Amount Of Free Amino Acids Research Articles

Differential hydrolysis of proteins of four microalgae by the digestive enzymes of gilthead sea bream and Senegalese sole

This study evaluates the in vitro protein hydrolysis of four microalgae (Tisochrysis lutea, Nannochloropsis gaditana, Tetraselmis suecica and Scenedesmus almeriensis) by intestinal proteases of gilthead sea bream (Sparus aurata) and Senegalese sole (Solea senegalensis). The hydrolysis of protein was monitored at different sampling times by electrophoretic techniques, and the quantification of the free amino acids released by proteases. Overall, S. aurata or S. senegalensis proteases hydrolysed microalgae protein in a similar way. The highest hydrolysis values (coefficient of protein degradation, CPD > 70%) were obtained for Tisochrysis and Nannochloropsis biomasses, which showed a progressive and almost complete proteolysis at the end of the in vitro assay. Tetraselmis and Scenedesmus protein was also hydrolysed, but SDS-PAGE revealed that two protein fractions remained virtually intact at the end of the in vitro assay. The final amount of free amino acids released in vitro by the fish digestive enzymes ranged from 9 to 25 g 100 g protein−1. A linear relationship between CPD and the amount of free amino acids released was found, a fact that suggests that microalgae protein is hydrolysed efficiently by the digestive proteases of both fish species. The present study provides information about the protein availability from selected microalgae, which will aid in the initial evaluation of the microalgae as potential protein sources in feeds of two important farmed fish species.

Comprehensive behavioral analysis and quantification of brain free amino acids of C57BL/6J congenic mice carrying the 1473G allele in tryptophan hydroxylase-2.

AimTryptophan hydroxylase 2 (Tph2) is a rate‐limiting enzyme for the biosynthesis of 5‐hydroxytryptamine (5‐HT, serotonin). Previous studies have reported that C1473G polymorphism of the murine Tph2 gene leads to decreased 5‐HT levels in the brain and abnormal behavioral phenotypes, such as impaired anxiety‐ and depression‐like behaviors. In this study, to confirm the effect of the C1473G polymorphism on mouse phenotypes, we conducted a comprehensive battery of behavioral tests and measured the amounts of brain free amino acids involved in the production of 5‐HT.MethodsWe obtained C57BL/6J congenic mice that were homozygous for the 1473G allele of Tph2 (1473G) and subjected them and their wild‐type littermates (1473C) to a battery of behavioral tests. Using reverse‐phase high‐performance liquid chromatography (HPLC), we measured the amounts of free amino acids in the 5‐HT and epinephrine synthetic/metabolic pathways in the frontal cortex, hippocampus, striatum, and midbrain.ResultsWe failed to detect significant differences between genotypes in depression‐like behaviors, anxiety‐like behaviors, social behaviors, sensorimotor gaiting, or learning and memory, while 1473G mice exhibited a nominally significant impairment in gait analysis, which failed to reach study‐wide significance. In the HPLC analysis, there were no significant differences in the amounts of 5‐HT, dopamine, norepinephrine, and epinephrine in the frontal cortex, hippocampus, striatum, and midbrain.ConclusionOur findings do not support the idea that congenic C57BL/6J mice carrying the 1473G allele may represent an animal model of mood disorder under normal conditions without stress.

The effects of carbohydrase, probiotic Lactobacillus paracasei and yeast Lindnera saturnus on the composition of a novel okara (soybean residue) functional beverage

Okara (soybean residue) is a food processing by-product and is often under-utilised due to its low digestibility and off-odour. To improve its composition, a combination of different biocatalysts was used. Okara was first treated with a carbohydrase Viscozyme® L, then fermented with probiotic Lactobacillus paracasei and/or yeast Lindnera saturnus. Viscozyme® L reduced the amount of insoluble fibre by 41.5% and increased soluble fibre by 117%. L. saturnus significantly increased the amount of esters in okara, leading to a perceptible fruity aroma. The final cocultured okara contained high cell counts of live probiotics, significantly less insoluble fibre, soluble fibre, and greater amounts of free amino acids, isoflavone aglycones and fruity esters. After 6 weeks, probiotic viability did not significantly change when stored at 5 °C, but decreased by 1.35 log colony-forming unit/mL when stored at 25 °C. Nonetheless, the amount of viable probiotic cells exceeded the minimum dosage for conferring health benefits. With enhanced nutritional and aroma profiles, the cocultured okara may be a functional probiotic beverage.

Quantitative analysis of amino acids in human and bovine colostrum milk samples through iTRAQ labeling

The types and quantity of proteins vary widely between bovine and human milk, with corresponding differences in free and hydrolytic amino acids. In this study, the free and hydrolytic amino acids of bovine and human colostrum were for the first time qualitatively and quantitatively determined using isobaric tags for relative and absolute quantification technology combined with liquid chromatography tandem mass spectrometry detection. Total free amino acid content was 0.32 g L-1 and 0.63 g L-1 in bovine and human colostrum respectively, with free amino acid content in human colostrum twice that of bovine colostrum. However, total hydrolytic amino acid content was 4.2 g L-1 and 2.2 g L-1 in bovine and human colostrum respectively. We found that the hydrolytic amino acid content in bovine colostrum was higher than that in human colostrum; however, the amount of free amino acids and the overall amino acid content in human colostrum were respectively substantially higher and more varied than in bovine colostrum. Our findings revealed differences between bovine and human colostrum, with these data providing the basis for further research into amino acid metabolomics and infant formula. © 2018 Society of Chemical Industry.

High Hydrostatic Pressure as a Tool to Reduce Formation of Biogenic Amines in Artisanal Spanish Cheeses.

Two artisanal varieties of cheese made in Spain, one made of ewes’ raw milk and the other of goats’ raw milk were selected to evaluate the effect of a high hydrostatic pressure (HHP) treatment at 400 MPa during 10 min at 2 °C on the formation of biogenic amines (BA). These conditions were applied at the beginning of the ripening (before the 5th day; HHP1) and in the case of ewes’ milk cheeses also after 15th days (HHP15). BA formation was greatly influenced by HHP treatments in both types of cheese. HHP1 treatments significantly reduced the amounts of BA after ripening, being tyramine and putrescine the most affected BA in goats’ milk cheeses and tyramine and cadaverine in ewes’ milk cheeses. The BA reduction in the HHP1 samples could be explained by the significant decrease in microbiological counts, especially in the LAB, enteroccocci and enterobacteria groups at the beginning of ripening. The proteolysis in these samples was also affected reducing the amount of free amino acids. Although proteolysis in ewes’ milk cheeses HHP15 was similar than in control samples a reduction of BA was observed probably because the decrease caused on microbial counts.

Effect of High-pressure Processing on the Quality Characteristics and Shelf-life Stability of Hanwoo Beef Marinated with Various Sauces.

The effects of high-pressure processing (HPP) treatment on the quality characteristics of low graded Hanwoo beef marinated with five different sauces (soy, fish, fish-soy, soy-fish and fish-soy-meat sauces) obtained from Asian countries were studied. The Hanwoo beef striploins were marinated with the aforementioned sauces (at ratio: 3:1 w/w) for 3 days at 4℃ before they were treated with HPP at 550 MPa for 5 min at 10℃. All the sauces used were equalized to a same salt level of 12.5%, and the samples marinated with a 12.5% brine solution were served as a control. After treating with the HPP, all the samples were stored for further 7 days at 4℃ for analyses. Results revealed that HPP treatments showed some effects on technological quality traits (pH, cooking loss and color) but had no effect on the collagen contents of the marinated beef. Noticeably, the HPP treatment led to the increases in amounts of free amino acids associated with monosodium glutamate–like taste and sweet taste in the samples marinated with fish sauce or soy-fish sauce, fish-soy sauce and fish-soy-meat sauce whereas, it only reduced these amino acids in the samples marinated with soy sauce or control. Furthermore, the total bacteria count in all the marinated beef samples treated with HPP were significantly (p<0.05) lower than those of the non-HPP-treated samples throughout the storage periods. It is concluded that HPP could be applied for enhancing the taste-active compounds production such as free amino acids, and improving the shelf-life stability of the marinated beef.

Application of the target fermentation in the technology of extended shelf-life meat-based products

In modern conditions, the expansion of the range of raw materials that can be used in the process of producing meat products is relevant. This is due both to the fluctuations in the state of the raw materials market (and its prices) on the scale of Ukraine, and the need to provide biologically-complete products of the growing population on a world scale. To perform these tasks one of the actively studied and used methods is the application of target fermentation. This technological approach has several advantages over other common methods of increasing biological value (the introduction of various fillers based on animal and plant proteins in the form of isolates, extrudates and emulsions).The advantages of using fermentation in the technology of meat-based products include - the lower consumption of additional raw materials (namely the enzyme) per unit weight of the finished product (which in most cases leads to lower cost), the complete or predominant absence of the enzyme in the finished product (due to thermal inactivation), simplification of the additional raw materials preparation process, a wide range of basic raw materials, with which it is possible to combine enzyme. Application of targeted fermentation can influence peptide bonds in the proteins of the main raw material, increasing the amount of free amino acids and increasing the biological value of the product. This technique requires further research and has some unresolved (in whole or in part) issues. These include, in particular, the regimes for the introduction and processing of raw enzymes with separate or simultaneous proteolysis of meat and vegetable raw materials, the composition of the mixture of gases in the development of a modified atmosphere for packaging of this type of product, the optimal composition of enzyme compositions, which could manifest synergistic effects when introduced in meat and vegetable systems, methods for improving organoleptic characteristics at minimum costs and minimizing the introduction of synthetic aromatic ingredients, specification of raw materials assortment for meat-based products followed by selection of the best recipes that have the potential maximum biological value. From the considered literature it can be concluded that these questions are actively solved by leading scientists and have the theoretical foundations for further solution, therefore the chosen direction of research (improvement of the technology of meat products of extended storage with the use of targeted fermentation) is perspective both on a scale domestic industry, and in general.

건조 구기자의 추출조건에 따른 유리아미노산의 변화

The amounts of free amino acids extracted from dried Gugija (Lycium chinensis Mill) were monitored under different extraction conditions. The response methodology was applied using the ethanol concentration (X1 0-80%) and extraction time (X2 1-5 h) as operational parameters with regard to various free amino acids (glycine, serine, alanine, threonine, proline, valine, methionine, isoleucine, leucine, tyrosine, tryptophan, phenylalanine, asparagine, lysine, arginine, histidine, carnosine, ornithine, aspartic acid, glutamic acid, phosphoserine, hydroxyproline, γ-amino-n-butyric acid, taurine, phosphoethanolamine, citrulline, β-alanine, β-amino-isobutyric acid, hydroxylysine, sarcocine, and ethanolamine) and their sum. Under the optimum conditions, the free amino acid contents were asparagine 186.28, phosphoethanolamine 166.21, proline 46.51, alanine 43.35, aspartic acid 27.23, hydroxyproline 21.17, glutamic acid 16.53, taurine 16.24, arginine 14.66, serine 11.65, γ-amino-n-butyric acid 10.82, leucine 10.52, tryptophan 8.75, ethanolamine 8.49, and total free amino acid 629 mg/100 g. The coefficients of determination (R2) of the models for methionine, arginine, histidine, carnosine, ornithine, aspartic acid, phosphoserine and γ-amino-n-butyric acid were within 0.9052-0.9810 (p&lt;0.01-0.05). For the total free amino acids, the R2 of the model was 0.8608 (p&lt;0.1), the extraction yield ranged from 282 to 641 mg/100 g depending on the extraction conditions and was the highest when extracted for 5 h with 20% ethanol.

Preparation of the rainbow trout bone peptides directed by nutritional properties and flavor analyses.

Rainbow trout bone proteins were prepared by heating at 121°C for 30 min, followed by filtration, concentration, and lyophilization. Nutritional properties and flavor analyses of hydrolysates digested by five different enzymes were investigated, respectively. Results showed that the crude protein content of rainbow trout bone was 15.90% and had a well‐balanced nutritional value. The content of total amino acids was 983.64 mg/g. The amount of free amino acids of hydrolysates digested by alkaline protease, neutral protease, flavourzyme, papain, and trypsin for 3 hr was 207.83, 224.13, 1,001.59, 283.26, and 303.64 mg/g, respectively. During the hydrolysis, the main flavor compounds were identified by GC‐MS to be alcohols, aldehydes, ketones, acids, and alkanes. After hydrolysis, the main molecular weight of peptides was focused on the range of 1,000–3,000 Da in all enzymatic hydrolysates. This study provided a theoretical basis to comprehensive utilization of rainbow trout bone in food industry.

CHANGES OF CONTENT OF FREE AMINO ACIDS IN GRAINS OF FOREST GROWING EASTERS OF EASTER TRANSBAIKALIA IN PULLING IN OSMOSITIC STRESS

In the course of studying the content of free amino acids in dry and germinating grains of wild cereals, some biochemical features of their dynamics were revealed depending on the osmotic pressure. In most species, except Agropyron cristatum, a significant increase in the concentration of amino acids occurred in the control on the first day after the start of the experiment; in the subsequent period, their decrease was observed. For Agropyron cristatum, a decrease in the index and a smooth increase after the first day were observed. Under the influence of osmolyte, the tendency to mobilize amino acids has changed and in some species (Stipa krylovii, Melica virgata, Melica turczaninowiana) the maximum amounts were observed on the first day from the beginning of the experiment, in the others to the second day. The total amount of free amino acids in the control and in the test was not significantly different. There was also a rapid mobilization of proteinogenic amino acids with increasing osmotic stress for the widespread Stipa krylovii and Agropyron cristatum in the region. A similar trend was noted for the xerophyte Tripogon chinensis. For grasses with a narrow ecological niche, which are characterized by xeromesophilia, osmotic stress suppressed the rapid mobilization of free amino acids. The content of individual groups of amino acids under the influence of osmotic stress was characterized by significant differences for species of the Melica genus in the number of acidic amino acids, for Tripogon chinensis an increase in the content of basic amino acids, and for Agropyron cristatum by a decrease in their concentration.

Vacuolar Protein Degradation via Autophagy Provides Substrates to Amino Acid Catabolic Pathways as an Adaptive Response to Sugar Starvation in Arabidopsis thaliana.

The vacuolar lytic degradation of proteins releases free amino acids that plants can use instead of sugars for respiratory energy production. Autophagy is a major cellular process leading to the transport of proteins into the vacuole for degradation. Here, we examine the contribution of autophagy to the amino acid metabolism response to sugar starvation in mature leaves of Arabidopsis thaliana. During sugar starvation arising from the exposure of wild-type (WT) plants to darkness, autophagic transport of chloroplast stroma, which contains most of the proteins in a leaf, into the vacuolar lumen was induced within 2 d. During this time, the level of soluble proteins, primarily Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), decreased and the amount of free amino acid increased. In dark-treated autophagy-defective (atg) mutants, the decrease of soluble proteins was suppressed, which resulted in the compromised release of basic amino acids, branched-chain amino acids (BCAAs) and aromatic amino acids. The impairment of BCAA catabolic pathways in the knockout mutants of the electron transfer flavoprotein (ETF)/ETF:ubiquinone oxidoreductase (etfqo) complex and the electron donor protein isovaleryl-CoA dehydrogenase (ivdh) caused a reduced tolerance to dark treatment similar to that in the atg mutants. The enhanced accumulation of BCAAs in the ivdh and etfqo mutants during the dark treatment was reduced by additional autophagy deficiency. These results indicate that vacuolar protein degradation via autophagy serves as an adaptive response to disrupted photosynthesis by providing substrates to amino acid catabolic pathways, including BCAA catabolism mediated by IVDH and ETFQO.

The dynamics of free amino acids in the grains Tripogon chinensis (Franch.) Hack. when germinating in the conditions of the osmotic stress

The content of free amino acids in seeds and sprouts of T. chinensis in the control and at an osmotic pressure of 5 atm. was determined. The group of acidic and basic amino acids predominates in seeds. An adaptive reaction to a physiological drought is the transformation of the free amino acids metabolism. This is expressed in an increase in the total amount of free amino acids at the osmotic pressure of 5 atm., providing the osmotic component of adaptation. Under the conditions of the osmotic stress, the concentration of acidic and basic amino acids increases up to 48 hours, this may be due to the continued hydrolysis of reserve proteins. Under the influence of the osmotic stress there are changes in the group of amino acids, the metabolic precursor of which is glutamic acid. The amino acids, a part of this group, exhibit protective, signaling properties. Thus, the increase in the arginine concentration and ornithine is noted; this indicates the activation of the ornithine cycle and on the increase of amino acids catabolism. The revealed features can ensure the successful germination of T. chinensis grains under the conditions of the physiological drought.

Application of plant proteolytic enzymes for tenderization of rabbit meat

The purpose of this study is to assess the tenderizing effect of plant proteolytic enzymes upon raw rabbit meat. Tests are performed on rabbit meat samples treated with papain and two vegetal sources of natural proteases (extracts of kiwifruit and ginger root). Two variants of marinade solutions are prepared from each vegetable raw materials- 50% (w/w) and 100 % (w/w), with a duration of processing 2h, 24h, and 48h. Changes in the following physicochemical characteristics of meat have been observed: pH, water-holding capacity, cooking losses and quantity of free amino acids. Differences in values of these characteristics have been observed, both between control and test samples, as well as depending of treatment duration. For meat samples marinated with papain and ginger extracts, the water-holding capacity reached to 6.74 ? 0.04 % (papain), 5.58 ? 0.09 % (variant 1) and 6.80 ? 0.11 % (variant 2) after 48 hours treatment. In rabbit meat marinated with kiwifruit extracts, a significant increase in WHC was observed at 48 hours, 3.37 ? 0.07 (variant 3) and 6.84 ? 0.11 (variant 4). The test samples also have reduced cooking losses compared to control samples. In control samples, cooking loss is increased from 13.79% (2 h) to 20.78 % (48 h). SDS-PAGE of meat samples after 48 h of treatment shows a reduction in the intensity of actin and myosin bands in all variants with papain and vegetal extracts. Electrophoretic pattern of test samples depicts proteolysis and degradation of muscle proteins.

VARIATIONS OF PROXIMAL COMPOSITION IN PILEA MICROPHYLLA (L.) LIEBM DUE TO DESICCATION AND REHYDRATION IMPACTS

Water deficiency is the most significant abiotic stress factor for land plants. Most plants are unable to survive desiccation to the air dry state. There are however a few species from lower plant groups to flowering plants that tolerate desiccation known as resurrection plants. So, the present investigation was undertaken tostudy the biochemical changes in Pileamicrophylla against desiccation (1, 3, 5 and 7 days) and rehydration (30 min) stress. As an initial part of the study total sugar, protein and proline content were analyzed and showed a gradual decline during the stress periods. The SDS-PAGE analysis of protein indicated thedisapperance of certain bands in the desiccated and rehydrated samples (7D) when compared to the control indicating the denaturation of proteins during stress. Similarly, the appearance of new bands (15kDa on 3D and 20 and 17kDa on the 5D) were noticed suggesting the formation of stress related proteins to tide over desiccation. The amount of free amino acids increased in P. microphylla, in pace with desiccation periods. Constitutive increase in the level of proline (the stress amino acid) accumulation is seen when compared with the control i.e., 6 fold higher than that of the control, after exposed to desiccation for 5 D. Increase in proline level relating to exposure time of desiccation stress suggests its role as osmolyte. Similarly, a reduction in chlorophyll level and an increase in carotenoid were also observed during stress. Decrease of total chlorophyll content was observed with duration of desiccation. The decrease in chlorophyll a and b was recovered during rehydration up to 5 D. Further studies are warranted at molecular level in terms of stress proteins and genes involved in desiccation tolerance in this plant.

Effect of milk origin on proteolysis and accumulation of biogenic amine during ripening of Dutch-type cheese

Dairy products from goat's milk are characterized by their distinctive aroma and their specific taste. However, the strong aroma can discourage some consumers. Properties of cheese can be modified by the combination of goat's and cow's milk. On the other hand, chemical diversity from different milk origin may affect the changes during ripening. The aim of the study was to compare the intensity of changes during ripening of model cheese samples produced with various ratios of goat's and cow's milk. The combinations 100:0 (100% goat's milk), 75:25, 50:50, 25:75 and 0:100 (100% cow's milk) were used for the manufacture of Dutch-type cheeses, which were ripened during a period of 84 days. Protein profile, free amino acid content and biogenic amine content were used for the description of cheese properties during storage. Cluster analysis showed different changes in the protein matrix of the examined samples. The results indicated that even low addition of cow's milk significantly affected the protein profile. However, the homology of protein profiles rose with the increasing ripening time. More intensive proteolysis occured in the samples with predominance of goat's milk. Moreover, cheese samples produced only from goat's milk presented a significant increase inthe amount of free amino acids after 14 days of ripening. The effect of milk origin on the production of biogenic amines was also examined. However, higher concentrations of biogenic amines were detected in samples manufactured from goat's milk. Tyramine, putrescine, histamine and phenylethylamine were detected during the storage of the samples. The total biogenic amine content exceeded 100 mg/kg in samples with predominance of goat's milk.

Drought stress affects bioactive compounds in potatoes (Solanum tuberosum L.) relevant to non-communicable diseases

Background: Potatoes react very sensitive to drought during growth, and appropriate plant stress responses may affect metabolites associated with the health quality of tubers.Objective: The aim of this study is to determine the effects of drought stress (DS) on soluble sugars, starch, crude protein, minerals, free amino acids (AAs) and fatty acids (FAs).Design: The experiment was carried out on three potato genotypes during two years with four replications. The plants were grown in pots, in a glasshouse with optimal water supply and under drought stress conditions. After harvest, the tubers of these two variants were analyzed for bioactive compounds relevant to non-communicable diseases (NCDs). Results: Apart from genotypic differences in most parameters, the results revealed that the DS caused a decline in glucose and fructose (P &lt; 0.05, all) in both years, whereas sucrose was increased, especially in the second year with severe stress (P &lt; 0.01). Starch was significantly reduced by moderate stress in the first year (P &lt; 0.01), but less affected in the second year. Crude proteins and total amounts of free amino acids (AAs) were clearly enhanced by the stress in both years (P &lt; 0.05, all), similarly as the minerals magnesium (Mg), potassium (K) and phosphorus (P) (P &lt; 0.05, all), whereas calcium (Ca) declined (P &lt; 0.05). The portion of α-linolenic acid (ALA) on total lipids was elevated in the stress variants (P &lt; 0.01), while oleic acid (OLA), its precursor decreased significantly (P &lt; 0.05), but only in the first year. In the second year, ALA was in general higher and not further induced by the stress. Also OLA was less affected in that year, similarly as all other FAs in both years. Interestingly, Myo-inositol (MI) and lipid acyl hydrolases (LAH) associated with modulation in cell membrane lipids raised by the drought stress in each year (P &lt; 0.01, all). In the second year, MI and LAH data of the drought stressed tubers correlated significantly (r = 0.90, P &lt; 0.01) indicating their joined action within plant stress responses.Conclusions: The biochemical changes induced by DS are not alarming with regard to NCDs. Decline in glucose, fructose and starch, and increase in crude proteins, free AAs, ALA, MI and minerals like Mg, K and P, on the other side, is profitable for the health benefits of tubers. However, a better quality is associated with a decrease in tuber yield.Keywords: potato, drought stress, bioactive compounds, chronic diseases

Effect of Monascus fermentation on color and proteolysis of Cantonese sausage

The effects of GIM3.439 Monascus fermentation on the Cantonese sausage was determined during fermentation conditions by comparing the color, p H, amino acidic nitrogen and sensory quality. The SDS-polyacrylamide gelelectrophoresis ( SDS-PAGE) and high performance liquid chromatography ( HPLC) were used to study the changes of protein, peptide and free amino acid ( FAA) during fermentation in Cantonese sausage.The results showed that the color of the fermented sausages is much redder than the control group. The content of amino acidic nitrogen of fermented sausages increased to 0.14%. SDS-PAGE pattern of water-soluble proteins and salt-soluble proteins throughout the fermenting in two groups indicated that fermentation of Monascus can promote the degradation of water-soluble and salt-soluble macromolecule proteins, and increase the total amount of small peptide and free amino acid in the product.The total amount of free amino acids increased from 580 mg/100 g to 930 mg/100 g.Monascus fermentation not only makes the product more attractive color, but also enriched the free amino acid content of sausage, and improve the sensory quality and nutritional value of sausage.

The Effect of Yeast Strain, Immobilisation, and Ageing Time on the Amount of Free Amino Acids and Amino Acids in Peptides of Sparkling Wines Obtained from cv. Dimrit Grapes

In this study, the influence of yeast strain, immobilisation, and ageing time with yeast were examined in relation to the amount of free amino acids and amino acids in the peptides of wines. Free and immobilised Saccharomyces bayanus and Saccharomyces cerevisiae yeasts were used in sparkling wine production. Samples from the base wine and sparkling wines were taken at 20, 40, 90, 180, 270 and 365 days of ageing with yeast. It was observed that the majority of differences between wine samples in terms of the amount of free amino acids and amino acids in peptides were due to ageing time. The amount of total free amino acids in wine made with Saccharomyces cerevisiae was higher than in that made with Saccharomyces bayanus. In addition, no differences were observed between free and immobilised yeast in terms of amino acids and amino acids in peptides.

Redox regulation of free amino acid levels in Arabidopsis thaliana.

Abiotic stresses induce oxidative stress, which modifies the level of several metabolites including amino acids. The redox control of free amino acid profile was monitored in wild-type and ascorbate or glutathione deficient mutant Arabidopsis thaliana plants before and after hydroponic treatment with various redox agents. Both mutations and treatments modified the size and redox state of the ascorbate (AsA) and/or glutathione (GSH) pools. The total free amino acid content was increased by AsA, GSH and H2 O2 in all three genotypes and a very large (threefold) increase was observed in the GSH-deficient pad2-1 mutant after GSH treatment compared with the untreated wild-type plants. Addition of GSH reduced the ratio of amino acids belonging to the glutamate family on a large scale and increased the relative amount of non-proteinogenic amino acids. The latter change was because of the large increase in the content of alpha-aminoadipate, an inhibitor of glutamatic acid (Glu) transport. Most of the treatments increased the proline (Pro) content, which effect was due to the activation of genes involved in Pro synthesis. Although all studied redox compounds influenced the amount of free amino acids and a mostly positive, very close (r > 0.9) correlation exists between these parameters, a special regulatory role of GSH could be presumed due to its more powerful effect. This may originate from the thiol/disulphide conversion or (de)glutathionylation of enzymes participating in the amino acid metabolism.

Deracemization of a Racemic Compound via Its Conglomerate-Forming Salt Using Temperature Cycling

Salts of chiral molecules, which originally crystallize as racemic compounds, could form conglomerates. The utilization of such conglomerate salts, as intermediates for the deracemization of corresponding racemic compounds, expands the theoretical application range of Viedma Ripening by roughly 10-fold. In the present study, the use of temperature cycling on conglomerate forming salts as an alternative technique for Viedma Ripening was studied. The racemic compound Phenylalanine (Phe) was successfully deracemized via its conglomerate-forming salt with 2,5-xylenesulfonic acid (XSA) by continuous heating–cooling cycles applied to its suspension in glacial acetic acid, coupled with a solution racemization reaction. In addition, the dependence of the deracemization rate on the operational parameters was studied. Enhanced racemization reaction kinetics, either by a larger amount of free amino acid or by a higher concentration of catalyst, was shown to accelerate the deracemization process. It seems to indicate...