g mol −1 and narrow to moderate polydispersities (M w /M n = 1.2−1.9) were synthesized, as confirmed by NMR and SEC. After removal of the benzyl protective groups, the accessibility and selective transformation of the focal amino group was demonstrated by NMR and MALDI−ToF MS. H 2 N-hbPG was then selectively grafted to a linear reactive ester polymer backbone, poly(pentafluorophenol methacrylate) (PPFPMA), to obtain linear polymers with highly branched side chains of high molecular weights (M n > 126 kg mol −1 ) and low polydispersities (M w /M n = 1.1−1.3), as shown by SEC. Successful attachment of the hyperbranched polyether structure to the linear backbone was confirmed by 19 F NMR and fluorescence spectroscopy. The modular approach introduced bears some analogy to the convergent dendrimer synthesis and describes the first linearhyperbranched graft-copolymers prepared in a graf ting-to approach, resulting in hyperbranched brush-type polymers with the highest molecular weight reported to date.
Sluggish or stuck fermentations cause significant financial losses for winemakers each year. In order to investigate the reasons for problems during spontaneous fermentation of Riesling must in a well-known German vineyard of the lower Moselle, yeast strains involved in must fermentation were identified during winemaking in the two years 2011 and 2012. Identification of the yeast isolates was performed by applying analyses of the ITS-1-5.8-ITS2 region and restriction fragment analyses of different gene sequences. It revealed that Saccharomyces (S.) bayanus and not Saccharomyces cerevisiae was the main fermenting yeast. Either S. bayanus finished the fermentation or led to stuck fermentation. After about four weeks of stuck, fermentation continued spontaneously S. bayanus was replaced by the triple hybrid S. cerevisiae × S. kudriavzevii × S. bayanus. The triple hybrid strain HL 78 was able to utilize fructose more efficiently than S. bayanus strain HL 77. The fructophilic character of the triple hybrid strain correlated with an enhanced uptake of radiolabeled fructose compared to glucose.In contrast to the usual starter culture S. cerevisiae, both isolates, S. bayanus strain HL 77 and the triple hybrid strain HL 78, could grow in the absence of ammonium when amino acids were present. However, the triple hybrid was able to consume glucose and especially fructose at lower amino acid concentrations. Thus, the triple hybrid strain HL 78 was a suitable strain to overcome stuck fermentation without changing the fermentation conditions and the aroma profile desired by the selected winery. It has already been successfully used to restart stuck fermentation. The procedure described here could be a useful approach for wine makers facing problems during spontaneous fermentation. Since the application of genetically modified yeast strains is not allowed for starter culture, based on these studies we suggest the generation of hybrid strains with desired phenotypical features from mother yeasts strains/species of a certain winery and their application in case that during a spontaneous fermentations a sluggish or stuck fermentation is observed.
During fermentation oenological yeast cells are subjected to a number of different stress conditions and must respond rapidly to the continuously changing environment of this harsh ecological niche. In this study we gained more insights into the cell adaptation mechanisms by linking proteome monitoring with knowledge on physiological behaviour of different strains during fermentation under model winemaking conditions. We used 2D-DIGE technology to monitor the proteome evolution of two newly discovered environmental yeast strains Saccharomyces bayanus and triple hybrid Saccharomyces cerevisiae × Saccharomyces kudriavzevii × S. bayanus and compared them to data obtained for the commercially available S. cerevisiae strain. All strains examined showed (i) different fermentative behaviour, (ii) stress resistance as well as (iii) susceptibility to stuck fermentation which was reflected in significant differences in protein expression levels. During our research we identified differentially expressed proteins in 155 gel spots which correspond to 70 different protein functions. Differences of expression between strains were observed mainly among proteins involved in stress response, proteins degradation pathways, cell redox homeostasis and amino acids biosynthesis. Interestingly, the newly discovered triple hybrid S. cerevisiae × S. kudriavzevii × S. bayanus strain which has the ability to naturally restart stuck fermentation showed a very strong induction of expression of two proteolytic enzymes: Pep4 and Prc1 that appear as numerous isoforms on the gel image and which may be the key to its unique properties. This study is an important step towards the better understanding of wine fermentations at a molecular level.
DOI: Bacchus meets proteomics. During fermentation, oenological yeast cells are subjected to a number of different stress conditions and must respond rapidly to the continuously changing environment of harsh ecological niche. In this study we gained more insights into the cell adaptation mechanisms by linking proteome monitoring with knowledge on physiological behaviour of different strains during fermentation under model winemaking conditions. See the article by Aleksandra Szopinska et al. on page 593 for more details.
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