Improvement of maltotriose fermentation by Saccharomyces cerevisiae

Stambuk, Boris U.; Alves, Sérgio L.; Hollatz, Cláudia; Zastrow, Claudio Roberto

doi:10.1111/j.1472-765x.2006.01982.x

Cited by 25 publications

(24 citation statements)

References 44 publications

(88 reference statements)

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“…10% for integrant 1) increase in maltose transport activity but a larger increase in maltotriose transport activity (2.5-fold for integrant 1), which is consistent with the replacement of transporters with high specificity for maltose (e.g., Malx1 transporters) by the broaderspecificity Agt1 transporters. Similar findings have been reported by other workers: overexpression of AGT1 increased maltotriose transport activity threefold but slightly decreased maltose transport activity (33), whereas specific deletion of AGT1 abolished maltotriose transport activity but caused a nearly 20% increase in maltose transport activity (1). To improve our understanding of how to increase transport activities (which is relevant to most biotechnological operations), it is evidently necessary to learn more about the processes that may limit the successful insertion of transporters into the plasma VOL.…”

Section: Discussionsupporting

confidence: 65%

Improved Fermentation Performance of a Lager Yeast after Repair of Its AGT1 Maltose and Maltotriose Transporter Genes

Vidgren

Huuskonen

Virtanen

et al. 2009

Appl Environ Microbiol

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The use of more concentrated, so-called high-gravity and very-high-gravity (VHG) brewer's worts for the manufacture of beer has economic and environmental advantages. However, many current strains of brewer's yeasts ferment VHG worts slowly and incompletely, leaving undesirably large amounts of maltose and especially maltotriose in the final beers. ␣-Glucosides are transported into Saccharomyces yeasts by several transporters, including Agt1, which is a good carrier of both maltose and maltotriose. The AGT1 genes of brewer's ale yeast strains encode functional transporters, but the AGT1 genes of the lager strains studied contain a premature stop codon and do not encode functional transporters. In the present work, one or more copies of the AGT1 gene of a lager strain were repaired with DNA sequence from an ale strain and put under the control of a constitutive promoter. Compared to the untransformed strain, the transformants with repaired AGT1 had higher maltose transport activity, especially after growth on glucose (which represses endogenous ␣-glucoside transporter genes) and higher ratios of maltotriose transport activity to maltose transport activity. They fermented VHG (24°Plato) wort faster and more completely, producing beers containing more ethanol and less residual maltose and maltotriose. The growth and sedimentation behaviors of the transformants were similar to those of the untransformed strain, as were the profiles of yeast-derived volatile aroma compounds in the beers.The main fermentable sugars in brewer's wort are maltose (ca. 60% of the total), maltotriose (ca. 25%), and glucose (ca. 15%). In traditional brewery fermentations, worts of about 11°P lato (°P) are used, corresponding to a total fermentable sugar concentration of about 80 g ⅐ liter Ϫ1 . Many modern breweries ferment high-gravity worts (15 to 17°P), and there are efforts to raise the concentration to 25°P, corresponding to a total sugar concentration of about 200 g ⅐ liter Ϫ1 . Industrial use of such very-high-gravity (VHG) worts is attractive because it offers increased production capacity from the same-size brew house and fermentation facilities, decreased energy consumption, and decreased labor, cleaning, and effluent costs (34,35).Whereas glucose, which is used first, is transported into yeast cells by facilitated diffusion, the ␣-glucosides maltose and maltotriose are carried by proton symporters (2, 26, 39). Maltose transport seems to have a high level of control over the fermentation rate. Thus, during the early and middle stages of fermentation of brewer's wort by a lager yeast, the specific rate of maltose consumption was the same as the specific zero-trans maltose uptake rate measured off line with each day's yeast in each day's wort spiked with [ 14 C]maltose (27). Furthermore, introducing a constitutive MAL61 (maltose transporter) gene into a brewer's yeast on a multicopy plasmid accelerated the fermentation of high-gravity worts (17). Maltotriose is the last sugar to be used in brewing fermentations, and significant amoun...

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Section: Discussionsupporting

confidence: 65%

Improved Fermentation Performance of a Lager Yeast after Repair of Its AGT1 Maltose and Maltotriose Transporter Genes

Vidgren

Huuskonen

Virtanen

et al. 2009

Appl Environ Microbiol

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“…In our experiments, the kinetic parameters were determined by the initial rates of H ϩ influx (Ͻ10 s) triggered by the cotransport of the sugar, and therefore, these experimental artifacts were avoided. The importance of the AGT1 permease for maltotriose active transport and fermentation is also evident from recent data showing that constitutive and enhanced expression of this gene is required for efficient maltotriose fermentation by S. cerevisiae (1,36). The recent discovery of new AGT1 alleles in industrial yeast strains (39), some of which seem to transport maltotriose more efficiently (30), opens new opportunities to increase yeast fitness for the fermentation of starch hydrolysates, preventing incomplete or sluggish maltotriose fermentations.…”

Section: Discussionmentioning

confidence: 84%

“…All yeast ␣-glucoside transport systems so far characterized are H ϩ symporters that use the electrochemical proton gradient to actively transport these sugars into the cell, even for downhill transport (7,30,36). Maltose transport into the cell is required for the full induction of MAL genes, and several previous studies have also shown that maltose uptake is the rate-limiting step for fermentation (21,27,41).…”

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confidence: 99%

Molecular Analysis of Maltotriose Active Transport and Fermentation by Saccharomyces cerevisiae Reveals a Determinant Role for the AGT1 Permease

Alves

Herberts

Hollatz

et al. 2008

Appl Environ Microbiol

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Incomplete and/or sluggish maltotriose fermentation causes both quality and economic problems in the ale-brewing industry. Although it has been proposed previously that the sugar uptake must be responsible for these undesirable phenotypes, there have been conflicting reports on whether all the known ␣-glucoside transporters in Saccharomyces cerevisiae (MALx1, AGT1, and MPH2 and MPH3 transporters) allow efficient maltotriose utilization by yeast cells. We characterized the kinetics of yeast cell growth, sugar consumption, and ethanol production during maltose or maltotriose utilization by several S. cerevisiae yeast strains (both MAL constitutive and MAL inducible) and by their isogenic counterparts with specific deletions of the AGT1 gene. Our results clearly showed that yeast strains carrying functional permeases encoded by the MAL21, MAL31, and/or MAL41 gene in their plasma membranes were unable to utilize maltotriose. While both highand low-affinity transport activities were responsible for maltose uptake from the medium, in the case of maltotriose, the only low-affinity (K m , 36 ؎ 2 mM) transport activity was mediated by the AGT1 permease. In conclusion, the AGT1 transporter is required for efficient maltotriose fermentation by S. cerevisiae yeasts, highlighting the importance of this permease for breeding and/or selection programs aimed at improving sluggish maltotriose fermentations.Several important industrial applications of the yeast Saccharomyces cerevisiae, such as brewing, baking, and the production of distilled beverages, rely on the efficient fermentation of starch hydrolysates rich in glucose and in the ␣-glucosides maltose and maltotriose. In brewer's wort, for example, the most abundant fermentable sugar is maltose (50 to 60%), followed by maltotriose (15 to 20%) and glucose (10 to 15%). Of these sugars, glucose is preferentially and rapidly utilized by the yeast cells, but process efficiency also requires the complete fermentation of both maltose and maltotriose. After glucose exhaustion, maltose is easily fermented by the majority of S. cerevisiae strains, and not only is maltotriose the least preferred sugar for uptake by these yeast cells, but many yeasts may not use it at all (23, 37, 44). The difficulty that some strains have in consuming maltotriose leads to one of the problems experienced by many breweries, namely, a high content of residual sugar in the finished beer, low ethanol yields, and atypical beer flavor profiles. Therefore, the rate of uptake and fermentation of maltotriose is one of the major determinants of fermentation efficiency and product quality. Due to its relevance for beer fermentation, maltotriose utilization has been studied mostly with the two classes of yeast strains used for brewing, S. cerevisiae ale strains and S. pastorianus lager strains. These studies have revealed that maltotriose utilization by ale strains is significantly slower than that by lager yeasts and that, consequently, residual maltotriose is more common at the end of ale fermentations (22,23,44...

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“…In a study of maltotriose utilization by S. cerevisiae, overexpression of AGT1 permease effected faster maltotriose consumption. 33) The identification and improvement of xylooligosaccharide transporters might make possible more effective hydrolysis of xylo-oligosaccharides.…”

Section: Discussionmentioning

confidence: 99%

Ethanol Production from Xylo-oligosaccharides by Xylose-FermentingSaccharomyces cerevisiaeExpressing β-Xylosidase

Fujii

Matsushika

et al. 2011

Bioscience, Biotechnology, and Biochemistry

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Construction of xylose- and xylo-oligosaccharide-fermenting Saccharomyces cerevisiae strains is important, because hydrolysates derived from lignocellulosic biomass contain significant amounts of these sugars. We have obtained recombinant S. cerevisiae strain MA-D4 (D-XKXDHXR), expressing xylose reductase, xylitol dehydrogenase and xylulokinase. In the present study, we generated recombinant strain D-XSD/XKXDHXR by transforming MA-D4 with a β-xylosidase gene cloned from the filamentous fungus Trichoderma reesei. The intracellular β-xylosidase-specific activity of D-XSD/XKXDHXR was high, while that of the control strain was under the limit of detection. D-XSD/XKXDHXR produced ethanol, and xylose accumulated in the culture supernatant under fermentation in a medium containing xylo-oligosaccharides as sole carbon source. β-Xylosidase-specific activity in D-XSD/XKXDHXR declined due to xylose both in vivo and in vitro. D-XSD/XKXDHXR converted xylo-oligosaccharides in an enzymatic hydrolysate of eucalyptus to ethanol. These results indicate that D-XSD/XKXDHXR efficiently converted xylo-oligosaccharides to xylose and subsequently to ethanol.

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Improvement of maltotriose fermentation by Saccharomyces cerevisiae

Cited by 25 publications

References 44 publications

Improved Fermentation Performance of a Lager Yeast after Repair of Its AGT1 Maltose and Maltotriose Transporter Genes

Improved Fermentation Performance of a Lager Yeast after Repair of Its AGT1 Maltose and Maltotriose Transporter Genes

Molecular Analysis of Maltotriose Active Transport and Fermentation by Saccharomyces cerevisiae Reveals a Determinant Role for the AGT1 Permease

Ethanol Production from Xylo-oligosaccharides by Xylose-FermentingSaccharomyces cerevisiaeExpressing β-Xylosidase

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