Addition Of Certain Amino Acids Research Articles

Dekkera bruxellensis--spoilage yeast with biotechnological potential, and a model for yeast evolution, physiology and competitiveness.

Dekkera bruxellensis is a non-conventional yeast normally considered a spoilage organism in wine (off-flavours) and in the bioethanol industry. But it also has potential as production yeast. The species diverged from Saccharomyces cerevisiae 200 mya, before the whole genome duplication. However, it displays similar characteristics such as being Crabtree- and petite positive, and the ability to grow anaerobically. Partial increases in ploidy and promoter rewiring may have enabled evolution of the fermentative lifestyle in D. bruxellensis. On the other hand, it has genes typical for respiratory yeasts, such as for complex I or the alternative oxidase AOX1. Dekkera bruxellensis grows more slowly than S. cerevisiae, but produces similar or greater amounts of ethanol, and very low amounts of glycerol. Glycerol production represents a loss of energy but also functions as a redox sink for NADH formed during synthesis of amino acids and other compounds. Accordingly, anaerobic growth required addition of certain amino acids. In spite of its slow growth, D. bruxellensis outcompeted S. cerevisiae in glucose-limited cultures, indicating a more efficient energy metabolism and/or higher affinity for glucose. This review tries to summarize the latest discoveries about evolution, physiology and metabolism, and biotechnological potential of D. bruxellensis.

Reducing Acrylamide in Fried Snack Products by Adding Amino Acids

ABSTRACT: The aims of this study were to develop commercial methods for reducing the acrylamide content in processed foods and apply them to commercial snacks. The formation of acrylamide in fried foods was found to depend on the composition of raw materials as well as the frying time and temperature. In potato chips, acrylamide was rapidly formed at over 160°C, with the amount proportional to the heating duration and temperature. Free amino acids were used to reduce acrylamide, with lysine, glycine, and cysteine having the greatest effects in the aqueous system. Lysine and glycine were effective at inhibiting the formation of acrylamide in wheat‐flour snacks. In potato snacks, the addition of 0.5% glycine to pallets reduced acrylamide by more than 70%. Soaking potato slices in a 3% solution of either lysine or glycine reduced the formation of acrylamide by more than 80% in potato chips fried for 1.5 min at 185°C. These results indicate that the addition of certain amino acids by soaking the uncooked products in appropriate solutions is an effective way of reducing acrylamide in processed foods.

Sit4 phosphatase is functionally linked to the ubiquitin-proteasome system.

Using a synthetic lethality screen we found that the Sit4 phosphatase is functionally linked to the ubiquitin-proteasome system. Yeast cells harboring sit4 mutations and an impaired proteasome (due to pre1-1 pre4-1 mutations) exhibited defective growth on minimal medium. Nearly identical synthetic effects were found when sit4 mutations were combined with defects of the Rad6/Ubc2- and Cdc34/Ubc3-dependent ubiquitination pathways. Under synthetic lethal conditions, sit4 pre or sit4 ubc mutants formed strongly enlarged unbudded cells with a DNA content of 1N, indicating a defect in the maintenance of cell integrity during starvation-induced G(1) arrest. Sit4-related synthetic effects could be cured by high osmotic pressure or by the addition of certain amino acids to the growth medium. These results suggest a concerted function of the Sit4 phosphatase and the ubiquitin-proteasome system in osmoregulation and in the sensing of nutrients. Further analysis showed that Sit4 is not a target of proteasome-dependent protein degradation. We could also show that Sit4 does not contribute to regulation of proteasome activity. These data suggest that both Sit4 phosphatase and the proteasome act on a common target protein.

Determinants of post-exercise glycogen synthesis during short-term recovery.

The pattern of muscle glycogen synthesis following glycogen-depleting exercise occurs in two phases. Initially, there is a period of rapid synthesis of muscle glycogen that does not require the presence of insulin and lasts about 30-60 minutes. This rapid phase of muscle glycogen synthesis is characterised by an exercise-induced translocation of glucose transporter carrier protein-4 to the cell surface, leading to an increased permeability of the muscle membrane to glucose. Following this rapid phase of glycogen synthesis, muscle glycogen synthesis occurs at a much slower rate and this phase can last for several hours. Both muscle contraction and insulin have been shown to increase the activity of glycogen synthase, the rate-limiting enzyme in glycogen synthesis. Furthermore, it has been shown that muscle glycogen concentration is a potent regulator of glycogen synthase. Low muscle glycogen concentrations following exercise are associated with an increased rate of glucose transport and an increased capacity to convert glucose into glycogen. The highest muscle glycogen synthesis rates have been reported when large amounts of carbohydrate (1.0-1.85 g/kg/h) are consumed immediately post-exercise and at 15-60 minute intervals thereafter, for up to 5 hours post-exercise. When carbohydrate ingestion is delayed by several hours, this may lead to ~50% lower rates of muscle glycogen synthesis. The addition of certain amino acids and/or proteins to a carbohydrate supplement can increase muscle glycogen synthesis rates, most probably because of an enhanced insulin response. However, when carbohydrate intake is high (> or =1.2 g/kg/h) and provided at regular intervals, a further increase in insulin concentrations by additional supplementation of protein and/or amino acids does not further increase the rate of muscle glycogen synthesis. Thus, when carbohydrate intake is insufficient (<1.2 g/kg/h), the addition of certain amino acids and/or proteins may be beneficial for muscle glycogen synthesis. Furthermore, ingestion of insulinotropic protein and/or amino acid mixtures might stimulate post-exercise net muscle protein anabolism. Suggestions have been made that carbohydrate availability is the main limiting factor for glycogen synthesis. A large part of the ingested glucose that enters the bloodstream appears to be extracted by tissues other than the exercise muscle (i.e. liver, other muscle groups or fat tissue) and may therefore limit the amount of glucose available to maximise muscle glycogen synthesis rates. Furthermore, intestinal glucose absorption may also be a rate-limiting factor for muscle glycogen synthesis when large quantities (>1 g/min) of glucose are ingested following exercise.

Effect of amino acids on the chemical oxidation of olive o-diphenols in model systems

Addition of certain amino acids ( l-tryptophan, l-histidine, l-cysteine and l-cystine) to model solutions of caffeic acid and hydroxytyrosol (the two most characteristic o-diphenols of ripe olives) improved the dark colour obtained after oxidation. A detailed study carried out with l-cysteine and caffeic acid showed that, after an initial inhibitory effect, increasing concentrations of amino acid led to darker solutions. The same effect was also found in hydroxytyrosol solutions with increasing amounts (2–8 mm) of cysteine without lag phase, except for 10 mm level. Cysteine also produced darker colour with oxidised storage brine of ripe olives. These results open the door to a possible use of this amino acid as additive or aid in processing to produce darker and homogeneous ripe olives.

Aspergillus sydowii MG 49 is a strong producer of thermostable xylanolytic enzymes

The mycelial fungus Aspergillus sydowii MG49 was found to produce xylanase (EC 3.2.1.8.) and β-xylosidase (EC 3.2.1.37) in high specific activity (72.8 and 9.8 U mg −1 protein, respectively) in a short incubation period of 72 h when grown on xylan as the sole carbon source. Xylose, the breakdown product of xylan, could also induce the production of both the xylanolytic enzymes efficiently . A. sydowii was capable of growth on several underutilized agricultural residues, which also led to the production of these enzymes in high specific activity. Xylanase enzyme produced was secreted extracellularly, but β-xylosidase was found to have intramycelial localization, unlike the reports of extracellular production of this enzyme by many of the other organisms. The optimum production pH for both the enzymes was 4.0, while the production temperature was 30°C. However, both these enzymes exhibited thermostable characteristics, having maximum in vitro enzyme activity at 60°C. Production of xylanase was found to be strongly influenced by the addition of certain amino acids in the enzyme fermentation medium, while the pretreatment of crude xylanolytic enzymes with additives such as metal ions and surfactants also affected the specific activity of the enzymes. This fungus did not produce any cellulolytic enzymes.

Heterotrophic nutrition inMelosira nummuloides, a possible role in affecting distribution in the Clyde Estuary

The benthic centric diatom Melosira nummuloides dominated sites of heavy pollution on the Clyde Estuary, occurring in conditions conducive to heterotrophic growth—positive correlation with BOD and suspended solids and negative correlation against light penetration of the water. A clone (Renf-1) of the organism, isolated from a polluted site and rendered axenic grew in culture through a range of light intensities, with compensating light below 150 lx. Some initial growth occurred in the dark on medium enriched with site water. Growth was best at a salinity of 10‰. for samples adapted to 4, 10 and 12‰.. Addition of certain amino acids to the medium caused significant enhancement of growth, due to leucine, arginine and serine at 0 klx, leucine, arginine and glutamic acid at 0·1 klx and glutamic acid at 3·3 klx. Eight amino acids were accumulated by carrier mediated methods in the dark. Kinetics for arginine uptake were best (low K m) in the dark and at a salinity of 10‰, with a corresponding greater growth e...

Influence of cultural conditions on phosphate accumulation of Arthrobacter globiformis PAB-6.

The influence of cultural conditions was examined on phosphate accumulation of the high phosphate accumulating bacterium, Arthrobacter globiformis PAB-6. This bacterium utilized nitrate and nitrite, as well as ammonium salts, as nitrogen source, and polyphosphates, organic phosphates, as well as inorganic phosphate, as phosphorus source. Ferric and calcium ions were found to be essential for high phosphate accumulation. Both growth and phosphate uptake were stimulated by addition of certain amino acids. Phenylalanine had an especially highly stimulatory effect. Optimal temperature and pH for efficient phosphate uptake were 25°C and between 7 and 8, respectively.

Influence of Micronutrients on Citric Acid Production by Candida lipolytica (Y 1095)

FeSO4 . 7 H2O, PbSO4, CuSO4 . 5 H2O, MnSO4 . 4 H2O, ZnSO4 . 7 H2O, CoCl2 . 6 H2O, and (NH4)6Mo7O24 . 4 H2O were added to the fermentation medium to investigate their potentialities on citric acid production by Candida lipolytica (Y 1095). FeSO4 . 7 H2O and MnSO4 . 4 H2O were more suitable than the other micronutrients for citric acid production. Addition of certain amino acids to the fermentation medium completely inhibited biosynthesis of citric acid by Candida lipolytica (Y 1095). When the fermentation medium was supplied with certain vitamins, yield of citric acid was increased in the presence of thiamine, nicotinic acid, and nicotinamide. The optimum concentration of thiamine which favoured yield of citric acid was 6 mg/l.

Induction and inhibition of the allantoin permease in Saccharomyces cerevisiae

Allantoin uptake in Saccharomyces cerevisiae is mediated by an energy-dependent, low-Km, active transport system. However, there is at present little information concerning its regulation. In view of this, we investigated the control of alloantoin transport and found that it was regulated quite differently from the other pathway components. Preincubation of appropriate mutant cultures with purified allantoate (commercial preparations contain 17% allantoin), urea, or oxalurate did not significantly increase allantoin uptake. Preincubation with allantoin, however, resulted in a 10- to 15-fold increase in the rate of allantoin accumulation. Two allantoin analogs were also found to elicit dramatic increases in allantoin uptake. Hydantoin and hydantoin acetic acid were able to induce allantoin transport to 63 and 95% of the levels observed with allantoin. Neither of these compounds was able to serve as a sole nitrogen source for S. cerevisiae, and they may be non-metabolizable inducers of the allantoin permease. The rna1 gene product appeared to be required for allantoin permease induction, suggesting that control was exerted at the level of gene expression. In addition, we have shown that allantoin uptake is not unidirectional; efflux merely occurs at a very low rate. Allantoin uptake is also transinhibited by addition of certain amino acids to the culture medium, and several models concerning the operation of such inhibition were discussed.

β -Diketoester und deren Enoläther als Aminosäure-Antagonisten. On Amino Acid Antagonists: β-Diketoesters and Their Corresponding γ-Enolethers

Starting with well known beta-diketoesters the corresponding gamma-enolethers are synthesized and described. Both classes of compounds inhibited the growth of some microorganisms. The inhibition is abolishable by addition of certain amino acids to the definite medium. A possible mechanism of inhibition is discussed and compared with the mechanism of some beta,gamma-unsaturated alpha-amino acids. The known unsaturated alpha-amino acids, their origin and their biological activity are summarized in two tables.

Some cultural conditions for the production of puromycin by Streptomyces alboniger

AbstractA simple synthetic medium was used in the fermentative production of puromycin to investigate the efficiencies of certain ingredients in stimulating the organism for higher yield. Addition of certain amino acids, especially L‐histidine, L‐glutamic acid, L‐proline, L‐aspartic acid, DL‐methionine, L‐leucine, β‐alanine, L‐isoleucine, DL‐alanine, L‐tyrosine and L‐glycine, increased the antibiotic yield compared with the control. Lactic acid was more suitable for antibiotic production than the other organic acids used, i.e. maleic, acetic, malic, tartaric and fumaric acids. Addition of certain vitamins, namely cobalamin (vitamin B12), nicotinic acid, vitamin B1 and folic acid, did not markedly increase the antibiotic yield. Certain trace elements, such as zinc, copper, iron, manganese and cobalt, played an important role in the biosynthesis of puromycin by Streptomyces alboniger NRRL B‐2403. The optimum concentrations of these trace elements were 0.2000, 0.0020, 0.0005, 0.3000, and 0.0050 g/litre respectively. The optimum concentration of K2HPO4 favouring biosynthesis of puromycin was 1.5 g/litre. The amino acids formed in the microbial cells of Streptomyces alboniger NRRL B‐2403 during the production of puromycin in the synthetic medium were determined quantitatively. Generally, all the amino acids recorded appeared in the microbial cells.

Some cultural conditions for the production of puromycin by Streptomyces alboniger

AbstractA simple synthetic medium was used in the fermentative production of puromycin to investigate the efficiencies of certain ingredients in stimulating the organism for higher yield. Addition of certain amino acids, especially L‐histidine, L‐glutamic acid, L‐proline, L‐aspartic acid, DL‐methionine, L‐leucine, β‐alanine, L‐isoleucine, DL‐alanine, L‐tyrosine and L‐glycine, increased the antibiotic yield compared with the control. Lactic acid was more suitable for antibiotic production than the other organic acids used, i.e. maleic, acetic, malic, tartaric and fumaric acids. Addition of certain vitamins, namely cobalamin (vitamin B12), nicotinic acid, vitamin B1 and folic acid, did not markedly increase the antibiotic yield. Certain trace elements, such as zinc, copper, iron, manganese and cobalt, played an important role in the biosynthesis of puromycin by Streptomyces alboniger NRRL B‐2403. The optimum concentrations of these trace elements were 0.2000, 0.0020, 0.0005, 0.3000, and 0.0050 g/litre respectively. The optimum concentration of K2HPO4 favouring bio‐synthesis of puromycin was 1.5 g/litre. The amino acids formed in the microbial cells of Streptomyces alboniger NRRL B‐2403 during the production of puromycin in the synthetic medium were determined quantitatively. Generally, all the amino acids recorded appeared in the microbial cells.

Characterization of a rifampin-resistant, conditional asporogenous mutant of Bacillus subtilis.

A rifampin-resistant, conditionally asporgoenous mutant of Bacillus subtilis was isolated that sporulates poorly in Sterlini-Mandelstam sporulation medium, but that sporulates normally in modified Difco sporulation medium. Rifampin-resistant (Rif-r) and conditional asporogenous (Spo-c) phenotypes co-transformed at 100% frequency. Preliminary genetic studies indicated the Rif-r trait to lie between cysA14 and ery, a locus (rnp) common to Rif-r mutants. Ribonucleic acid polymerase from strains bearing this mutation was found to be rifampin resistant in vitro. The loss of ability to sporulate in Sterlini-Mandelstam medium was found to be corrected, to a large extent, by addition to the medium of arginine, methionine, valine, and isoleucine. Several other amino acids had small effects, whereas others had no effect at all. The restorative effect is approximately additive. Growth studies indicated that Rif-r strains grew more rapidly than the corresponding parent in minimal medium at temperatures higher than 37 C. Addition of certain amino acids to the medium resulted in identical growth rates at these temperatures. Extracellular protease and esterase activities of the Rif-r Spo-c mutant were normal. A slight difference was found in the heat sensitivity of partially purified ribonucleic acid polymerase preparations of this mutant compared to the wild type.

Studies on the Metabolism of Biotin Vitamers by Microorganisms

The production of biotin and bisnorbiotin from biotin diaminocarboxylic acid by the resting cell system of microorganisms was studied. It was found that the resting cells of Bacillus sphaericus convert biotin diaminocarboxylic acid into biotin, and the cells of Rhodotorula rubra potently convert it into bisnorbiotin through biotin. The conversion products from biotin diaminocarboxylic acid by these resting cell systems were chromatographically identified as biotin and bisnorbiotin. These conversions were markedly stimulated by addition of certain amino acids, especially alanine and glutamic acid, suggesting the important role of amino compound in the formation of ureido ring of biotin and bisnorbiotin molecules. This reaction occurred rather favorably under aerobic conditions.

Studies on the Metabolism of Biotin Vitamers by Microorganisms

The production of biotin and bisnorbiotin from biotin diaminocarboxylic acid by the resting cell system of microorganisms was studied. It was found that the resting cells of Bacillus sphaericus convert biotin diaminocarboxylic acid into biotin, and the cells of Rhodotorula rubra potently convert it into bisnorbiotin through biotin. The conversion products from biotin diaminocarboxylic acid by these resting cell systems were chromatographically identified as biotin and bisnorbiotin. These conversions were markedly stimulated by addition of certain amino acids, especially alanine and glutamic acid, suggesting the important role of amino compound in the formation of ureido ring of biotin and bisnorbiotin molecules. This reaction occurred rather favorably under aerobic conditions.

The effects of the addition of certain amino acids to enamel decalcifying buffers

In comparing the property of different acids of dissolving powdered enamel, it was found that an aspartic acid-sodium hydroxide pH 4.0 buffer was from 40 to 60 per cent less effective than several other similarly tested acids.1 Normally, it might be expected that at the same con­ stant pH,, buffer solutions of acids of ap­ proximately the same anion concentra­ tion, not capable of reacting with enamel to form insoluble precipitates, would show only small differences in their dis­ solving capacity. The result, therefore, obtained at constant pH, suggested that the effect of active acidity, that is, hydro­ gen ion concentration, may be greatly modified by its associated anion, in this case aspartate ion. Many acids, including the amino acids, have been found in or can gain access to the mouth.2-9 It is likely, therefore, that since acid decalcifi­ cation is considered part of the caries process, not one but a mixture of acids is involved. These mixtures probably exist as buffer systems containing hydrogen ion supplied by a variety of acids, including aspartic acid. In view of the apparently reduced ef­ fectiveness of hydrogen ion (acidity) in dissolving enamel in the presence of as­ partate ion as compared to other anions at pH 4.0, it was thought worthwhile to investigate the effect of the presence of aspartate ion on the decalcifying action of other acids. In addition to aspartic acid, it was decided to test several other amino acids. In order to study the effect of the pres­ ence of different amino acids on the de­ calcifying property of other acids which may be present in the mouth, four such acids— acetic, lactic, citric and pyruvic— were selected because they represent a cross section ranging from the very weak (acetic) to the relatively strong organic acids (pyruvic). These acids were first tested as simple buffers, at pH 4.0, for their property of dissolving enamel; they were then retested at the same pH after the addition of one of the following amino

Protein Supplementation, Influence of Addition of Certain Amino Acids and Vitamin B12 to Proteins in Enriched Milled Wheat Flour on Growth, Protein Efficiency, and Liver Fat Deposition

Protein Supplementation, Influence of Addition of Certain Amino Acids and Vitamin B₁₂ to Proteins in Enriched Milled Wheat Flour on Growth, Protein Efficiency, and Liver Fat Deposition

479. Studies on the biological value of the proteins (nitrogen) of dried skim milk: effects of the addition of certain amino-acids, of age of rat and of level of protein intake

1. It has been shown that the biological value of undeteriorated dried skim milk is depressed to the same extent by the addition of 1·25% L-lysine as by the addition of 1·25% D-lysine. The latter is not used by the rat. It is therefore concluded that the added L-lysine is surplus to the animal's needs and that the apparent lowering of the biological value is due to excretion of the lysine in the urine.2. The slightly greater loss in the biological value of milk stored in air-pack compared with gas-pack was eliminated by the addition of 0·5% L-histidine to the former. Histidine is not a limiting amino-acid in the control or stored gas-pack milks for either young or adult rats.3. A lower biological value was found for the control milk with adult than with young rats at 4 and 8% levels of intake. No further lowering in the biological value of the stored milk, deficient in lysine, was observed with adult rats, the value obtained for this milk being independent of the age of the rat. These results are in keeping with the known lowered requirements of the adult rat for lysine.4. The significance of these findings in relation to the known amino-acid requirements of young and adult rats is discussed.

Cultivation of Rabies Virus in vitro

I HAVE reported1 that rabies virus can multiply in vitro in a cell-free medium containing steamed sheep-brain extract, sheep serum, glycine and peptone. The effect of the addition of certain amino-acids and accessory factors on the growth of the virus in this medium has been investigated.