Polyphenol Oxidase Activity Research Articles

Synthesis and Evaluation of 1,4-Dihydropyridine-Based Urea Derivatives as Polyphenol Oxidase Inhibitors

This study investigated the potential inhibitory effects of nine novel synthesized urea-substituted 1,4-dihydropyridine derivatives (DT-DEN-1-9) on polyphenol oxidase (PPO) activity. The compounds were synthesized via the Hantzsch reaction, providing a series of structurally diverse urea and thiourea-modified 1,4-dihydropyridines. Polyphenol oxidase enzyme was extracted from banana (Musa cavendishii) and purified using affinity chromatography with a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity gel. The purified enzyme's activity was measured spectrophotometrically using catechol as the substrate, monitoring the increase in absorbance at 420 nm. The inhibitory effects of the synthesized compounds on PPO activity were evaluated through in vitro assays. Various concentrations of each compound were incorporated into the enzyme reaction mixture, and the residual PPO activity was determined. The percentage of PPO activity was calculated relative to a control reaction without inhibitors. IC50 values, representing the concentration of inhibitor required to reduce enzyme activity by 50%, were determined using Lineweaver-Burk plots. Among the tested compounds, DT-DEN-6, featuring a phenyl thiourea substituent, exhibited the most potent inhibition with an IC50 value of 100.14 μM. DT-DEN-8, containing a 2,5-dichlorophenyl thiourea moiety, also showed strong inhibitory activity with an IC50 below 150 μM. Structure-activity relationships were observed, with electron-withdrawing substituents generally enhancing inhibitory potency. Conversely, DT-DEN-5, bearing a 4-(trifluoromethyl)phenyl thiourea substituent, exhibited the weakest inhibition profile (IC50: 233.33 μM). Our findings provide valuable insights for the design of next-generation PPO inhibitors, potentially leading to the development of novel anti-browning agents for applications in food preservation and other industries where control of enzymatic browning is crucial.

The Eliciting Effect of Aqueous Extracts from Ascophyllum nodosum Algae on the Cultivation of Arugula (Eruca sativa Mill.) Microgreens

This study showed the eliciting effect of aqueous extracts from Ascophyllum nodosum on the development of Eruca sativa microgreens in a quartz-based substrate. There is no information in the literature on the impact of its use on the quality, bioactive compound content, and nutritional value of arugula microgreens. Assays that have been made include the following: total phenolic content (TPC), total flavonoid content (TFV), enzymes such as phenylalanine ammonia (PAL) and polyphenol oxidase (PPO), and enzymes involved in the scavenging of reactive oxygen species such as catalase (CAT) and superoxide dismutase (SOD). The antioxidant activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) was also evaluated. The total phenolic content of arugula microgreens increased significantly after an application of aqueous extracts of A. nodosum to the substrate. The greatest increase in flavonoid content (89%) and antioxidant activity against DPPH (82%) was observed at a concentration of 2.5%. The highest increase in activity of CAT (68.2%), SOD (25%), PAL (13-fold), and PPO (84.2%) was observed with the application of 5% extract. In conclusion, the use of Ascophyllum nodosum algae affects TPC and TFV, antioxidant activity, PAL, PPO, SOD, and CAT in the microgreens studied. By prioritising organic and environmentally friendly extracts, growers can contribute to a more sustainable and healthier food system, especially in the case of the production of Eruca sativa microgreens.

Carbon Dots-Mediated Photodynamic Treatment Reduces Postharvest Senescence and Decay of Grapes by Regulating the Antioxidant System.

Grapes are susceptible to mold and decay during postharvest storage, and developing new technologies to extend their storage period has important application value. Photodynamic technology (PDT) in concurrence with carbon dots (CDs) proposes an innovative and eco-friendly preservation strategy. We examined the effects of carbon dots combined with photodynamic treatment on postharvest senescence and antioxidant system of table grape. The compounding of photodynamic technology with a 0.06 g L-1 CDs solution could possibly extend the postharvest storage period of grape berries. Through this strategy, we achieved a decreased rate of fruit rotting and weight loss alongside the delayed deterioration of fruit firmness, soluble solids, and titratable acid. As paired with photodynamic technology, CDs considerably decreased the postharvest storage loss of phenols, flavonoids, and reducing sugars as compared to the control group. Concurrently, it remarkably postponed the build-up of hydrogen peroxide (H2O2), superoxide anion (O2∙-), and malondialdehyde (MDA); elevated the levels of reduced ascorbic acid (AsA) and reduced glutathione (GSH); lowered the levels of dehydroascorbic acid (DHA) and oxidized glutathione (GSSG); raised the ratios of AsA/DHA and GSSH/GSSG; encouraged the activities of superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL); and inhibited the activities of polyphenol oxidase (PPO) and lipoxygenase (LOX). Furthermore, it enhanced the iron reduction antioxidant capacity (FRAP) and DPPH radical scavenging capacity of grape berries. CDs combined with photodynamic treatment could efficiently lessen postharvest senescence and decay of grape berry while extending the storage time.

Chlorine Dioxide Delays Enzymatic Browning in Postharvest Cherimoya and Enables Establishment of Kinetics Substrate Model

Cherimoya (Annona squamosa L.) is a nutrient-rich fruit. However, it is not easy to store because of its susceptibility to browning. In order to prolong the storage period of cherimoya, the fruit was treated with chlorine dioxide (ClO2) at different concentrations (20, 40, 60, 80, and 100 mg L−1) and stored at 15 °C for 8 days. The quality and biochemical indexes of the fruit were investigated using a chromameter, high-performance liquid chromatography and scanning electron microscopy, etc. The results showed that all the treatments with various concentrations of ClO2 could delay the increase in the browning index, loss of weight, and decrease in hardness. Meanwhile, ClO2 treatment effectively reduced the consumption of starch, titratable acids, and phenolics as well as inhibited the polyphenol oxidase (PPO) activity and enzymatic oxidation. It can be seen from the Fourier transform infrared spectrum (FTIR) that the C=O stretching peak at 1731 cm−1 disappeared at a ClO2 concentration of 60 mg L−1. We think the ClO2 treatment may inhibit the oxidation of phenol to quinone. According to the Arrhenius formula, the values of the apparent activation energy (Ea) for enzymatic browning reaction were estimated. The Ea with catechol in cherimoya pericarp and flesh were 67.00 and 47.83 kJ mol−1, respectively. It was found that the phenolic enzyme reaction with catechol has a much smaller Ea and a higher affinity for PPO. Therefore, treatment with ClO2 at a suitable concentration for cherimoya stored at 15 °C could effectively maintain fruit quality and prolong the storage period; the most appropriate concentration is 60 mg L−1.

Anti-browning action of melatonin is dependent on the type of tissue in minimally processed sweet potatoes

This study explored the impact of exogenous melatonin on oxidative damage, protective mechanisms against oxidation, and reactions leading to browning, as well as the accumulation of antioxidants in minimally processed white-fleshed and orange sweet potato roots. Sweet potato roots with white and orange pulp were subjected to minimal processing and immersion in melatonin solutions at concentrations of 0, 10, 100, and 1000 µmol L−1. Following packaging, these were stored at 5 ± 2 °C for 20 days. Results indicate that increasing melatonin concentrations significantly reduced browning symptoms in both white and orange sweet potato slices. This reduction was associated with decreased levels of hydrogen peroxide (H2O2), thiobarbituric acid-reactive substances (TBARs), and electrolyte leakage, indicating reduced cell membrane damage. Enhanced protection was observed through increased activity of antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase and higher levels of antioxidant metabolites, including vitamin C and phenolic compounds, as confirmed by in vitro assays for antioxidant capacity (FRAP and DPPH), however, the levels of total carotenoids, anthocyanins, and yellow flavonoids did not show a significant difference between the melatonin treatments. Notably, sweet potato slices treated with higher melatonin doses of 100 and 1000 µmol L−1 exhibited reduced phenylalanine ammonia-lyase activity and phenolic compound accumulation. This effect, coupled with lower polyphenol oxidase (PPO) and peroxidase (POD) activities, likely contributed to prolonged preservation quality by maintaining cellular redox homeostasis.

Effect of Alginate Oligosaccharides on Oxidative Reactions in Sweet Basil During Low-Temperature Storage

This study aimed to investigate the antioxidant effect of alginate oligosaccharides (AOS) on sweet basil leaves preserved at low temperatures. This investigation was divided into 3 treatments and 3 replications using a completely randomized design (CRD) experiment. Specifically, the effects of dipping basil leaves in AOS solutions at different concentrations (100 and 200 mg L−1) and in distilled water (control) for 1 min were compared. Cell deterioration due to cold storage was investigated based on the variation in oxidative reactions in the cells, causing an accumulation of free radicals. The AOS-treated sweet basil leaves had a 12-day shelf life, compared to just 9 days for those in the control group. Those treated with AOS at 100 mg L−1 exhibited the lowest levels of phenylalanine ammonia-lyase, lipoxygenase, hydrogen peroxide, peroxidase and malondialdehyde content. On the contrary, the contents of phenolic compounds, polyphenol oxidase, catalase and superoxide dismutase increased in the treated leaves during storage compared to those observed in the control treatment. HIGHLIGHTS Alginate oligosaccharides (AOS) enhanced antioxidant effects in sweet basil leaves stored at low temperatures. Basil leaves treated with AOS at 100 and 200 mg L⁻¹ had an extended shelf life of 12 days, compared to 9 days for untreated controls. AOS treatment reduced oxidative stress markers, including phenylalanine ammonia-lyase, lipoxygenase, hydrogen peroxide, peroxidase, and malondialdehyde. AOS-treated leaves showed increased phenolic compounds, polyphenol oxidase, catalase, and superoxide dismutase activity. AOS treatment may mitigate chilling injury and improve postharvest quality in sweet basil leaves. GRAPHICAL ABSTRACT

Pre-harvest foliar spraying of calcium and zinc preserves berries quality and mitigates chilling injury of grape during cold storage

The current study was conducted to elucidate the effect of single and combined post-veraison sprays of calcium nitrate (Ca, 2 %) and zinc sulfate (Zn, 1 %) on post-harvest quality attributes of ‘Sahebi’ grapes during cold storage. Grapes foliar-sprayed with combination of Ca and Zn showed higher flavonols (28 % myricetin, 4 % quercetin, and 15 % kaempferol), flavanols (6 % catechin, 29 % epicatechin, and 10 % epi‑gallocatechin) and anthocyanins (21 % malvidin, 16 % cyaniding and 13 % peonidin, 22 % petunidin) than controls. Moreover, Ca and Zn foliar application was also effective in preserving the levels of trans-resveratrol and phenolic acids in grape berries. The higher amount of phenolic compounds in Ca + Zn-treated grapes was accompanied with higher activity of antioxidant enzymes, lower activity of polyphenol oxidase, and lower incidence of fungal decay. In general, post veraison spray of Ca and Zn is promising viticultural operation for preserving berries bioactive compound and mitigating chilling injury of grape during cold storage.

Exogenous inoculation of Pediococcus pentosaceus SSC12 positively regulates anthocyanin biosynthesis to alleviate browning of postharvest litchi (Litchi chinensis Sonn.)

Litchi is prone to pericarp browning after-harvest, which seriously affects the quality of litchi and causes huge loss. Pericarp browning is closely related to anthocyanin metabolism. Lactic acid bacteria (LAB), a kind of probiotics, is used for food preservation. The aim of this study was to investigate whether and how inoculation of LAB strain Pediococcus pentosaceus SSC12 of litchi fruit affect the pericarp browning and anthocyanin metabolism in postharvest through transcriptome and metabolome analyses. This is the first work showing that strain SSC12 suppressed development of browning and maintained the coloration of litchi pericarp at 10 ± 1 °C. Strain SSC12 upregulated 8 key differentially expressed genes (DEGs) associated with anthocyanin biosynthesis and transport, while downregulated 3 key DEGs involved in anthocyanin degradation in anthocyanin synthesis pathway. Strain SSC12 caused increase in 9 different anthocyanin-related metabolites levels and phenylalanine ammonia lyase activity, disease in peroxidase, laccase and polyphenol oxidase activities. Taken together, strain SSC12 suppressed browning of litchi via elevateing anthocyanin synthesis and transport and inhibiting anthocyanin degradation. These findings suggested that strain SSC12 might serve as a potential probiotic strains to alternative for chemical reagents in postharvest fruit preservation and contribute to the exploration of newgreen approachs for postharvest losses.

Trichoderma-Bioenriched Vermicompost Induces Defense Response and Promotes Plant Growth in Thai Rice Variety "Chor Khing".

Vermicompost (VC) produced by African nightcrawler earthworms (Eudrilus eugeniae) is a natural fertilizer with a rich microbial community. Trichoderma asperelloides PSU-P1 is an effective antagonistic microorganism with multifaceted activity mechanisms. This research aimed to develop Trichoderma-bioenriched vermicompost (TBVC) to promote plant growth and induce the defense response in the Thai rice variety "Chor Khing". T. asperelloides PSU-P1 was tested against Rhizoctonia solani, the pathogen of sheath blight disease, using a dual-culture assay. The results showed that T. asperelloides PSU-P1 effectively inhibited R. solani in vitro growth by 70.48%. The TBVC was prepared by adding a conidial suspension (108 conidia/mL) to vermicompost. The viability of Trichoderma persisted in the vermicompost for 6 months and ranged from 1.2 to 2.8 × 107 CFU/mL. Vermicompost water extracts significantly enhanced seed germination, root length, and shoot length compared to a control group (p < 0.05). Plants that received the TBVC displayed significantly longer shoot and root lengths and higher total chlorophyll content than control plants (p < 0.05). The TBVC induced defense response by increasing the enzyme activity of peroxidase (POD) and polyphenol oxidase (PPO) in comparison with control plants. Rice grown in the TBVC had a significantly reduced incidence of sheath blight caused by R. solani in comparison with control rice (p < 0.05). Furthermore, the fungal community of rice plants was analyzed via the high-throughput next-generation sequencing of the internal transcribed spacer (ITS). The fungal community in the TBVC had greater alpha diversity than the community in the VC. Phylum Ascomycota was dominant in both samples, and a heat map showed that Trichoderma was more prevalent in the TBVC than in the VC. Our results indicate that the enrichment of VC with Trichoderma increases growth, enhances the defense response, and reduces the incidence of sheath blight disease in the Thai rice variety "Chor Khing".

Integrated microbiome and metabolomic analysis of Spodoptera litura under Metarhizium flavoviride qc1401 stress.

Metarhizium spp. have emerged as an alternative to chemical pesticides for protecting crops from insect pest. Here, we investigated midgut microbial community and metabolites of Spodoptera litura at three different timepoints after infection with Metarhizium flavoviride. The innate immune system of S. litura was activated with levels of polyphenol oxidase, carboxylesterase, multifunctional oxidase, and glutathione S-transferase activity significantly increasing. Exposure to the fungal pathogen also altered bacterial abundance and diversity in host's midgut, and these changes varied depending on the time elapsed since exposure. We identified more operational taxonomic units in the treated samples as compared to the control samples at all tested time points. A total of 372 metabolites were identified, and 88, 149, and 142 differentially accumulated metabolites (DAMs) were identified between the treatment and control groups at 3 timepoints after treatment, respectively. Based on the changes of DAMs in response to M. flavoviride infection at different timepoints and significantly enriched KEGG pathways, we speculated that "tyrosine metabolism," "galactose metabolism," "ATP-binding cassette transporters," "neuroactive ligand-receptor interaction," "purine metabolism," "arginine and proline metabolism," "beta-alanine metabolism," "lysosome," and "carbon metabolism" may participate in the metabolic-level defense response. An integrated pathway-level analysis of the 16S-rDNA and metabolomic data illustrated the connections and interdependencies between the metabolic responses of S. litura and the midgut microorganisms to M. flavoviride infection. This work emphasizes the value of integrated analyses of insect-pathogen interactions, provides a framework for future studies of critical microorganisms and metabolic determinants of these interactions, establishes a theoretical basis for the sustainable use of M. flavoviride.

Long-term mulched drip irrigation facilitates soil organic carbon stabilization and the dominance of microbial stochastic assembly processes

Mulched drip irrigation (MDI) is generally accepted as a method to decrease soil salinization and improve crop yields in arid and semi-arid regions. However, there remain gaps in how MDI drives soil organic carbon (SOC) dynamic microbial assembly processes with time, and the mediating role of microorganisms remains unclear. In this study, we investigated the aforementioned issues across soil profiles in cotton fields with different years of MDI. The results showed that MDI did not cause the differences in SOC, particular organic carbon (POC), and mineral-associated organic carbon (MOC) in soil layers. The POC and MOC contents had a parabola relationship with time, and showed an opposite trend in soil. After 15 years of MDI, the ratio of MOC/SOC increased to a peak value of 50 % and 52 % in topsoil and subsoil, respectively; the ratio of POC/SOC decreased to valley values of 50 % and 48 %, respectively (P < 0.05). Long-term MDI reduced the differences in oxidase between soil layers but accelerated SOC loss by increasing polyphenol oxidase activity (P < 0.05). Compared with that of other years, with 10 years of MDI, bacterial Shannon diversity decreased to a valley value, and fungal Shannon diversity reached to a top value in subsoil (P < 0.05). In general, stochastic processes were mainly controlled by dispersal limitation, and undominated processes dominated microbial assembly; however, there was a close relationship between bacterial communities and organic carbon fractions. The high percentage of positive linkages among microorganisms indicated that long-term MDI was beneficial for carbon fixation. Additionally, a decrease of fungal oligotroph/copiotroph ratio, the relative abundance of Ascomycota and Basidiomycota was beneficial for the accumulation of SOC and POC in topsoil (P < 0.05). In conclusion, long-term MDI is useful for the fixation of organic carbon via improving soil POC content and strengthening linkages within community assemblies.

Vitamin C as a functional enhancer in the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab, Scylla paramamosain

This experiment was conducted to explore the effects of dietary vitamin C supplementation on non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab (Scylla paramamosain). Mud crabs with an initial weight of 14.67 ± 0.13 g were randomly divided into 6 treatments and fed diets with 0.86 (control), 44.79, 98.45, 133.94, 186.36 and 364.28 mg/kg vitamin C, respectively. The experiment consisted of 6 treatments, each treatment was designed with 4 replicates and each replicate was stocked with 8 crabs. After 42 days of feeding experiment, 2 crabs were randomly selected from each replicate, and a total of 8 crabs in each treatment were carried out 72 h low-temperature challenge experiment. The results showed that crabs fed diets with 186.36 and 364.28 mg/kg vitamin C significantly improved the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in hemolymph and hepatopancreas (P < 0.05). Crabs fed diet with 133.94 mg/kg vitamin C significantly decreased the concentration of nitric oxide (NO) and the activity of nitric oxide synthase (NOS) in hemolymph (P < 0.05). Diet with 133.94 mg/kg vitamin C was improved the activity of polyphenol oxidase (PPO) and the concentration of albumin (ALB) in hemolymph. Crabs fed diet with 133.94 mg/kg vitamin C showed lower concentration of malondialdehyde (MDA) in hemolymph and hepatopancreas than those fed the other diets. Meanwhile, crabs fed diet with 98.45 mg/kg vitamin C showed higher activity of total superoxide dismutase (T-SOD) in hemolymph, and crabs fed diet with 133.94 mg/kg vitamin C showed higher activity of T-SOD in hepatopancreas. Crabs fed diet with 186.36 mg/kg vitamin C significantly decreased the concentration of reduced glutathione (GSH) and the activity of glutathione peroxidase (GSH-PX) in hepatopancreas (P < 0.05). In normal temperature, crabs fed diets with 133.94 mg/kg vitamin C significantly up-regulated the expression levels of gpx (glutathione peroxidase) and trx (thioredoxin) in hepatopancreas compared with the control treatment (P < 0.05). The highest expression levels of relish, il16 (interleukin 16), caspase 2 (caspase 2), p38 mapk (p38 mitogen-activated protein kinases) and bax (bcl-2 associated x protein) in hepatopancreas were found at crabs fed control diet (P < 0.05). Moreover, crabs fed diet with 133.94 mg/kg vitamin C showed higher expression levels of alf-3 (anti-lipopolysaccharide factor 3) and bcl-2 (B-cell lymphoma 2) in hepatopancreas than those fed the other diets (P < 0.05). Under low-temperature stress, crabs fed diet with 133.94 mg/kg vitamin C significantly improved the expression levels of hsp90 (heat shock protein 90), cat (catalase), gpx, prx (thioredoxin peroxidase) and trx in hepatopancreas (P < 0.05). In addition, dietary with 133.94 vitamin C significantly up-regulated the expression levels of alf-3 and bcl-2 (P < 0.05). Based on two slope broken-line regression analysis of activity of PPO against the dietary vitamin C level, the optimal dietary vitamin C requirement was estimated to be 144.81 mg/kg for juvenile mud crab. In conclusion, dietary 133.94–144.81 mg/kg vitamin C significantly improved the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab.

Continuous flow high-pressure homogenization for preserving the nutritional quality and stability of watermelon juice under simulated market storage conditions

This study examined the efficacy of continuous flow high-pressure homogenization (CFHPH) under varying pressures, inlet temperatures, and flow rates, in preserving the nutritional quality and stability of watermelon juice during simulated market conditions and compared it with traditional high-temperature short-time (HTST) processing. The retention of ascorbic acid, carotenoids, and amino acids was analyzed using liquid chromatography, while PPO (polyphenol oxidase) and POD (peroxidase) enzyme activity was assessed using a UV–vis spectrophotometer.We observed a significant decrease (p ≤ 0.05) in ascorbic acid levels after 15 days of storage. For carotenoids, the impact was influenced by the interaction of pressure, flow rate, and inlet temperature within CFHPH, with no clear trend emerging regarding their preservation over 45 days of storage at 4 °C. However, overall retention of carotenoids surpassed that of HTST samples. Both methods enhanced free amino acid contents significantly and decreased PPO and POD activity, with HTST being slightly more effective. Ornithine and histidine concentrations significantly increased, with up to a fourfold rise in samples treated with 300 MPa pressure and up to a tenfold rise for HTST at 95 °C after 45 days of storage. This study suggests optimizing the CFHPH process to enhance the shelf-life and nutritional value of watermelon juice, offering consumers a healthier and longer-lasting choice. Industrial relevanceOur findings highlight CFHPH's higher retention of bioactive compounds, reduction in degradative enzyme activity, and enhancement of the amino acid profile, making it a compelling choice for the fruit juice processing industry. Despite the energy-intensive nature of CFHPH, its ability to preserve vital bioactive compounds like carotenoids and ascorbic acid addresses the growing consumer demand for nutritious and stable juice options. The benefits of CFHPH in maintaining juice quality and nutritional value may outweigh the associated energy costs, making it a promising technology for fruit juice processing.

JrPPO1/2 play distinct roles in regulating walnut fruit browning by different spatiotemporal expression and enzymatic characteristics

Polyphenol oxidase (PPO) activity drives walnut fruit browning, but the roles of its only two-family genes, JrPPO1 and JrPPO2, remain unclear. This study explores the spatiotemporal expression and enzymatic characteristics of JrPPO1 and JrPPO2 in walnut. Treatment with the PPO activator CuSO4 and H2O2 accelerated fruit browning and up-regulated JrPPO1/2 expression, whereas treatment with the PPO inhibitor ascorbic acid delayed browning, down-regulating JrPPO1 and up-regulating JrPPO2 expression. Compared to mJrPPO1, mJrPPO2 can exhibited better enzyme activity at higher temperatures (47 °C) and in more acidic environments (pH 4.25). mJrPPO2 exhibited a higher substrate specificity over mJrPPO1, and the preferred substrates are catechol, chlorogenic acid, and epicatechin. Additionally, mJrPPO2 adapted better to low concentration of oxygen (as low as 1.0% O2) and slightly elevated CO2 levels compared to mJrPPO1. Subcellular localization and spatiotemporal expression patterns showed that JrPPO1 is only expressed in green tissues and located in chloroplasts, while JrPPO2 is also located in chloroplasts, partly associated with membranes, and is expressed in both green and non-green tissues. Silencing JrPPO1/2 with virus-induced gene silencing (VIGS) reduced fruit browning, maintained higher total phenols, and decreased MDA production. Notably, silencing JrPPO1 had a greater impact on browning than JrPPO2, indicating JrPPO1's greater contribution to PPO activity and fruit browning in walnut fruits. Consequently, JrPPO1 can be effectively regulated both at the molecular level and by manipulating environmental conditions, to achieve the objective of controlling fruit browning.

Chemical Composition of Seeds in Soybean Glycine soja (Fabaceae) of Amur Oblast.

The wild soybean Glycine soja Sieb. et Zucc. is an ancestor of the cultivated soybean Glycine max (L.) Merr. and a source of many valuable genes missing in the G. max genome, including genes that determine stress resistance to adverse environmental factors. Biochemical parameters (protein, oil, ascorbic acid, carotene, higher fatty acids, and specific activities and multiple forms of enzymes of the oxidoreductase and hydrolase classes) were studied in five G. soja accessions from the collection of the All-Russian Institute of Soybean (КА-1413, КА-342, КBl-29, КBl-24, and Kеl-72). The accessions provide unique natural gene banks. Wild seeds were collected in three districts (Arkharinskii, Blagoveshchensk, and Belogorskii) of Amur Oblast. Based on superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), ribonuclease (RNase), acid phosphatase, esterase, and amylase (AML) activities and biochemical parameters of seeds, the G. soja accession KA-1413 was found to have higher contents of protein, oleic acid, and linolenic acid; a lower polyphenol oxidase specific activity; and higher activities of SODs, esterases, and RNases. The accession KA-1413 was therefore recommended to use as a source of dominant genes in breeding to increase the adaptive potential of new soybean varieties. A higher heterogeneity of multiple forms was observed for SOD, AML, RNase, and esterase, which can provide markers of adaptation to environmental conditions.

Variations in quality attributes of pulsed light-treated table grape juice during refrigerated storage (4°C) and ambient conditions (25°C).

Pulsed light (PL) pasteurization is being explored as a substitute for the conventional thermal pasteurization of juices in recent times due to better retention of nutrients and overall quality. However, the long-term stability of the PL-pasteurized juice must be investigated to promote its application by the industry. The effect of PL treatment (effective fluence of 1.15 J·cm-2) and thermal treatment (90°C for 60 s) on microbial quality, enzyme activity, bioactive compounds, sensory acceptance, and color profile of table grape juice during storage at 4 and 25°C was investigated in this study. The PL pasteurization enhanced the microbial shelf-life of the juice (<6 log10cfu·mL-1) from 5 to 35 days at 4°C. The PL and thermally-pasteurized juice demonstrated a shelf-life of only 10 days when stored at 25°C. The total soluble solids and titratable acidity did not alter significantly throughout the storage period. The peroxidase, polyphenol oxidase, and pectin methylesterase activities were below 10% for the PL and thermally-treated beverage when stored at 4°C. The sensory acceptability of the PL-pasteurized juice after 35 days of refrigerated storage (6.9±0.3) was close to the untreated juice (7.2±0.3) and greater than thermally-treated juice (6.2±0.2). After the 35th day of storage at 4°C, PL-treated grape juice retained 55%, 12%, and 15.3% more phenolics, flavonoids, and antioxidant capacity, respectively, than the thermally-pasteurized juice. Hence, PL pasteurization can effectively prolong the shelf-life of table grape juice while achieving microbial and enzymatic stability, along with high sensory and nutritional appeal. PRACTICAL APPLICATION: Exploring non-thermal methods like pulsed light (PL) pasteurization as a substitute for conventional thermal methods is gaining recognition for its ability to retain nutrients and improve overall juice quality. However, the industry's adoption depends on understanding the shelf-stability of PL-pasteurized juice. This study specifically investigates the practical applications of PL treatment in comparison with conventional thermal treatment in enhancing microbial safety and enzymatic stability in table grape juice. The findings contribute insights into optimizing the shelf life of table grape juice and preserving its quality, supported by microbial, enzymatic, and sensory evaluations.

Does Bidens pilosa L. Affect Carbon and Nitrogen Contents, Enzymatic Activities, and Bacterial Communities in Soil Treated with Different Forms of Nitrogen Deposition?

The deposition of nitrogen in soil may be influenced by the presence of different nitrogen components, which may affect the accessibility of soil nitrogen and invasive plant-soil microbe interactions. This, in turn, may alter the success of invasive plants. This study aimed to clarify the influences of the invasive plant Bidens pilosa L. on the physicochemical properties, carbon and nitrogen contents, enzymatic activities, and bacterial communities in soil in comparison to the native plant Pterocypsela laciniata (Houtt.) Shih treated with simulated nitrogen deposition at 5 g nitrogen m-2 yr-1 in four forms (nitrate, ammonium, urea, and mixed nitrogen). Monocultural B. pilosa resulted in a notable increase in soil pH but a substantial decrease in the moisture, electrical conductivity, ammonium content, and the activities of polyphenol oxidase, β-xylosidase, FDA hydrolase, and sucrase in soil in comparison to the control. Co-cultivating B. pilosa and P. laciniata resulted in a notable increase in total soil organic carbon content in comparison to the control. Monocultural B. pilosa resulted in a notable decrease in soil bacterial alpha diversity in comparison to monocultural P. laciniata. Soil FDA hydrolase activity and soil bacterial alpha diversity, especially the indices of Shannon's diversity, Simpson's dominance, and Pielou's evenness, exhibited a notable decline under co-cultivated B. pilosa and P. laciniata treated with nitrate in comparison to those treated with ammonium, urea, and mixed nitrogen.

Effect of Nitrogen Fertilizer on Capsaicinoids and Related Metabolic Substances of Dried Chili Pepper Fruit

Reducing fertilizer pollution is an important direction for modern ecological agriculture. Commonly, excessive nitrogen is applied to pepper. Capsaicin is one of the most important economic qualities of spicy peppers, but the effect of nitrogen on capsaicin is still inconsistent. This study aims to elucidate the impact of nitrogen fertilizer on capsaicin accumulation and to provide guidance on fertilizer application on highly spicy chili peppers. The experiment was conducted with five nitrogen fertilizer concentrations: N1 (urea 750 kg ha−1), N2 (urea 562.5 kg ha−1), N3 (urea 375 kg ha−1), N4 (urea 187.5 kg ha−1), and N0 (no nitrogen fertilizer). Nitrogen treatment was applied to two varieties with different spiciness levels from the seedling stage. The fruits in different layers of pepper plants were sampled on the 20th, 35th, and 50th day after anthesis, and the fruits’ size, content of capsaicin, capsaicin precursors, capsaicin competitors, as well as capsaicin-related enzyme activities and gene expression level were analyzed. The results indicate that, when applying N2 and N3, both chili pepper varieties exhibited higher fruit length, diameter, weight, and yield values. There were increased contents of total phenol, flavonoids, and tannins in both fruit varieties with N2 application. Moreover, the placenta weights of the bottom, middle, and top layers of the fruits on the 35th day were improved by 40.14%, 26.80%, and 55.91% for ‘Honglong 23’ and 55.10%, 37.04%, and 75.56% for ‘Hongxi’ compared with N0. At the same time, under N2 treatment, the phenylalanine ammonia-lyase (PAL) enzyme activity of capsaicin synthase significantly increased. In contrast, the capsaicin-degrading enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO) decreased notably. The expression levels of capsaicin-synthetic genes such as phenylalanine cleavage enzyme gene (PAL), acyltransferase gene (AT3), 4-Coumaroyl coenzyme A ligase gene (4CL), cinnamate 4-hydroxylase gene (C4H), caffeoyl coenzyme A-3-oxo-methyltransferase gene (COMT), paminotransferase gene (PAMT), and hydroxycinnamyltransferase gene (HCT) were up-regulated in N2 fruits, which led to a significant increase in capsaicin content compared with the other four nitrogen amounts. A further reduction in nitrogen application to N3 and N4 resulted in a decrease in the precursor substance’s total phenol content and PAL activity and an increase in the competitive substance’s flavonoid, lignin, POD, and PPO enzyme activities. At the same time, the expression levels of capsaicinoid synthetic genes were downregulated in the N3 and N4 treatments, leading to a low content of total capsaicinoids. The capsaicinoid content showed a trend of 35th day &gt; 50th day &gt; 20th day for both varieties. Additionally, the contents of total capsaicinoids, total phenols, flavonoids, and lignins, as well as PAL enzyme activity, and the expression levels of PAL, AT3, 4CL, C4H, COMT, PAMT, and HCT exhibited characteristics of bottom layers &gt; middle layers &gt; top layers. The activities of POD and PPO gradually increased from the bottom to the top layers. The N2 (562.5 kg ha−1) treatment resulted in increases in placenta mass, maximum capsaicinoid precursor substance of total phenol content, and synthase enzyme activity, as well as decreases in capsaicinoid competing substances and degradative enzyme activity, so there were more substances available for capsaicin synthesis. Combined with the higher fruit weight and capsaicinoid content in the N2 treatment, N2 was considered a suitable nitrogen fertilizer dosage for highly spicy chili pepper cultivation.

Impact mechanisms of various surfactants on the biodegradation of phenanthrene in soil: Bioavailability and microbial community responses

The present study was conducted to systematically explore the mechanisms underlying the impact of various surfactants (CTAB, SDBS, Tween 80 and rhamnolipid) at different doses (10, 100 and 1000 mg/kg) on the biodegradation of a model polycyclic aromatic hydrocarbon (PAH) by indigenous soil microorganisms, focusing on bioavailability and community responses. The cationic surfactant CTAB inhibited the biodegradation of phenanthrene within the whole tested dosage range by decreasing its bioavailability and adversely affecting soil microbial communities. Appropriate doses of SDBS (1000 mg/kg), Tween 80 (100, 1000 mg/kg) and rhamnolipid at all amendment levels promoted the transformation of phenanthrene from the very slow desorption fraction (Fvslow) to bioavailable fractions (rapid and slow desorption fractions, Frapid and Fslow), assessed via Tenax extraction. However, only Tween 80 and rhamnolipid at these doses significantly improved both the rates and extents of phenanthrene biodegradation by 22.1–204.3 and 38.4–76.7 %, respectively, while 1000 mg/kg SDBS had little effect on phenanthrene removal. This was because the inhibitory effects of anionic surfactant SDBS, especially at high doses, on the abundance, diversity and activity of soil microbial communities surpassed the bioavailability enhancement in dominating biodegradation. In contrast, the nonionic surfactant Tween 80 and biosurfactant rhamnolipid enhanced the bioavailability of phenanthrene for degradation and also that to specific degrading bacterial genera, which stimulated their growth and increased the abundance of the related nidA degradation gene. Moreover, they promoted the total microbial/bacterial biomass, community diversity and polyphenol oxidase activity by providing available substrates and nutrients. These findings contribute to the design of suitable surfactant types and dosages for mitigating the environmental risk of PAHs and simultaneously benefiting microbial ecology in soil through bioremediation.

Salicylic acid inhibition on browning of fresh-cut taro by regulating phenolic compounds and active oxygen metabolism

Surface browning of fresh-cut taro limits storage shelf-life and affects customer satisfaction. This study investigated the effects of salicylic acid (SA) on the browning of fresh-cut taro and explored the possible mechanism of SA in inhibiting browning. A 10 mmol/L SA treatment effectively delayed browning, improved soluble starch content, and reduced weight loss. Furthermore, by regulating the activities of phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO), SA treatment reduced the contents of total phenol, flavonoid, soluble quinone, and monomer phenolic acid, indicating that it inhibited phenol metabolism, decreased the synthesis of colored secondary metabolites, and suppressed surface browning in fresh-cut taro. On the other hand, SA treatment enhanced the activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD), reduced lipoxygenase (LOX) activity, enhanced ascorbic acid (AsA) and glutathione (GSH) levels. It decreased malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion radicals (O2−·) production, indicating reduced oxidative damage. Thus, SA treatment improved the antioxidant system, reduced the accumulation of reactive oxygen species, and delayed phenolic oxidation, effectively inhibiting browning. These findings reveal SA as a feasible method for preserving fresh-cut fruits and vegetables.