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)|
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|
|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.
- 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 “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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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 CaNO3 treatments. 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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
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.Hide Abstract
A 2-year multisite study of viticultural and environmental factors affecting rotundone concentration in Duras red wine.
Geffroy, O., Descôtes, J., Levasseur-Garcia, C., Debord, C., Denux, J. P. & Dufourcq, T. (2019). OENO One, 53(3).
Aim: A study was carried out in 2013 and 2014 to determine the key environmental and viticultural variables affecting the concentration of rotundone, the black pepper aroma compound, in Vitis vinifera L. cv. Duras red wines at 10 different vineyard blocks. Methods and Results: For each block, data for fruit quality attributes, as well as climatic and agronomical variables, were collected. Rotundone was quantified in wines prepared by microvinification techniques (in a 1-L Erlenmeyer flask). Rotundone concentration varied across blocks from 63 ng/L to 239 ng/L in 2013 and from 25 ng/L to 115 ng/L in 2014. Three separate partial least squares regression models were constructed to predict rotundone concentration in wines in 2013, in 2014, and in both vintages. Gluconic acid, a secondary metabolite of Botrytis cinerea, had a substantial contribution to the 2013 and multivintage models, with a negative regression coefficient with rotundone concentration. Other predictors were associated with abiotic factors such as cumulative rainfall, thermal index, hours of sunshine and mean daily irradiation. Conclusions: Our results indicate that mesoscale climatic variables are the key factors determining rotundone concentration, and also suggest that Botrytis cinerea may be involved in rotundone degradation. Significance and impact of the study: Our findings may assist grape growers producing Duras red wines to select specific vineyard blocks with the aim of producing wines with a desired rotundone concentration. They also open up new fields of investigation into mechanisms involved in possible rotundone degradation by Botrytis cinerea.Hide Abstract
Resveratrol Reduced Liver Damage After Liver Resection in a Rat Model by Upregulating Sirtuin 1 (SIRT1) and Inhibiting the Acetylation of High Mobility Group Box 1 (HMGB1).
Yu, S., Zhou, X., Xiang, H., Wang, S., Cui, Z. & Zhou, J. (2019). Medical Science Monitor: International Medical Journal of Experimental and Clinical Research, 25, 3212.
Background: Liver failure after resection for liver cancer is associated with increased patient mortality. This study aimed to investigate the mechanism of the protective effects of resveratrol, a natural plant-derived compound, on liver injury in a rat model of partial hepatectomy. Materials and Methods: Adult male Sprague-Dawley (SD) rats (n=60) were divided into the sham group (n=20), the liver resection group (n=20), and the liver resection plus resveratrol-treated group (n=20). Liver resection removed 2/3 of the liver resection; resveratrol was given at a dose of 30 mg/kg/day from one week before surgery until death. Liver injury was assessed by serum liver function tests, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl-transferase (γ-GT) and total bilirubin, histological examination of the rat liver, and liver cell apoptosis using the TUNEL assay. High mobility group box 1 (HMGB1) expression was measured by enzyme-linked immunoassay (ELISA). Sirtuin 1 (SIRT1) and acetylated HMGB1 (Ac-HMGB1) expression were detected by Western blot. Normal human liver cells and HepG2 liver cancer cells were incubated with acetylated HMGB1, and albumin production and ammonia elimination assays were performed. Results: Resveratrol reduced postoperative liver injury as shown by reduced ALT, AST, γ-GT, and total bilirubin levels, maintained liver structure, and reduced cell apoptosis. Resveratrol treatment reduced the expression and acetylation levels of HMGB1 via the SIRT1 signaling pathway. Resveratrol reversed Ac-HMGB1 induced dysfunction in liver cells cultured in vitro. Conclusions: Resveratrol reduced liver damage after liver resection in a rat model by upregulating SIRT1 and reducing the acetylation of HMGB1.Hide Abstract
Juice clarification with pectinase reduces yeast assimilable nitrogen in apple juice without affecting the polyphenol composition in cider.
Ma, S., Neilson, A., Lahne, J., Peck, G., O'Keefe, S., Hurley, E. K., Sandbrook, A. & Stewart, A. (2018). Journal of Food Science, 83(11), 2772-2781.
The term “cider” refers to the fermented beverage produced from apples. The rapid growth in the cider industry coupled with the prominence of traditional, or craft, approaches emphasizes the need for research on cider production. A common problem in ciders is the production of sulfur off‐aromas by yeast during fermentation. Prefermentation juice clarification has the potential to reduce the occurrence of unwanted sulfur off‐aromas. Concerns that prefermentation juice clarification will reduce the yeast assimilable nitrogen (YAN) and polyphenols in the juice have limited the application of this practice by cider makers. In this study, 3 clarification methods were applied to ‘York’ apple juice, that is, static settling, centrifugation, and pectinase. Raw (control) and clarified juice were fermented to cider, and the impact of clarification on the physicochemical parameters, amino acids and polyphenol content of the juice and cider was assessed. Juice clarification by pectinase decreased YAN by 50%, while static settling and centrifugation increased the concentration of most amino acids by 83%. All clarification treatments lowered the concentration of total polyphenols in the juice (from 60% to 30%, P < 0.05) and affected the individual polyphenols in the juice but these changes were not evident in the ciders. These findings demonstrate that prefermentation juice clarification results in changes in the chemistry profiles of apple juice. These changes were however not evident in the ciders. This approach therefore has the potential to limit the production of sulfur off‐aromas during cider production without adverse effects on quality.Hide Abstract
Sommer, S. & Cohen, S. D. (2018). Fermentation, 4(2), 39.
Red wines ferment in contact with skins to extract polyphenols and anthocyanins that help build, establish, and stabilize color. Concentration and composition vary among genera, species, and cultivars. For this study, 11 grapes representing Vitis vinifera (Cabernet Sauvignon, Merlot, Cabernet Franc, Barbera, Syrah, Petite Sirah, Mourvedre), Vitis labrusca (Concord), Muscadinia rotundifolia (Noble), and French-American hybrids (Marquette, Chambourcin) were selected. All cultivars were fermented on skins while color extraction was monitored daily. Each grape was also extracted using six different methods (microwave, and ultrasound assisted, Glorie procedure, ITV Standard (Institut Technique de la Vigne et du Vin), AWRI method (Australian Wine and Research Institute), solvent extraction of skins) and compared to color characteristics of the wines produced by fermentation. Results show that the extraction pattern varies among cultivars. Post-fermentation maceration, pressing, and sulfur dioxide addition lead to color loss up to 68 percent of the original maximum with the highest loss for native American grapes and hybrid varieties. Extraction procedures over-estimate color in the finished wine but are more accurate if compared to peak extraction levels during fermentation. Color loss and suitability of different extraction procedures to predict color characteristics of fermented wine strongly depend on the complexity of the anthocyanin spectrum and therefore the cultivar used.Hide Abstract
Karst, D. J., Scibona, E., Serra, E., Bielser, J. M., Souquet, J., Stettler, M., Broly, H., Soos, M., Morbidelli, M. & Villiger, T. K. (2017). Biotechnology and Bioengineering, 114(9), 1978-1990.
Mammalian cell perfusion cultures are gaining renewed interest as an alternative to traditional fed-batch processes for the production of therapeutic proteins, such as monoclonal antibodies (mAb). The steady state operation at high viable cell density allows the continuous delivery of antibody product with increased space-time yield and reduced in-process variability of critical product quality attributes (CQA). In particular, the production of a confined mAb N-linked glycosylation pattern has the potential to increase therapeutic efficacy and bioactivity. In this study, we show that accurate control of flow rates, media composition and cell density of a Chinese hamster ovary (CHO) cell perfusion bioreactor allowed the production of a constant glycosylation profile for over 20 days. Steady state was reached after an initial transition phase of six days required for the stabilization of extra- and intracellular processes. The possibility to modulate the glycosylation profile was further investigated in a Design of Experiment (DoE), at different viable cell density and media supplement concentrations. This strategy was implemented in a sequential screening approach, where various steady states were achieved sequentially during one culture. It was found that, whereas high ammonia levels reached at high VCD values inhibited the processing to complex glycan structures, the supplementation of either galactose or manganese as well as their synergy significantly increased the proportion of complex forms. The obtained experimental data set was used to compare the reliability of a statistical response surface model to a mechanistic model of N-linked glycosylation. The latter outperformed the response surface predictions with respect to its capability and reliability in predicting the system behavior (i.e. glycosylation pattern) outside the experimental space covered by the DoE design used for the model parameter estimation. Therefore, we can conclude that the modulation of glycosylation in a sequential steady state approach in combination with mechanistic model represents an efficient and rational strategy to develop continuous processes with desired N-linked glycosylation patterns.Hide Abstract
Beaumont, M., Jaoui, D., Douard, V., Mat, D., Koeth, F., Goustard, B., Mayeur, C., Mondot, S., Hovaghimian, A., Feunteun, S. L., Chaumontet, C., Davila, A., Tomé, D., Souchon, I., Michon, C., Fromentin, G., Blachier, F. & Leclerc, M. (2017). Molecular Nutrition & Food Research, 61(10), 1700078.
Scope: Few studies have evaluated in vivo the impact of food structure on digestion, absorption of nutrients and on microbiota composition and metabolism. In this study we evaluated in rat the impact of two structures of protein emulsion in food on gut microbiota, luminal content composition, and intestinal characteristics. Methods and results: Rats received for 3 weeks two diets of identical composition but based on lipid-protein matrices of liquid fine (LFE) or gelled coarse (GCE) emulsion. LFE diet led to higher abundance, when compared to the GCE, of Lactobacillaceae (Lactobacillus reuteri) in the ileum, higher β-diversity of the caecum mucus-associated bacteria. In contrast, the LFE diet led to a decrease in Akkermansia municiphila in the caecum. This coincided with heavier caecum content and higher amount of isovalerate in the LFE group. LFE diet induced an increased expression of i) amino acid transporters in the ileum ii) glucagon in the caecum, together with an elevated level of GLP-1 in portal plasma. However, these intestinal effects were not associated with modification of food intake or body weight gain. Conclusion: Overall, the structure of protein emulsion in food affects the expression of amino acid transporters and gut peptides concomitantly with modification of the gut microbiota composition and activity. Our data suggest that these effects of the emulsion structure are the result of a modification of protein digestion properties.Hide Abstract
Yin, H., Zhang, R., Xia, M., Bai, X., Mou, J., Zheng, Y. & Wang, M. (2017). Microbial Cell Factories, 16(1), 109.
Background: Acetic acid bacteria (AAB) are widely applied in food, bioengineering and medicine fields. However, the acid stress at low pH conditions limits acetic acid fermentation efficiency and high concentration of vinegar production with AAB. Therefore, how to enhance resistance ability of the AAB remains as the major challenge. Amino acids play an important role in cell growth and cell survival under severe environment. However, until now the effects of amino acids on acetic fermentation and acid stress resistance of AAB have not been fully studied. Results: In the present work the effects of amino acids on metabolism and acid stress resistance of Acetobacter pasteurianus were investigated. Cell growth, culturable cell counts, acetic acid production, acetic acid production rate and specific production rate of acetic acid of A. pasteurianus revealed an increase of 1.04, 5.43, 1.45, 3.30 and 0.79-folds by adding aspartic acid (Asp), and cell growth, culturable cell counts, acetic acid production and acetic acid production rate revealed an increase of 0.51, 0.72, 0.60 and 0.94-folds by adding glutamate (Glu), respectively. For a fully understanding of the biological mechanism, proteomic technology was carried out. The results showed that the strengthening mechanism mainly came from the following four aspects: (1) Enhancing the generation of pentose phosphates and NADPH for the synthesis of nucleic acid, fatty acids and glutathione (GSH) throughout pentose phosphate pathway. And GSH could protect bacteria from low pH, halide, oxidative stress and osmotic stress by maintaining the viability of cells through intracellular redox equilibrium; (2) Reinforcing deamination of amino acids to increase intracellular ammonia concentration to maintain stability of intracellular pH; (3) Enhancing nucleic acid synthesis and reparation of impaired DNA caused by acid stress damage; (4) Promoting unsaturated fatty acids synthesis and lipid transport, which resulted in the improvement of cytomembrane fluidity, stability and integrity. Conclusions: The present work is the study to show the effectiveness of Asp and Glu on metabolism and acid stress resistance of A. pasteurianus as well as their working mechanism. The research results will be helpful for development of nutrient salts, the optimization and regulation of high concentration of cider vinegar production process.Hide Abstract