Nitrite Concentrations Research Articles

Optimizing nitrite content in powders from plasma-activated egg whites for meat preservation using response surface methodology

The study optimized the production of powders from two types of egg whites to be used as a nitrite source for meat curing, establishing a maximum utilization limit of 2%. The necessary quantity of nitrite was established through response surface methodology to guarantee its efficacy as a preservative agent and adherence to regulatory standards. High R2 values (0.9946 for hen, 0.9962 for ostrich) validated critical factors: plasma treatment time and distance, with minimal impact from drying temperature. Under specific experimental conditions (155.93 min, 16.84 cm, 41.10 °C), obtained nitrite concentration of 4000 mg kg⁻1 was confirmed through experiments. Stability tests showed that nitrite levels remained stable over four weeks under different conditions including vacuum and air-sealed packaging, as well as different temperatures (−18 °C, 4 °C, and 26 °C). Future research should investigate long-term stability, the formation of additional compounds, and the functional properties of powders to confirm their potential for food applications.

Nitrate and Nitrite Concentrations in Fingertip Serum Following Beetroot Juice Ingestion Correlate with Those in Venous Plasma.

Dietary nitrate (NO3-) supplementation can offer health benefit and improve exercise performance by increasing nitric oxide (NO) through NO3--nitrite (NO2-)-NO pathway. Individuals may benefit from dietary NO3- supplementation by monitoring blood [NO3-] and [NO2-], although a simple and practical method for assessing blood [NO3-] and [NO2-] has not been established. We examined whether fingertip serum samples could substitute for venous plasma samples in assessing [NO3-] and [NO2-]. Ten young adults consumed 140 mL of nitrate-rich beetroot juice. Fingertip serum and venous plasma samples were collected at baseline and every hour for up to 4 h after ingestion. [NO3-] and [NO2-] were similar between samples at baseline, whereas they were higher in fingertip serum throughout the post-ingestion periods. Significant correlations existed between fingertip serum vs. venous plasma for both [NO3-] and [NO2-] throughout post-drink periods, except [NO3-] assessed at 2 and 4 h after ingestion of beetroot juice. We show that although fingertip serum [NO3-] and [NO2-] overestimate those measured by venous plasma after dietary NO3- intake (125-141% and 156-183% of venous values), [NO3-] and [NO2-] in fingertip serum samples may be utilized for assessing blood [NO3-] and [NO2-] levels, although [NO3-] assessment may lack precision compared to [NO2-].

Effects of different particle size microplastics and di-n-butyl phthalate on photosynthesis and quality of spinach

As agricultural technology advances, microplastics (MP), which result from the degradation of widely used plastic products, have gradually accumulated in the soil, raising serious environmental concerns. This study explores the toxic effects of di-n-butyl phthalate (DnBP) on spinach, focusing on various particle sizes and MP concentrations through hydroponic experiments. Experimental results demonstrated that MP/DnBP combined pollution significantly reduced key photosynthetic parameters, including net photosynthetic rate, stomatal conductance, and transpiration rate, compared to treatments with DnBP or MP alone. Additionally, there was an increase in intercellular carbon dioxide concentration, suggesting that the inhibition of photosynthesis was due to non-stomatal factors. Moreover, spinach exposed to combined pollution conditions exhibited a notable decrease in maximum light energy conversion efficiency, electron transfer efficiency, and chlorophyll content. This disruption affected the synthesis of ribulose-1,5-bisphosphate carboxylase. On the other hand, the contents of ascorbic acid and glutathione in spinach roots and leaves increased, indicating the plant’s defense mechanisms were activated in response the toxic effects of MP and DnBP. Despite this, there was a significant reduction in soluble protein and soluble sugar content and a marked increase in nitrite content, reflecting a decline in spinach quality. This decline was attributed to the exacerbation of DnBP’s toxic effects by MP. Overall, MP/DnBP combined pollution reduced the quality of spinach by impairing photosynthesis and sugar metabolism, potentially amplifying ecological risks to crop plants. This study provides insight into the synergistic effects of MP and DnBP on plant health.

Fish production, water quality, and the role of nitrification as an ammonia removal process in intensively aerated hybrid catfish ponds

AbstractSix 0.1‐ha earthen ponds with 45 kW/ha of aeration capacity were stocked with hybrid catfish (Ictalurus punctatus x I. furcatus) ranging from 15,000 to 90,000 fish ha−1 in 15,000 fish ha−1 increments to analyze the effect of nitrogen loading on ammonia accumulation and fish production. Minimum dissolved oxygen (DO) concentration was maintained above 3.0 mg O2 L−1 to prevent hypoxia‐induced appetite reduction. Stocking density did not impact survival but decreased average fish harvest weight and increased food conversion ratio (FCR). Gross production increased with stocking density and ranged from 7249 to 35,674 kg ha−1. Average total (TAN) and un‐ionized ammonia (NH3) were not different among stocking densities despite greater nitrogen inputs in ponds with higher feeding rates. Nitrite () and nitrate () concentrations were significantly higher in ponds with higher stocking densities, suggesting that nitrification increased with nitrogen loading. Phytoplankton assimilation of ammonia is the primary ammonia removal process in traditional catfish ponds with modest fish densities and feeding rates. However, in intensively aerated ponds with high feeding rates, nitrification can become an important process for ammonia removal. These data indicate that small earthen hybrid catfish ponds with high aeration capacities can increase catfish production without ammonia accumulating.

Concentrated precipitation electrolyte for reviving ultrathin lithium metal anode

Realizing high-performance lithium metal batteries requires the presence of a robust solid-electrolyte interphase (SEI) on the Li metal surface that forms before or during operation. Herein, high concentrations of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrite (LiNO3) are employed to create a novel concentrated precipitation electrolyte (CPE) and form an inorganic-rich SEI. It is found that an ultrathin Li metal anode (thickness of 25 μ m) in the CPE remains highly reversible over 300 cycles with an average Coulombic efficiency (CE) of 97.21 % in an asymmetric Cu|Li cell. The CPE enables superior stability to the LiFePO4 (LFP) cathode at a high mass loading of ∼15 mg cm−2 and reaches a capacity retention of 82.8 % after 100 cycles with an average CE of 99.94 %. This study elucidates the mechanism of LiTFSI and LiNO3 in enhancing the physiochemical properties of the SEI surface layer. It is believed that this design concept and the findings can be broadened to optimize SEIs via electrolyte engineering for practical Li metal batteries.

Nitrate, Nitrite, and Iodine Concentrations in Commercial Edible Algae: An Observational Study.

Edible algae are a natural source of nutrients, including iodine, and can also contain nitrogen in the form of nitrate (NO3-) and nitrite (NO2-) as they can fix nitrogen from seawater. This study aimed to analyse the NO3-, NO2-, and iodine concentrations in eighteen macroalgae and five microalgae species commercially available in the United Kingdom. NO3- and NO2- concentrations were measured using high-performance liquid chromatography (HPLC), and iodine was determined using inductively coupled plasma mass spectrometry (ICP-MS). NO3- and iodine concentrations in macroalgae (NO3-: 4050.13 ± 1925.01 mg/kg; iodine: 1925.01 ± 1455.80 mg/kg) were significantly higher than in microalgae species (NO3-: 55.73 ± 93.69 mg/kg; iodine: 17.61 ± 34.87 mg/kg; p < 0.001 for both). In the macroalgae group, nori had the highest NO3- (17,191.33 ± 980.89 mg/kg) and NO2- (3.64 ± 2.38 mg/kg) content, as well as the highest iodine content. Among microalgae, Dunaliella salina had the highest concentration of NO3- (223.00 ± 21.93 mg/kg) and iodine (79.97 ± 0.76 mg/kg), while Spirulina had the highest concentration of NO2- (7.02 ± 0.13 mg/kg). These results indicate that commercially available edible algae, particularly macroalgae species, could be a relevant dietary source of NO3- and iodine.

Roxarsone reduces earthworm-mediated nutrient cycling by suppressing aggregate formation and enzymic activity in soil with manure application

The application of manure and earthworms are frequently used in fertilization practices to improve C, N, and P cycling in soil, which may be adversely affected by roxarsone (ROX), as an organoarsenical pollutant. To effectively address this issue, in this work, the interactive impacts of ROX and earthworm Eisenia foetida on the aggregate formation, input of organic carbon (OC), and changes in the available N and P following 56-day cultivation were systematically investigated. Compared to the control, earthworms increased the mean weight diameter (MWD) of the soil aggregates from 0.6 to 1.1 mm. Thereby, they activated soil enzymes including catalase (CAT), sucrase (SC), urease (UE), and neutral phosphatase (NP), with the soil's pH decreased to 7.1. Consequently, the values of OC, soluble nitrite (NO3-N), and Olsen-P content were respectively increased by 0.78-, 1.69-, and 0.87- folds in the E treatment (14.3 vs. 25.5 g/kg, 12.8 vs. 33.3 mg/kg, and 7.8 vs. 14.6 mg/kg). Although the changes in the R treatment were slight, ROX reduced the earthworm-mediated improvements of soil fertility during the application of the RE treatment compared to the E treatment, i.e., the values of MWD, OC, NO3-N, and Olsen-P were reduced to 0.9 mm, 20.4 g/kg, 25.4 mg/kg, and 11.6 mg/kg, respectively. From the well-fitted structural equation models, it was demonstrated that earthworms enhanced the aggregate formation and nutrient cycling of OC, NO3-N, and Olsen-P, which were inhibited by ROX. Overall, these adverse effects can be offset by earthworm addition, which can play the dual role of monitor and driver for the soil properties. Our work provides insightful strategies for ROX-bearing manure management.

Substitution of Animal Fat and Sodium Nitrite with Hemp Seed Oil: Effect on the Nutritional Value, Sensory Characteristics, and Shelf Life of Fermented Salami.

Recently, products of plant origin have been utilized to extend the shelf life of meat products. This study examined the impact of hemp seed oil as a replacement for animal fat and sodium nitrite on the nutritional, physicochemical, technological, and sensory traits of fermented salamis. Five treatments were prepared: S0 (100 mg/kg NaNO2), S1 (2% hemp oil and 50 mg/kg NaNO2), S2 (4% hemp oil and 50 mg/kg NaNO2), S3 (2% hemp oil), and S4 (4% hemp oil). The addition of hemp seed oil did not affect proximate composition but improved fatty acid composition and lipid quality nutritional indices. Microbial growth was consistent across all treatments. Active acidity (pH) and water activity (aw) were influenced by hemp seed oil and/or sodium nitrite. Salamis containing only hemp seed oil exhibited lower redness and chroma values during storage. Hemp seed oil led to higher lipid peroxidation, mitigated by sodium nitrite. The addition of hemp seed oil and varying levels of sodium nitrite significantly impacted salami texture. Sensory evaluation showed consumer acceptance of hemp seed oil-enhanced salamis. In conclusion, hemp seed oil can be used as a functional ingredient to improve the nutritional value and healthiness of fermented meat products when combined with reduced sodium nitrite content.

A Cross-Sectional Study Comparing Oxidative Stress in Patients with Epilepsy Treated with Old and New Generation Antiseizure Medications.

Background and Objectives: Oxidative stress resulting from a disturbance of the endogenous redox system is suspected in numerous diseases of the central nervous system, including epilepsy. In addition, antiseizure medications (ASMs), especially those of the old generation, may further increase oxidative stress. To evaluate the effects of ASM generation on oxidative stress, we conducted a cross-sectional study in patients with epilepsy treated with old, new, and polytherapy. Materials and Methods: The antioxidant activity of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, as well as the concentrations of malondialdehyde, protein carbonyl, nitrate, nitrite, and glutathione in reduced and oxidized forms, were measured in 49 patients with epilepsy and 14 healthy controls. In addition, the plasma concentrations of ASMs and metabolites of carbamazepine and valproic acid were measured in the patients. Results: Patients with epilepsy showed increased activities of superoxide dismutase and catalase (p < 0.001), concentrations of glutathione disulfide and markers of nitric oxide metabolism (p < 0.001), and decreased activities of glutathione peroxidase, glutathione reductase, glutathione, and nitrite concentrations (p ≤ 0.005) compared to healthy controls. A comparison of ASM generations revealed increased levels of superoxide dismutase and catalase (p ≤ 0.007) and decreased levels of glutathione peroxidase and glutathione reductase (p ≤ 0.01) in patients treated with old ASMs compared to those treated with new generation ASMs. In addition, an increase in protein carbonyl and nitric oxide metabolites (p ≤ 0.002) was observed in patients treated with old generation ASMs compared to those treated with new generation ASMs. Most oxidative stress parameters in patients receiving polytherapy with ASMs were intermediate between the results of patients treated with the old and new generations of ASMs. Conclusions: An increase in oxidative stress markers and modulation of antioxidant enzyme activities was observed in patients with epilepsy compared to controls. The results of our study showed significantly higher oxidative stress in patients treated with old ASMs compared to those treated with new generation ASMs.

The Effects of Acute Beetroot Juice Intake on Glycemic and Blood Pressure Responses When Controlling for Medication in Individuals with Type 2 Diabetes: A Pilot Study.

Physical inactivity and poor dietary choices contribute to the rise in cardiometabolic diseases in the United States. It remains critical to identify strategies that may mitigate the negative impact of these behaviors. Several studies have shown that the consumption of dietary inorganic nitrate may improve vascular health and glucose regulation in animal models and some human studies. However, the improvements in glucose regulation have yet to be corroborated in humans with type 2 diabetes (T2D). Therefore, the purpose of this study was to assess the acute effects of beetroot juice (BRJ) on glycemic and hemodynamic responses in individuals with T2D while controlling for medication. Seven participants with a clinical diagnosis of T2D were recruited into this study and were temporarily removed from blood pressure- and glucose-lowering medications. Hemodynamic measurements (pulsewave velocity) and an oral glucose tolerance test (glycemic response) were measured following consumption of either BRJ or a denitrolized placebo. Saliva and blood samples were collected at baseline and two and four hours post supplementation to measure changes in nitrate and nitrite concentrations. We detected significant improvements in total plasma glucose exposure (p = 0.022) and the SVR change score (p = 0.009) in the BRJ condition. This study demonstrated that BRJ consumption can improve oral glucose tolerance in individuals with T2D while controlling for medication; however, future larger-cohort randomized controlled trials are needed to confirm if BRJ is a viable treatment for glucose control in individuals with T2D.

Reduction with zinc — Impact on the determination of nitrite and nitrate ions using microfluidic paper-based analytical devices

We used a microfluidic paper-based analytical device (μPAD) to investigate the influence that zinc reduction exerts on the determination of nitrite and nitrate ions in natural water samples. The μPAD consists of layered channels for the reduction of nitrate to nitrite with zinc powder and the subsequent detection of nitrite with Griess reagent. The amount of zinc, number of layers, and reaction time for the reduction were optimized to obtain an intense signal for nitrate. Initially, the sensitivity to nitrate corresponded to 55% that of nitrite, which implied an incomplete reduction. We found, however, that zinc decreased the sensitivity to nitrite in both the μPAD and spectrophotometry. The sensitivity to nitrite was decreased by 48% in spectrophotometry and 68% in the μPAD following the reaction with zinc. One of the reasons for the decreased sensitivity is attributed to the production of ammonia, as we elucidated that both nitrite and nitrate produced ammonia via the reaction with zinc. The results suggest that the total concentration of nitrite and nitrate must be corrected by constructing a calibration curve for nitrite with zinc, in addition to developing curves for nitrate with zinc and for nitrite without zinc. Using these calibration curves, the absorbance at different concentration ratios of nitrite and nitrate ions could be reproduced via calculation using the calibration curves with zinc for nitrite and nitrate. Eventually, the developed μPAD was applied to the determination of nitrite and nitrate ions in natural water samples, and the results were compared with those using a conventional spectrophotometric method. The results of the μPAD are in good agreement with those of conventional spectrophotometry, which suggests that the μPAD is reliable for the measurement of nitrite and nitrate ions in natural water samples.

Advanced fiber optic sensors for quantitative nitrite detection: Comparative analysis of plasmonic tilted fiber Bragg gratings and fiber optic tips with ion-imprinted polymers

The presence of nitrite, a prevalent contaminant in natural environments, presents a significant environmental and human health concern. Hence, it is imperative to develop a sensor with the ability to quantitatively detect nitrite. This study focuses on the design and development of i) probe 1: tilted fiber Bragg gratings (TFBGs) and ii) probe 2: fiber optic tip-based plasmonic sensors utilizing ion-imprinted polymers. The concentration of nitrite was assessed at various levels using both sensing configurations. The outcomes indicated that the TFBGs-based sensor exhibited a sensitivity and limit of detection (LOD) of 0.469 nm/ln(μg/mL) and 0.142 μg/mL in the linear detection range of 0.5–50 μg/mL. The fiber optic tip-based sensor exhibited a sensitivity and LOD of 1.16 nm/ln(μg/mL) and 0.176 μg/mL within the 1–50 μg/mL linear detection range. The obtained sensing results reveal that the sensors presented in this study are able to accurately detect nitrite at various concentrations in a quantitative manner. Moreover, an assessment was conducted to examine the selectivity and reusability of the sensor individually, yielding satisfactory results.

Corrosion behavior of steel bar in magnesium oxysulfide cement-based materials: The role of chloride and nitrite

Magnesium oxysulfide (MOS) cement has emerged as a promising cementitious material due to the high strength and excellent durability, but research on its rust inhibition remains limited. In this study, the chloride and nitrite were introduced in the MOS cement composites, aiming to investigate the corrosion properties and reveal the rust inhibition mechanism of steel bar under different W/C ratio. Experimental results show that the corrosion area ratios reach the largest value of approximately 98% and the lowest value of approximately 3%, respectively, as the chloride and nitrite contents increase to 2%. Compared with chloride, the effect of W/C ratio on the mass loss of steel bar is gradually weakened when the nitrite content is larger than 0.5%. Based on the natural potential, the change of corrosion degree mainly occurs after 28d. In addition, the corrosion potential of steel bar decreases and corrosion rate increases with the increase of chloride content in MOS cement composites. Conversely, the presence of Mg(NO2)2 from nitrite engenders an opposite effect. Besides, the increase of W/C ratio results in higher electrochemical parameters. At this time, the rust inhibition mechanism is revealed based on the micro-structure analysis.

Assessment of water quality in wells and springs across various districts of Taza City, Morocco.

The aim of this study is to assess groundwater pollution in the city of Taza, Morocco. This was accomplished through hydrochemical and biological investigations, focusing on analyzing the physicochemical and bacteriological parameters of groundwater. Water samples were collected from wells and sources within Taza City on a monthly basis during the spring and summer of 2023. These samples were subjected to analysis to identify physicochemical and bacteriological characteristics. The findings revealed multiple contaminations, primarily stemming from two sources: significant microbial pollution observed in 100% of samples due to runoff percolation and discharge of domestic and industrial wastewater, and varying degrees of chemical pollution observed across all samples. The results underscored deviations from national standards, notably in parameters such as dissolved oxygen, nitrate, and nitrite concentrations. These parameters exhibited values either lower or higher than the established norm.

Groundwater quality analysis in Hail region of northwest Saudi Arabia based on physicochemical investigation

The acquired groundwater data from seventeen wells were hydrochemically analyzed for Sulfate, Chloride, Ammonia, Nitrate, Nitrite, pH, EC (Electrical Conductivity), TDS (Total Dissolved Solids), total hardness, and total alkalinity concentrations and then compared to the national and international standards. The results range as follows: pH (6.65–8.26), EC (382–1214 μS·cm−1), Total hardness (72–310 ppm), TDS (258–775 ppm), Total alkalinity (54–138 ppm), Cl- (19–202 ppm), Ammonia (NH3) (0.0 to 1.5 mg/liter), Nitrate (NO3) (4.7 to 65.6 ppm), Nitrite (NO2) (0.007 to 0.05 ppm), and sulfate (SO4) (29–278 ppm). About 70.58 % of the study area’s groundwater samples have TDS levels below 500 mg/l, which are considered safe for drinking. The EC of the groundwater found that 100 % of the samples fall within the allowed level. Based on these results, the groundwater quality is suitable for drinking and irrigation purposes in Hail region. Hence, this research shows that using GIS and chemical analysis of groundwater could be useful tools for the decision-making process of local and international authorities and water resources management.

The use of automatic belt feeders in a Penaeus vannamei pilot scale super-intensive nursery and grow-out with biofloc system

This study aimed to evaluate the effect of using automatic belt feeders (BF) on water quality, growth of Penaeus vannamei, and partial budget in super-intensive pilot scale systems with biofloc technology. A nursery phase (2300 shrimp m−2) and a grow-out phase (400 shrimp m−2) were carried out with the following feeding management strategies, all with three repetitions: T1: by hand, T2: by hand + BF12h; T3: BF24h. In the nursery, a spike in total ammonia concentration was observed in the first weeks of the trial in treatment T1, possibly due to nutrients from uneaten feed. Nitrite was higher in T1 treatment than in T2 and T3. Nitrate was lower in the treatment T1 than in T2 and T3. At the grow-out trial, nitrite was higher in treatment T1 than in T2 and T3. These results indicated a slower nitrification process in T1 and more efficient in treatments where automatic feeders were used since an accumulation of nitrate was observed throughout the trials and low concentrations of nitrite were observed both in the nursery and the grow-out. In the nursery and the grow-out, the T3 treatment had a higher final weight and a lower feed conversion ratio. Furthermore, the T3 treatment had a higher yield than the T1 treatment. Treatment T3 had the highest net benefit/cost, considering the entire production cycle (nursery and grow-out). Our results strongly indicate that using automatic belt feeders allows an improvement in water quality, promotes shrimp growth, improves yield, reduces feed use, and improves the net benefits in P. vannamei super-intensive nursery and grow-out with biofloc systems.

Repercussions of Lactiplantibacillus plantarum HYY‐DB9 and Levilactobacillus brevis GIM 1.773 on the degradation of nitrite, volatile compounds, and sensory assessment of traditional Chinese paocai

SummaryPaocai, as one of the most widely consumed traditional fermented foods in China, is dominated by lactic acid bacteria (LAB), which exert a significant influence on the dynamics of metabolites, microecological changes, and sensory quality. In this study, five different paocai groups were designed for fermentation using Lactiplantibacillus plantarum HYY‐DB9 (LP), Levilactobacillus brevis GIM 1.773 (LB), a mixture of two LABs (LP + LB), pasteurisation (PST), and natural fermentation (NF). Nitrite content, pH, titratable acidity, viable cell counts (LAB and yeasts), metabolites (organic acids and volatile substances), and sensory evaluation were determined for each group. The results demonstrated that the mixed fermentation with two LABs (LP + LB) significantly reduced nitrite content. Organic acids produced by LAB played a crucial role in the degradation process, particularly lactic acid which exhibited the most pronounced effect on nitrite degradation. Furthermore, artificial inoculation of LAB fermentation resulted in improved taste and flavour of paocai along with increased production of alcohols, esters, and acids compared to traditional natural fermentation. These findings have important implications for enhancing paocai quality control and managing nitrite content while also providing an excellent fermentation agent for fermented paocai.

Intrinsic oxidase-mimicking activity of nitrite upon visible light illumination and its colorimetric detection in saliva

Small molecules with enzyme-like properties have recently attracted considerable attention. Herein, we discovered that nitrite possesses intrinsic oxidase-mimicking activity upon visible light, catalyzing the oxidation of the typical chromogenic substrate in the absence of H2O2. Notably, nitrite exhibited a markedly high value of Kcat, approximately 4, 7, and 4000-fold greater than that of Acr+-Mes, Eosin Y, and Diacetyl, respectively. Comprehensive investigation elucidated that O2•⁻ and •OH are the primary reactive oxygen species (ROS) responsible for the oxidation of 3,3′,5,5′-tetramethylbenzidine dihydrochloride hydrate (TMB). Leveraging the linear correlation between the absorbance of oxidized TMB (oxTMB) at 652 nm and nitrite concentration, a simple colorimetric approach for nitrite detection was successfully established in the range of 1–75 μM with a detection limit of 0.14 μM. Moreover, the proposed strategy could be applied to determine the nitrite concentration in saliva, exhibiting a great prospect for clinical diagnosis. This work contributes novel insights into the exploration of small-molecule enzyme mimics.

Effect of inoculating Lactiplantibacillus plantarum Y279 on bacterial community structure and quality of fermented Yujiaosuan

The unique flavor and extended shelf life were identified as essential characteristics of Yu jiaosuan (YJS), while challenges of fermentation control and poor stability were noted to have hindered its industrialization. The effects of Y279 inoculation on the bacterial community structure and quality improvement of YJS were investigated in this study. The results showed that after fermentation with Y279, the total acidity and amino nitrogen concentration of YJS were increased by 0.40 g/kg and 18.45 mg/100 g, respectively, while the pH, TBARS value, and nitrite content were significantly decreased by 0.28, 0.2, and 0.0048 mg/kg, respectively. High-throughput sequencing confirmed that Lactobacillus and Weissella were the dominant genera in the inoculated fermentation group. Forty-five differential metabolites were identified, involving three tastant-related pathways: arginine and proline metabolism, arginine biosynthesis, and purine metabolism. Additionally, molecular docking revealed substances in these differential metabolites that were bound to taste receptors via traditional hydrogen and carbon-hydrogen bonds. The results of sensory evaluation showed that the umami and sourness taste and color of the inoculated fermentation group were enhanced.This study offers theoretical guidance for the use of fermentation agents to improve YJS quality.

Suitability of coconut bran and biochar as a composite substrate for lettuce cultivation in aquaponic systems

Growth substrates are essential for aquaponic systems and play an important role in vegetable growth and water quality. In this study, we explored an innovative combination of coconut bran and coconut shell biochar (CSB) as a composite growth substrate for lettuce cultivation in aquaponic systems. The study included the control (100 % coconut bran as the growth substrate) and treatment groups (T1–T5; containing 10 %, 20 %, 30 %, 40 %, and 50 % CSB as the growth substrate, respectively). The substrate properties; lettuce growth performance; and soil enzyme activity, nitrogen content, and abundance of microbial communities in the substrate were analyzed to determine the optimal substrate. Our findings indicated that CSB incorporation significantly altered the properties of the substrate, resulting in increased dry and bulk densities, pH, and water-holding capacity, and decreased electrical conductivity, water-absorption capacity, and porosity. Furthermore, the fresh weight of lettuce was notably increased in the treatment groups. The activities of fluorescein diacetate hydrolase, urease, nitrate reductase, and hydroxylamine reductase initially increased and further decreased, reaching the maximum in the T3 group. Conversely, the activity of nitrite reductase and contents of available nitrogen, nitrate-nitrogen, and ammonium-nitrogen in the substrates initially decreased and further increased, with the minimum values observed in the T3 group. The microbial sequencing results indicated that CSB incorporation significantly increased the microbial diversity and relative abundance of microorganisms associated with nitrogen transformation. Moreover, 30 % CSB incorporation exhibited the greatest effect on lettuce growth, with a 34.5 % and 31.6 % increase in fresh weight compared to the control during the growth and harvest periods, respectively. This study indicated the enormous potential of biochar in the research and development of green technologies for substrate amendment in aquaponic systems.