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Ammonia Assay Kit (Rapid)

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00:04  Introduction
00:55   Principle
01:33    Reagent Preparation
02:10    Procedure
04:52    Calculations

Ammonia Assay Kit Rapid K-AMIAR Scheme
Product code: K-AMIAR

96 assays (manual) / 960 assays (microplate) / 960 assays (auto-analyser)

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Content: 96 assays (manual) / 960 assays (microplate) / 960 assays (auto-analyser)
Shipping Temperature: Ambient
Storage Temperature: Short term stability: 2-8oC,
Long term stability: See individual component labels
Stability: > 2 years under recommended storage conditions
Analyte: Ammonia, Nitrogen, YAN
Assay Format: Spectrophotometer, Microplate, Auto-analyser
Detection Method: Absorbance
Wavelength (nm): 340
Signal Response: Decrease
Linear Range: 0.2 to 7 µg of ammonia per assay
Limit of Detection: 0.07 mg/L
Reaction Time (min): ~ 5 min
Application examples: Grape juice, wine, fruit juices, soft drinks, dairy products (e.g. milk), dietetic food, soy sauce, eggs and egg products, cheese, meat, processed meat, seafood, bakery products (and baking agents), fertilisers, pharmaceuticals, tobacco, cosmetics, water, Kjeldahl analysis, paper (and cardboard), water and other materials (e.g. biological cultures, samples, etc.).
Method recognition: Methods based on this principle have been accepted by MEBAK

Ammonia Assay Kit, for the rapid measurement and analysis of ammonia in all samples, including grape juice and wine (and other foods/beverages).

Note for Content: The number of manual tests per kit can be doubled if all volumes are halved.  This can be readily accommodated using the MegaQuantTM  Wave Spectrophotometer (D-MQWAVE).

Browse all nitrogen assay kits.

Scheme-K-AMIAR K-AMIAR megazyme

  • Extended cofactors stability. Dissolved cofactors stable for > 1 year at 4oC.
  • Very rapid reaction due to use of uninhibited glutamate dehydrogenase 
  • Enzyme supplied as stabilised suspension 
  • Very competitive price (cost per test)  
  • All reagents stable for > 2 years as supplied  
  • Mega-Calc™ software tool is available from our website for hassle-free raw data processing 
  • Standard included
  • Suitable for manual, microplate and auto-analyser formats
Megazyme publication

Megazyme “advanced” wine test kits general characteristics and validation.

Charnock, S. J., McCleary, B. V., Daverede, C. & Gallant, P. (2006). Reveue des Oenologues, 120, 1-5.

Many of the enzymatic test kits are official methods of prestigious organisations such as the Association of Official Analytical Chemicals (AOAC) and the American Association of Cereal Chemists (AACC) in response to the interest from oenologists. Megazyme decided to use its long history of enzymatic bio-analysis to make a significant contribution to the wine industry, by the development of a range of advanced enzymatic test kits. This task has now been successfully completed through the strategic and comprehensive process of identifying limitations of existing enzymatic bio-analysis test kits where they occurred, and then using advanced techniques, such as molecular biology (photo 1), to rapidly overcome them. Novel test kits have also been developed for analytes of emerging interest to the oenologist, such as yeast available nitrogen (YAN; see pages 2-3 of issue 117 article), or where previously enzymes were simply either not available, or were too expensive to employ, such as for D-mannitol analysis.

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Megazyme publication

Grape and wine analysis: Oenologists to exploit advanced test kits.

Charnock, S. C. & McCleary, B. V. (2005). Revue des Enology, 117, 1-5.

It is without doubt that testing plays a pivotal role throughout the whole of the vinification process. To produce the best possible quality wine and to minimise process problems such as “stuck” fermentation or troublesome infections, it is now recognised that if possible testing should begin prior to harvesting of the grapes and continue through to bottling. Traditional methods of wine analysis are often expensive, time consuming, require either elaborate equipment or specialist expertise and frequently lack accuracy. However, enzymatic bio-analysis enables the accurate measurement of the vast majority of analytes of interest to the wine maker, using just one piece of apparatus, the spectrophotometer (see previous issue No. 116 for a detailed technical review). Grape juice and wine are amenable to enzymatic testing as being liquids they are homogenous, easy to manipulate, and can generally be analysed without any sample preparation.

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Effects of plantago species herbage and silage on in vitro ruminal fermentation and microbiome.

Kara, K., Yılmaz, S., Önel, S. E. & Özbilgin, A. (2022). E Italian Journal of Animal Science, 21(1), 1569-1583.

The present study aimed to compare the nutrient composition, in vitro ruminal fermentation values and microbiome in the ruminal fermentation of herbage and silage of the Plantago media, P. major and P. lanceolata species. The lactic acid (LA) content of P. lanceolata silage was higher than those of other plantago silages (p < 0.05). The α-linolenic, w-3, polyunsaturated (PUFA), medium chain (MCFA) and long-chain fatty acids (LCFA) of plantago silages were lower than those of plantago herbages (p < 0.05). The neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents, total gas and methane production, metabolic energy (ME) and organic matter digestion (OMD) values and ammonia-nitrogen concentration in the in vitro fermentation fluid of P. major silage were lower than those of other plantago silages (p < 0.05). The in vitro ruminal methane production and community of archaea Methanobrevibacter in the microbiome of P. major herbage were higher than that of P. media and P. lanceolata herbages. The ensiling process significantly increased the in vitro total gas production, acetic acid concentration and Prevotellaceae bacteria of P. media and P. lanceolate compared their herbages. As a result, P. lanceolata and P. media silages provided high-quality silage fermentation; the nutrient composition was not lost to a great extent in the silage environment and the ruminal fibrolytic bacterial composition was positively affected. Plantago major silage could not provide a good silage quality and the in vitro ruminal fermentation and ruminal fibrolytic bacteria community value were negatively affected.

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Development and Analysis of an intensified batch-fed wine fermentation process.

Miller, K. V., Arefaine, E., Arikal, A., Cantu, A., Cauduro Girardello, R., Oberholster, A., Heymann, H. & Block, D. E. (2022). Fermentation, 8(6), 268.

White wine fermentations are typically performed in an entirely batchwise manner, with yeast nutrients only added at the beginning of fermentation. This leads to slow (2+ weeks) fermentation cycle times, with large capital expenditures required to increase winery processing capacity. Prior attempts to speed fermentations via increasing temperature have resulted in unpalatable wine, and continuous fermentation processing is uneconomical and impractical in the winery setting. In this work, we measured yeast nutrient consumption as a function of fermentation progression at the 300 mL scale, and from this derived an equation to optimize yeast nutrient concentration as a function of fermentation progression. These findings were applied at the pilot scale in 150 L fermentors, which resulted in a 60% cycle time reduction versus “best practices” control fermentations. The resultant wines were compared via GC-MS as well as by a trained sensory panel. Organoleptic analysis found statistically significant, but overall, small differences in sensory characteristics between the control and process intensified wines. This intensified fermentation process shows great promise for fermented beverage producers wishing to maximize equipment utilization and debottleneck wineries or other beverage fermentation facilities.

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The film-forming Pichia spp. in a winemaker's toolbox: A simple isolation procedure and their performance in a mixed-culture fermentation of Vitis vinifera L. cv. Gewürztraminer must. 

Scansani, S., van Wyk, N., Nader, K. B., Beisert, B., Brezina, S., Fritsch, S., semmler, H., Pasch, L., Pretorius, I. S., Wallbrunn, C., Schnell, S. & Rauhut, D. (2022). International Journal of Food Microbiology, 365, 109549.

Certain yeast species belonging to the Pichia genus are known to form a distinctive film on grape must and wine. In a mixed-culture type fermentation, Pichia spp. (P. kluyveri in particular) are known to impart beneficial oenological attributes. In this study, we report on an easy isolation method of Pichia spp. from grape must by exploiting their film-forming capacity on media containing 10% ethanol. We isolated and identified two Pichia species, namely Pichia kudriavzevii and Pichia kluyveri, and subsequently co-inoculated them with Saccharomyces cerevisiae to ferment Gewürztraminer musts. Noteworthy differences included a significant increase in the 2-phenethyl acetate levels with the P. kluyveri co-fermentation and a general increase in ethyl esters with the P. kudriavzevii co-fermentation. Both Pichia co-inoculations yielded higher levels of glycerol in the final wines. Based on all the wine parameters we tested, the P. kluyveri strain that was isolated performed similarly to a commercial P. kluyveri strain.

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Inhibitory effect of lignin on the hydrolysis of xylan by thermophilic and thermolabile GH11 xylanases.

Kellock, M., Rahikainen, J., Borisova, A. S., Voutilainen, S., Koivula, A., Kruus, K. & Marjamaa, K. (2022). Biotechnology for Biofuels and Bioproducts, 15(1), 1-18.

Background: Enzymatic hydrolysis of lignocellulosic biomass into platform sugars can be enhanced by the addition of accessory enzymes, such as xylanases. Lignin from steam pretreated biomasses is known to inhibit enzymes by non-productively binding enzymes and limiting access to cellulose. The effect of enzymatically isolated lignin on the hydrolysis of xylan by four glycoside hydrolase (GH) family 11 xylanases was studied. Two xylanases from the mesophilic Trichoderma reesei, TrXyn1, TrXyn2, and two forms of a thermostable metagenomic xylanase Xyl40 were compared. Results: Lignin isolated from steam pretreated spruce decreased the hydrolysis yields of xylan for all the xylanases at 40 and 50 °C. At elevated hydrolysis temperature of 50 °C, the least thermostable xylanase TrXyn1 was most inhibited by lignin and the most thermostable xylanase, the catalytic domain (CD) of Xyl40, was least inhibited by lignin. Enzyme activity and binding to lignin were studied after incubation of the xylanases with lignin for up to 24 h at 40 °C. All the studied xylanases bound to lignin, but the thermostable xylanases retained 22–39% of activity on the lignin surface for 24 h, whereas the mesophilic T. reesei xylanases become inactive. Removing of N-glycans from the catalytic domain of Xyl40 increased lignin inhibition in hydrolysis of xylan when compared to the glycosylated form. By comparing the 3D structures of these xylanases, features contributing to the increased thermal stability of Xyl40 were identified. Conclusions: High thermal stability of xylanases Xyl40 and Xyl40-CD enabled the enzymes to remain partially active on the lignin surface. N-glycosylation of the catalytic domain of Xyl40 increased the lignin tolerance of the enzyme. Thermostability of Xyl40 was most likely contributed by a disulphide bond and salt bridge in the N-terminal and α-helix regions.

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Effects of ensiling length and storage temperature on the nutritive value and fibre-bound protein of three tropical legumes ensiled alone or combined with sorghum.

Aloba, T. A., Corea, E. E., Mendoza, M., Dickhoefer, U. & Castro-Montoya, J. (2022). Animal Feed Science and Technology, 283, 115172.

Changes in the nutritive value of forages are imminent under different ensiling conditions. Thus, a study was conducted to assess the effects of ensiling length and storage temperature on the nutritive value, fermentation characteristics and fibre-bound protein of three tropical forage legumes, sorghum and mixtures of sorghum and the legumes. Soybean (Glycine max), jack bean (Cannavalia ensiformis), lablab (Lablab purpureus) and sorghum (Sorghum bicolor) were solely grown and harvested, and the legumes were wilted before ensiling. Mixtures of sorghum and each legume were handmade on a percentage fresh weight basis of 60:40. Each forage and mixtures (400 g) were ensiled in polythene vacuum bags with homofermentative lactic acid bacteria inoculation for 30, 75 and 180 days. A set of mini silos were stored indoors, and another batch was stored outdoors. HOBO Pro v2 data loggers were deployed to monitor the ambient temperature of the storage locations during the entire ensiling period (from day 0-180). Measurements included nutrient analysis, fermentation quality and fibre bound protein characteristics. The hourly ambient temperature for outdoor and indoor storage ranged from 16° to 61°C vs 18-35°C, respectively. Proximate constituents of all silages were influenced by ensiling length. Significant changes were primarily detected in fermentation products of legume silages between 30 and 75 d of ensiling. There were reduced fermentation products for silages stored outdoors. The ensiling length influenced proportions of neutral detergent insoluble nitrogen (NDIN) and acid detergent insoluble nitrogen (ADIN) with outdoor silages resulting in a higher proportion of NDIN and ADIN compared to indoor silages. Overall, a short period of ensiling preserves the nutritional quality of ensiled forages compared to prolonged storage at high ambient temperatures typical of the tropics that increase nutrient losses. Thus, changes in the nutritional composition of forages during ensiling should be considered during ration formulations.

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Enabling Biological Nitrogen Fixation for Cereal Crops in Fertilized Fields.

Wen, A., Havens, K. L., Bloch, S. E., Shah, N., Higgins, D. A., Davis-Richardson, A. G., et al. (2021). ACS Synthetic Biology, 10(12), 3264-3277.

Agricultural productivity relies on synthetic nitrogen fertilizers, yet half of that reactive nitrogen is lost to the environment. There is an urgent need for alternative nitrogen solutions to reduce the water pollution, ozone depletion, atmospheric particulate formation, and global greenhouse gas emissions associated with synthetic nitrogen fertilizer use. One such solution is biological nitrogen fixation (BNF), a component of the complex natural nitrogen cycle. BNF application to commercial agriculture is currently limited by fertilizer use and plant type. This paper describes the identification, development, and deployment of the first microbial product optimized using synthetic biology tools to enable BNF for corn (Zea mays) in fertilized fields, demonstrating the successful, safe commercialization of root-associated diazotrophs and realizing the potential of BNF to replace and reduce synthetic nitrogen fertilizer use in production agriculture. Derived from a wild nitrogen-fixing microbe isolated from agricultural soils, Klebsiella variicola 137-1036 (“Kv137-1036”) retains the capacity of the parent strain to colonize corn roots while increasing nitrogen fixation activity 122-fold in nitrogen-rich environments. This technical milestone was then commercialized in less than half of the time of a traditional biological product, with robust biosafety evaluations and product formulations contributing to consumer confidence and ease of use. Tested in multi-year, multi-site field trial experiments throughout the U.S. Corn Belt, fields grown with Kv137-1036 exhibited both higher yields (0.35 ± 0.092 t/ha ± SE or 5.2 ± 1.4 bushels/acre ± SE) and reduced within-field yield variance by 25% in 2018 and 8% in 2019 compared to fields fertilized with synthetic nitrogen fertilizers alone. These results demonstrate the capacity of a broad-acre BNF product to fix nitrogen for corn in field conditions with reliable agronomic benefits.

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Growth and energy storage responses vary seasonally in the Australasian snapper Chrysophrys auratus with only modest changes in aerobic scope.

Cook, D., Herbert, N. & Jerrett, A. (2021). Marine Ecology Progress Series, 659, 199-217.

Many temperate marine species cope with profound seasonal changes in temperature. One way in which these species have adapted to these conditions is by adopting life-history traits that employ seasonally dependent growth, maximising growth in the warmer summer period before experiencing a period of negligible growth and maintenance in the cooler winter period. This strategy is considered to ensure that temperate species survive the unproductive winter period. However, in the field of eco-physiology, the inability to grow in low temperature environments is considered to result from physiological limitations on growth and digestion imposed by low aerobic scope (AS) at low temperatures. In this study, we investigate the seasonal growth, bioenergetic changes and metabolic oxygen requirements (including AS) of the Australasian snapper (Sparidae: Chrysophrys auratus) over natural seasonal cycles. We demonstrate that snapper undergo marked growth over a 7 mo period spanning spring, summer and autumn, then negligible (or even negative) growth in the winter. These growth responses coincide with marked changes in physiological character, including changes in energy storage, body composition, gonadal development and haematological variation. The biological changes observed occur in combination with a broad AS curve that was relatively insensitive to the seasonal temperatures experienced in their natural range. Within this broad AS curve, variations in growth rate could not be explained by changes in AS, and vastly different rates of biological activity were observed despite only modest change in AS availability. The relevance of the oxygen capacity-limited thermal tolerance framework to the seasonal responses of snapper is discussed.

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Growth and metabolic properties of halophilic and alkaliphilic lactic acid bacterial strains of Marinilactibacillus psychrotolerans isolated from surface-ripened soft cheese.

Suzuki, T., Matsutani, M., Matsuyama, M., Unno, R., Matsushita, H., Sugiyama, M., Yasmasato, K., Koizumi, Y. & Ishikawa, M. (2021). International Dairy Journal, 112, 104840.

The behaviour of halophilic and alkaliphilic lactic acid bacteria (HALAB) during maturation of salted and surface-ripened soft cheese remains unclear; thus, physiological properties of HALAB was investigated. Marinilactibacillus psychrotolerans was the predominant HALAB (106-1010 cfu g−1) in the cheese rind of Maroilles cheese. To elucidate HALAB behaviour during maturation, sterilised cheese was matured using M. psychrotolerans B7-9-5 as an adjunct culture. During the ripening period, concentrations of lactate and acetate decreased and increased, respectively. Strain B7-9-5 produced only acetate from lactate under aerobic conditions, and the relevant genes are present in its genome. Unlike in the marine strain, strain B7-9-5 contains gene clusters for lactose and citrate catabolism and utilised these carbohydrates for growth. Thus, when carbon sources are limited during ripening, this strain survives by utilising, if any, lactate, lactose and citrate, and it may contribute to flavour formation during ripening of salted and surface-ripened soft cheeses.

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Modelling of S. cerevisiae and T. delbrueckii pure culture fermentation in synthetic media using a compartmental nitrogen model.

Brou, P., Patricia, T., Beaufort, S. & Brandam, C. (2020). OENO One, 54(2), 299-311.

Aim: The objective of the present work is to propose a model describing the evolution of the pure culture fermentation of two oenological yeasts: S. cerevisiae and T. delbrueckii. Methods and results: For both yeasts, pure culture fermentation was performed in a synthetic medium with different initial concentrations of yeast available nitrogen. The datasets obtained from those experiments were used to identify the parameters of the proposed model. Conclusions: The developed comprehensive model of wine-making fermentation is based on the partition of assimilated nitrogen between the constitutive and the storage compartments. It efficiently describes the evolution of S. cerevisiae and T. delbrueckii pure cultures. This mass-balance model provides a stoichiometric approach in biomass production, unlike nitrogen backboned models used in winemaking. Moreover, it gives an estimation of non-accessed data such as nitrogen partition between vacuole and cytosol during T. delbrueckii fermentation. Significance and impact of the study: The developed model is robust enough to precisely describe the fermentation evolution of two pure culture yeasts and therefore has future potential for modelling mixed culture fermentations of S. cerevisiae and T. delbrueckii.

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Soil Nitrogen Fertilization Increases Yeast Assimilable Nitrogen Concentrations in ‘Golden Russet’and ‘Medaille d’Or’Apples Used for Cider Production.

Karl, A. D., Brown, M. G., Ma, S., Sandbrook, A., Stewart, A. C., Cheng, L., Mansfield, A. K. & Peck, G. M. (2020). Hort. Science, 55(8), 1345-1355.

The recent growth in the U.S. hard-cider industry has increased the demand for cider apples (Malus×domestica Borkh.), but little is known about how to manage orchard soil fertility best to optimize horticultural performance and juice characteristics for these cultivars. To assess whether nitrogen fertilizer applied to the soil can improve apple juice and cider quality, calcium nitrate (CaNO3) fertilizer was applied at different rates to the soil beneath ‘Golden Russet’ and ‘Medaille d’Or’ trees over the course of three growing seasons. The experiment started when the trees were in their second leaf. The trees were cropped in their third and fourth leaf. At the end of the first growing season of the experiment, the greatest fertilizer rate increased tree trunk cross-sectional area (TCSA) by 82% relative to the control, but this difference did not persist through to the end of the study. Yield and crop load were unaffected by the nitrogen fertilization treatments. Increasing the nitrogen fertilizer rate correlated positively with more advanced harvest maturity in ‘Golden Russet’ fruit, which resulted in greater soluble solid concentration (SSC). Fruit from the greatest fertilizer rate treatment had an average starch pattern index (SPI) that was 1 U greater than in the control, and an SSC that was 3% greater than the control. The fertilizer treatments did not affect juice pH, titratable acidity (TA), or total polyphenol concentrations. Yeast assimilable nitrogen (YAN) concentrations were increased by nitrogen fertilization for both cultivars in both harvest years. The greatest fertilizer treatment increased juice primary amino nitrogen by 103% relative to the control. Greater nitrogen fertilization rates correlated positively with less hydrogen sulfide production during the fermentation of ‘Golden Russet’ juice from the first, but not the second, harvest. During the first year, cumulative hydrogen sulfide production for the ‘Golden Russet’ control treatment was 29.6 μg·L-1 compared with the ‘Golden Russet’ high treatment, which cumulatively produced 0.1 μg·L-1. Greater maximum fermentation rates and shorter fermentation durations correlated positively with increased fertilization rate for both cultivars after the second harvest. High treatment fermentations had maximum fermentation rates 110% greater, and fermentation durations 30% shorter than the control. Other horticultural and juice-quality parameters were not affected negatively by the CaNOtreatments. In orchards producing apples specifically for the hard-cider industry, nitrogen fertilizer could increase juice YAN, thus reducing the need for exogenous additions during cider production.

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Saccharomyces uvarum yeast isolate consumes acetic acid during fermentation of high sugar juice and juice with high starting volatile acidity.

Inglis, D., Kelly, J., van Dyk, S., Dowling, L., Pickering, G. & Kemp, B. (2020). OENO One, 54(2).

Aim: A Saccharomyces uvarum isolate was assessed for its ability to metabolize acetic acid present in juice and during the fermentation of partially dehydrated grapes. The impact on other yeast metabolites was also compared using an S. uvarum isolate and an S. cerevisiae wine yeast. The upper limit of fruit concentration that allowed the S. uvarum isolate to ferment wines to < 5 g/L residual sugar was defined. Methods and results: Cabernet franc grapes were partially dehydrated to three different post-harvest sugar targets (24.5 °Brix, 26.0 °Brix, and 27.5 °Brix) along with non-dehydrated grapes (21.5 °Brix control). Musts from all treatments were vinified with either the S. uvarum isolate CN1, formerly identified as S. bayanus, or S. cerevisiae EC1118. All wines were successfully vinified to less than 5 g/L residual sugar. Fermentation kinetics between the two yeasts were similar for all wines other than 27.5 °Brix, where CN1 took three days longer. During fermentation with CN1, acetic acid peaked on day two, then decreased in concentration, resulting in final wine acetic acid lower than that measured on day two. Wines fermented with EC1118 showed an increase in acetic acid over the time-course of fermentation. Significantly lower wine oxidative compounds (acetic acid, acetaldehyde and ethyl acetate) and higher glycerol resulted in wine produced with CN1 in comparison to EC1118. Both yeasts produced comparable ethanol at each Brix level tested. Further studies showed that CN1 lowered acetic acid seven-fold from 0.48 g/L in juice to 0.07 g/L in wine whereas EC1118 reduced acetic acid to 0.18 g/L. Conclusions: The autochthonous S. uvarum yeast isolate successfully fermented partially dehydrated grapes to < 5 g/L sugar up to 27.5 ºBrix. The consumption rate of acetic acid was faster than its production during fermentation, resulting in low acetic acid, acetaldehyde and ethyl acetate in wine in comparison to a commercial S. cerevisiae yeast while consistently producing higher glycerol. Significance and impact of the study: The S. uvarum yeast isolate can metabolize acetic acid during fermentation to significantly lower acetic acid, ethyl acetate and acetaldehyde in wine. It can also reduce acetic acid by seven-fold from the starting juice to the finished wine, which could have potential application for managing sour rot arising in the vineyard or during the dehydration process in making appassimento-style wines.

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Unveiling dynamic metabolic signatures in human induced pluripotent and neural stem cells.

e Sá, J. V., Simão, D., Terrasso, A. P., Silva, M. M., Brito, C., Isidro, I. A., Alves, P. M. & Carrondo, M. J. (2020). PLoS Computational Biology, 16(4), e1007780.

Metabolism plays an essential role in cell fate decisions. However, the methods used for metabolic characterization and for finding potential metabolic regulators are still based on characterizing cellular metabolic steady-state which is dependent on the extracellular environment. In this work, we hypothesized that the response dynamics of intracellular metabolic pools to extracellular stimuli is controlled in a cell type-specific manner. We applied principles of process dynamics and control to human induced pluripotent stem cells (hiPSC) and human neural stem cells (hNSC) subjected to a sudden extracellular glutamine step. The fold-changes of steady-states and the transient profiles of metabolic pools revealed that dynamic responses were reproducible and cell type-specific. Importantly, many amino acids had conserved dynamics and readjusted their steady state concentration in response to the increased glutamine influx. Overall, we propose a novel methodology for systematic metabolic characterization and identification of potential metabolic regulators.

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Influence of Nutrient Supplementation on Torulaspora Delbrueckii Wine Fermentation Aroma.

Mecca, D., Benito, S., Beisert, B., Brezina, S., Fritsch, S., Semmler, H. & Rauhut, D. (2020). Fermentation, 6(1), 35.

This study was performed with the aim of characterizing the fermentative performance of three commercial strains of Torulaspora delbrueckii and their impact on the production of volatile and non-volatile compounds. Laboratory-scale single culture fermentations were performed using a commercial white grape juice. The addition of commercial nutrient products enabled us to test the yeasts under two different nutrient conditions. The addition of nutrients promoted fermentation intensity from 9% to 20 % with significant differences (p < 0.05) among the strains tested. The strain diversity together with the nutrient availability influenced the production of volatile compounds.

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Switching from Fatty Acid Oxidation to Glycolysis Improves the Outcome of Acute‐On‐Chronic Liver Failure.

Yu, Z., Li, J., Ren, Z., Sun, R., Zhou, Y., Zhang, Q., Wang, Q., Cui, G., Li, J., Li, A., Duan, Z., Xu, Y., Wang, Z., Yin, P., Piao, H., Lv, J.,Liu, X., Wang, Y., Fang, M., Zhuang, Z., Xu, G. & Kan, Q. (2020). Advanced Science, 7(7), 1902996.

Acute‐on‐chronic liver failure (ACLF) has a high mortality rate. Metabolic reprogramming is an important mechanism for cell survival. Herein, the metabolic patterns of ACLF patients are analyzed. An in vitro model of ACLF is established using Chang liver cells under hyperammonemia and hypoxia. A randomized clinical trial (ChiCTR‐OPC‐15006839) is performed with patients receiving L‐ornithine and L‐aspartate (LOLA) daily intravenously (LOLA group) and trimetazidine (TMZ) tid orally (TMZ group) based on conventional treatment (control group). The primary end point is 90‐day overall survival, and overall survival is the secondary end point. By analyzing metabolic profiles in liver tissue samples from hepatitis B virus (HBV)‐related ACLF patients and the controls, the metabolic characteristics of HBV‐related ACLF patients are identified: inhibited glycolysis, tricarboxylic acid cycle and urea cycle, and enhanced fatty acid oxidation (FAO) and glutamine anaplerosis. These effects are mainly attributed to hyperammonemia and hypoxia. Further in vitro study reveals that switching from FAO to glycolysis could improve hepatocyte survival in the hyperammonemic and hypoxic microenvironment. Importantly, this randomized clinical trial confirms that inhibiting FAO using TMZ improves the prognosis of patients with HBV‐related ACLF. In conclusion, this study provides a practical strategy for targeting metabolic reprogramming using TMZ to improve the survival of patients with HBV‐related ACLF.

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Nutrient Addition to Low pH Base Wines (L. cv. Riesling) during Yeast Acclimatization for Sparkling Wine: Its Influence on Yeast Cell Growth, Sugar Consumption and Nitrogen Usage.

Kemp, B., Plante, J. & Inglis, D. L. (2020). Beverages, 6(1), 10.

In traditional method sparkling wine production, to carry out a successful second alcoholic fermentation, yeast are acclimatized to stressful base wine conditions. Base wines typically have low pH, low nutrient concentrations, high acid concentrations, contain sulfur dioxide (SO2), and high ethanol concentrations. Supplementing yeast during the acclimatization stages prior to second alcoholic fermentation with different nutrient sources was assessed to determine the impact on yeast growth, sugar consumption and nitrogen usage. Four treatments were tested with Saccharomyces cerevisiae strain EC1118: the control (T1) with no additives; addition of diammonium phosphate (DAP) during acclimatization, (T2); Go-Ferm® inclusion during yeast rehydration (GF), (T3); and DAP + GF (T4). Results (n = 4) indicated that supplementing with DAP, GF or DAP + GF increased both the rate of sugar consumption and the concentration of viable cells during the yeast acclimatization phase in comparison to the control. Treatments supplemented with DAP + GF or DAP alone resulted in yeast consuming 228 and 220 mg N/L during the acclimatization phase, respectively. Yeast treated only with GF consumed 94 mg N/L in comparison to the control, which consumed 23 mg N/L. The time required to reach the target specific gravity (1.010) during acclimatization was significantly reduced to 57 h for yeast treated with DAP and GF, 69 h for yeast treated with DAP only and 81 h for yeast rehydrated with GF in comparison to 105 h for the control. Our results suggest that nutrients used during yeast acclimatization could have an important impact on the kinetics of second alcoholic fermentation.

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The Use of CRISPR-Cas9 Genome Editing to Determine the Importance of Glycerol Uptake in Wine Yeast During Icewine Fermentation.

Muysson, J., Miller, L., Allie, R. & Inglis, D. L. (2019). Fermentation, 5(4), 93.

The high concentration of sugars in Icewine juice causes formidable stress for the fermenting Saccharomyces cerevisiae, causing cells to lose water and shrink in size. Yeast can combat this stress by increasing the internal concentration of glycerol by activating the high osmolarity glycerol response to synthesize glycerol and by actively transporting glycerol into the cell from the environment. The H+/glycerol symporter, Stl1p, has been previously characterized as being glucose repressed and inactivated, despite osmotic stress induction. To further investigate the role of Stl1p in Icewine fermentations, we developed a rapid single plasmid CRISPR-Cas9-based genome editing method to construct a strain of the common Icewine yeast, S. cerevisiae K1-V1116, that lacks STL1. In an Icewine fermentation, the ∆STL1 strain had reduced fermentation performance, and elevated glycerol and acetic acid production compared to the parent. These results demonstrate that glycerol uptake by Stl1p has a significant role during osmotically challenging Icewine fermentations in K1-V1116 despite potential glucose downregulation.

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Using common viticultural practices to modulate the rotundone and 3-isobutyl-2-methoxypyrazine composition of Vitis vinifera L. cv. Fer red wines from a temperate climate wine region with very cool nights.

Geffroy, O., Calzi, M. L., IBPFELT, K., Yobrégat, O., Feilhès, C. & Dufourcq, T. (2019). OENO One, 53(4).

Aim: Rotundone and 3-isobutyl-2-methoxypyrazine (IBMP) are two potent aroma compounds responsible for pepper and bell pepper notes in red wines, respectively. The aim of the study was to modulate, through common viticultural practices, the volatile composition in these two molecules of Fer red wines from a temperate climate wine region with very cool nights, located in the southwest of France. Methods and results: Three viticultural practices (leaf removal 10 days after berry set, removal of lateral shoots, and delayed harvest 7 days after the control) were investigated in 2015 and in 2016. Rotundone concentrations up to 69 ng/L were found in experimental wines. IBMP concentrations were below perception level in wines from 2016 and below detection level in wines from 2015, a vintage with particularly hot climatic conditions between berry set and bunch closure. Delayed harvest induced an increase in rotundone concentration while leaf removal and the removal of lateral shoots had no significant impact on rotundone concentration. Delayed harvest and the removal of lateral shoots were the most efficient practices to decrease IBMP in wines. The three techniques made it possible to increase the odour activity values (OAV) ratio of OAV rotundone to OAV IBMP, with the greatest impact observed for delayed harvest. Conclusion: According to our results, delayed harvest appears to be the best practice to modulate the volatile composition of Fer wines toward an increase in the OAV rotundone to OAV IBMP ratio. Significance and impact of the study: Our results may assist local grape growers to modulate the volatile composition of their wines.

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Protective Effect of an Avocado Peel Polyphenolic Extract Rich in Proanthocyanidins on the Alterations of Colonic Homeostasis Induced by a High-Protein Diet.

Cires, M. J., Navarrete, P., Pastene, E., Carrasco-Pozo, C., Valenzuela, R., Medina, D. A., Andriamihaja, M., Beaumont, M., Blachier, F. & Gotteland, M. (2019). Journal of Agricultural and Food Chemistry, 67(42), 11616-11626.

Avocado peel, a byproduct from the avocado pulp industry, is a promising source of polyphenolic compounds. We evaluated the effect of a proanthocyanidin-rich avocado peel polyphenol extract (AvPPE) on the composition and metabolic activity of human fecal microbiota cultured for 24 h in a bioreactor in the presence of high protein (HP) amounts and the effect of the resulting culture supernatants (CSs) on HT-29Glc–/+ and Caco-2 cells. AvPPE decreased the HP-induced production of ammonia, H2S, propionate, and isovalerate and increased that of indole and butyrate. Microbiota composition was marginally affected by HP, whileAvPPE increased the microorganisms/abundance of phylum Actinobacteria, families Coriobacteriaceae and Ruminococcaceae, and genus Faecalibacterium. AvPPE failed to prevent the HP-induced decrease of HT-29Glc–/+ cell viability and energy efficiency but prevented the HP-induced alterations of barrier function in Caco-2 cells. Additionally, the genotoxic effect of the CSs upon HT-29Glc–/+ was attenuated by AvPPE. Therefore, AvPPE may be considered as a promising product for improving colonic homeostasis.

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Hazard Statements : H302, H315, H319, H360
Precautionary Statements : P201, P202, P264, P270, P280, P301+P312, P302+P352, P305+P351+P338, P330, P337+P313, P501
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