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Research background: The development of a novel process for the production of xylooligosaccharides (XOS) based on the 4R concept is made possible by the integration of numerous techniques, especially enzymatic modification together with the physical pretreatment of renewable materials. This study aims to integrate the use of agricultural wastes for the production of xylanase by a new strain of Penicillium sp. and value-added products, XOS. Experimental approach: For the production of xylanase, a solid-state fermentation was performed using wheat bran as substrate. To obtain the most active crude extract of xylanase, the time frame of cultivation was first adjusted. Then, the downstream process for xylanase purification was developed by combining different membrane separation units with size exclusion chromatography. Further characterisation included determination of the optimal pH and temperature, determination of the molecular mass of the purified xylanase and analysis of kinetic parameters. Subsequently, the hydrolytic ability of the partially purified xylanase in the hydrolysis of alkali-extracted hemicellulose from soybean hulls was investigated. Results and conclusions: Our results show that Penicillium rubens produced extracellular xylanase at a yield of 21 U/g during solid-state fermentation. Using two ultrafiltration membranes of 10 and 3 kDa in combination with size exclusion chromatography, a yield of 49 % and 13-fold purification of xylanase was achieved. The purified xylanase (35 kDa) cleaved linear bonds ß-(1â4) in beechwood xylan at a maximum rate of 0.64 µmol/(min·mg) and a Michaelis constant of 44 mg/mL. At pH=6 and 45 °C, the purified xylanase showed its maximum activity. The xylanase produced showed a high ability to hydrolyse the hemicellulose fraction isolated from soybean hulls, as confirmed by thin-layer chromatography. In the hydrothermally pretreated hemicellulose hydrolysate, the content of XOS with different degrees of polymerisation was detected, while in the non-pretreated hemicellulose hydrolysate, the content of xylotriose and glucose was confirmed. Novelty and scientific contribution: Future research focusing on the creation of new enzymatic pathways for use in processes to convert renewable materials into value-added products can draw on our findings.
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Klebsiella pneumoniae is a 2,3-butanediol producing bacterium. Nevertheless, a design and construction of L-valine production strain was studied in this paper. The first step of 2,3-butanediol synthesis and branched-chain amino acid synthesis pathways share the same step of α-acetolactate synthesis from pyruvate. However, the two pathways are existing in parallel and do not interfere with each other in the wild-type strain. A knockout of budA blocked the 2,3-butanediol synthesis pathway and resulted in the L-valine production. The budA coded an α-acetolactate decarboxylase and catalyzed the acetoin formation from α-acetolactate. Furthermore, blocking the lactic acid synthesis by knocking out of ldhA, which is encoding a lactate dehydrogenase, improved the L-valine synthesis. 2-Ketoisovalerate is the precursor of L-valine, it is also an intermediate of the isobutanol synthesis pathway, while indole-3-pyruvate decarboxylase (ipdC) is responsible for isobutyraldehyde formation from 2-ketoisovalerate. Production of L-valine has been improved by knocking out of ipdC. On the other side, the ilvE, encoding a transaminase B, reversibly transfers one amino group from glutamate to α-ketoisovalerate. Overexpression of ilvE exhibited a distinct improvement of L-valine production. The brnQ encodes a branched-chain amino acid transporter, and L-valine production was further improved by disrupting brnQ. It is also revealed that weak acidic and aerobic conditions favor L-valine production. Based on these findings, L-valine production by metabolically engineered K. pneumonia was examined. In fed-batch fermentation, 22.4 g/L of L-valine was produced by the engineered K. pneumoniae ΔbudA-ΔldhA-ΔipdC-ΔbrnQ-ilvE after 55 h of cultivation, with a substrate conversion ratio of 0.27 mol/mol glucose.
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Klebsiella pneumoniae , Valina , Vias Biossintéticas/genética , Butileno Glicóis/metabolismo , Klebsiella pneumoniae/genéticaRESUMO
Ethylene glycol and glycolic acid are bulk chemicals with a broad range of applications. The ethylene glycol and glycolic acid biosynthesis pathways have been produced by microorganisms and used as a biological route for their production. Unlike the methods that use xylose or glucose as carbon sources, xylonic acid was used as a carbon source to produce ethylene glycol and glycolic acid in this study. Amounts of 4.2 g/L of ethylene glycol and 0.7 g/L of glycolic acid were produced by a wild-type Escherichia coli W3110 within 10 H of cultivation with a substrate conversion ratio of 0.5 mol/mol. Furthermore, E. coli strains that produce solely ethylene glycol or glycolic acid were constructed. 10.3 g/L of glycolic acid was produced by E. coli ΔyqhD+aldA, and the achieved conversion ratio was 0.56 mol/mol. Similarly, the E. coli ΔaldA+yqhD produced 8.0 g/L of ethylene glycol with a conversion ratio of 0.71 mol/mol. Ethylene glycol and glycolic acid production by E. coli on xylonic acid as a carbon source provides new information on the biosynthesis pathway of these products and opens a novel way of biomass utilization.
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Escherichia coli/metabolismo , Etilenoglicol/metabolismo , Glicolatos/metabolismo , Aldeído Oxirredutases/deficiência , Aldeído Oxirredutases/metabolismo , Aldeído Redutase/genética , Aldeído Redutase/metabolismo , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Deleção de GenesRESUMO
Protease, cellulase, and α-amylase producing Bacillus subtilis strain was cultivated by solid-state fermentation technique using soybean meal as a substrate. The aim of the present study was to establish a highly efficient enzymes' extraction method as a first stage in downstream processing. The conventional extraction procedure was optimized by determining pH, stirring rate, solid/liquid ratio, and time of extraction on enzymes' recoveries from fermented soybean meal. Yields of leached enzymes were compared to the amounts of enzymes that are achieved with ultrasound-assisted extraction (UAE). UAE was established to be superior method for obtaining higher yields of proteases (up to 330 IU) and α-amylases (825 IU), under significantly shorter extraction time and gaining more concentrated product. However, the obtained model predicts that conventional process led to a product with a higher cellulolytic activity (≥7.5 IU).
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Bacillus subtilis/enzimologia , Celulase/isolamento & purificação , Fermentação , Glycine max/metabolismo , Peptídeo Hidrolases/isolamento & purificação , Ondas Ultrassônicas , alfa-Amilases/isolamento & purificação , Celulase/biossíntese , Celulase/metabolismo , Peptídeo Hidrolases/biossíntese , Peptídeo Hidrolases/metabolismo , Glycine max/química , alfa-Amilases/biossíntese , alfa-Amilases/metabolismoRESUMO
This study focuses on the influence of operating conditions on Alcalase-catalyzed egg white protein hydrolysis performed in a continuously stirred tank reactor coupled with ultrafiltration module (10 kDa). The permeate flow rate did not significantly affect the degree of hydrolysis (DH), but a significant increase in process productivity was apparent above flow rate of 1.9 cm3 min-1. By contrast, an increase in enzyme/substrate (E/S) ratio provided an increase in DH, but a negative correlation was observed between E/S ratio and productivity. The relationship between operating conditions and antioxidant properties of the hydrolysates, measured by three methods, was studied using Box-Behnken experimental design and response surface methodology. The statistical analysis showed that each variable (impeller speed, E/S ratio, and permeate flow rate) had a significant effect on the antioxidant capacity of all tested systems. Nevertheless, obtained response functions revealed that antioxidative activity measured by DPPH, ABTS and FRAP methods were affected differently by the same operating conditions. High impeller speeds and low permeate flow rates favor ABTS while high impeller speeds and high permeate flow rates had a positive effect on the DPPH scavenging activity. On the other hand, the best results obtained with FRAP method were achieved under moderate operating conditions. The integration of the reaction and ultrafiltration membrane separation in a continuous manner appears to be a right approach to improve and intensify the enzymatic process, enabling the production of peptides with desired antioxidant activity.
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In this study, alcalase (protease from Bacillus licheniformis) immobilization by adsorption, enzyme crosslinking and covalent enzyme binding to activated chitosan microbeads were examined. The biocatalysts highest activity was obtained by covalent immobilization of alcalase onto a solid support. The alcalase covalent immobilization onto different types of chitosan beads obtained by inverse emulsion technique and electrostatic extrusion was studied. Parameters examined under different conditions were beads diameter, enzyme loading, enzyme capacity yield, and biocatalyst activity. The highest activity and enzyme loading of 23.6 IU/mg protein and 340.2 mg/g, respectively, were achieved by the enzyme immobilized onto chitosan microbeads obtained by the electrostatic extrusion technique. FT-IR analysis was used to confirm formation of alcalase-chitosan conjugates. The activity of optimally produced alcalase-chitosan microbeads was then verified in the industrially feasible reaction systems of egg white and soy protein hydrolysis. The high degree of hydrolysis of 29.85 ± 0.967% after 180 min and five successive reuses obtained under real conditions (50 °C, pH 8) verified the covalently bound alcalase to chitosan beads a promising candidate for use in industrial egg white protein hydrolysis process.
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Quitosana/metabolismo , Subtilisinas/metabolismo , Biocatálise , Concentração de Íons de Hidrogênio , Hidrólise , Espectroscopia de Infravermelho com Transformada de Fourier , TemperaturaRESUMO
Kaolin showed as a very perspective carrier for the enzyme immobilization and it was used for the adsorption of horseradish peroxidase (HRP). The effects of the enzyme concentration and pH on the immobilization efficiency were studied in the reaction with pyrogallol and anthraquinone dye C.I. Acid Violet 109 (AV 109). In addition, Fourier transform infrared spectroscopy, scanning electron microscopy and analysis by Brunauer-Emmett-Teller were performed for kaolin, thermally activated kaolin and the immobilized enzyme. It has been shown that 0.1 IU of HRP-kaolin decolorized 87 % of dye solution, under the optimal conditions (pH 5.0, temperature 24 °C, dye concentration 40 mg/L and 0.2 mM of H2O2) within 40 min. The immobilized HRP decolorization follows the Ping Pong Bi-Bi mechanism with dead-end inhibition by the dye. The biocatalyst retained 35 ± 0.9 % of the initial activity after seven cycles of reuse in the decolorization reaction of AV 109 under optimal conditions in a batch reactor. The obtained kinetic parameters and reusability study confirmed improvement in performances of k-HRP compared to free, indicating that k-HRP has a great potential for environmental purposes.
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Armoracia/química , Enzimas Imobilizadas/química , Caulim/química , Proteínas de Plantas/química , Peroxidase do Rábano Silvestre/químicaRESUMO
Two anthraquinonic dyes, C.I. Acid Blue 225 and C.I. Acid Violet 109, were used as models to explore the feasibility of using the horseradish peroxidase enzyme (HRP) in the practical decolorization of anthraquinonic dyes in wastewater. The influence of process parameters such as enzyme concentration, hydrogen peroxide concentration, temperature, dye concentration, and pH was examined. The pH and temperature activity profiles were similar for decolorization of both dyes. Under the optimal conditions, 94.7% of C.I. Acid Violet 109 from aqueous solution was decolorized (treatment time 15 min, enzyme concentration 0.15 IU/mL, hydrogen peroxide concentration 0.4 mM, dye concentration 30 mg/L, pH 4, and temperature 24°C) and 89.36% of C.I. Acid Blue 225 (32 min, enzyme concentration 0.15 IU/mL, hydrogen peroxide concentration 0.04 mM, dye concentration 30 mg/L, pH 5, and temperature 24°C). The mechanism of both reactions has been proven to follow the two substrate ping-pong mechanism with substrate inhibition, revealing the formation of a nonproductive or dead-end complex between dye and HRP or between H2O2 and the oxidized form of the enzyme. Both chemical oxygen demand and total organic carbon values showed that there was a reduction in toxicity after the enzymatic treatment. This study verifies the viability of use of horseradish peroxidase for the wastewaters treatment of similar anthraquinonic dyes.
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Antraquinonas/metabolismo , Benzenossulfonatos/metabolismo , Corantes/metabolismo , Peroxidase do Rábano Silvestre/metabolismo , Ácidos Sulfônicos/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Temperatura , Indústria Têxtil , Águas ResiduáriasRESUMO
This study reports the synthesis of polymeric matrices based on N-isopropylacrylamide and itaconic acid and its application for immobilization of lipase from Candida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45 °C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic activity in an aqueous medium and esterolytic activity in an organic medium have been evaluated. Maximum reaction rate (V max) and Michaelis-Menten constants (K m ) were also determined for immobilized lipase. Storage stability of lipase was increased as a result of immobilization process. Furthermore, the operational stability and reusability of the immobilized lipase in esterification reaction have been studied, and it was observed that after 10 cycles, the residual activity for entrapped lipase was as high as 50%, implying that the developed hydrogel and immobilized system could provide a promising solution for the flavor ester synthesis at the industrial scale.
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Acrilamidas/química , Candida/química , Candida/enzimologia , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Lipase/análise , Succinatos/química , Catálise , Esterificação/fisiologia , Ésteres , Lipase/metabolismoRESUMO
Nanofibers made of natural proteins have caught the increasing attention of food scientists because of their edibility, renewability, and possibility for various applications. The objective of this study was to prepare nanofibers based on pumpkin leaf protein concentrate (LPC) as a by-product from some crops and gelatin as carriers for vitamin B12 using the electrospinning technique. The starting mixtures were analyzed in terms of viscosity, density, surface tension, and electrical conductivity. Scanning electron micrographs of the obtained nanofibers showed a slight increase in fiber average diameter with the addition of LPC and vitamin B12 (~81 nm to 109 nm). Fourier transform infrared spectroscopy verified the physical blending of gelatin and LPC without phase separation. Thermal analysis showed the fibers had good thermal stability up to 220 °C, highlighting their potential for food applications, regardless of the thermal processing. Additionally, the newly developed fibers have good storage stability, as detected by low water activity values ranging from 0.336 to 0.376. Finally, the release study illustrates the promising sustained release of vitamin B12 from gelatin-LPC nanofibers, mainly governed by the Fickian diffusion mechanism. The obtained results implied the potential of these nanofibers in the development of functional food products with improved nutritional profiles.
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Novel glucoside of physiological active vanillyl alcohol was synthesized for the first time using maltase from Saccharomyces cerevisiae as catalyst, and established its structure as 4-hydroxy-3-methoxybenzyl-α-D: -glucopyranoside. The key reaction factors for this transglucosylation reaction were optimized using response surface methodology and the highest yield so far in maltase catalyzed transglucosylation reaction was obtained. It was found out that optimum temperature of reaction was 37 °C, optimal maltose concentration was 60% (w/v), optimal pH was 6.6, and optimal concentration of vanillyl alcohol was 158 mM. Under these conditions, yield of glucoside was 90 mM with no by product formation. It was shown that this compound posses good antioxidant activity as well as stability in gastrointestinal tract. It was demonstrated that it is hydrolyzed on brush border membrane of enterocytes, so it can serve in protecting gastrointestinal system from oxidation, as well as source of anticonvulsive drug after the hydrolysis of glucoside on brush border membrane of small intestine.
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Anisóis/química , Antioxidantes/química , Álcoois Benzílicos/química , Glucosídeos/química , Glicosídeos/química , Anisóis/farmacologia , Antioxidantes/farmacologia , Cromatografia Líquida , Glucosídeos/farmacologia , Glicosilação , Temperatura Alta , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Espectrometria de MassasRESUMO
The aim of this study was to investigate covalent immobilization of horseradish peroxidase (HRP) on magnetic nanoparticles (Mag) encapsulated in calcium alginate beads (MABs) for color degradation, combining easy and fast removal of biocatalyst from the reaction mixture due to its magnetic properties and strong binding due to surface alginate functional groups. MABs obtained by extrusion techniques were analyzed by optical microscopy, FEG-SEM and characterized regarding mechanical properties, magnetization and HRP binding. HRP with initial concentration of 10 mg/gcarrier was successfully covalently bonded on MABs (diameter ~1 mm, magnetite/alginate ratio 1:4), with protein loading of 8.9 mg/gcarrier, immobilization yield 96.9% and activity 32.8 U/g. Immobilized HRP on MABs (HRP-MABs) was then used to catalyze degradation of two anthraquinonic dyes, Acid Blue 225 (AB225) and Acid Violet 109 (AV109), as models for wastewater pollutants. HRP-MABs decolorized 77.3% and 76.1% of AV109 and AB225, respectively after 15 min under optimal conditions (0.097 mM H2O2, 200 mg of HRP-MABs (8.9 mg/gcarrier), 0.08 and 0.1 g/mg beads/dye ratio for AV109 and AB225, respectively). Biocatalyst was used for 7 repeated cycles retaining 75% and 51% of initial activity for AB225 and AV109, respectively, showing potential for use in large scale applications for colored wastewater treatment.
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This study presents the state-of-art research about the assembly of soy proteins in nanocarriers, liposomes, and its design includes different physicochemical strategies and approaches: two-step enzymatic hydrolysis of soy concentrate, hydrolysate encapsulation by using phospholipids and cholesterol, and application of ultrasonication. Achieved results revealed that ultrasonication, together with cholesterol addition into phospholipid layers, improved the stability of nanoliposomes, and a maximum EE value of 60.5 % was obtained. Average size of peptide-loaded nanoliposomes was found to be from 191.1 to 286.7 nm, with a ζ potential of -25.5 to -34.6 mV, and a polydispersity index of 0.250-0.390. Ultrasound-assisted encapsulation process did not lead to a decrease in the antioxidant activity of the trapped peptides. FTIR has indicated an effective hydrophobic interaction between phosphatidylcholine and hydrolysate peptides. TEM and SEM have confirmed the spherical nanocarrier structure and unilamelarity. Prolonged gastrointestinal release and stability of peptides have been enabled by liposome nanocarriers.
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Soy protein concentrate (SPC) was hydrolyzed using several commercial food-grade proteases (Alcalase, Neutrase, papain, Everlase, Umamizyme, Flavourzyme) and their combination to obtain promising ingredients in the manufacture of functional bakery products. In all cases, the hydrolysis caused nutritional, sensory, and rheological changes in SPC, as well as protein structural changes like increased surface hydrophobicity and content of exposed SH groups with the magnitude of these changes depending on enzyme specificity. The hydrolysis with the combination of Neutrase and Flavourzyme (NeuFlav) increased essential amino acid content by 9.8% and that of Lys by 32.6% compared to SPC. This hydrolysate showed also significant antioxidant activities including ABTS and superoxide anion scavenging activity and metal-chelating ability. The addition of all hydrolysates in wheat flour decreased water adsorption and increased development time to some extent due to gluten network weakening, but also decreased the rate of starch retrogradation, contributing to the increase of the shelf-life of bakery products. The NeuFlav tasted less bitter than other hydrolysates, while E-nose provided a discrimination index of 93 between control and hydrolysates. It appeared that the addition of the NeuFlav hydrolysate in a cookie formulation improved protein content and nutritional quality and directed to its higher general consumer acceptability than cookies formulated with only wheat flour.
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The objective of this paper was the investigation of a suitable Sepabeads(®) support and method for immobilization of lipase from Candida rugosa. Three different supports were used, two with amino groups, (Sepabeads(®) EC-EA and Sepabeads(®) EC-HA), differing in spacer length (two and six carbons, respectively) and one with epoxy group (Sepabeads(®) EC-EP). Lipase immobilization was carried out by two conventional methods (via epoxy groups and via glutaraldehyde), and with periodate method for modification of lipase. The results of activity assays showed that lipase retained 94.8% or 87.6% of activity after immobilization via epoxy groups or with periodate method, respectively, while glutaraldehyde method was inferior with only 12.7% of retention. The immobilization of lipase, previously modified by periodate oxidation, via amino groups has proven to be more efficient than direct immobilization of lipase via epoxy groups. In such a way immobilized enzyme exhibited higher activity at high reaction temperatures and higher thermal stability.
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Enzimas Imobilizadas/química , Resinas Epóxi/química , Proteínas Fúngicas/química , Glutaral/química , Lipase/química , Ácido Periódico/química , Adsorção , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Oxirredução , Polímeros , TemperaturaRESUMO
In this study, we assessed the effects of microwave irradiation of wheat gluten proteins as a pretreatment performed in a microwave reactor that could accurately control process parameters as a function of power and temperature, as well as comparing it with conventional heat treatment. The aim was to identify suitable combinations of partial enzymatic hydrolysis and microwave pretreatment parameters to produce gluten hydrolysates with reduced allergenicity and conserved techno-functional features for food application. FTIR analysis, and total and reactive SH group contents confirmed that the microwave-controlled heating can significantly change the secondary structure and conformation of gluten protein. The microwave treatment had the largest effect at 200 W and 100 °C, at which the content of gluten has been reduced by about 2.5-fold. The microwave pretreatment also accelerated the enzymatic hydrolysis of gluten, changing the kinetic profile. The apparent hydrolysis rate constants (k2) were 1.00, 3.68, 3.48, 4.64 and 4.17 min-1 for untreated gluten, and those pretreated with microwave power of 200, 400, 600 and 800 W, respectively. Compared to the heat treatment, it appeared that microwave specific non-thermal effects had a significant influence on the gluten structure and allergenicity and, in combination with the enzymatic hydrolysis, ultimately yielded protein hydrolysates with enhanced antioxidant and functional properties.
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This work aims to characterize a novel system for thyme essential oil delivery based on the combination of natural emulsifiers (soy protein and soy lecithin) and alginate, produced using the extrusion technique. The formulations are optimized concerning alginate and soy protein concentrations (both 1 to 1.5 wt.%), and consequently lecithin amount, in order to achieve spherical beads in the range 2.0 to 2.3 mm and 1.2 to 1.4 mm, wet and dry, respectively. Fourier-transform infrared analysis was performed, proving that there are interactions between all components. Lecithin-soy protein synergistic combination improved entrapment efficiency of total polyphenols (for nearly 12%) and decreased thymol release in a simulated gastric solution for nearly 35%, in comparison with beads without lecithin. The addition of lecithin enhances the thermal properties of the polysaccharide-protein systems at 50 °C after 3 hr of heating. The mechanical stability of the biopolymer carriers is improved with lecithin addition and the elastic modulus varied from 80.06 to 123.7 kPa, depending on the formulation. Alginate/soy protein/lecithin are effective carriers for the encapsulation, protection, and controlled release of thyme essential oil. PRACTICAL APPLICATION: There is unfortunately growing human resistance to antibiotics. This work offers a novel system for effective protection and controlled release of thyme essential oil in the small intestine. The mechanical and thermal properties of the carrier were estimated as they indicate how the beads will be able to resist stress during their incorporation into food (i.e. cookies-mixing, baking). The proposed approach offers ''green advantage'' as arises from all-natural materials.
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Emulsificantes/química , Óleos Voláteis , Thymus (Planta)/química , Preparações de Ação Retardada , Humanos , Óleos Voláteis/química , Óleos Voláteis/farmacocinéticaRESUMO
Horseradish peroxidase (HRP) is a highly specific enzyme with great potential for use in the decolorization of synthetic dyes. A comprehensive study of HRP immobilization using various techniques such as adsorption and covalent immobilization on the novel carrier Purolite® A109 with a special focus on enzymatic decolorization and toxicity of artificially colored wastewater. The immobilized preparations with an activity of 156.21 ± 1.41 U g-1 and 85.71 ± 1.62 U g-1 after the HRP adsorption and covalent immobilization, respectively, were obtained. Stability and reusability of the immobilized preparations were also evaluated. A noteworthy decolorization level (~90%) with immobilized HRP was achieved. Phytotoxicity testing using Mung bean seeds and acute toxicity assay with Artemia salina has confirmed the applicability of the obtained immobilized preparation in industrial wastewater plants for the treatment of colored wastewater.
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Antraquinonas/química , Enzimas Imobilizadas/química , Peroxidase do Rábano Silvestre/química , Descoloração da Água , Antraquinonas/toxicidade , Biodegradação Ambiental/efeitos dos fármacos , Corantes/química , Corantes/toxicidade , Humanos , Desintoxicação por Sorção/métodosRESUMO
Stillage is the main by-product of bioethanol production and the cost of its treatment significantly affects the economy of bioethanol production. A process of thermal sterilization before lactic acid fermentation (LAF) is energy demanding and is causing deterioration of valuable compounds in stillage. In this study, ultrasound (UT) and plasma (PT) treatments were used for microbial inactivation, and a significant reduction in the number of viable microorganisms in the stillage after PT and UT was observed. After application of treatment, LAF by Lactobacillus rhamnosus ATCC 7469 was initiated. The concentration of LA is used to quantify the efficiency of the stillage revalorization. The highest LA productivity of 1.21 g/Lh and yield of 0.82 g/g were obtained after PT, while UT of 10 min provided productivity of 1.02 g/Lh and LA yield of 0.69 g/g. The results were benchmarked against closed LAF. Around 20% better revalorization of stillage by PT was achieved when compared with conventional sterilization. In addition, an excellent L (+) LA stereoselectivity of 95.5% was attained after PT. From the aspect of energy efficiency, that of PT was three times lower than UT and almost ten times lower than thermal sterilization, but it is the most expensive due to the high consumption of gas which could reduce application of closed Ar atmosphere on larger scales. This way, a simpler and energy efficient process for LA production on stillage was accomplished by "open" fermentation.
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Eliminação de Resíduos Líquidos/métodos , Fermentação , Ácido Láctico , Lacticaseibacillus rhamnosus , UltrassomRESUMO
The objective of this study was to discover the relationship between the ultrasound probe treatment (UPT) on egg white proteins (EWPs) before EWPs hydrolysis by different proteases, and the functional properties of the obtained hydrolysates. To fulfill this goal, the protein solubility, foaming, and emulsifying properties were studied as a function of the UPT time and then related to the surface characteristics and structural properties. The changes in the hydrolysates microstructures and macromolecular conformation, induced by the UPT, were followed using scanning electron microscope analyzis (SEM) and Fourier transforms infrared spectroscopy (FTIR). The results showed that UPT influenced (P < 0.05) the proteolysis of egg white proteins for all examined treatment times. Alcalase hydrolysates (AHs) and papain hydrolysates (PHs) were found to have a higher solubility, as a consequence of their relatively higher foaming, and emulsifying properties compared to the untreated hydrolysates. The changes in surface hydrophobicity, sulfhydryl content and surface charge of AHs and PHs indicated unfolding of EWPs affected by ultrasound. SEM analyzis showed that UPT destroyed the microstructures of AHs and PHs, while FTIR spectra indicated remarkable changes in the macromolecular conformation of AHs and PHs after UPT. This study revealed that by combining ultrasound pre-hydrolysis treatment under controlled conditions with thoughtful proteases selection, hydrolysates with improved functional properties could be produced, enhancing utilization of EWPs in food products.