Polyphenol Oxidase Activity Research Articles

Carbon Dot-Mediated Photodynamic Treatment Improves the Quality Attributes of Post-Harvest Goji Berries (Lycium barbarum L.) via Regulating the Antioxidant System.

Carbon dots (CDs) have been proposed as photosensitizers in photodynamic treatment (PDT), owing to their excellent biological attributes and budding fruit preservation applications. In the present study, CDs (4.66 nm) were synthesized for photodynamic treatment to improve the quality attributes in post-harvest goji berries. The prepared CDs extended the storage time of the post-harvest goji berries by 9 d. The CD-mediated PDT postponed the hardness and decay index loss, reduced the formation of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2•-) significantly, and delayed the loss of vital nutrients like the total protein, phenols, and flavonoids. The CD-mediated PDT improved the catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), phenylalanine ammonia-lyase (PAL), glutathione reductase (GR), and superoxide dismutase (SOD) activities, but did not improve polyphenol oxidase (PPO) activity. In addition, The CD-mediated PDT induced the accumulation of ascorbic acid (ASA) and glutathione (GSH). Overall, a CD-mediated PDT could extend the storage time and augment the quality attributes in post-harvest fresh goji berries by regulating the antioxidant system.

Impact of Pre-drying Treatments on Antioxidant Activities and Quality of Dried Golden Oyster Mushroom (Pleurotus citrinopileatus)

The effects of three pre-drying treatments including blanching in hot water (60oC-70oC for 3 and 5 min), soaking in NaCl (1-4% w/v for 10 and 20 min), and soaking in citric acid (0.2-0.8% w/v for 10 and 20 min) on dried Golden oyster mushroom (GOM) were studied. Color values (L*, a*, and b*), browning index (BI), polyphenol oxidase (PPO) activity, protein content, flavonoid content (FC), total phenolic content (TPC), and antioxidant activities (metal chelating activity and DPPH radical scavenging activity) of dried mushrooms were evaluated. All pretreated mushrooms had significantly higher lightness (L*) and lower a* and b* values compared to those of un-pretreated ones. Decreases in BI and PPO activity were observed in pretreated mushrooms. Higher blanching temperatures, concentrations of NaCl and citric acid, and time yielded lower protein content, TPC, and FC. Among the pretreatments, the highest antioxidant activities were observed in citric acid treated GOM. Thus, blanching and chemical pretreatments could enhance the lightness and lower BI of dried GOM, although they lowered the nutrient levels and antioxidant activities of the dried GOM.

Studies on the effect of cinnamon essential oil-micelles combined with 1-MCP/PVA film on postharvest preservation of apricots

Apricot is respiration climacteric fruit. They have high postharvest respiratory intensity, high ethylene release and are easily infected by pathogenic fungi, which greatly shortens the postharvest storage life. This study investigated the effect of Cinnamon essential oil-micelles (CEO-micelles) and biodegradable polymer Polyvinyl Alcohol (PVA) eletrospunning nano fibers films based 1-Methylcyclopropene-Polyvinyl Alcohol films (1-MCP/PVA films) on the quality and antioxidant enzyme activities of apricots during storage. The results showed that compared with CEO-micelles or 1-MCP/PVA films treatment alone, the 1-MCP/PVA + CEO-micelles combined treatment could more effectively inhibit the decay of apricots, reduce the peak value of respiration rate and ethylene production, delay the decrease of loss-weight rate, firmness, total soluble solids (TSS) and titratable acid (TA), and maintain better appearance. In addition, compared with single treatment, combined treatment significantly decreased the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2), increased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), and inhibited the increase of polyphenol oxidase (PPO) activity. These results showed that the combination of CEO-micelles and 1-MCP fibers could effectively inhibit the deterioration of fruit quality, improve the antioxidant capacity of apricots and delay postharvest senescence.

Low oxygen concentration alleviates banana peel browning by inhibiting membrane lipid oxidation and polyphenol oxidase activity

SummaryBananas, a common fruit in our daily diet, often develop physiological disorders during the late ripening period, resulting in browning, which reduces their suitability for consumption. In this study, we inhibited the browning phenomenon by reducing the oxygen concentration to improve their storage period. Compared with banana fruit treated with high oxygen concentration, banana fruit treated with low oxygen concentration had higher hardness and significantly delayed weight loss. The analysis showed that low oxygen concentration enhanced the antioxidant capacity of banana skin cells by maintaining the DPPH scavenging capacity of antioxidant substances in the banana peel. The activity of the membrane‐degrading enzyme LOX is reduced, and the permeability of the cells is reduced, thus maintaining the structural integrity of the cells. Scanning electron microscope analysis showed that the integrity of the cell membrane was well maintained under low oxygen concentration, which restricted the reaction of phenols and PPO enzymes to produce quinones under the action of oxygen, and inhibited the browning phenomenon. These results suggest that low oxygen concentrations inhibit banana Browning by maintaining the structural integrity of cell membranes.

Shrub and patch size of moss crusts regulate soil multifunctionality in a temperate desert of Central Asia

AbstractThe shrub and patch size of moss crusts can significantly affect plant and soil nutrients. The effects and relationships of shrubs and moss crusts on soil multifunctionality are unclear. This study aimed to understand the spatial heterogeneity of soil multifunctionality in moss crust patches and shrubs. Soil organic carbon, nutrient, and enzyme activities under moss crust patches were measured. Interestingly, the soil polyphenol oxidase (PPO) and peroxidase (POD) activities, carbon‐related soil multifunctionality index (C‐SMF), nitrogen‐related soil multifunctionality index (N‐SMF), phosphorus‐related soil multifunctionality index (P‐SMF), and soil multifunctionality index (SMF) increased with increasing patch size in moss crusts. The patch size of moss crusts had no significant effect on the C‐SMF, N‐SMF, P‐SMF, and SMF under the shrub. The soil C‐SMF, N‐SMF, P‐SMF, and SMF under shrubs were significantly higher than that in exposed areas (EAs). The soil PPO, POD, N‐SMF, P‐SMF, and SMF under dead shrubs were significantly higher than those under living shrubs and in EAs. Evaluation and composition analysis of C‐SMF, N‐SMF, and P‐SMF indicated that moss crust promotes the increase of P‐SMF, and that shrub promotes the increase of C‐SMF and N‐SMF. Moss crust patches mainly affected phosphorus functionality, increasing phosphorus cycling. Shrub promotes soil carbon and nitrogen functionality. This study elucidates the effect of moss crust patch size on soil multifunctionality influenced by shrub growth in desert ecosystems and provides further new insights into the soil processes and functions. Results are beneficial for the comprehensive utilization of fertile islands and its enhancement of beneficial ecological functions, such as maintaining soil nutrition, quality, health, and vegetation restoration, and lay a foundation for future research on nutrient absorption and utilization between mosses and shrubs.

Effects of long-term no-tillage and different stover mulching amounts on soil carbon and nitrogen contents and enzyme activities of carbon and nitrogen cycle in Mollisols.

To understand the effects of different stover mulching amounts in no-tillage on soil carbon and nitrogen contents and enzyme activities, finding a stover mulching amount which can meet the requirement of soil carbon and nitrogen accumulation while maximizing economic benefits, we conducted a long-term conservation tillage field experiment since 2007 in Mollisols area of Northeast China. We analyzed soil carbon and nitrogen contents, enzyme activities and economic benefits under conventional tillage (Control, CT), no-tillage without stover mulching (NT0), no-tillage with 33% stover mulching (NT33), no-tillage with 67% stover mulching (NT67), and no-tillage with 100% stover mulching (NT100) before planting in May 2020. The results showed that compared with CT, NT0 did not affect soil organic carbon (SOC) and total nitrogen (TN) contents, but increased soil organic carbon recalcitrance and decreased the availability of dissolved organic nitrogen (DON) and ammonium nitrogen. Compared with NT0, no-tillage with stover mulching significantly increased SOC contents in 0-10 cm layer and increased with the amounts of stover. In addition, NT67 and NT100 significantly increased SOC stocks, facilitating the accumulation of soil organic matter. The effects of different stover mulching amounts on soil nitrogen content in 0-10 cm layer were different. Specifically, NT33 increased DON content and DON/TN, NT67 increased DON content, while NT100 increased TN content. Compared with CT, NT0 decreased peroxidase (POD) activity in 0-10 cm layer. Compared with NT0, NT33 increased β-glucosidase (βG), cellobiase (CB), 1,4-β-N-acetylglucosaminidase (NAG), polyphenol oxidase (PPO) and POD activities, while NT67 only increased CB, NAG and POD activities in 0-10 cm soil layer, both alleviated microbial nutrient limitation. NT100 increased PPO activity in 10-20 cm layer. NT33 increased carbon conversion efficiency of stover compared with NT100, and had the highest economic benefit. In all, no-tillage with 33% stover mulching was the optimal strategy, which could promote nutrient circulation, boost stover utilization efficiency, improve the quality of Mollisols, and maximize guaranteed income.

Salicylic Acid Spray Delays Sand Pear Fruit Senescence during Room Temperature Shelf Life by Regulating Antioxidant Capacity and Senescence-Related Genes.

'Whangkeumbae' (Pyrus pyrifolia) is a variety of sand pear fruit well-known for its smooth surface and good taste. However, the fruit quality is adversely affected by postharvest ethylene production. Therefore, improving postharvest shelf life by regulating fruit senescence is critical to promoting the 'Whangkeumbae' fruit industry. Here, we investigated the effect of salicylic acid (SA) spray on fruit senescence in sand pears during room temperature shelf life. Exogenous SA reduced polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content during room temperature shelf life. Additionally, SA effectively maintained the fruit skin coloration and increased the activity of antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). SA treatment inhibited PpPPO1 expression and upregulated PpSOD1, PpAPX6, and PpGST2 expression. Furthermore, SA application downregulated the expression of PpACO2, PpEIN3a, PpNCED1, and PpAOC2, while upregulating PpNPR-1, PpTAR2, and PpCOMT1 during room temperature shelf life. SA treatment also influenced cell wall metabolism and modification genes by inhibiting PpPG1, PpPME2, and PpCEL3 and inducing PpPGIP1 expression. Additionally, SA treatment affected sugar and acid metabolism genes and increased the expression of PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH, but suppressed the expression of PpcyNADP-ME. The Pearson correlation analysis indicated that PPO activity and MDA content were positively correlated with the expression of PpPPO1, PpACO2, PpEIN3a, PpNCED1, PpAOC2, PpPG1, PpPME2, PpCEL3, and PpcyNDA-MDH. Conversely, these factors were negatively associated with the activities of SOD, POD, CAT, and APX, as well as the expression levels of PpSOD1, PpPOD1, PpCAT1, PpAPX6, PpGST2, PpNPR-1, PpTAR2, PpCOMT1, PpPGIP1, PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH. Our results reveal that exogenous SA could delay fruit senescence in sand pear fruit by regulating various biochemical and molecular mechanisms and can be used to effectively extend fruit shelf life during room temperature storage. However, further research is necessary to determine whether the fruits sprayed with SA are suitable for direct human consumption.

Evaluating the effects of chitosan incorporated with seabuckthorn leaf extract composite edible coatings on the shelf life of peach (Prunus persica L.) fruits

Peaches are highly nutritious and delicious fruits with a limited shelf life. The present study was aimed to test the efficiency of chitosan (CHI) coatings incorporated with seabuckthorn leaf extract (ST) in extending the shelf life of peach fruits at refrigerated temperature. Peach fruits of ‘Elberta’ cultivar were coated with one of the following treatment combinations: distilled water (control), CHI (1.0%), CHI (1%) + ST (0.5%), CHI (1%) + ST (1.0%), CHI (1%) + ST (1.5%) and CHI (1%) + ST (2.0%) and then stored at 4 °C for 25 days. The combined treatment of CHI and ST showed a synergistic effect in significantly decreasing the skin browning and maintaining the firmness during the storage period, corroborated by the decline in the polyphenol oxidase, cellulase and pectinase enzyme activity. In particular, fruits treated with CHI (1%) + ST (1.5%) and CHI (1%) + ST (2.0%) showed maximum efficiency in retaining the physico-chemical attributes, increasing the antioxidant potential and controlling the browning during post harvest period upto 25 days under refrigerated temperature at 4 °C. Furthermore, besides maintaining the quality parameters, the treated fruits showed a significant reduction in microbial spoilage and maintaining the acceptable sensory attributes. Therefore, the study employing the incorporation of Seabuckthorn leaf extract into chitosan edible coating could be a valuable addition and promising approach to different existing preservation techniques towards extending the shelf life of peach fruits.

Different responses of lipids and lignin phenols to nitrogen addition in meadow grassland soil

PurposeNitrogen (N) enrichment can affect the composition and stability of soil organic carbon (SOC) pools by altering vegetation and soil properties. However, the response of plant-derived carbon components in soil to different N addition levels is unclear. We investigated the changes and potential driving processes of plant-derived carbon components (especially lignins and lipids) in meadow grassland soils under long-term N addition in eastern Inner Mongolia, China.Materials and methodsBiomarker technology was utilised to analyse changes in plant-derived carbon components (C>20 free lipids, bound lipids, and lignin phenols) in soil under different N addition levels, including changes in soil chemical properties, enzyme activity, plant biomass, and diversity under N addition, as well as the specific pathways involved.Results and discussionWe found that high levels of N addition significantly reduced the concentration of soil lignin phenols whereas increased the accumulation of lipids (free and bound lipids). Compared with changes in plant biomass and diversity, soil chemical properties and enzyme activity play a more significant role in regulating the accumulation and degradation of plant-derived carbon. Structural equation modelling (SEM) showed that decreases in lignin phenol concentration were related to specific biochemical decomposition processes (increased polyphenol oxidase activity and decreased C/N). The increase in lipids associated with the protective effects of minerals mediated by pH.ConclusionsIn general, plant-derived carbon components showed inconsistent responses to N addition, lignin phenol concentration decreased and lipid concentration increased, which was mainly related to the change of soil biochemical properties. Plant-derived carbon components only showed significant changes under high N addition levels. Furthermore, our research indicates that SOC sequestration and functioning are highly dependent on soil biochemical properties, which weakens the influence of changes in plant carbon input on soil carbon storage.

Effect of ultrasonication on the quality of amla pulp (Emblica officinalis): Optimization and comparison with the thermal processing

Amla pulp was treated with ultrasonication technique under the different set of designed conditions in order to optimize the ultrasonic conditions. A two factor four level Taguchi design was adopted to study the effect of ultrasonic intensity (180 – 717 W/cm2) and treatment time (4 – 16 min) on the ascorbic acid, naringin, total phenolic content, titratable acidity, total soluble solids, browning index, polymethylesterase and polyphenol oxidase activity of amla pulp. The optimal conditions were determined as ultrasonic intensity, 359 W/cm2 and treatment time, 12 min on the basis of S/N ratio analysis. Optimized ultrasonicated pulp was compared with the thermally treated pulp (90 °C/ 5 s) to observe the effect on quality parameters. Enzymatic activity reduced to a lower level at optimal ultrasonic processing conditions. Total phenolic content increased after ultrasonication treatment. LCMS of the optimized sample depicted the presence of compounds like ascorbic acid, corilagin, gallic acid, kaempferol, chebulagic acid and many more. Thermal treatment showed lower retention of bioactives and there were notable losses in ascorbic acid and total phenolic content. Browning index was also higher than control and ultrasonicated pulp sample. Microstructure of ultrasonicated sample showed damage to cells but thermal treated sample exhibited major cell damage.

Effects of 1-methylcyclopropene on skin greasiness and quality of 'Yuluxiang’ pear during storage at 20°C

During storage at 20°C, specific pear cultivars may exhibit a greasy texture and decline in quality due to fruit senescence. Among these varieties, 'Yuluxiang’ is particularly susceptible to peel greasiness, resulting in significant economic losses. Therefore, there is an urgent need for a preservative that can effectively inhibit the development of greasiness. Previous studies have demonstrated the efficacy of 1-methylcyclopropene (1-MCP) in extending the storage period of fruits. We hypothesize that it may also influence the occurrence of postharvest peel greasiness in the 'Yuluxiang’ pears. In this study, we treated 'Yuluxiang’ pears with 1-MCP. We stored them at 20°C while analyzing the composition and morphology of the surface waxes, recording enzyme activities related to wax synthesis, and measuring indicators associated with fruit storage quality and physiological characteristics. The results demonstrate that prolonged storage at 20°C leads to a rapid increase in skin greasiness, consistent with the observed elevations in L*, greasiness score, and the content of total wax and greasy wax components. Moreover, there were indications that cuticular waxes underwent melting, resulting in the formation of an amorphous structure. In comparison to controls, the application of 1-MCP significantly inhibited increments in L* values as well as grease scores while also reducing accumulation rates for oily waxes throughout most stages over its shelf period, additionally delaying transitions from flaky-wax structures towards their amorphous counterparts. During the initial 7 d of storage, several enzymes involved in the biosynthesis and metabolism of greasy wax components, including lipoxygenase (LOX), phospholipase D (PLD), and β-ketoacyl-CoA synthase (KCS), exhibited an increase followed by a subsequent decline. The activity of LOX during early shelf life (0–7 d) and the KCS activity during middle to late shelf life (14–21 d) were significantly suppressed by 1-MCP. Additionally, 1-MCP effectively maintained firmness, total soluble solid (TSS) and titratable acid (TA) contents, peroxidase (POD), and phenylalanine ammonia-lyase (PAL) activities while inhibiting vitamin C degradation and weight loss. Furthermore, it restrained polyphenol oxidase (PPO) activity, ethylene production, and respiration rate increase. These findings demonstrate that 1-MCP not only delays the onset of peel greasiness but also preserves the overall storage quality of 'Yuluxiang’ pear at a temperature of 20°C. This study presents a novel approach for developing new preservatives to inhibit pear fruit peel greasiness and provides a theoretical foundation for further research on pear fruit preservation.

Halotolerant Pseudomonas koreensis S4T10 mitigate salt and drought stress in Arabidopsis thaliana.

Salt and drought are documented among the most detrimental and persistent abiotic stresses for crop production. Here, we investigated the impact of Pseudomonas koreensis strain S4T10 on plant performance under salt and drought stress. Arabidopsis thaliana Col-0 wild type and atnced3 mutant plants were inoculated with P. koreensis or tap water and exposed to NaCl (100 mM) for five days and drought stress by withholding water for seven days. P. koreensis significantly enhanced plant biomass and photosynthetic pigments under salt and drought stress conditions. Moreover, P. koreensis activated the antioxidant defence by modulating glutathione (GSH), superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) activities to scavenge the reactive oxygen species produced due to the stress. In addition, the application of P. koreensis upregulated the expression of genes associated with antioxidant responses, such as AtCAT1, AtCAT3, and AtSOD. Similarly, genes linked to salt stress, such as AtSOS1, AtSOS2, AtSOS3, AtNHX1, and AtHKT1, were also upregulated, affirming the positive role of P. koreensis S4T10 in streamlining the cellular influx and efflux transport systems during salt stress. Likewise, the PGPB inoculation was observed to regulate the expression of drought-responsive genes AtDREB2A, AtDREB2B, and ABA-responsive genes AtAO3, AtABA3 indicating that S4T10 enhanced drought tolerance via modulation of the ABA pathway. The results of this study affirm that P. koreensis S4T10 could be further developed as a biofertilizer to mitigate salt and drought stress at the same time.

Characterization of Sodium Alginate‐Based Edible Active Coating Incorporated with Dendrobium officinale Polysaccharides and Its Application in Grape Packaging

AbstractIn the present study, Dendrobium officinale polysaccharides (DOPs) are incorporated into sodium alginate (SA) for the development of SA‐DOPs films. The physical, mechanical, and functional properties of SA‐DOPs composite films and their ability to preserve fresh grapes are investigated. The results reveal that the addition of DOPs can significantly enhance the thickness, swelling ratio, tensile strength, elongation at break, and thermal stability of the films (p < 0.05) whereas the water solubility and water vapor permeability are decreased. Fourier transform‐infrared (FT‐IR) spectroscopy results reflect interaction of chemical groups and bonds between SA and DOPs. The result of scanning of electron microscopy (SEM) indicates smooth for SA‐DOPs films while control film exhibits rough. The SA‐DOPs films exhibit potential antioxidant effects on 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) free radicals. Furthermore, the composite films exhibit remarkable inhibition of the growth of Escherichia coli and Staphylococcus aureus (p < 0.05). In addition, the SA‐DOPs coatings can effectively reduce weight loss, inhibit polyphenol oxidase activity, extend the shelf life of the grapes at room temperature (25 ± 1 °C) for 14 days. These results indicate that the SA‐DOPs edible coatings might be a promising candidate in food preservation industries.

A novel hybrid sensor array based on the polyphenol oxidase and its nanozymes combined with the machine learning based dual output model to identify tea polyphenols and Chinese teas

A novel sensor array was developed based on the enzyme/nanozyme hybridization for the identification of tea polyphenols (TPs) and Chinese teas. The enzyme/nanozyme with polyphenol oxidase activity can catalyze the reaction between TPs and 4-aminoantipyrine (4-AAP) to produce differences in color, and the sensor array was thus constructed to accurately identify TPs mixed in different species, concentrations, or ratios. In addition, a machine learning based dual output model was further used to effectively predict the classes and concentrations of unknown samples. Therefore, the qualitative and quantitative detection of TPs can be realized continuously and quickly. Furthermore, the sensor array combining the machine learning based dual output model was also utilized for the identification of Chinese teas. The method can distinguish the six teas series in China, and then precisely differentiate the more specific tea varieties. This study provides an efficient and facile strategy for the identification of teas and tea products.

Combination of Sodium Nitroprusside and Controlled Atmosphere Maintains Postharvest Quality of Chestnuts through Enhancement of Antioxidant Capacity.

The purpose of this study was to clarify the effect of CA (controlled atmosphere, 2-3% O2 + 3% CO2) and NO (nitric oxide, generated by 0.4 nM sodium nitroprusside), alone or combined (CA + NO), on the physio-chemical properties, enzyme activities and antioxidant capacities of chestnuts during storage at 0 °C for 180 d. Compared with control (CT), CA and CA+NO both improved the storage quality of the samples, but only CA resulted in more ethanol production. Moreover, these improvements were further enhanced and ethanol synthesis was inhibited by the addition of NO. A spectrometer was used to assess the production of phenolic content (TPC) and activities of phenylalanine ammonia-lyase (PAL), superoxide dismutas (SOD), peroxidase (POD), catalase (CAT) and polyphenol oxidase (PPO) as influenced by CA or CA+NO treatments. Higher TPC, PAL, SOD, POD, CAT, and lower PPO were observed in CA alone, and more so in the combination with NO group. The increased antioxidant production and enhanced antioxidant activities contributed to scavenging reactive oxygen species (ROS) and reducing malondialdehyde (MDA). This study unveiled the correlations and differences between the effects of CA and CA+NO on storage quality, providing valuable insights into postharvest preservation and suggesting that the combination (CA+NO) was more beneficial for quality maintenance in chestnuts.

Assessment of microwave drying for rapid and convenient analysis of medicinal plants for quality assurance.

The safety and quality of many medicinally important herbs are compromised since farmers and small organizations are involved in the cultivation, aggregation, and primary processing of these herbs. Such organizations often lack adequate quality control facilities. To improve the safety and quality of herbal products, simple, rapid, and affordable quality control systems are required. The aim of this study was to assess the suitability of microwave oven-drying for moisture content (MC) determination and sample preparation of herbs in small organizations. Microwave oven-drying (720 W) and convective oven-drying at 105°C for MC determination were compared. The effects of three different drying methods (microwave oven-drying, low-temperature convective drying, and freeze-drying) on in vitro antioxidant and polyphenol oxidase (PPO) activity were determined, similarity analysis was conducted using HPLC signature spectra, and validation was performed with LC-MS focusing on one herb. Microwave oven-drying at 720 W significantly reduced the drying time (from hours to minutes), whereas the spatial variationof temperature in convective ovens set at 105°C can cause about 10% underestimation of MC. Microwave oven-dryingshowed similar macro-properties like freeze-drying and higher extractability (10%-20%) and in vitro antioxidant capacity (33%-66%) and lower PPO activity compared to low-temperature convective drying. HPLC signature spectra revealed strongsimilarity ofsoluble components between freeze-dried and microwave oven-dried herbs. LC-MS analysis demonstrated more common compounds between freeze-driedand microwave oven-driedCentella asiatica extracts, whereas convective tray-dried samples had fewer compounds common with samples obtained by freeze-drying or microwave oven-drying. Microwave oven-drying is rapid (tens of min) and shows small batch-to-batch variation compared to oven-drying at 105°C. The in vitro antioxidant assays and signature spectra can be used for assessing the source and purity or quality of a specific herb variety.

The maturity, humus content, and microbial metabolic function of sheep manure compost on the Qinghai-Tibet Plateau can be significantly improved by reducing the moisture content.

The Qinghai-Tibet Plateau (QTP) is characterized by an extreme hypoxia, which may lead to lack of sufficient oxygen for compost production, and thus seriously affecting the compost quality. The moisture content (MC) has a direct effect on the oxygen content of composting pile. At present, the research on the optimum moisture content of compost production on the QTP is still lacking. This study aimed to investigate the influences of MC on fermentation quality of sheep manure composting on the QTP and to further analyze the changes of microbial metabolic function and enzyme activity under different MC. Composting experiment with low MC (45%) and conventional MC (60%) was conducted in both summer and autumn. The results showed that the composting efficiency of 45% MC was better than 60% in both seasons, which was mainly manifested as longer high-temperature period (summer:16d vs 14d, autumn: 7d vs 2d), higher germination index (summer:136.1% vs 128.6%, autumn:103.5% vs 81.2%), and more humus synthesis (summer:159.8g/kg vs 151.2g/kg, autumn:136.1k/kg vs 115.5k/kg). The 45% MC can improve microbial metabolism, including increasing the abundance of functional genes involved in carbohydrate metabolism, amino acid metabolism, and nucleotide metabolism and improving the activities of cellulase, β-glucosidase, protease, polyphenol oxidase, and peroxidase. In conclusion, 45% MC can improve the fermentation efficiency and products quality of sheep manure compost on QTP.

Thiourea as a polyphenol oxidase inhibitor enhances host infection by the entomopathogenic nematode, Heterorhabditis beicherriana

Entomopathogenic nematodes (EPN) are potent microbial biocontrol agents applied commercially against various economically important insect pests. The efficacy of EPN in the field may be partially reduced when compared to chemical insecticides due to its sensitivity to environmental stressors like temperature, desiccation, and UV light. Thus, researchers have developed methods to enhance the effectiveness of EPN, such as screening or breeding stress-resistant strains and creating adjuvants for EPN protection in the field. This study used another strategy to lower the host’s immunity so that the anti-infection ability of the pest wanes, and the virulence of EPN waxes accordingly. In addition to its use as a plant growth regulator, thiourea also functions as an inhibitor of polyphenol oxidase (PO) in insects. Thiourea can inhibit a key interaction in the humoral immunity of insects, so we utilized it to enhance the efficacy of EPN. To investigate the effects of thiourea on PO activity inhibition and EPN pathogenesis, we studied the effects of thiourea on survival, infectivity, reproduction, and host searching ability of the EPN, Heterorhabditis beicherriana, and monitored in vivo and in vitro polyphenol oxidase activity of the model insect host, Galleria mellonella. The survival of H. beicherriana infective juveniles (IJs) was barely affected after exposure to 0.5 mM and 1 mM thiourea solution, and the reproductive output of H. beicherriana IJs (after applying 50, 100 and 200 IJs per host) in 0.5 mM and 1 mM thiourea was not different compared to the control. However, the LD50 of G. mellonella larvae caused by H. beicherriana without thiourea was significantly higher than H. beicherriana IJs in thiourea. Moreover, thiourea inhibited in vivo and in vitro polyphenol oxidase activity of G. mellonella infected by EPNs at different concentrations. Thus, thiourea can improve the biological control efficacy of EPNs, and the enhanced environmentally friendly approach may apply to diverse cropping systems.

In silico guided pre-treatment of sugarcane juice with natural inhibitors of polyphenol oxidase (PPO) is a new and effective strategy for development of spray-dried formulation.

Sugarcane juice is a popular beverage and is also processed to produce sugar. The polyphenol oxidase (PPO) in sugarcane juice causes enzymatic browning and makes the process of sugar production complex and cumbersome. Storage of sugarcane juice is also hampered by the high sugar content and rapid microbial fermentation. The present research assessed the potential of lemon juice (LJ) and ginger extract (GE) as natural inhibitors of PPO. Enzyme kinetics and the mechanism of inhibition of LJ and GE were studied. Primary investigation was carried out using molecular docking approach to assess the inhibitory potential of LJ and GE and to determine the nature of interaction between the enzyme and inhibitors. Extracts were used as inhibitors and studies revealed that both reduced the PPO activity. Subsequently, pure bioactive inhibitors such as ascorbic acid, citric acid, and 6-shogaol present in these natural extracts were used to study the mode of inhibition of PPO. Citric acid decreased PPO activity by lowering pH, while ascorbic acid was found to be a competitive inhibitor of PPO with a Ki of 75.69µM. The proportion of LJ and GE required in sugarcane juice was optimized on the basis of browning index and sensory acceptance. Further, the sugarcane cane juice after inhibition of PPO under optimized conditions was spray dried and evaluated for reconstitution properties. The product formulated in the present study is a new and effective approach to address quality-compromising issues associated with long-term storage of cane juice.

Development and characterization of chia oil-activated ginger starch-feather keratin biocomposite for prolonged post-harvest preservation of tomato fruits

In response to the challenges posed by current postharvest preservation methods, this study focuses on the development and characterization of a ginger starch-waste feather keratin (GS-FK) composite functionalized with chia oil (CO). Composite films functionalized with 0.5 (GS-FK-CO0.5), 1.0 (GS-FK-CO1.0), and 1.5 (GS-FK-CO1.5) mL of chia oil were fabricated and characterized using standard analytical techniques. GS-FK-CO films in comparison to GS-FK showed increases in thickness and tensile strength, as well as reductions in moisture content, transparency, water solubility, WVP, and elongation at break. GS-FK-CO films demonstrated superior thermal stability and were evaluated for their efficacy in the post-harvest management of tomato fruits. Following coating and storage at 25 ± 2 °C for 21 days, the GS-FK-CO coated tomato fruits exhibited significantly (p > 0.05) lower weight loss, pH, brix value, and ripening index compared to the uncoated control. GS-FK-CO coated fruits in comparison to control displayed elevated levels of titratable acidity, ascorbic acid, and total phenolic acid, along with suppressed activities of polyphenol oxidase, pectin methyl esterase, and polygalacturonase. This study underscores the potential of the chia oil functionalized GS-FK biocomposite as a promising packaging alternative for extended shelf life and enhanced preservation of tomato fruits.