Production Of AA Research Articles

Production of AA 2014 Matrix Wollostanite/Wood Ash Solid Waste Particle Reinforced Hybrid Composite with Powder Metallurgy and Investigation of Its Structural Properties

In this study, using AA 2014 aluminum alloy, AA2014/wollastanite, AA2014/wood ash, and AA2014/wollastanite/wood ash composite hybrid materials were produced by powder metallurgy method. The powders, whose mixing ratios were determined by weight, were mixed in a 3-dimensional mixer for 30 min. The prepared mixture powders were pressed uniformly under a pressure of 700 MPa, and cylindrical materials with a diameter of 10 mm were obtained. Then, the materials were sintered for 1 h under argon gas flow at a temperature of 600°C. The density, microstructure, hardness, and wear behavior of the materials were examined. It was observed that the density of the composite materials increased relatively compared to AA 2014 alloy. As the particle reinforcement ratios increased, porosity amounts also increased in the composite and especially in the hybrid materials. In the wood ash-reinforced composite materials, the particles were distributed more homogeneously in the microstructure. The highest hardness value obtained was 70.65 HV in AA2014/15% wollastanite composite material. The weight loss increased in the materials created by particle reinforcement, and the lowest weight loss (170 mg) was determined in this material.

Full NLO QCD predictions for Higgs-pair production in the 2-Higgs-doublet model

After the discovery of the Higgs boson in 2012 at the CERN Large Hadron Collider (LHC), the study of its properties still leaves room for an extended Higgs sector with more than one Higgs boson. 2-Higgs doublet models (2HDMs) are well-motivated extensions of the Standard Model (SM) with five physical Higgs bosons: two CP-even states h and H, one CP-odd state A, and two charged states H^pm _{}. In this letter, we present the calculation of the full next-to-leading order (NLO) QCD corrections to hH and AA production at the LHC in the 2HDM at small values of the ratio of the vacuum expectation values, tan beta , including the exact top-mass dependence everywhere in the calculation. Using techniques applied in the NLO QCD SM Higgs pair production calculation, we present results for the total cross section as well as for the Higgs-pair-mass distribution at the LHC. We also provide the top-quark scale and scheme uncertainties which are found to be sizeable.

A ratiometric fluorescent probe for simultaneous detection of L-ascorbic acid and alkaline phosphatase activity based on red carbon dots/polydopamine nanocomposite

Herein, efficient red carbon dots (R-CDs) were synthesized by one-step hydrothermal treatment of N-(4-amino phenyl) acetamide and (2,3-difluoro phenyl) boronic acid. The optimal emission peak of R-CDs was at 602 nm (under 520 nm excitation) and the absolute fluorescence quantum yield of R-CDs was 12.9%. Polydopamine, which was formed by the self-polymerization and cyclization of dopamine in alkaline condition, emitted characteristic fluorescence with peak position of 517 nm (under 420 nm excitation) and affected the fluorescence intensity of R-CDs through inner filter effect. L-Ascorbic acid (AA), which was the hydrolysis product of L-ascorbic acid-2-phosphate trisodium salt under the catalytic reaction of alkaline phosphatase (ALP), effectively prevented the polymerization of dopamine. Combined with the ALP-mediated AA production and the AA-mediated polydopamine generation, the ratiometric fluorescence signal of polydopamine with R-CDs was correlated closely with the concentration of both AA and ALP. Under optimal conditions, the detection limits of AA and ALP were 0.28 μM during linear range of 0.5–30 μM and 0.044 U/L with linear range of 0.05–8 U/L, respectively. This ratiometric fluorescence detection platform can efficiently shield the background interference of sophisticated samples by introducing a self-calibration as reference signal in a multi-excitation mode, which can detect AA and ALP in human serum samples with satisfactory results. Such R-CDs/polydopamine nanocomposite provides a steadfast quantitative information and makes R-CDs be excellent candidate for biosensors via combining target recognition strategy.

Malathion detection based on polydopamine enhanced oxidase-mimetic activity of palladium nanocubes

Nowadays, fabricating simple and efficient pesticide detection methods become a research focus due to the great threat pesticide residues posed to human health and environment. Herein, we constructed a high-efficiency and sensitive colorimetric detection platform for malathion detection based on polydopamine-dressed Pd nanocubes (PDA-Pd/NCs). The Pd/NCs coated with PDA exhibited excellent oxidase-like activity, which was attributed to the substrates accumulation and accelerated electron transfer induced by PDA. What's more, we successfully achieved sensitive detection of acid phosphatase (ACP) using 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate, relying on the satisfactory oxidase activity from PDA-Pd/NCs. However, the addition of malathion could inhibit the activity of ACP and limit the production of medium AA. Therefore, we constructed a colorimetric assay for malathion based on PDA-Pd/NCs + TMB + ACP system. The wide linear range (0–8 μM) and low detection limit (0.023 μM) indicate excellent analytical performance, which is superior to most malathion analysis methods previously reported. This work not only provides a new idea for dopamine coated nano-enzyme to improve its catalytic activity, but also creates a new tactics for the detection of pesticides such as malathion.

Metal Matrix Alloy AA 6061 Produced by Stir Casting Method

Abstract. In compared to base alloy, aluminum composites made from the AA6061 alloy perform better and have better material properties. The current work provides a thorough analysis of the AA 6061 metal matrix composite (MMC) produced using a traditional stir casting technique. Process parameters and characterization techniques have both been discussed. Upon review, it was found that the most often employed reinforcements for the production of AA 6061 metal matrix nano composite (MMNC) were Al2O3, B4C, SiC, and TiC. Other acceptable reinforcements, such as hybrid, inorganic, nanomaterial, and organic reinforcements, are being considered in the current trend. The AA 6061 hybrid composites have comparable superior qualities to single component composites because they contain two or more reinforcements. There is a tonne of room for AA study. Research on the AA 6061 nanocomposite, which has significantly higher strength and wear resistance and is suitable for aerospace and defence applications, has a lot of potential.

A facile process for adipic acid production in high yield by oxidation of 1,6-hexanediol using the resting cells of Gluconobacter oxydans

BackgroundAdipic acid (AA) is one of the most important industrial chemicals used mainly for the production of Nylon 6,6 but also for making polyurethanes, plasticizers, and unsaturated polyester resins, and more recently as a component in the biodegradable polyester poly(butylene adipate terephthalate) (PBAT). The main route for AA production utilizes benzene as feedstock and generates copious amounts of the greenhouse gas NO2. Hence, alternative clean production routes for AA from renewable bio-based feedstock are drawing increasing attention. We have earlier reported the potential of Gluconobacter oxydans cells to oxidize 1,6-hexanediol, a potentially biobased diol to AA.ResultsThe present report involves a study on the effect of different parameters on the microbial transformation of 1,6-hexanediol to adipic acid, and subsequently testing the process on a larger lab scale for achieving maximal conversion and yield. Comparison of three wild-type strains of G. oxydans DSM50049, DSM2003, and DSM2343 for the whole-cell biotransformation of 10 g/L 1,6-hexanediol to adipic acid in batch mode at pH 7 and 30 °C led to the selection of G. oxydans DSM50049, which showed 100% conversion of the substrate with over 99% yield of adipic acid in 30 h. An increase in the concentrations of the substrate decreased the degree of conversion, while the product up to 25 g/L in batch and 40 g/L in fed-batch showed no inhibition on the conversion. Moreover, controlling the pH of the reaction at 5–5.5 was required for the cascade oxidation reactions to work. Cell recycling for the biotransformation resulted in a significant decrease in activity during the third cycle. Meanwhile, the fed-batch mode of transformation by intermittent addition of 1,6-hexanediol (30 g in total) in 1 L scale resulted in complete conversion with over 99% yield of adipic acid (approximately 37 g/L). The product was recovered in a pure form using downstream steps without the use of any solvent.ConclusionA facile, efficient microbial process for oxidation of 1,6-hexanediol to adipic acid, having potential for scale up was demonstrated. The entire process is performed in aqueous medium at ambient temperatures with minimal greenhouse gas emissions. The enzymes involved in catalyzing the oxidation steps are currently being identified.

Highly Selective Carbonylation of CH3Cl to Acetic Acid Catalyzed by Pyridine‐Treated MOR Zeolite

AbstractThe selective conversion of methane to high value‐added chemicals under mild conditions is of great significance for the commercially viable and sustainable utilization of methane but remains a formidable challenge. Herein, we report a strategy for efficiently converting methane to acetic acid via CH3Cl as an intermediate. Up to 99.3 % acetic acid and methyl acetate (AA+MA) selectivity was achieved over pyridine‐pretreated MOR (MOR‐8) under moderate conditions of 523 K and 2.0 MPa. Water, conventionally detrimental to carbonylation reaction over zeolite catalysts, was conducive to the production of AA in the current reaction system. In the 100 h continuous test with the MOR‐8 catalyst, the average AA+MA selectivity remained over 98 %. AA was formed by carbonylation of methoxy groups within 8‐membered rings of MOR followed by hydrolysis. This strategy provided an approach for highly efficient utilization of methane to oxygenates under mild reaction conditions.

Highly Selective Carbonylation of CH3 Cl to Acetic Acid Catalyzed by Pyridine-Treated MOR Zeolite.

The selective conversion of methane to high value-added chemicals under mild conditions is of great significance for the commercially viable and sustainable utilization of methane but remains a formidable challenge. Herein, we report a strategy for efficiently converting methane to acetic acid via CH3 Cl as an intermediate. Up to 99.3 % acetic acid and methyl acetate (AA+MA) selectivity was achieved over pyridine-pretreated MOR (MOR-8) under moderate conditions of 523 K and 2.0 MPa. Water, conventionally detrimental to carbonylation reaction over zeolite catalysts, was conducive to the production of AA in the current reaction system. In the 100 h continuous test with the MOR-8 catalyst, the average AA+MA selectivity remained over 98 %. AA was formed by carbonylation of methoxy groups within 8-membered rings of MOR followed by hydrolysis. This strategy provided an approach for highly efficient utilization of methane to oxygenates under mild reaction conditions.

A colorimetric smartphone-based platform for pesticides detection using Fe-N/C single-atom nanozyme as oxidase mimetics

In this study, a novel highly sensitive colorimetric platform has been designed for malathion assay based on Fe-N/C SAzyme. The as-synthesized SAzyme can directly oxidize 3,3´,5,5´-tetramethylbenzidine (TMB) to generate blue colored oxidized TMB. L-ascorbic acid-2-phosphate (AA2P), a substrate of acid phosphatase (ACP), could be hydrolyzed to AA, thereafter inhibit the oxidization reaction of TMB, leading to a conspicuous blue color fading. With the addition of malathion hindered the ACP activity and limited the AA production, resulting in the recovery of the catalytic activity of single-atom nanozyme. Under optimized operational conditions, a novel colorimetric assay has been designed for malathion detection with LOD of 0.42 nM. Besides, quantification of malathion in environmental and food samples was achieved based on the proposed strategy. In addition, the successfully integrated paper/smartphone sensor provided sensitive, and rapid, reliable detection of malathion with a LOD of 1 nM.

Viral Infection Drives the Regulation of Feeding Behavior Related Genes in Salmo salar.

The feeding behavior in fish is a complex activity that relies on the ability of the brain to integrate multiple signals to produce appropriate responses in terms of food intake, energy expenditure, and metabolic activity. Upon stress cues including viral infection or mediators such as the proinflammatory cytokines, prostaglandins, and cortisol, both Pomc and Npy/Agrp neurons from the hypothalamus are stimulated, thus triggering a response that controls both energy storage and expenditure. However, how appetite modulators or neuro-immune cues link pathogenesis and energy homeostasis in fish remains poorly understood. Here, we provide the first evidence of a molecular linkage between inflammation and food intake in Salmon salar. We show that in vivo viral challenge with infectious pancreatic necrosis virus (IPNV) impacts food consumption by activating anorexic genes such as mc4r, crf, and pomcb and 5-HT in the brain of S. salar. At the molecular level, viral infection induces an overall reduction in lipid content in the liver, favoring the production of AA and EPA associated with the increment of elovl2 gene. In addition, infection upregulates leptin signaling and inhibits insulin signaling. These changes are accompanied by a robust inflammatory response represented by the increment of Il-1b, Il-6, Tnfa, and Pge2 as well as an increased cortisol level in vivo. Thus, we propose a model in which hypothalamic neurons respond to inflammatory cytokines and stress-related molecules and interact with appetite induction/inhibition. These findings provide evidence of crosstalk between pathogenesis-driven inflammation and hypothalamic–pituitary–adrenocortical axes in stress-induced food intake behavior in fish.

Fluorescence sensor for organophosphorus pesticide detection based on the alkaline phosphatase-triggered reaction

The threat of organophosphorus pesticide (OPP) residue to food safety and human health has caused widespread concern. In this paper, a sensitive fluorescence sensor for OPP detection was constructed based on the alkaline phosphatase (ALP) -triggered in situ reaction. In this method, ALP catalyses the dephosphorylation of the substrate l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AAP) to generate l-ascorbic acid (AA). AA instantly combines with o-phenylenediamine (OPD) to form 3-(1,2-dihydroxyethyl)furo[3,4-b]quinoxalin-1(3H)-one (DFQ), which contains a quinoxaline core skeleton fluorophore and emits a strong fluorescence intensity at 425 nm. The existence of OPPs inhibits the activity of ALP and the production of AA and DFQ. As a result, the fluorescence intensity obviously decreases. Under optimal conditions, the fluorescence intensity linearly depends on the logarithm of chlorpyrifos concentration over a wide range of 20 pg/mL ∼1000 ng/mL with a detection limit of 15.03 pg/mL (S/N = 3), which is lower than the previously reported values. The sensor with its satisfactory accuracy and precision has been successfully applied to the detection of chlorpyrifos in leeks and celery samples with recoveries of 94.5–106.7% and an inter-assay relative standard deviation (RSD) below 11.51%. OPPs can be semiquantitatively determined by the colour changes in ultraviolet light. The superiority of the sensor is due to its visual simplicity without complex fluorescence labelling procedures and costly instruments.

Experimental erosion-corrosion analysis of friction stir welding of AA 5083 and AA 6061 for sub-sea applications

Aluminum Alloys find extensive use in sub-sea installations, marine applications that include deep sea mining and in various naval underwater requirements due to their excellent corrosion and wear resistant properties. Friction Stir Welding (FSW) is a solid - state welding process adopted for the production of AA 5083- AA 6061 joints for structures of deep sea crawlers and other sub-sea applications. The present work throws light on the parameters relevant to the sub-sea which lead to the maximum erosion corrosion behavior (mass loss) of friction stir welded AA 5083- AA 6061 joints produced using 6 mm thick plates. The study was conducted in a slurry jet erosion apparatus, in which the erosion-corrosion response of FSW joints of AA 5083 and AA 6061 for various combinations of pH values, velocity of impingement and orientation conditions was evaluated, using Taguchi method. The Signal to Noise (S/N) ratio response for the erosion-corrosion behavior is presented based on experimental results. The results showed the pH as the most influencing parameter which affected the erosion corrosion behavior, contributing upto 86.89%, followed by 4.12% and 4.41% respectively, by the velocity and angle of impingement. ANOVA analysis was performed for the examination of the differences among group means.

Production and high temperature wear characterization of AA 7075/Al2O3/Graphite hybrid nanocomposites by enhanced stir and ultrasound assisted casting method

AA7075 based metal matrix composites are mainly focused on having improved mechanical and tribological properties at high temperature. Aluminium based hybrid nanocomposites have been fabricated through mechanical stirring and ultrasonic cavitation-assisted solidification process by reinforcing alumina and Graphite (Gr) nanoparticles. The three different materials have been studied for high-temperature environment tribological behaviour by taking the applied load, sliding velocity and temperature as process parameters. Design of experiment approach, namely Box-Behnken design, has been utilized for experiments. Results have been analyzed using ANOVA, and optimized parameters have been obtained using desirability approach to have better tribological characterization in AA7075 based hybrid nanocomposites. The AA7075(material-I) has more wear loss and coefficient of friction as compared to AA7075/3 wt% Al2O3/1 wt%Gr (material-II) and AA7075/1 wt% Al2O3/3 wt%Gr (material-III). It is observed that wear loss and coefficient of friction increases with increase in operating parameters. It is also exhibited that temperature has more effect as compared to other parameters on the wear loss and coefficient of friction. The material -II has low wear loss and coefficient as compared to other materials. As expected, the optimal operating condition for each of the material is found to be lower values of the operating range of each parameter used in current experimentation. The optimal temperature, load, and sliding speed are estimated for each of the three materials. At optimal operating conditions, the wear behaviour of material-II is much better as compared to material-I and material-III.

Development and Evaluation of New Methods for Estimating Albedo-Areas for Three-Axis Stabilized Geosynchronous Satellites

Although direct measurements of the projected areas of various Geosynchronous Earth Orbit (GEO) satellite facets are impossible without high-resolution imaging, estimates of the albedo-Area (aA) product lead to the possibility of inferring the geometric size of an RSO based on the illuminated area. Such size estimates are an integral part of its identity because satellite mission capabilities can be inferred. We are engaged in parallel development of two methods for calculating aA for the body/communication antennas structures and one method for the solar panels. We have previously reported on the Two Facet Model (2FM) method for body aA, and here we discuss a method based on differences between new observations and a baseline catalog that has been constructed from the GEO Observations with Longitudinal Diversity Simultaneously (GOLDS) data. We report on evaluations of the 2FM and Differential Method (DM) algorithm results. We also discuss a new method of estimating solar panel aA by fitting new data that include specular glints. All of these measurement methods are compared to models and simulations that serve as a proxy for ground truth. Because of the partially directional nature of the composite Bi-directional Reflectivity Distribution Function (BRDF) of all bus-mounted appendages, variance of body aA results is expected to be significant. Short-term and long-term variance of the derived aAs will also be discussed.

Effect of medium and incubation time on production of AA, DHA and EPA from Aspergillus oryzae by solid state fermentation

Lately, artificial surfactant is more often used than natural surfactant for petroleum industry. The main advantages of using natural surfactant is because the continuous availability. Single Cell Oil, which utillizes one-cell microorganism, can be a solution, such as Aspergillus oryzae, to produce AA, DHA & EPA. A. oryzae was cultivated on Potato Dextrose Agar (PDA), Czapek Dox Agar (CDA) and Malt Extract Agar (MEA), and then the incubation times are 2,4,5,6 and 7 days in optimal medium. Lipids were extracted using ethanol and n-hexane. The characterization of lipid was done by gas chromatography (GC) method. The most optimal medium is CDA with a lipid concetration of 0,18 g. The best incubation time on CDA medium was 5 days with 0,216 g lipid content containing 0,123 g unsaturated fatty acid, 0,0613 g PUFA and 0,0615 g MUFA. The unsaturated fatty acid composition produced on the 5th day was 29.2% oleate; 29.1% linoleate and ± 0.046% EPA.

Effect of pH, temperature and medium agitation rate in production of AA, DHA, EPA from Aspergillus oryzae with submerged fermentation

There are several substances that needs to be fulfill to keep the brain cell growth such as AA, DHA and EPA. Fungi is one of the alternative source of omega 3, omega 6, omega 9 especially AA, DHA and EPA. This research variates operating condition that is suitable for the growth of Aspergillus oryzae in AA, DHA, and EPA fatty acid production with Submerged Fermentation using synthetic medium. Aspergillus oryzae cultivated in medium using glucose as carbon source and Ammonium sulfate and yeast extract as nitrogen source. The extraction method using ethanol and n-hexane as solvent. The result shows that optimum agitation rate for unsaturated fatty acid production of Aspergillus oryzae is 120 RPM, lipid yield 28,28% and unsaturated fatty acid content 50,36 % and EPA content 2,42 %. Optimum medium pH for PUFA production of Aspergillus oryzae is 6, lipid yield 22,35 % and unsaturated fatty acid content 45,5 %. optimum incubation temperature for unsaturated fatty acid production of Aspergillus oryzae is 25 °C, lipid yield 13,19 % and unsaturated fatty acid content 62,15 %. Unsaturated fatty acids produced from Aspergillus oryzae are oleic, linoleic, linolenic and EPA.

Association of ALOX12 gene polymorphism with all-cause and cardiovascular mortality in diabetic nephropathy.

Cardiovascular (CV) events are the first cause of death in patients with chronic renal disease (CKD) and in patients with type 2 diabetes mellitus (DM2). The combination of CKD and DM2 elevates the risk of both cardiovascular disease (CVD) and death in this high-risk population. Besides traditional risk factors, such as dyslipidemia, smoking, obesity, and carotid atherosclerosis, novel factors are under investigation such as genetic polymorphisms. Lipoxygenases (LOXs) and their genes are of critical importance in oxidative stress, inflammation, and atherosclerosis. The aim of the study is to clarify a potential ALOX12 role in CVD presence and progress of diabetic patients in different stages of nephropathy. We studied 145 patients with a documented history of DM2 for at least 10years and diabetic nephropathy (DN), mean age 68±9years, body mass index 31±5kg/m2, and different stages of renal disease, depending on glomerular filtration rate. The sample population consisted of two groups: 108 DM2 patients with DN in all five stages of CKD and 37 DM2 patients as controls. Anthropometric and clinical characteristics, interview for history of previous CV event, and assessment of carotid intima-media thickness (cIMT) were recorded at baseline. All patients were genotyped for ALOX12 polymorphisms with focus on rs14309. Genotypes (AA, AG, and GG) were evaluated for any possible role in CVD, and grouping was performed on A genotype, which is the dominant model. All participants were followed over a period of 7years, and the end points studied were all-cause mortality, CV mortality, and CV events. CV events were defined as myocardial infarction (MI), stroke, or peripheral artery disease. The GG genotype has been significantly associated with cIMT levels above 0.86mm and with history of MI. Regarding the presence of an atherosclerotic plaque in either carotid artery, no significant association was found when the genotypes were assessed on their own. After grouping, though, GG genotype revealed a significant association between carotid plaque formation and atheromatosis. Kaplan-Meier analysis revealed that ALOX12 gene GG genotype predicted all-cause mortality, CV mortality, and CV events. Similarly, when AA and AG genotypes were grouped, Kaplan-Meier analysis showed that patients with GG genotype presented an even more significant higher all-cause mortality, CV mortality, and CV events compared with AA and AG genotypes combined. After adjustment for several traditional risk factors, multivariate Cox proportional hazard analysis showed that patients with the GG genotype had a significant higher risk of all-cause mortality, a threefold increase in CV mortality, and a twofold increased risk for CV events compared to patients with the AA or the AG genotype. ALOX12 rs14309 GG genotype expression was found to be significantly associated with MI, higher cIMT, increased CV events, CV, and overall mortality. This phenomenon could be partially explained by the increased platelet proaggregatory activity of AA products and the control they exert in thrombotic occurrence and plaque formation.

Cytochrome P450-derived eicosanoids and heart function.

The cytochrome P450 monooxygenase system (CYP) is a multigene superfamily of enzymes, which are important in the metabolism of foreign and endogenous compounds. CYP isoforms metabolize a number of n-3 and n-6 polyunsaturated fatty acids (PUFA), including linoleic acid (18:2n6, LA), arachidonic acid (20:4n6, AA), ecosapentaenoic acid (20:5n3, EPA) and docosahexaenoic acid (22:6n3, DHA) into bioactive lipid mediators, termed eicosanoids. CYP-derived eicosanoids have numerous effects toward physiological and pathophysiological events within the body, which depends on the type, quantity and timing of metabolites produced. Alterations in fatty acid composition and concentrations have been shown to have a role in cardiovascular disease (CVD). The functional role of CYP isozymes and CYP-derived eicosanoids toward physiological and pathophysiological processes in the heart is a rapidly expanding field of research. Numerous studies have investigated the beneficial and detrimental effects of CYP epoxygenase derived metabolites of AA, epoxyeicosatrienoic acids (EET) and CYP ω-hydroxylase products, hydroxyeicosatetraenoic acids (HETE), toward both cardiac and vascular function and disease. Emerging research is revealing the importance of other lipid mediators generated from CYP isozymes, such as epoxyeicosatetraenoic acids (EEQ) and epoxydocosapentaenoic acids (EDP), formed from the metabolism of EPA and DHA and metabolites of LA. Important determinants such as genetics, gender and age have a role in regulating the CYP-derived eicosanoids produced from the metabolism n-3 and n-6 PUFA. Obtaining a better understanding of the complex role CYP-derived eicosanoids have within the heart will provide valuable insight for both basic and clinical researchers investigation CVD.

Effect of Bacillus subtilis mutants on growth performance of piglets fed tryptophan- and valine-deficient diets

The objective was to determine the concentration of L-Trp and L-Val to be substituted by feeding piglets Bacillus subtilis strains developed to overproduce Trp (B. subtilis Trp mutant [BsTrp]) and Val (B. subtilis Val mutant [BsVal]) and by using equations obtained in 3 dose-response studies with Leu, Trp, and Val. A Leu-deficient diet with BsVal was included to distinguish between a general probiotic effect and in situ AA production. Eight diets were formulated for each of the 3 studies: 6 diets with 6 levels of AA and 2 diets with BsTrp or BsVal at 10x or 100x standard doses added to the second lowest level of Leu, Trp, and Val. Pigs (n = 16; 7-9 kg BW) were fed ad libitum from 1 wk after weaning. Blood samples were taken on d 8 and 15. The effect of BsTrp and BsVal was evaluated by expressing the improvement in daily gain and feed intake in equiv-alents of grams L-Leu, L-Trp, or L-Val per kilogram feed using curvilinear plateau and broken-line equations obtained by modeling the 6 AA levels. Bacillus subtilis Val mutant increased animal performance corresponding to 0.88 and 0.39 g L-Leu and 0.17 and 0.44 g L-Val per kilogram feed for 10x and 100x doses, respectively. Bacillus subtilis Trp mutant was equivalent to 0.02 and 0.11 g L-Trp/kg feed for 10x and 100x doses, respectively. Bacillus subtilis Val mutant (10x dose) increased (P < 0.05) plasma Val concentration in the Val study. Bacillus subtilis Trp mutant tended (P = 0.06) to increase Trp plasma concentrations. In conclusion, dietary inclusion of B. subtilis mutants indicated some improvements in the performance of pigs fed AA-deficient diets, which could be related to intestinal synthesis and release of L-Trp and L-Val, to protease activity, or to a general probiotic effect.

Effect of high-pressure treatment on hard cheese proteolysis

The application of high hydrostatic pressure (HHP) treatment has been proposed to reduce the ripening time of cheese via modifications in the enzymatic activities or the substrate reactivity. Investigations on the effect of HHP on cheese proteolysis have been undertaken with either encouraging results or little effect according to the treatment conditions and the type of cheese, but information concerning the effect of HHP on the ripening of hard cooked cheese is still lacking. In this report, we describe the effect of HHP treatment on Reggianito cheese proteolysis. For that purpose, 1-d-old miniature cheeses (5.5-cm diameter and 6-cm height) were treated at 100 or 400MPa and 20°C for 5 or 10min, and control cheeses in the trial were not pressurized. All cheeses were ripened at 12°C during 90d. The HHP did not affect gross composition of the cheeses, but microbial load changed, especially because the starter culture count was significantly lower at the beginning of the ripening of the cheeses treated at 400MPa than in controls and cheeses treated at 100MPa. Cheeses treated at 400MPa for 10min had significantly higher plasmin activity than did the others; the residual coagulant activity was not affected by HHP. Proteolysis assessment showed that most severe treatments (400MPa) also resulted in cheeses with increased breakdown of αS1- and β-CN. In addition, nitrogen content in soluble fractions was significantly higher in cheeses treated at 400MPa, as well as soluble peptides and free AA production. Peptide profiles and individual and total content of free AA in 60-d-old treated cheese were as high as in fully ripened control cheeses (90d). Holding time had an effect only on pH-4.6-soluble nitrogen fraction and plasmin activity; cheese treated for 10min showed higher values than those treated for 5min, at both levels of pressure assayed. We concluded that HHP treatments at 400MPa applied 1d after cheesemaking increased the rate of proteolysis, leading to an acceleration of the ripening process in Reggianito Argentino cheese, whereas 100-MPa treatments did not lead to significant changes.