Physicochemical Variations Research Articles

A deconvolution analysis strategy on the thermoreconstitution process of Co/Fe layered double hydroxides: Complementary correlations between physicochemical variations and thermokinetic analyses

A variety of physicochemical analyses were systematically conducted on the complex thermoreconstitution process of Co/Fe layered double hydroxides, and deconvolution analysis strategy was utilized in elucidating the reconstitution process. The thermal analysis of Co/Fe layered double hydroxides indicated that approximately 27.8 % weight loss, three weight loss peaks and two pronounced endothermic phenomena were detected via thermogravimetry, differential thermogravimetry, and differential scanning calorimetry, respectively. In the thermoreconstitution process of Co/Fe layered double hydroxides, scanning electron microscopy images indicated that the layered structure gradually collapsed, fractured into pieces, and partially melted. Meanwhile, significant X-ray diffraction peak broadening phenomena were detected and further confirmed by the d-spacing values in high-resolution transmission electron microscope images, which were mainly caused by the lattice expansion effect and the heterogeneous microstrain effect. Three reactions were deconvolved from the differential thermogravimetry curves, and the thermokinetic models of Reaction 2 indicated that volatile components in the form of H2O and CO2 escaped from the solid-state residuals via a one-dimensional diffusion reaction model. The major products in solid-state residuals were cubic Cobalt(III) oxide and Iron(II, III) oxide. The thermokinetic models played a complementary role in elucidating the physicochemical variations that occurred throughout the thermoreconstitution process of Co/Fe layered double hydroxides.

A Comparative Analysis of Innate Immune Responses and the Structural Characterization of Spike from SARS-CoV-2 Gamma Variants and Subvariants.

The SARS-CoV-2 P.1 variant, responsible for an outbreak in Manaus, Brazil, is distinguished by 12 amino acid differences in the S protein, potentially increasing its ACE-2 affinity and immune evasion capability. We investigated the innate immune response of this variant compared to the original B.1 strain, particularly concerning cytokine production. Blood samples from three severe COVID-19 patients were analyzed post-infection with both strains. Results showed no significant difference in cytokine production of mononuclear cells and neutrophils for either variant. While B.1 had higher cytopathogenicity, neither showed viral replication in mononuclear cells. Structural analyses of the S protein highlighted physicochemical variations, which might be linked to the differences in infectivity between the strains. Our studies point to the increased infectivity of P.1 could stem from altered immunogenicity and receptor-binding affinity.

A pocket companion to cell-free DNA (cfDNA) preanalytics.

The cumulative pool of cell-free DNA (cfDNA) molecules within bodily fluids represents a highly dense and multidimensional information repository. This "biological mirror" provides real-time insights into the composition, function, and dynamics of the diverse genomes within the body, enabling significant advancements in personalized molecular medicine. However, effective use of this information necessitates meticulous classification of distinct cfDNA subtypes with exceptional precision. While cfDNA molecules originating from different sources exhibit numerous genetic, epigenetic, and physico-chemical variations, they also share common features that complicate analyses. Considerable progress has been achieved in mapping the landscape of cfDNA features, their clinical correlations, and optimizing extraction procedures, analytical approaches, bioinformatics pipelines, and machine learning algorithms. Nevertheless, preanalytical workflows, despite their profound impact on cfDNA measurements, have not progressed at a corresponding pace. In this perspective article, we emphasize the pivotal role of robust preanalytical procedures in the development and clinical integration of cfDNA assays, highlighting persistent obstacles and emerging challenges.

Monolignol Potential and Insights into Direct Depolymerization of Fruit and Nutshell Remains for High Value Sustainable Aromatics.

The inedible parts of nuts and stone fruits are low-cost and lignin-rich feedstock for more sustainable production of aromatic chemicals in comparison with the agricultural and forestry residues. However, the depolymerization performances on food-related biomass remains unclear, owing to the broad physicochemical variations from the edible parts of the fruits and plant species. In this study, the monomer production potentials of ten major fruit and nutshell biomass were investigated with comprehensive numerical information derived from instrumental analysis, such as plant cell wall chemical compositions, syringyl/guaiacyl (S/G ratios, and contents of lignin substructure linkages (β-O-4, β-β, β-5). A standardized one-pot reductive catalytic fractionation (RCF) process was applied to benchmark the monomer yields, and the results were statistically analyzed. Among all the tested biomass, mango endocarp provided the highest monolignol yields of 37.1 % per dry substrates. Positive S-lignin (70-84 %) resulted in higher monomer yield mainly due to more cleavable β-O-4 linkages and less condensed C-C linkages. Strong positive relationships were identified between β-O-4 and S-lignin and between β-5 and G-lignin. The analytical, numerical, and experimental results of this study shed lights to process design of lignin-first biorefinery in food-processing industries and waste management works.

Characterization and evaluation of flour's physico-chemical, functional, and nutritional quality attributes from edible and non-edible parts of papaya

Papaya fruits different edible and non-edible portions are valued for the abundance of numerous nutrients and therapeutic benefits. The study was aimed to examine the physico-chemical properties, bioactive compounds (total phenolics and total flavonoids), antioxidant activity and microstructure analysis of the peel, pulp and seed flour of both ripe and unripe papaya. The results demonstrated the different portions of both ripe and unripe papaya fruit flour differed significantly with respect to almost all quality attributes within them. The physico-chemical variations have been evaluated through evaluation of the pH, moisture content, TSS, and ascorbic acid content of the papaya fruits during both ripening stages. Statistically significant variations (p < 0.05) were observed between two distinct stages of ripening. The concentration of ascorbic acid in the fruit revealed a notable increase as it matured, while the pH, moisture, and TSS all exhibited a substantial decrease (p < 0.05) during the immature stage. The unripe peel showed the most significant level of bulk density, tapped density, swelling capacity, crude fiber, and TFC whereas the unripe seed showed the highest value of ash, crude fat, and TPC. For the rest of the value, ripe pulp and seed flour showed a significantly higher value than others. The total phenolic content in seed flour and the total flavonoid content of peel flour were 196.9 ± 0.03 and 164.9 ± 0.08 mgQE/100 g, respectively, at unripe conditions. An immense amount of antioxidant activity was found in ripe (20.48 ± 0.54%) and unripe (16.05 ± 0.32%) peels flour. The flour granules' diverse morphological forms and particle sizes were identified by SEM analysis. The versatility of papaya and its various components provides opportunities for applications in the food, pharmaceutical, cosmetic, and agricultural industries. The papaya fruit flour of different portions have unique functional, nutritional, and morphological characteristics that may contribute to the development of gluten free flour based value added baked products.

Chemical composition, structural features, and physicochemical properties of starches from Thai indigenous rice varieties

ABSTRACT Thai indigenous rice varieties provide valuable genetic resources due to their environmental resilience, but it is yet to be elucidated whether their endosperm starches are suitable for whole grain consumption or industrial applications. Here, 19 Thai indigenous rice starches were explored for compositional, structural, and physicochemical characteristics. Grain reducing sugar, protein, and amylose contents significantly differed among genotypes. Their starches were categorized as waxy, very low-, and low-amylose starches. The varieties with low-amylose starches displayed higher amylose content but lower crystallinity than the varieties with waxy and very low-amylose starches. The largest median starch granule size (d(0.5)) was also observed in most varieties with low-amylose starches. The starch compositional and structural variations contributed to substantial differences in starch physicochemical properties among these genotypes. The partial least squares discriminant analysis revealed that amylose content, setback, swelling power, reducing sugar, C- and A-type granules, d(0.5), and final viscosity could discriminate the low-amylose starches from the waxy and very low-amylose starches. Notably, correlation analyses revealed that amylose content was the most crucial factor determining starch physicochemical properties of these varieties. Starch compositional, structural, and physicochemical variations among the indigenous rice varieties can be adopted as alternative industrial raw materials and as genetic resources for future breeding programs.

Inferring the health of coral reefs on the Egyptian coast of the Gulf of Aqaba for three branching-coral species

ABSTRACTThis investigation examined the vulnerability of three branching coral species (Acropora humilis, Pocillopora damicornis, and Stylophora pistillata) to environmental changes within the marine reserves of Taba, Nuweiba, and Dahab in the Gulf of Aqaba. Coral growth rates were assessed as a key indicator of coral reef vitality, reacting to shifting physicochemical parameters. A. humilis manifested the highest growth rate, followed by S. pistillata and P. damicornis. Site-specific data analysis found Dahab displayed the greatest coral proliferation, with Taba exhibiting the least. Accounting for seasonal changes, spring showed maximal coral growth. Statistical analysis revealed a positive correlation between salinity and coral growth rate, contrasted by a negative correlation with variables such as pH, PO4-P, and silicate (SiO4-Si). This work underscores the significant influence of environmental factors on coral growth rates, and by extension, the health of coral reef ecosystems. These findings are integral to coral reef management, suggesting mitigation of adverse environmental factors could enhance these ecosystems’ resilience against climatic shifts and human-induced stressors. By combining species, site, seasonal, and physicochemical variations, this research underlines the importance of localized conservation strategies.

A Study on Syrup of Juniperus excelsa Cones Grown in Türkiye

For beverage products, some analytical tests are conducted prior to packaging and distribution. However, physicochemical properties may affect product quality adversely in a number of ways. Liquids with high dissolved solids may impact inferior palatability and may induce an unfavorable physiological reaction in the transient consumer. In this study, it was to evaluate some certain physicochemical properties of syrup which was made from Juniperus excelsa’s berries collected from four different geographical locations managed by the Regional Directorate of Forestry authorities in Turkiye. Considerable physicochemical variations were found among Juniperus excelsa’s berry-based syrup products. The lowest value of pH: 5.46 was found with syrup prepared from Yalvaç-Isparta, (sample C), followed by pH: 5.75 from Hisarcık-Kütahya, (sample D), pH: 5.80 Ağlasun-Burdur (sample B), and pH: 6.32 Gazipaşa-Antalya (sample A), respectively. However, syrup prepared from sample C showed the highest values of electrical conductivity (EC), total dissolved solids (TDS), sugar content (Brix), and also distinguished from the others by highest oxidation-reduction potential (ORP). It was found to be 3136.1 uS/cm for EC, 1568 ppm for TDS, 1.90 °Bx for Brix and 188.6 mV for ORP. However, the highest turbidity value of 67.6 NTU was found with sample D while the lowest with sample A (39 NTU). These values may be good criteria for the botanical origin of syrup and therefore, it may be used in syrups prepared from Juniperus excelsa’s berries.

Formulation and Development of Polyherbal Ointment containing Clerodendrum serratum, Solanum xanthocarpum, and Nyctanthes arbortristis Extracts and Assessment of Anti-inflammatory Activity in Carrageenan-Induced Paw Edema Model

In this study, our objective was to explore the phytochemical constituents of Clerodendrum serratum (CS), Solanum xanthocarpum (SX), and Nyctanthes arbortristis (NA) and evaluate their anti-inflammatory activity. Subsequently, we aimed to develop a polyherbal ointment formulation incorporating these extracts. The phytochemical screening of the CS extract showed carbohydrates, steroids, terpenoids, flavonoids, saponins, and tannins. Similarly, the SX extract exhibited the presence of all these constituents, along with the additional presence of alkaloids. The NA extract demonstrated the presence of alkaloids, tannins, glycosides, and flavonoids. CS roots exhibited notable inhibition of inflammation at the given doses and periods of 1 to 5 hours, surpassing the effectiveness of the standard anti-inflammatory drug, indomethacin. The polyherbal ointments were found to be greenish, non-transparent, and with acceptable pH. F3 formulation demonstrated excellent viscosity of 1200 cp, making it easy to apply on the skin. Furthermore, formulation F3 demonstrated exceptional spreadability, covering a diameter of 1.8 cm, surpassing the other formulations. Importantly, all polyherbal formulations were non-irritant when applied to the skin, as evidenced by the absence of edema or erythema upon application to rat skin. F3 formulation indicated no physicochemical variations in comparison to initial results in stability studies. Even after the 6-month stability study, the ointment formulation maintained a smooth and greenish consistency, signifying its durability and stability. These findings suggest that the developed polyherbal ointment formulation can be stored at room temperature without any additional requirements. Overall, this polyherbal ointment formulation represents a promising alternative approach to existing topical formulations for the effective treatment of inflammatory conditions.

Microbiological and Physicochemical Variations during Spontaneous Fermentation of Plantain Must.

Major losses are recorded every year in the plantain production sector in Côte d'Ivoire. These losses are mainly due to poor harvesting, transport, and storage conditions. Local processing of this food crop into other products could help limit postharvest losses. The aim of this study was to evaluate some microbiological and physicochemical parameters during the fermentation of plantain must for the production of an alcoholic beverage. Physicochemical parameters such as pH, titratable acidity, and reducing sugars were measured using a pH meter by titration and the Bernfeld method, respectively. Refractometric dry extract and alcohol content were measured using a refractometer. Loads of mesophilic aerobic germs, total coliforms, streptococci, and yeasts were determined by standard microbiological methods. Values for refractometric dry extract (10°B-4.5°B), reducing sugars (8.25-0 mg/mL), and pH (4.37-3.36) decrease during fermentation. The highest alcohol content (11%) is obtained after four days of fermentation of plantain must. In contrast to total coliforms (5.27-3.61 log10 cfu/mL), loads of mesophilic aerobic germs (4.84-9.8 log10 cfu/mL) increase during fermentation. Yeast and streptococci loads reach their peaks at 7.81 log10 cfu/mL and 8.15 log10 cfu/mL, respectively, after six (6) days of fermentation before dropping off. Plantain must could be used to produce distilled alcoholic beverages.

An Intensive Study on Algal Diversity in the Ancient Man-Made Aquatic Ecosystem of Tiruvallur, South India: Exploration for Sustainable Development.

Eco-friendly and beneficial nature algae make it prominent in our earth as well as for human life. In recent decades, microalgal applications is sought in varied fields from the remediation of wastes to the production of pharmaceutical products. Still, more extensive research on bioprospecting should to conducted to get the genus-specific or species-specific applications of microalgae with high efficiency. This inquiry was carried out (October 2021 to September 2022) for the effectual understanding of microalgal composition structure along with seasonal physicochemical variations in the age-old holy tank at Tiruvallur, southeast India. This inquiry also acts as the source data and makes the bioprospecting process easier. It also ignites the researchers to address the microalgae seasonal composition structure of peculiar wet environments. A total of 41 microalgae species were recorded, in which six major algal groups were in order of, Chlorophyceae > Bacillariophyceae > Cyanophyceae > Euglenophyceae > Zygnematophyceae > Trebouxiophyceae. Mean seasonal abundance was highest in the summer season (351 cells/L) and lowest in the monsoon (113 cells/L). One-way ANOVA showed seasonal variations of physicochemical parameters, in which the majority of them attained their peak during summer. Mean values of water temperature, pH, salinity, total dissolved solids, total solids, electrical conductivity, chemical oxygen demand, total hardness, total alkalinity, ammonia, nitrite-nitrogen, and nitrate-nitrogen for the summer were 31.43°C, 8.53, 0.56 ppt, 383mg/L, 525mg/L, 0.85 mS/cm, 46.27mg/L, 300ppm, 251.67ppm, 1.51mg/L, 0.62mg/L, and 0.70mg/L, respectively. Karl Pearson's correlation revealed a most significant relationship between water quality factors and algal density. The Shannon's diversity index (2.78-3.39) indicated moderately rich microalgal diversity in the study area. Palmer's pollution index stated that the temple tank was organically polluted all over the study period except November.

Sensor-based field methods for pedology and soil surveys: Protocol suggestions for Brazilian tropical soils

Although limited alternatives have been proposed to describe soils by using proximal sensors under natural conditions, efforts must be made to apply the newest technologies to assist in soil characterization and mapping. Our main objective was: to create a protocol incorporating technology that assists pedologists: (i) to compare soil horizonation by using visible, near, and shortwave infrared (Vis-NIR-SWIR) spectroscopy, mid-infrared spectroscopy (MIR), portable X-ray fluorescence (pXRF) indices, and conventional field observations; (ii) to identify mineralogical and physico-chemical variations between soil horizons by using proximal sensors, with inferences about pedogenic processes; and (iii) to expand punctual information to spatial dimensions with RGB images and terrain attributes. Seven soil profiles located through a toposequence evaluation were analyzed on a farm in the São Paulo State, Brazil. First, when the area consisted of exposed soils, images were obtained by Landsat and an unmanned aerial vehicle (UAV), and a digital surface model (DSM) was then built by stereoscopy, which was subsequently used to calculate thirteen terrain attributes. Each soil profile was evaluated with devices directly in the field (except for the MIR analyses, for which soil samples were brought to the laboratory and dried). Several indices were calculated from the pXRF data during the profile analysis, while principal component analyses (PCA) were performed to reduce the dimensions of the spectral data. Four datasets for each soil profile (VIS-NIR-SWIR, pXRF, MIR, and a combination of all the data) were submitted for k-means clustering analysis and the similarities among the layers were evaluated. Following the profile evaluation, spatialization was performed based on single bands from the RGB image and PCA using terrain attributes. The data were sampled to a punctual view of 370 points, classified, and then interpolated with the spline method. The Vis-NIR-SWIR spectral range, together with soil color, provided better correspondence with conventional field observations. We observed that the combined use of Vis-NIR-SWIR, MIR, and pXRF helped to identify and describe the soil profiles appropriately. Proximal sensors also allowed us to make more robust inferences regarding pedogenesis. We delineated soil information profiles in soil units by using the spatial dimension's terrain attributes and, RGB images from a UAV.

Synergism lubrication of graphene and carbon nanotube in polymeric composites under drying sliding condition

The internal lubrication of polyimide (PI) with added graphene oxides (GOs) and carbon nanotubes (MWCNTs), as well as their binary hybrid nano-additives (GCNTs), were contrastively investigated under dry sliding conditions. The friction coefficient of neat PI or its nanocomposites decreases as a stepwise increase of the load fitting a negative exponential equation while growing linearly as a stepwise increase of the velocity. Micromorphological and physicochemical variations occurring at friction interfaces have been analyzed using X-ray photoelectron spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy results. Given the structural discrepancy between GOs and MWCNTs, the obtaining results showed that the different microcosmic tribological mechanisms for GCNTs enable to produce a synergistic lubricating effect, resulting in facilitating the complicating interface sliding between nanocomposites and steel balls.

Variability of kernel morphological and flour physicochemical properties in tropical dent corn hybrids

Abstract. Humam BK, Suwarno WB, Azrai M, Makkulawu AT, Efendi R. 2023. Variability of kernel morphological and flour physicochemical properties in tropical dent corn hybrids. Biodiversitas 24: 1600-1609. Corn is an important crop worldwide for food, feed, and industry. The aims of this study were to study kernel morphological and corn flour physicochemical properties and hybrids selection according to nutritional values for food industries. Plant materials were 15 test hybrids and four check varieties, namely RK457, RK57, BISI18, and NASA29. Kernel morphological and corn flour physicochemical variations are influenced by kernel type. All dent hybrids had 40/0 mesh corn flour yielded significantly higher compared to NASA29. °Dent scores were negatively correlated to 40/0 mesh corn flour yields. The total and soluble carbohydrates of dent corn flour hybrids are significantly higher compared to semi-dent and semi-flint corn flour hybrids. According to corn flour nutritional values in polygon GT biplot analysis, dent hybrids had relatively high starch, total carbohydrate, and soluble carbohydrate contents. Semi-dent hybrids had relatively high moisture, crude protein, and total ash contents. Semi-flint hybrid had relatively high crude fat and crude fiber contents. Cluster-2 was dominated by dent hybrids according to the fuzzy clustering method and selected as potential hybrids. MSM53 was the female parent of dent hybrids in cluster-2. Potential hybrids could be evaluated further by corn flour functional properties analysis.

Physico-chemical variations of shale with artificial maturation: In the presence and absence of water

Pyrolysis is widely employed to simulate the oil generation process in the lab. This method has been used so far to study systematic evolution of pore structures or geochemical properties of source rocks during thermal maturation. Although the importance, variations in mechanical properties of shale samples during the pyrolysis which plays important role in unconventional reservoir development are rarely studied. Herein, we combined grid nanoindentation method with gas adsorption, organic petrology and bulk geochemical analysis to evaluate changes in mechanical properties of shale samples under anhydrous pyrolysis (AHP) and hydrous pyrolysis (HP). The results showed that thermal maturity (%BRo) of the products is different under these two separate pyrolysis methods. Moreover, at the same pyrolysis temperature, mechanical parameters (i.e., Young's modulus, hardness, and fracture toughness) of the HP product were found to be smaller than those of the AHP product. During the pyrolysis (temperature from 300 to 450 °C), the reduction in the mechanical parameters (mean Young's modulus, mean hardness, and mean fracture toughness) following AHP and HP are more than 40%, which must be considered in the development of unconventional reservoirs where mechanical parameters are critical for successful field operations. Most importantly, this study confirmed that water is a significant factor in physico-chemical parameters of the pyrolyzates, which should be considered in the development plans of the formations that will undergo in situ conversion.

UV accelerated aging of unidirectional flax composites: Comparative study between recycled and virgin polypropylene matrix

Previous studies on the photooxidation of natural fiber composites have focused on using short fibers and virgin matrices. In this work, unidirectional flax fiber composites with virgin and recycled polypropylene matrix were prepared by thermocompression to compare their accelerated aging. These composites were exposed to two accelerated xenon arc UV exposures where only the irradiance was modified. A multi-scale characterization was carried out to evaluate the consequences of the photooxidation on their mechanical and physicochemical properties with time. Results show that the photooxidation was limited to the surface. In addition, the photo-degradation of the surfaces of both composites was identified by the appearance of cracks, the variation of crystallinity, the decrease in weight average molar mass, and the appearance of new chemical products. These physicochemical variations are more evident with increasing irradiance. Despite these variations, the mechanical tensile properties of recycled matrix composites remain relatively indifferent to the two UV exposures compared to those with virgin polypropylene. It can be concluded that recycled polypropylene, if well selected, can replace virgin polypropylene in natural fiber composites for better mechanical resistance to photooxidation.

Identification and characterization of plant-derived biomarkers and physicochemical variations in the maturation process of Triadica cochinchinensis honey based on UPLC-QTOF-MS metabolomics analysis

The maturation patterns of nectar into honey are not well understood. The current work selected Triadica cochinchinensis honey (TCH) at three maturity stages to systematically investigate the variation patterns in physicochemical parameters and metabolites. Based on both targeted and untargeted metabolomics analyses, the N1, N5, N10-(E)-tricoumaryl spermidine was identified as the plant-derived characteristic compound in TCH. A total of 26 compounds were quantified by UPLC-QTOF-MS using an external standard calibration method. Two patterns of the honey maturation process were identified based on the 723 metabolite signature transformations. The first was that the levels of plant-derived compounds with strong reducing activity were reduced, such as spermidine, flavonoids, and their derivatives. In contrast, the second pattern was that the maturation process of honey was accompanied by the formation of lactone glycoside analogs and organic acids, which may be facilitated by the enzymatic transformation of enzymes secreted by the bees.

Spontaneous combustion and oxidation kinetic characteristics of alkaline-water-immersed coal

Most scholars used distilled-water-immersed coal to study the reasons why water-immersed coal was prone to self-ignition, while mine water in field was mostly alkaline. Thus, the influence of the alkalinity of mine water on the self-ignition properties of water-immersed coal was explored. Experimental results showed that during the low-temperature oxidation process, the CO productions of DL, ZX, XT alkaline-water-immersed coals were higher than that of raw coals when the temperature was increased to 392, 382, 370 K respectively. Compared with raw coals, the average apparent-activation-energies (Ea) of the distilled-water-immersed DL, ZX, XT coals decreased by 6.89%, 5.94%, 7.75%, respectively. Moreover, that of the alkaline-water-immersed coals decreased by 15.83%, 11.76%, 16.64%, respectively. The reduction in the average apparent Ea of the alkaline-water-immersed coal was approximately twice that of the distilled-water-immersed coal. Further investigation revealed that the content of oxygen-containing functional groups in alkaline-water-immersed coals were obviously more than those of the distilled-water-immersed coal. Therefore, the self-ignition ability of the alkaline-water-immersed coal was greater than distilled-water-immersed coal. Compared with the single soaking effect of pure water on coal, many physicochemical variations produced by the reactions of alkali ions with coal may be the main reason for the self-ignition of water-immersed coal.

Lake metabolic processes and their effects on the carbonate weathering CO2 sink: Insights from diel variations in the hydrochemistry of a typical karst lake in SW China

The precipitation of carbonate minerals does not invariably result in CO2 emission to the atmosphere, because dissolved inorganic carbon (DIC) can be partially utilized by terrestrial aquatic phototrophs, thus generating an autochthonous organic carbon (AOC) sink. However, little is known about the potential effects of this mechanism on carbon cycles in DIC-rich lakes, mainly due to the lack of detailed documentation of the related processes, which limits our ability to accurately evaluate and predict the magnitude of this carbon sink. We conducted field observations in Fuxian Lake, a large and representative karst lake in the Yunnan-Guizhou Plateau, SW China. Continuous diel monitoring was conducted to quantitatively assess the coupled relationship between lake metabolism and DIC cycling and its influence on the carbonate weathering-related CO2 sink. We found that the diel physicochemical variations and isotopic characteristics were mainly controlled by the metabolism of aquatic phototrophs, evidenced by a significant relationship between net ecosystem production and diel DIC cycling, and demonstrating the significance of DIC fertilization in supporting high primary production in karst lakes. The data showed that a reduction in photosynthesis occurred in the afternoon of almost every day, which can be explained by the lower CO2/O2 ratio that increased the potential for the photorespiration of aquatic plants, thus reducing photosynthesis. We found that a net autotrophic ecosystem prevailed in Fuxian Lake, suggesting that the lake functions more as a sink than a source of atmospheric CO2. Considering carbonate weathering, the estimated AOC sink amounted to 650–704 t C km−2 yr−1, demonstrating both the potentially significant role of metabolism in lacustrine carbon cycling and the potential of the combination of photosynthesis and carbonate weathering for carbon sequestration. Our findings may help to quantitatively estimate the future impact of lake metabolism on carbon cycling, with implications for formulating management policies needed to regulate the magnitude of this carbon sink.

Influence of modified governing liquid on shelf-life parameters of high-moisture mozzarella cheese

The roles of mesophilic lactobacilli in cheese manufacturing and ripening have been widely studied, but their impacts, especially as additives in preserving liquids, on the high-moisture mozzarella cheese quality parameters remained underexplored. The current study studied and compared the effects of four preserving liquid formulations - brine solution (sodium chloride, as control), a salt mixture solution, and two lactobacilli solutions (Lactiplantibacillus plantarum IMC 509 in brine solution) or SYNBIO® (a 1:1 ratio of Lacticaseibacillus rhamnosus IMC 501 and Lacticaseibacillus paracasei IMC 502) – on the microbial, chemical (volatile fatty acids), physicochemical (moisture, weight, pH, colour), texture (adhesiveness, hardness, cohesiveness, gumminess, springiness, chewiness) and sensorial qualities of mozzarella stored for 30 days at 4 °C. The quality of the governing solution, including microbial content, lactobacilli viability, pH, turbidity, and smell, was also monitored. For the first 10 days of storage, all samples demonstrated similar physicochemical variations: the firmness and chewiness of the mozzarella lessened, the pH values of the liquid decreased, but cheese microbial growth increased, as did the levels of free fatty acids, the mozzarella pH values and skin whiteness. At day 20, mozzarella stored in mesophilic lactobacilli liquid, especially SYNBIO®, had a spongy structure, tasted more bitter and sour, and had lower pH values than mozzarella in the simple brine solution. Moreover, the cheese sample and liquid of SYNBIO® also presented higher coliform and Pseudomonas spp. counts than that detected in the control, the SYNBIO® liquid, especially in the later period of storage, exhibited a yogurt smell and increased turbidity. By contrast, Mozzarella packed into salt mixture liquid exhibited somewhat more adhesiveness and gumminess, a saltier taste and slightly higher microbial counts than the control sample. The mozzarella samples differed slightly in colour and texture as well. The overall quality changes suggested that the use of the studied mesophilic lactobacilli as governing liquid additives may not be appropriate for high-moisture mozzarella cheese preservation.