Higher Peroxidase Activity Research Articles

Production of high-value oxidative enzymes by Cyathus bulleri on agricultural and agri-food wastes for application in the textile sector.

Ligninolytic and other oxidative enzymes have emerged as promising biocatalysts in several industries. Since their production at a low cost is necessary for any large-scale application, we demonstrate the use of rice bran (RB), an agricultural waste and agri-food wastes such as potato peelings (PP), banana peelings (BP), and green pea peelings (GPP) for their production. High activity of laccase (12 U/ml), manganese peroxidase (16.11 ± 1.43 U/ml), and aryl alcohol oxidase (1.25 U/ml) was obtained on the PP on the 12th day of growth and ~ 6 U/ml of lytic polysaccharide monooxygenase was obtained on the 14th day of growth demonstrating PP to be a good substrate for their production. RB served as the next best substrate for the production of these enzymes. While the GPP was effective for the production of laccase (9.2 U/ml), this and the BP were not good substrates for the production of other enzymes. Efficient (48-82%) decolorization of several azo-, triarylmethane- dyes, and real textile effluent, without the addition of any mediator, demonstrated the high oxidative ability of the crude culture filtrate produced on the PP (CF-PP), which was a significant improvement compared to the treatment given by the previously reported culture filtrate obtained on wheat bran (CF-WB). An extensive breakdown of Reactive Orange (RO) 16 was demonstrated using CF-PP resulting in the formation of a new product at m/z of 294.05 (6-acetamido-3,4-dioxo-3,4-dihydronapthalene-2-sulfonate), previously reported to be produced on ozonation/advanced oxidation of RO16. The predominant laccase and manganese peroxidase isoforms produced on the PP were also identified.

Bioremediation and stress alleviation of HBCD in plant-soil by bacterial strain HBCD-sjtu

The inherent toxic nature of hexabromocyclododecane (HBCD) and its adverse effects pose a grave risk to both ecosystems and human health. HBCD has greatly influenced the soil-plant interface. The current investigation set out to examine the effects of strain Bacillus sp. HBCD-sjtu on HBCD degradation in soil, the morphophysiological traits, and antioxidative enzyme activity in wheat under different HBCD-stress conditions (0, 0.2, 0.4, and 0.6 mM HBCD). Wheat plants injected with strain HBCD-sjtu showed dramatically enhanced growth features in comparison to control plants. Plants inoculated with HBCD-sjtu showed homeostasis despite HBCD stress increasing total soluble sugars (TSS), free proline, hydrogen peroxide (H2O2), protein content, malondialdehyde (MDA), and high activity of peroxidase (POD) and ascorbate peroxidase (APX) in leaves. The formation of the new metabolite 1,5,9-cyclododecatriene (CDT) after HBCD degradation was identified on the basis of gas chromatography-mass spectrometry (GC–MS) analyses. The results indicated that HBCD-sjtu improved the growth of wheat plants under both HBCD and non-HBCD conditions. Additional research on the effect of HBCD on plant development, alongside the exploration of innovative, environmentally sustainable approaches for HBCD degradation and its conversion into alternative intermediates, could yield valuable insights and potential applications from this study.

The Effect of Benzo(1,2,3)-thiadiazole-7-carbothioic Acid S-Methyl Ester (BTH) and Its Cholinium Ionic Liquid Derivative on the Resistance Induction and Antioxidant Properties of Tomato (Solanum lycopersicum L.).

Tomatoes are one of the most important vegetables thanks to their taste attributes and nutritional value. Their cultivation is threatened by various pathogens including viruses. The application of resistance inducers (RI), such as benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) may be used to enhance plant performance against viruses. Here we aimed to compare the impact of BTH and its choline derivative (Chol-BTH) on resistance induction and antioxidant properties of healthy plants and tomato mosaic virus (ToMV)-infected ones. The response of tomato plants to treatment with BTH or Chol-BTH was manifested by increased expression of not only pathogenesis-related (PR) genes but also WRKY and Jasmonate Zim-domain protein (JAZ) genes and increased jasmonic acid (JA) levels. The effect of BTH as a resistance inducer was observed early after application, while with Chol-BTH the plant defense system reacted more strongly after 8 days. The antioxidant properties of RI-treated tomatoes are related to both glutathione content and peroxidase activity. In the case of BTH, an increase in these activities occurred early after application, while in the case of Chol-BTH, the glutathione level was particularly high in the plant early after treatment, and high peroxidase activity was observed 8 days post-treatment. Overall, the collected results indicate that Chol-BTH, due to its physicochemical parameters (e.g., good solubility) and biological activity (increased expression of lignification-related genes, supported by increases in peroxidase activity and total phenolic compounds levels), can also be a very useful agent inducing tomato resistance against viral pathogens.

Transcriptome and physiological analysis revealed the difference of resistance to fresh-cut browning among sweetpotato genotypes

Sweetpotato [Ipomoea batatas (L.) Lam.] storage roots tend to become brown due to damage incurred during harvest, transportation, processing and storage. Understanding the mechanism of sweetpotato browning is of great significance for breeding varieties with low browning, which have greater economic value. In this study, after analysis of the Browning Degree (BD) of 76 sweetpotato genotypes and analyzing the correlations between BD, the activities and contents of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) for 21 genotypes, two genotypes, S07 (browning-resistant) and S28 (easily browned), were selected to elucidate the differences in the browning mechanism after fresh-cutting by physiological and transcriptome analyses. Genotype S28 had higher PAL, POD and PPO activities and a higher phenolic content after fresh-cutting compared with the basal level and genotype S07. Cell compartmentalization was severely damaged in fresh-cut S28. An RNA-Seq analysis showed that the phenylpropanoid biosynthesis in S28 was more active and gene families of related enzymes were more actively expressed. In conclusion, sweetpotato browning is due to a high content of phenolic compounds, and the high activity of PPO and POD resulting from the up-regulation of related genes. This study provided high quality breeding materials and a relevant theoretical basis for breeding browning-resistant sweetpotato varieties.

Some Physiological Effects of Nanofertilizers on Wheat-Aphid Interactions.

The increasing use of nanofertilizers in modern agriculture and their impact on crop yield and pest management require further research. In this study, the effects of nano-Fe, -Zn, and -Cu (which are synthesized based on nanochelating technology), and urea (N) fertilizers on the antioxidant activities of wheat plants (cv. Chamran), and the wheat green aphid Schizaphis graminum (Rondani) are investigated. The authors observed the highest levels of phenolics in non-infested nano-Zn-treated plants (26% higher compared with control). The highest H2O2 levels are in the infested and non-infested nano-Zn-treated and infested nano-Fe-treated plants (in infested nano-Zn and nano-Fe treated plants, 18% and non-infested nano-Zn-treated plants, 28% higher compared with control). The highest peroxidase (POX) activity is observed in the infested and non-infested N-treated and non-infested water-treated plants (almost 14%, 37%, and 46% higher than control, respectively). The lowest activity is in the infested plants' nano-Zn and -Fe treatments (almost 7 and 5 folds lower compared to the control, respectively). The highest and lowest catalase (CAT) activity are in the infested N-treated plants (almost 42% higher than control) and water-treated plants, respectively. The infested nano-Zn, -Fe, -Cu and Hoagland-treated plants showed the highest superoxide dismutase (SOD) activity. Regarding the antioxidant enzyme activities of S. graminum, the highest POX activity is in the nano-Cu treatment (more than two folds higher compared with control); the highest CAT and SOD activities are in the nano-Cu and -Zn treatments. It can be concluded that the application of nanofertilizers caused increasing effects on the wheat plant's antioxidant system and its resistance to S. graminum.

Sensitive and Label-Free Colorimetric Detection of Glyphosate Based on the Suppression Peroxidase-Mimicking Activity of Cu(II) Ions.

The sensitive and accurate determination of glyphosate (Glyp) is urgently demanded because it is closely correlated with human health and environmental safety. In this work, we proposed a sensitive and convenient colorimetric assay by employing copper ion peroxidases for the detection of Glyp in the environment. Free Cu(II) ions displayed high peroxidase activity and can catalytically oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB, resulting in an obviously visible discoloration reaction. Once the Glyp is added, the ability of copper ions to mimic peroxidase can be largely suppressed because of the generation of Glyp-Cu2+ chelate. The favorable selectivity and sensitivity were demonstrated in the colorimetric analysis of Glyp. Furthermore, this rapid and sensitive method was successfully applied in the accurate and reliable determination of glyphosate in the real sample, holding promising applications in pesticide determination in the environment.

A colorimetric biosensor to track Trop-2 status of tumor cells for diagnosis of breast cancer

The emergence of antibody-drug conjugates (ADCs) targeting trophoblast cell-surface antigen-2 (Trop-2) has reshaped the therapeutic landscape of advanced breast cancer. Accurate profiling of the Trop-2 status of tumor cells can facilitate the identification of patients who will benefit from Trop-2-targeting therapy; however limited analytical method has hindered this process. In this study, we have proposed a specific and sensitive biosensor for visual tracking of the Trop-2 status of breast cancer cells based on tetrahedral DNA nanostructure (TDN)-decorated Fe-based metal-organic framework nanoparticles (TDN-PCN-222 (Fe)). In the design, a dual-aptamer-assisted biomimetic capture strategy shows high capture efficiency while maintaining the viability and original phenotype of captured cells, ensuring the accurate profiling of the Trop-2 status. Meanwhile, by using the high intrinsic peroxidase activity and excellent targeting ability of Trop-2-specific aptamer-linked TDN-PCN-222 (Fe), specific detection of Trop-2-positive tumor cells can be achieved with a limit of detection (LOD) of 10 cells/mL, and the Trop-2 status of tumor cells can be visually tracked. Moreover, the proposed biosensor has been successfully used for tracking the Trop-2 status of tumor cells in breast cancer tissues, suggesting that our method has great promise for clinical applications.

In vitro antioxidant and lipid-lowering properties of free and bound phenolic compounds from buckwheat hulls

Polyphenols can perform preventive and alleviating functions in many metabolic disorders. Buckwheat hulls, usually discarded as waste, are known to have plenty of phenolic compounds. The present study aimed to explore the composition and in vitro lipid-lowering and antioxidant activities of the free and bound phenolic compounds (FPBH and BPBH) in buckwheat hulls. The contents of phenolic compounds in FPBH and BPBH were 150.25 ± 6.25 mg g−1 and 44.25 mg g−1 respectively, indicating that free phenols were the main form of phenols in buckwheat hulls. Rutin and syringic acid was the most abundant phenolic compounds in FPBH and BPBH respectively. The results of DPPH and ABTS free radical scavenging ability showed that the antioxidant activity of FPBH was significantly higher than that of BPBH. In vitro assessments showed that both FPBH and BPBH could significantly alleviate lipid accumulation and oxidative stress in oleic acid (OA)-treated HepG2 cells with a dose-dependent manner by decreasing the levels of intracellular ROS, mitochondrial membrane potential (MMP), triglyceride (TG), total cholesterol (TC) and low density lipoprotein (LDL-C) as well as significantly improving intracellular total antioxidant capacity (TAC), the levels of high density lipoprotein (HDL-C) and activities of glutathione peroxidase.(GSH-Px), superoxide dismutase (SOD) and catalase (CAT). Meanwhile, FPBH was more effective than BPBH at the same concentration. It was concluded that phenolic compounds in buckwheat hulls might have great potential to develop functional foods in improving oxidative damage and lipid metabolism disorders.

Biomineralization of pretilachlor by free and immobilized fungal strains isolated from paddy field.

The excessive use of pretilachlor (a chloroacetamide herbicide) has raised concern throughout the world as it has been reported as highly toxic. The present study deals with isolating and screening pretilachlor degrading fungal strains. The strains Aspergillus ficuum (AJN2) and Aspergillus sp. (PDF1) isolated using enrichment technique were able to degrade 79% and 73% of pretilachlor respectively as analyzed using HPLC. Further, the immobilization technique was used in the study the pretilachlor degradation ability of the isolated strains. The immobilized spores of the strains AJN2 and PDF1 mineralized 84% and 95% of pretilachlor respectively. The degradation dynamics study revealed that the DT50 value of the herbicide was reduced to 2.4 d in aqueous medium due to the enhanced enzymatic activity. The enzymatic study showed high lignin peroxidase and manganese peroxidase activity by the strains AJN2 and PDF1 respectively. The study confirmed the efficient degradation of pretilachlor by Aspergillus ficuum (AJN2).

The effect of fungicides on the physiological and biochemical state of lupine plants after seed treatment

Goal. To assess the effect of fungicides on the content of chlorophyll and the activity of antioxidant enzymes (peroxidase, catalase) in lupine plants after seed treatment.
 Methods. Laboratory and vegetation studies were carried out in the laboratory of analytical chemistry of pesticides of pesticides of the Institute of Plant Protection. The seeds of yellow lupine (Lupinus luteus L., variety Obriy) were treated with combined fungicides from different chemical classes: triazoles (cyproconazole, difenoconazole, tebuconazole, prothioconazole), phenylpyrroles (fludioxonil), carboxamides (carboxin), dithiocarbamates (thiram). Determination of the content of fungicides in plants was carried out using chromatographic methods of analysis. Chlorophyll content, peroxidase and catalase activity were determined by physicochemical methods according to generally accepted methods.
 Results. Fungicides activated the antioxidant systems of plants, depending on their physicochemical properties (in particular, the octanol-water partition coefficient Kow) and their content in plants (C, mg/kg). An increase in peroxidase activity (up to 89% compared to the control) was established within 30 days, which indicates the activation of antioxidant processes aimed at maintaining oxidative homeostasis in plants. The change in catalase activity under the influence of fungicides was inversely correlated with peroxidase activity, which is explained by the formation of adaptive mechanisms of ROS homeostasis. The high activity of peroxidase, compared to catalase, testifies to the important role of this enzyme in the redox reactions of plant resistance under the influence of fungicides. The total chlorophyll content under the action of fungicides, increased by 6—20%, compared to the control.
 Conclusions. Seed treatment with fungicides affects the course of redox reactions in plants, causing changes in the activity of key enzymes. The high activity of peroxidase against the background of fluctuations in catalase activity indicates the direct effect of fungicides on the state of antioxidant systems and the important role of peroxidase in maintaining ROS homeostasis. The stimulatory effect of fungicides on the accumulation of chlorophyll at the initial stages of growth of lupine plants was established, the content of which exceeded the control indicator by 6—20% by development phase. Changes in the activity of antioxidant enzymes (catalase and peroxidase) and the content of chlorophyll can serve as criteria for determining the levels of adaptation of lupine plants to the stress effect of fungicides.

Close coupling of plant functional types with soil microbial community composition drives soil carbon and nutrient cycling in tundra heath

AimsThis study aimed at elucidating divergent effects of two dominant plant functional types (PFTs) in tundra heath, dwarf shrubs and mosses, on soil microbial processes and soil carbon (C) and nutrient availability, and thereby to enhance our understanding of the complex interactions between PFTs, soil microbes and soil functioning.MethodsSamples of organic soil were collected under three dwarf shrub species (of distinct mycorrhizal association and life form) and three moss species in early and late growing season. We analysed soil C and nutrient pools, extracellular enzyme activities and phospholipid fatty acid profiles, together with a range of plant traits, soil and abiotic site characteristics.ResultsShrub soils were characterised by high microbial biomass C and phosphorus and phosphatase activity, which was linked with a fungal-dominated microbial community, while moss soils were characterised by high soil nitrogen availability, peptidase and peroxidase activity associated with a bacterial-dominated microbial community. The variation in soil microbial community structure was explained by mycorrhizal association, root morphology, litter and soil organic matter quality and soil pH-value. Furthermore, we found that the seasonal variation in microbial biomass and enzyme activities over the growing season, likely driven by plant belowground C allocation, was most pronounced under the tallest shrub Betula nana.ConclusionOur study demonstrates a close coupling of PFTs with soil microbial communities, microbial decomposition processes and soil nutrient availability in tundra heath, which suggests potential strong impacts of global change-induced shifts in plant community composition on carbon and nutrient cycling in high-latitude ecosystems.

Physiological and biochemical determinants of drought tolerance in tetraploid vs diploid sour orange citrus rootstock

ABSTRACT Citrus plants face various abiotic stresses like drought during their life span which significantly affect their active growth and development. Tetraploid (4×) plants are more adaptable to environmental constraints than diploid (2×) plants by inducing critical physiological and biochemical processes. In this study, tetraploid and their corresponding diploid sour orange rootstocks were subjected to drought stress for 12 days. Results revealed that drought stress significantly affected plant physiology by reducing photosynthesis rate, stomatal conductance, transpiration rate, and leaf colour, which was prominent in diploid plants compared to tetraploid plants. In diploid plants, phenotypic differences (i.e. wilting and rolling of leaves) were also significant. Diploids with more accumulation of malondialdehyde and hydrogen peroxide in their leaves and roots exhibited more oxidative damage. It was observed that tetraploid plants had higher activities of peroxidase and catalase enzymes, while lower superoxide dismutase was recorded in the leaves and roots of plants. Higher glycine betaine, proline, total soluble protein, total phenolic content, and antioxidant activities were also observed in the leaves and roots of tetraploids. Overall, results suggest that tetraploids in citrus can have better defence mechanisms that help them to sustain under water deficit scenarios.

Amorphous Fe-Containing Phosphotungstates Featuring Efficient Peroxidase-like Activity at Neutral pH: Toward Portable Swabs for Pesticide Detection with Tandem Catalytic Amplification.

Peroxidase-mimetic materials are intensively applied to establish multienzyme systems because of their attractive merits. However, almost all of the nanozymes explored exhibit catalytic capacity only under acidic conditions. The pH mismatch between peroxidase mimics in acidic environments and bioenzymes under neutral conditions significantly restricts the development of enzyme-nanozyme catalytic systems especially for biochemical sensing. To solve this problem, here amorphous Fe-containing phosphotungstates (Fe-PTs) featuring high peroxidase activity at neutral pH were explored to fabricate portable multienzyme biosensors for pesticide detection. The strong attraction of negatively charged Fe-PTs to positively charged substrates as well as the accelerated regeneration of Fe2+ by the Fe/W bimetallic redox couples was demonstrated to play important roles in endowing the material with peroxidase-like activity in physiological environments. Consequently, integrating the developed Fe-PTs with acetylcholinesterase and choline oxidase led to an enzyme-nanozyme tandem platform with good catalytic efficiency at neutral pH for organophosphorus pesticide response. Furthermore, they were immobilized onto common medical swabs to fabricate portable sensors for paraoxon detection conveniently based on smartphone sensing, showing excellent sensitivity, good anti-interference capacity, and low detection limit (0.28 ng/mL). Our contribution expands the horizon of acquiring peroxidase activity at neutral pH, and it will also open avenues to construct portable and effective biosensors for pesticides and other analytes.

Enhanced Peroxidase-Like and Antibacterial Activity of Ir-CoatedPd-Pt Nanodendrites as Nanozyme.

To inhibit the growth of bacteria, the DA-PPI nanozyme with enhanced peroxidase-like activity was synthesized. The DA-PPI nanozyme was obtained by depositing high-affinity element iridium (Ir) on the surface of Pd-Pt dendritic structures. The morphology and composition of DA-PPI nanozyme were characterized using SEM, TEM, and XPS. The kinetic results showed that the DA-PPI nanozyme possessed a higher peroxidase-like activity than that of Pd-Pt dendritic structures. The PL, ESR, and DFT were employed to explain the high peroxidase activity. As a proof of concept, the DA-PPI nanozyme could effectively inhibit E. coli (G-) and S. aureus (G+) due to its high peroxidase-like activity. The study provides a new idea for the design of high active nanozymes and their application in the field of antibacterial.

Gum Arabic influences the activity of antioxidant enzymes during androgenesis in barley anthers

This study investigated the antioxidant activity of gum Arabic (GA) during androgenesis in barley anthers. After stress pretreatment the anthers were cultured in the presence of 10 mg L−1 GA (Gm) or on control medium (Cm) and compared with respect to activity of selected antioxidant and respiratory enzymes and endogenous hydrogen peroxide (H2O2) content. The anthers from Cm and Gm differed in the strategy against H2O2 overproduction, in that the total peroxidase (POX) activity and the number of POX isoforms were significantly higher in Gm- than in Cm-cultured material. High POX activity on Gm paralleled with H2O2 decrease, suggesting the utilization of this chemical for the POX-mediated cell wall formation and reconstruction during growth of multicellular structures. The total superoxide dismutase (SOD) activity on Cm and Gm were at similar level for most of the culture period but the activity of MnSOD was dozen times higher on Gm and this coincided with high activity of fumarase and cytochrome c oxidase. It indicates close interplay between efficient antioxidative protection and high metabolic rate accompanying efficient androgenesis. Mass spectrometry analysis confirmed the presence of POX and other antioxidative and defense enzymes in protein fraction of GA used in the experiments, however as revealed by 2,2-diphenyl-1-picrylhydrazyl assay, the Gm and Cm displayed similar total antioxidant capacity. Thus, the effect of GA on androgenic cultures of barley can be linked to its influence on the activity of anther antioxidant system, rather than its native antioxidative properties.

Residual polyphenol oxidase and peroxidase activities in high pressure processed bok choy (Brassica rapa subsp. chinensis) juice did not accelerate nutrient degradation during storage

Polyphenol oxidase (PPO) and peroxidase (POD) cannot be fully inactivated by commercial high pressure processing (HPP) operations, and their residual activities may accelerate nutrient degradation during storage. This study hence aimed to establish the effect of residual enzyme activity on nutrient preservation in bok choy (Brassica rapa subsp. chinensis) juice. Bok choy juice was treated at 600 MPa for up to 20 min and enzyme inactivation, nutrient retention immediately after treatment and nutrient preservation during storage were determined. High residual PPO (85.1 ± 2.6%) and POD (68.5 ± 1.0%) activities remained after 20 min of treatment. Increasing the pressure holding time to enhance enzyme inactivation did not compromise total antioxidant capacity, vitamin C, carotenoids, isothiocyanates and vitamin K levels. Neither did it significantly reduce the vitamin C degradation rate during refrigerated storage. Maximising enzyme inactivation may thus not be necessary for nutrient preservation during the storage of HPP-treated bok choy juice. Industrial relevance textWith HPP, an increase in pressure or holding time is required to achieve higher levels of enzyme inactivation. Without the need to maximize PPO and POD inactivation, juice processors may employ the minimum pressure and holding time required for microbial inactivation. As vegetative bacteria are typically less resistant to HPP inactivation than these enzymes, this could translate to reduced energy costs and increased throughput.

High-Throughput Approach for Facile Access to Hetero-Dinuclear Synergistic Metal Complex for H2O2 Activation and Its Implications.

Hetero-dinuclear synergic catalysis is a promising approach for improving catalytic performance. However, employing it is challenging because the design principles for the metal complex are still not well understood. Further, these complexes have a broader set of possibilities than mononuclear or homometallic systems, increasing the time and effort required to understand them. In this study, we explored a high-throughput approach to obtain a new hetero-dinuclear synergistic metal complex for H2O2 activation. From the 1152 combinations of metal complex candidates obtained by changing three variables (metal ions, unsymmetrical dinucleating ligands, and pH), the lead complex (L3-(Ni, Co)), which has the highest peroxidase activity, was derived using colorimetric parallel analysis. A series of control experiments revealed that L3 plays a crucial role in the formation of active L3-(Ni, Co) complexes, Co2+ acts as a catalytic center, and Ni2+ serves as an assistant catalytic site within L3-(Ni, Co). In addition, the catalytic efficiency of L3-(Ni, Co), which was 125 times that of the homo-bimetallic complex (L3-(Co, Co)), revealed clear hetero-bimetallic synergism in the buffer. The ultraviolet-visible study and electron paramagnetic resonance-based spin-trap experiment provided mechanistic insight into H2O2 activation by the intermediate, which was found to be induced by the reaction of L3-(Ni, Co) and H2O2. Moreover, the intermediate could act as a donor of the hydroperoxyl radical (•OOH) in the buffer. Furthermore, L3-(Ni, Co) demonstrated potential for application as a signal transducer for H2O2 in an enzyme-coupled cascade assay that can be used for the colorimetric detection of glucose.

A chemometric approach to evaluate the effects of probe-type ultrasonication on the enzyme inactivation and quality attributes of fresh amla juice.

The enzymatic browning induced in amla juice due to the high activity of polyphenol oxidase (PPO) and peroxidase (POD) is one of the critical issues faced by the industry. The present study assessed the suitability of non-thermal, high-intensity ultrasound (US) on the inactivation of PPO and POD in fresh Indian Gooseberry juice. Ultrasonic waves, using a 6mm titanium alloy probe were irradiated in the juice at a maximum power of 455W and frequency of 20kHz. The subsequent effects on biochemical attributes were studied using response surface methodology. Inactivation rates of 90.72% and 73.18%, respectively, for PPO and POD enzymes, were observed at the highest US intensity and exposure time. Numerical optimisation using the three-factor, three-level Box-Behnken design suggested that an optimum process at 70% (energy density: 1610 Wcm-2) pulsed at 5s on and 5s off for 7min 30s resulted in PPO and POD inactivation of the order of 76.42% and 64.57% respectively. At these experimental conditions, the optimized levels of biochemical attributes i.e., ascorbic acid (738.50mg/100mL), total phenols (17.10mg/mL), DPPH antioxidant activity (58.47%), tannins (7.11µg/mL), colour change (ΔE=9.04) and flavonoids (6.14mg/mL) were achieved. The overall statistical models were significant for all the responses except for reducing sugars. Furthermore, the approximation equations for individual responses indicated that the goodness of fit was adequate (R2>0.90). The results suggested that ultrasound is a suitable processing technique for amla juice stabilisation compared to thermal treatments that result in the loss of quality.

Determination activities of optimal conditions of peroxidase in hot Pepper and Broccoli

The activities of peroxidase (POD) in hot pepper pericarp and broccoli were evaluated using spectrophotometric method. The enzymes were extracted from the pepper pericarp and broccoli 5 g with 20 mL of 0.1 M phosphate buffer solution pH (7. 0). POD activities were determined using guaiacol as a substrate. The effects of the concentration of enzyme extract, substrate concentration, hydrogen peroxide concentration, pH and temperature were investigated. The highest activity of POD was at (2.5 mg /ml) and (2mg/ml) enzyme concentration for hot peper and broccoli respectivily .The highest activity of using guaiacol concentration of 100 mM and 16 mM for hot peper and broccoli respectivily. POD was maximal optimized with guaiacol and 24 mM H2O2. The optimum pH was 6.0 and 7.0 for POD for hot peper and broccoli respectivily . The optimum temperature was 40°C and 30 °C for hot peper and broccoli respectivily. These optimum conditions were used to determine the enzyme activities in hot pepper and broccoli sample.

Efficient Degradation of Tetracycline Antibiotics by Engineered Myoglobin with High Peroxidase Activity

Tetracyclines are one class of widely used antibiotics. Meanwhile, due to abuse and improper disposal, they are often detected in wastewater, which causes a series of environmental problems and poses a threat to human health and safety. As an efficient and environmentally friendly method, enzymatic catalysis has attracted much attention. In previous studies, we have designed an efficient peroxidase (F43Y/P88W/F138W Mb, termed YWW Mb) based on the protein scaffold of myoglobin (Mb), an O2 carrier, by modifying the heme active center and introducing two Trp residues. In this study, we further applied it to degrade the tetracycline antibiotics. Both UV-Vis and HPLC studies showed that the triple mutant YWW Mb was able to catalyze the degradation of tetracycline, oxytetracycline, doxycycline, and chlortetracycline effectively, with a degradation rate of ~100%, ~98%, ~94%, and ~90%, respectively, within 5 min by using H2O2 as an oxidant. These activities are much higher than those of wild-type Mb and other heme enzymes such as manganese peroxidase. As further analyzed by UPLC-ESI-MS, we identified multiple degradation products and thus proposed possible degradation mechanisms. In addition, the toxicity of the products was analyzed by using in vitro antibacterial experiments of E. coli. Therefore, this study indicates that the engineered heme enzyme has potential applications for environmental remediation by degradation of tetracycline antibiotics.