Direct production of allitol from D-fructose by a coupling reaction using D-tagatose 3-epimerase, ribitol dehydrogenase and formate dehydrogenase

Allitol was produced from D-fructose via a new NADH-regenerating enzymatic reaction system using D-tagatose 3-epimerase (D-TE), ribitol dehydrogenase (RDH), and formate dehydrogenase (FDH). D-fructose was epimerized to D-psicose by the D-TE of Pseudomonas cichorii ST-24 and the D-psicose was subsequently reduced to allitol by the RDH of an RDH-constitutive mutant, X-22, derived from Klebsiella pneumoniae IFO 3321. NADH regeneration for the reduction of D-psicose by the RDH was achieved by the irreversible formate dehydrogenase reaction, which allowed the D-psicose produced from d-fructose to be successively transformed to allitol with a production yield from D-fructose of almost 100%. The reactions progressed without any by-product formation. After separation of the product from the reaction mixture by a simple procedure, a crystal of allitol was obtained in a yield exceeding 90%. This crystal was characterized and determined to be allitol by HPLC analysis, its IR and NMR spectra, its melting point, and optical rotation measurement.     

Enzymatic hydrolysates from tuna backbone and the subsequent Maillard reaction with different ketohexoses

Enzymatic hydrolysates from tuna backbone were prepared, and the subsequent Maillard reaction with rare sugars (d ‐psicose, d ‐sorbose and d ‐tagatose) was investigated. The hydrolysates were found to contain a large number of short peptides under 1000 Da and were good sources of essential amino acids. In assays of free radical scavenging activity and reducing power, the Maillard reaction products from rare sugars, especially d ‐tagatose, performed better than that from d ‐fructose. After heating at 55 °C for 48 h, the scavenging capacity of the hydrolysates for 1,1‐diphenyl‐2‐picryl‐hydrazyl radicals improved by 8.9‐ and 16‐fold in the presence of d ‐fructose and d ‐tagatose. Hence, hydrolysates with high nutrient contents could be prepared from fish by‐products via proteolysis, and the Maillard reaction of rare sugars may greatly promote the antioxidant activity of the hydrolysates.     

Food properties of egg white protein modified by rare ketohexoses through Maillard reaction

d ‐psicose (Psi), a rare ketohexose, improves food properties of proteins through the Maillard reaction (MR) much more than d ‐fructose (Fru). This encouraged us to investigate the improvement of food properties of proteins through MR with various rare ketohexoses (d ‐psicose, Psi; d ‐tagatose, Tag; and d ‐sorbose, Sor). The food properties of egg white protein (EWP) after reaction with Psi, Tag, Sor and Fru were studied. Psi‐EWP (43.3 μmol TE g^?1) and Tag‐EWP (43.4 μmol TE g^?1) had the highest antioxidant activity, followed by Sor‐EWP (38.4 μmol TE g^?1) and Fru‐EWP (38.9 μmol TE g^?1). MR enhanced the breaking stress of heat‐induced EWP gels by 224–267%. The breaking stress was higher in Psi‐EWP (81.1 kN m^?2), Tag‐EWP (80.0 kN m^?2) and Sor‐EWP (77.8 kN m^?2) than in Fru‐EWP (71.6 kN m^?2). Furthermore, the foaming capacity was highest in Psi‐EWP and Sor‐EWP. Rare ketohexoses improved food properties of EWP more than Fru. Overall, Psi offered the greatest functional improvement.     

A COMBINATION OF GLUTAMINASE AND pH CONTROL PREVENTS THE NONENZYMATIC CONVERSION OF l-GLUTAMINE INTO l-2-PYRROLIDINE-5-CARBOXYLIC ACID IN FOOD PROCESSING

A strategy using Alicyclobacillus F‐62 glutaminase was established to minimize the nonenzymatic production of l ‐2‐pyrrolidine‐5‐carboxylic acid (l ‐pyroglutamic acid, savorless amino acid) and maximize the enzymatic production of l ‐glutamic acid (savorous [umami] amino acid) from l ‐glutamine in food‐protein processing. The nonenzymatic production rate of l ‐pyroglutamic acid was influenced by pH and temperature, and decreased over a pH range of 4–6 at 30C. Under optimum conditions (30C and pH 5.0), the l ‐glutamic and l ‐pyroglutamic acids obtained from 1 mM l ‐glutamine in the presence of glutaminase from Alicyclobacillus F‐62 were 0.96 and 0.03 mM, respectively. This novel method is useful for the efficient production of l ‐glutamic acid during food‐protein processing.     

Arginine and nitric oxide synthase: Regulatory mechanisms and cardiovascular aspects

l ‐Arginine (l ‐Arg) is a conditionally essential amino acid in the human diet. The most common dietary sources of l ‐Arg are meat, poultry and fish. l ‐Arg is the precursor for the synthesis of nitric oxide (NO); a key signaling molecule via NO synthase (NOS). Endogenous NOS inhibitors such as asymmetric‐dimethyl‐l ‐Arg inhibit NO synthesis in vivo by competing with l ‐Arg at the active site of NOS. In addition, NOS possesses the ability to be “uncoupled” to produce superoxide anion instead of NO. Reduced NO bioavailability may play an essential role in cardiovascular pathologies and metabolic diseases. l ‐Arg deficiency syndromes in humans involve endothelial inflammation and immune dysfunctions. Exogenous administration of l ‐Arg restores NO bioavailability, but it has not been possible to demonstrate, that l ‐Arg supplementation improved endothelial function in cardiovascular disease such as heart failure or hypertension. l ‐Arg supplementation may be a novel therapy for obesity and metabolic syndrome. The utility of l ‐Arg supplementation in the treatment of l ‐Arg deficiency syndromes remains to be established. Clinical trials need to continue to determine the optimal concentrations and combinations of l ‐Arg, with other protective compounds such as tetrahydrobiopterin (BH₄), and antioxidants to combat oxidative stress that drives down NO production in humans.     

Effect of d‐Psicose Used as Sucrose Replacer on the Characteristics of Meringue

Excessive intake of sugar‐rich foods leads to metabolic syndrome. d ‐Psicose (Psi) not commonly found in nature, is noncalorie sweetener with a suppressive effect on the blood glucose level. Thus, Psi has the potential to be utilized as a sucrose (Suc) replacer in sugar‐rich foods, including meringue‐based confectionery (MBC). In this study, we investigated the effect of Psi on the physical and chemical properties of meringue. Meringue was made by whipping egg white and Suc (at a weight ratio of 1:1) and baking at 93 °C for 2 h. Thirty percent of the total weight of Suc was replaced with d ‐ketohexoses such as Psi, d ‐fructose, d ‐tagatose, and d ‐sorbose. The meringues containing d ‐ketohexoses had higher specific volume than the meringue not containing d ‐ketohexoses (Ct‐meringue). Baking of meringue caused differences between Psi and the other d ‐ketohexose meringues. Meringue containing Psi (P30‐meringue) had the highest breaking stress (7.00 × 10⁵ N/m²) and breaking strain (4.40%), resulting in the crunchiest texture. In addition, P30‐meringue also had the highest antioxidant activity (491.84 μM TE/mg‐meringue determined by ABTS method) and was the brownest due to a Maillard reaction occurring during baking. The replacement of Suc with Psi improved the characteristics of baked meringue. Thus, Psi was found to be useful in modifying the physical and chemical properties of MBC.     

d‐Mannose: Properties,Production, and Applications: An Overview

d ‐Mannose is a C‐2 epimer of d ‐glucose, which is a natural monosaccharide. It can be obtained from both plants and microorganisms. Chemical synthesis and biotransformation of d ‐mannose from d ‐fructose or d ‐glucose by using d ‐mannose isomerases, d ‐lyxose isomerases, and cellobiose 2‐epimerase were intensively studied. d ‐Mannose is an important component of polysaccharides and glycoproteins. It has been widely used in the food, pharmaceutical, and poultry industries, acting as the source of dietary supplements, starting material for the synthesis of drugs and blocking colonization in animal feeds. d ‐Mannose is a glyconutrient with high research value in basic science because of its structure and function. This article presents a review of current studies on sources, characteristics, production, and application of d ‐mannose.     

Lactic acid fermentation of brewer's spent grain hydrolysate by Lactobacillus rhamnosus with yeast extract addition and pH control

Lactic acid (LA) is a versatile chemical with a wide range of applications in food, pharmaceutical, cosmetic, textile and polymer industries. Brewer's spent grain (BSG) is the most abundant brewing by‐product. In this study BSG hydrolysates were used for LA fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate the effects of pH control during fermentation, reducing sugar content and yeast extract content in BSG hydrolysate on LA fermentation parameters. The pH control greatly increased reducing sugar utilization, l ‐(+)‐LA content, yield and volumetric productivity. The highest l ‐(+)‐LA yield and volumetric productivity were achieved with the reducing sugar content of 54 g/L. Yeast extract addition significantly increased reducing sugar utilization, l ‐(+)‐LA content, L. rhamnosus cell viability, l ‐(+)‐LA yield and volumetric productivity. The highest l ‐(+)‐LA content (39.38 g/L), L. rhamnosus cell viability (9.67 log CFU/mL), l ‐(+)‐LA yield (91.29%) and volumetric productivity (1.69 g/L/h) were achieved with the reducing sugar content of 54 g/L and yeast extract content of 50 g/L. Copyright © 2017 The Institute of Brewing & Distilling     

l‐Citrulline Supplementation‐Increased Skeletal Muscle PGC‐1α Expression Is Associated with Exercise Performance and Increased Skeletal Muscle Weight

Scope

l ‐citrulline has recently been reported as a more effective supplement for promoting intracellular nitric oxide (NO) production compared to l ‐arginine. Here, the effect of l ‐citrulline on skeletal muscle and its influence on exercise performance were investigated. The underlying mechanism of its effect, specifically on the expression of skeletal muscle peroxisome proliferator‐activated receptor‐gamma coactivator‐1α (PGC‐1α), was also elucidated.

Methods and results

Six‐week‐old ICR mice were orally supplemented with l ‐citrulline (250 mg kg^?1) daily, and their performance in weight‐loaded swimming exercise every other day for 15 days, was evaluated. In addition, mice muscles were weighed and evaluated for the expression of PGC‐1α and PGC‐1α‐regulated genes. Mice orally supplemented with l ‐citrulline had significantly higher gastrocnemius and biceps femoris muscle mass. Although not statistically significant, l ‐citrulline prolonged the swimming time to exhaustion. PGC‐1α upregulation was associated with vascular endothelial growth factor α (VEGFα) and insulin‐like growth factor 1 (IGF‐1) upregulation. VEGFα and IGF‐1 are important for angiogenesis and muscle growth, respectively, and are regulated by PGC‐1α. Treatment with NG‐nitro‐l ‐arginine methyl ester hydrochloride (l ‐NAME), a nitric oxide synthesis inhibitor, suppressed the l ‐citrulline‐induced PGC‐1α upregulation in vitro.

Conclusion

Supplementation with l ‐citrulline upregulates skeletal muscle PGC‐1α levels resulting in higher skeletal muscle weight that improves time to exhaustion during exercise.

     

Umami Taste Enhancement of MSG/NaCl Mixtures by Subthreshold L-α-Aromatic Amino Acids

l ‐Phenylalanine (l ‐Phe) and l ‐tyrosine (l ‐Tyr) are L‐α‐aromatic amino acids that have recently been discovered to be important components of the savory fractions of soy sauce in addition to l ‐glutamate. Their effects are evaluated on the umami or savory taste of monosodium L‐glutamate (MSG), with or without sodium chloride (NaCl). Because l ‐Phe at subthreshold concentration (1.0 mM) significantly enhances an umami taste of a MSG/NaCl mixture (P= 0.000), combinations of 4 subthreshold concentrations (0, 0.5, 1.5, and 5.0 mM) of l ‐Phe with a weakly suprathreshold MSG (4.0 mM) and NaCl (80 mM) mixture were then rated for salty and umami intensities relative to those of standard solutions. L‐Phe was found to significantly enhance the umami tastes of the MSG/NaCl mixtures when it was added in a concentration range of 0.5 to 5.0 mM (P= 0.000). However, neither the umami taste of MSG alone nor the salty taste of NaCl alone was intensified. In a further experiment, l ‐Tyr at the 3 subthreshold concentrations (0, 0.5, and 1.5 mM) studied was shown to have the same activity as L‐Phe. The phenomenon of umami or savory enhancement by subthreshold aromatic amino acids in the soy sauce system has been established.     

Enzymatic production of natural sweetener trilobatin from citrus flavanone naringin using immobilised α‐l‐rhamnosidase as the catalyst

An efficient and cost‐effective enzymatic production method for preparation of a high‐valued natural sweetener (dihydrochalcone glucoside trilobatin) was developed by the combination of hydrogenation and enzymatic hydrolysis reactions with α‐l ‐rhamnosidase as the catalyst in aqueous medium. This technology is adopting the cheap and largely available citrus flavanone naringin as the starting material for trilobatin synthesis, and the present enzymatic technology is possibly utilised by commercial for scale‐up production. The production is a straightforward two‐step process, in which naringin was hydrogenated into naringin dihydrochalcone and followed by removal of the rhamnosyl group of naringin dihydrochalcone by enzymatic hydrolysis using immobilised α‐l ‐rhamnosidase as the catalyst. Under optimised conditions, an overall yield of 96% was achieved with a very low loading of α‐l ‐rhamnosidase catalyst at 60 °C in a neutral aqueous buffer solution within 2 h. The immobilised α‐l ‐rhamnosidase catalyst can be recycled for 10 reactions (90% yield retained).     

Metabolism of oligosaccharides and aldehydes and production of organic acids in soymilk by probiotic bifidobacteria

Four strains of Bifidobacterium were assessed for α‐galactosidase activity in MRS broth using p‐nitrophenyl‐α‐d ‐galactopyranoside as substrate. Bifidobacteria were then used to ferment soymilk prepared from soy protein isolate (SPI), with and without d ‐glucose and l ‐cysteine supplementation. Measurements of pH and the quantification of oligosaccharides, organic acids and aldehydes in soymilk were done after 0, 12, 24, 36 and 48 h of incubation. The presence of d ‐raffinose stimulated the α‐galactosidase activity of B. longum BB536 (BB536) and B. pseudolongum 20099 (BP20099). In soymilk, oligosaccharides and aldehydes were effectively metabolized by Bifidobacterium; d ‐glucose and l ‐cysteine supplementation enhanced the hydrolysis of raffinose and stachyose. BB536 and BP20099 degraded a significantly greater level of oligosaccharides and aldehydes than B. animalis Bb‐12 and B. longum 1941 (P < 0.05). Raffinose and stachyose were completely metabolized by BB536 after 48 h. In soymilk without any supplementation, hexanal and pentanal were not detected after 12 h of fermentation with BB536 and BP20099. BB536 was the highest producer of organic acids, with an average acetic acid/l (+)‐lactic acid ratio of 0.7.     

Influence of nitrogen on the biological aging of sherry wine

Nitrogen compounds are essential to the growth and metabolism of yeasts. The uptake and metabolism of nitrogen compounds by Saccharomyces cerevisiae depend not only on the strain and its physiological condition, but also on the chemical and physical properties of its environment. The effect of the addition of different amino acids (L ‐proline, L ‐threonine, L ‐arginine, L ‐glutamic acid, L ‐leucine and L ‐valine) to nitrogen‐depleted natural or nitrogen‐free synthetic wine on the cell growth, flor velum formation and sherry wine compound production was investigated under controlled biological aging by S. cerevisiae var. capensis strain G1 a typical flor yeast. The formation of flor velum was dependent on particular amino acid, oxygen availability and the composition of wine. Consumption of glycerol was related with the cell growth; in contrast, acetaldehyde tended to be released. Amino acid supplementation resulted in the release to wine of amino acids, esters and higher alcohols. The amino acid which was released in nearly all cases was L ‐leucine. Addition of L ‐glutamic acid resulted in the release mainly of ethyl acetate, in the case of L ‐leucine isoamyl alcohols were released, and for L ‐valine isobutanol. In the three cases, 1,1‐diethoxyethane was released in large quantities. The findings might indicate that the regulation of metabolism succeeds in the most efficient balancing of the redox potential. Copyright © 2006 Society of Chemical Industry     

l‐histidine improves water retention of heat‐induced gel of chicken breast myofibrillar proteins in low ionic strength solution

The effects of 5 mm l ‐histidine (l ‐His) on water‐binding capacity, gel strength, thermal gelling properties of chicken breast myofibrillar proteins (MPs) in 1 mm NaCl or 0.6 m NaCl solutions (pH 7.0) were investigated. l ‐His could significantly increase the solubility and thermal gelling ability of MPs in 1 mm NaCl. l ‐His at 1 mm NaCl shortened the water relaxation time and decreased the water mobility of MPs gel. l ‐His promoted the formation of MPs gel structure with small pores and thin strands at 1 mm NaCl. These resulted in the enhanced water retention and weak gel strength of MPs in low ionic strength solution. The water‐binding capacity of MPs gels formed in 1 mm NaCl containing 5 mm l ‐His was equivalent to that with 0.6 m NaCl. The information could offer certain theoretical foundation to apply l ‐His as sodium salt substitute for developing low‐salt meat gelling product with high yield.     

Monitoring Technology for Gamma‐Aminobutyric acid Production in Polished Mochi Barley Grains using a Carbon Dioxide Sensor

Gamma‐aminobutyric acid (GABA) has many biological functions, including the inhibition of blood pressure increases and acceleration of growth hormone secretion. In this study, we discovered the utility of measuring the concentration of carbon dioxide (CO₂) dissolved in the reaction solution, for development of a real‐time and convenient technique to estimate GABA production. In addition to mochi barley bran, we examined the polished grains of three species: mochi barley (a variant of hulless barley), barley, and Japanese millet, all soaked in l ‐glutamic acid (l ‐Glu) solution at pH 4.5. We found a positive correlation between GABA and CO₂ concentrations, and the production of CO₂ was suppressed in the absence of l ‐Glu at pH 4.5. These results suggest that GABA content can be easily predicted by measuring the aqueous CO₂ content using a CO₂ sensor, during the process of GABA production in polished mochi barley grains and bran.     

Efficient production of L‐lactic acid by Crabtree‐negative yeast Candida boidinii

Industrial production of L ‐lactic acid, which in polymerized form as poly‐lactic acid is widely used as a biodegradable plastic, has been attracting world‐wide attention. By genetic engineering we constructed a strain of the Crabtree‐negative yeast Candida boidinii that efficiently produced a large amount of L ‐lactic acid. The alcohol fermentation pathway of C. boidinii was altered by disruption of the PDC1 gene encoding pyruvate decarboxylase, resulting in an ethanol production that was reduced to 17% of the wild‐type strain. The alcohol fermentation pathway of the PDC1 deletion strain was then successfully utilized for the synthesis of L ‐lactic acid by placing the bovine L ‐lactate dehydrogenase‐encoding gene under the control of the PDC1 promoter by targeted integration. Optimizing the conditions for batch culture in a 5 l jar‐fermenter resulted in an L ‐lactic acid production reaching 85.9 g/l within 48 h. This productivity (1.79 g/l/h) is the highest thus far reported for L ‐lactic acid‐producing yeasts. DDBJ/EMBL/GenBank nucleotide database with Accession Nos. AB440630 and AB440631. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of l‐lysine/l‐arginine on the emulsion stability,textural, rheological and microstructural characteristics of chicken sausages

The effects of l ‐lysine (Lys), l ‐arginine (Arg) and soya protein isolated (SPI) on the physicochemical properties of chicken sausages were investigated. The results showed that the addition of Lys/Arg significantly decreased total expressible fluid and expressible fat, but significantly increased hardness, springiness, cohesiveness and chewiness of chicken sausage. Moreover, Lys and Arg were more effective than SPI. Rheology indicated that Lys/Arg increased final storage modulus and final loss modulus. Also, scanning electron microscope and confocal laser scanning microscopy disclosed that Lys or Arg was conducive to the formation of regular and uniform oil droplet surrounded integrate membrane. Overall, Lys/Arg exhibited a potential in the preparation of emulsion‐type meat products.     

Enzymatic Synthesis of l‐Ascorbyl Fatty Acid Esters Under Ultrasonic Irradiation and Comparison of Their Antioxidant Activity and Stability

A series of novel l ‐ascorbyl fatty acid esters were synthesized by catalization of Novozym^® 435 under ultrasonic irradiation and characterized by infrared spectroscopy, electrospray ionization mass spectra, and nuclear magnetic resonance. Their properties especially antioxidant activity and stability were investigated. The results showed that the reducing power, the scavenging activity of hydroxyl radical and 2,2‐diphenyl‐1‐picrylhydrazyl radical were decreased with the increase of the number of carbon atoms in fatty acid. The hydroxyl radical scavenging activity and reducing power of l ‐ascorbyl saturated fatty acid esters were better than that of tert‐butylhydroquinone. The induction period in lipid oxidation of l ‐ascorbyl saturated fatty acid esters and tert‐butylhydroquinone were longer than that of l ‐ascorbyl unsaturated fatty acid esters and l ‐ascorbic acid both in soybean oil and lard. Besides, the l ‐ascorbyl fatty acid esters showed different stabilities in different conditions by comparing with l ‐ascorbic acid, and the l ‐ascorbyl saturated fatty acid esters were more stable than l ‐ascorbyl unsaturated fatty acid esters in ethanol solution.     

The IRC7 gene encodes cysteine desulphydrase activity and confers on yeast the ability to grow on cysteine as a nitrogen source

Although cysteine desulphydrase activity has been purified and characterized from Saccharomyces cerevisiae, the gene encoding this activity in vivo has never been defined. We show that the full‐length IRC7 gene, encoded by the YFR055W open reading frame, encodes a protein with cysteine desulphydrase activity. Irc7p purified to homogeneity is able to utilize l ‐cysteine as a substrate, producing pyruvate and hydrogen sulphide as products of the reaction. Purified Irc7p also utilized l ‐cystine and some other cysteine conjugates, but not l ‐cystathionine or l ‐methionine, as substrates. We further show that, in vivo, the IRC7 gene is both necessary and sufficient for yeast to grow on l ‐cysteine as a nitrogen source, and that overexpression of the gene results in increased H₂S production. Strains overexpressing IRC7 are also hypersensitive to a toxic analogue, S‐ethyl‐l ‐cysteine. While IRC7 has been identified as playing a critical role in converting cysteine conjugates to volatile thiols that are important in wine aroma, its biological role in yeast cells is likely to involve regulation of cysteine and redox homeostasis. Copyright © 2015 John Wiley & Sons, Ltd.