Microbial Properties Research Articles

Effect of ozone gassing time and stirring duration on peroxide value, microbial decontamination, aflatoxin detoxification and sensorial characteristics of dried pistachios

Aflatoxin contamination in agricultural products such as pistachios threatens human health. Ozone has intense antimicrobial activity against microorganisms. The effect of ozone-treated time (3,4 and 5 hours) and stirring time (10, 15 and 20 minutes) on microbial, aflatoxin content, peroxide value, and sensory properties of aflatoxin contaminated pistachios were investigated in this study. The microbial test results also show a significant reduction of microbial load in ozone-treated samples. According to the results, ozone gas caused a significant reduction in aflatoxin levels in pistachio kernels. Aflatoxins B1, B2, G1, G2 and total which was 33.5, 1.5, 0.06, 0. 31 and 35.13 ppb in the control sample, reached 0 ppb after 5 hours of ozone-treatment (15 or 20 min). The results show that the longer the ozone gas is gasified, the higher the peroxide value. The lowest and highest peroxide value was observed in the control and the ozone-treated sample for 5 hours (stirring the samples every 20 minutes), respectively. All peroxide values were below the allowable limit (1 meq/kg). The results of sensory evaluation show that ozonation did not have a negative effect on the falvor, texture, and color score of pistachios, but only had a significant effect on the aroma of pistachios that were ozone-treated for 5 hours. According to results, 3 hours of ozonation and stirring of pistachios every 20 minutes is recommended as the best treatment for reducing microbial load, aflatoxin content, peroxide value and maintaining the sensory properties of dried pistachios.

Bacterial composition and cultural dynamics of microgreens-associated microbiota during selective enrichment for Listeria monocytogenes.

Widely-regarded as a so-called "superfood", microgreens have become an increasingly significant food crop from both nutritional and agricultural standpoints. However, similar to other produce commodities that are also cultivated using modernized indoor-farming methods, there have been mounting concerns over the potential risks of consuming microgreens contaminated by Listeria monocytogenes. To gain insights into the microbial properties of microgreens, this study characterized the bacterial composition of fresh microgreen retail products using amplicon sequencing of 16S rRNA genes. Dominated by Gammaproteobacteria, a total of 36 shared genera were identified as putative constituents of the microgreen core microbiome. By monitoring the dynamics of microgreen-borne bacteria undergoing a Listeria-selective cultural enrichment procedure, it was revealed that, regardless of the presence or absence of L. monocytogenes, off-target bacteria of the Klebsiella and Enterococcus genera were significantly enriched from microgreens by the primary enrichment step, with the secondary enrichment step continuing to promote the expansion of Enterococcus population. While Listeria was generally neither the most-enriched nor the dominant taxon in cultures sampled at different enrichment stages, significant enrichment of Lysinibacillus and Bacillus bacteria were detected in microgreens contaminated with L. monocytogenes, suggesting they could be co-enriched in competition with Listeria.

Development and Assessment of a Batch Type Ohmic Heating System for Milk Processing

This study aims to develop and assess the performance of a batch-type ohmic heating system for the thermal processing of cow and buffalo milk, particularly investigating whether the ohmic system affects the nutritional and microbial quality of the milk. An experimental setup was fabricated with a 7-liter capacity, utilizing an agitator as one electrode and the vessel surface as the other. The system was tested for heating milk from 32°C to target temperatures of 75°C and 92°C. Key processing parameters, including agitator speed and applied voltage, were optimized for both milk types. The physicochemical and microbial properties of the ohmically heated milk were evaluated, along with performance metrics such as heating rates, power consumption, and system efficiency. The developed ohmic heating system achieved heating rates of 4.29°C/min for cow milk and 2.85°C/min for buffalo milk. Cow milk demonstrated lower energy consumption, requiring less time and voltage compared to buffalo milk, with system performance coefficients of 58% for cow milk and 50% for buffalo milk. However, fouling on the agitator surface was identified as a challenge for industrial applications. Importantly, the ohmic heating process preserved the nutritional content while effectively reducing microbial load, confirming its potential for dairy processing. In conclusion, the batch-type ohmic heating system exhibited high efficiency and rapid heating capabilities for both cow and buffalo milk, indicating its viability for commercial use. Future research should focus on addressing fouling issues and further optimizing the system, enhancing the overall potential of ohmic heating technology in the dairy industry.

Appraisal of Heavy Metal Risk Hazards of Eisenia fetida-Mediated Steel Slag Vermicompost on Oryza sativa L.: Insights from Agro-Scale Inspection and Machine Learning Analytics

The steel industry drives world economic growth, yet it generates heavy metal-rich steel slag, which jeopardizes the environment. The utilization of vermi-technology is essential for the sustainable transformation of toxic steel waste slag (SW) into organic amendments, although field-scale use of vermiprocessed SW remains unexplored. To bridge the gap, this study evaluated the efficacy of vermiprocessed SW as an organic supplement for rice field cultivation, focusing on heavy metal (HM) bioavailability, human health risk, and yield in comparison to raw slag and NPK fertilizer. The results indicated a considerable decrease in the bioavailable fraction of heavy metals in T4 (1:1 SW vermicompost 50% + 50% fertilizer). In treatments, T9 (100% SW) and T10 (50% SW + 50% fertilizer) (FIAM) free ion activity modeling confirmed grain absorption of HMs, and the FIAM HQ values indicated the health risk for the direct application of steel slag waste on the field. The risk factor evaluation of HMs’ presence in treatments T9 and T10 established the possible cancer risk for living beings. Similarly, machine learning models like SOBOL sensitivity analysis and artificial neural networks revealed potential threats associated with HMs on different treatments, respectively. The correlation coefficient revealed the negative effects of bioavailable HMs on various soil microbial and enzymatic properties. Moreover, the abundant yield of rice was attributed to the combination treatment (1:1 50% + NPK 50%), which paved the way for an alternative agronomic approach based on the utilization of vermicomposted steel waste slag.

Response of Potato Yield, Soil Organic Matter, Microbial Properties, and Pesticide Residues to Different Cropping Systems and Nutrient Management in North Pakistan

Response of Potato Yield, Soil Organic Matter, Microbial Properties, and Pesticide Residues to Different Cropping Systems and Nutrient Management in North Pakistan

Microbial communities of urban and industrial polluted soils in the Russian Arctic

The Russian Arctic presents a unique environment for studying the effects of anthropogenic pressure on soil microbial communities under severe climatic conditions. This study investigated the impact of chemical pollution on soil microbial properties by comparing urban and industrially polluted soils in Murmansk region with natural Podzols. Urban soils exhibited significant alterations, including shifts in pH and increased carbon and nutrient contents compared to natural soils. Industrially polluted soils near the copper‑nickel smelter were characterized by elevated heavy metal concentration, while those near the aluminum smelter showed high fluorine and aluminum content. In both cases, carbon content and pH remained similar to natural soils. Industrial emissions significantly changed the soil microbiome, with effects varying depending on the pollution source and chemical composition of the emissions. Soils near the copper‑nickel smelter showed a decline in bacterial gene copies and actinomycete mycelium length, with a predominance of Chloroflexii and Ascomycota. Conversely, soils near the aluminum smelter exhibited less pronounced changes, with Proteobacteria and Basidiomycota being prevalent. Despite these differences, both industrially impacted sites displayed reduced microbial diversity, regardless of the composition of the emissions. In contrast, urban soils demonstrated increased microbial diversity, likely attributed to the emergence of new, favorable ecological niches. Microbial communities in both cities were similar, dominated by Proteobacteria and Ascomycota, and displayed an increase in bacterial gene copies compared to natural soils. These findings highlight the contrasting influences of urban and industrial development on soil microbial communities. While industrial activities suppress microbial life, urbanization fosters the creation of new niches, promoting microbial diversity. This underscores the potential of urban soils to support diverse microbial communities, which is crucial for sustainable development and ecological strategies in Arctic cities.

Production and characterization of biosurfactants from lactic acid bacteria in Dadiah for strawberries edible coating

Biosurfactants are amphiphilic components applied in various fields, one of which is preserving agricultural products. Biosurfactants can be used as additives in edible coatings to prevent microbial adhesion by reducing surface tension on the fruit surface. They also play a role in increasing the moisture barrier and slowing down the physiological changes of fruit. Nonetheless, biosurfactants were often produced by non-GRAS bacteria. GRAS biosurfactant-producing bacteria are urgently needed for application in food products. This study aims to isolate and characterize biosurfactant-producing strains of lactic acid bacteria from Dadiah and evaluate their efficacy in reducing microbial adhesion on strawberries. From four selected isolates found in Dadiah, Lactiplantibacillus plantarum was the best candidate, producing biosurfactant with index emulsification (EI24) of 64.48 ± 0.37% with a CMC of 1 g/l. LC-MS and FT-IR characterized the biosurfactants as glycolipids. The rate of antibacterial and anti-adhesive tests on Escherichia coli ATCC 8739 were 18.79 ± 5.23% and 55.26 ± 0.02%, while on Staphylococcus aureus ATCC 6738 were 31.60 ± 2.63% and 74.63 ± 0.00% at a concentration of 3000 mg/l. However, no anti-fungal activity against Rhizopus stolonifer and Aspergillus niger was observed at the same concentration. Compared to SDS, biosurfactants demonstrated non-toxicity with an LC50 value of 2.94 x 108 mg/l. A combination of 1% chitosan reduced the number of fungal cells by 29.76 ± 3.25% on 125 mg/l biosurfactant and bacterial cells by 31.91 ± 5.06% on 1000 mg/l biosurfactant after 10 days, indicating their potential to reduce fruit spoilage and enhance microbial anti-adhesive properties of edible coatings.

Reseeding increased plant biomass production and soil fertility, but not plant species diversity in degraded grasslands in China

Reseeding is a primary measure to restore degraded grasslands. Numerous studies have conducted experiments to investigate how the properties of grassland ecosystems respond to reseeding in China. However, there is a lack of summary of the results of these studies. Here, we conducted a hierarchical random-effects meta-analysis on the effects of reseeding on plant, soil, and microbial properties. We collected 19 variables, including plant biomass, species diversity and richness, soil organic carbon content, soil total and available nutrients, soil water content, soil microbial biomass and diversity, and enzyme activity, from a dataset of 1363 paired observations (degraded vs. reseeded) from 75 publications. The results showed that reseeding increased aboveground and belowground plant biomass by 70.2% and 68.0% on average, respectively. Reseeding increased soil organic carbon, phosphorus, and potassium contents, but did not affect soil nitrogen levels. Reseeding increased soil microbial nitrogen under conditions of tillage and fertilization. Reseeding age was found to have a positive correlation with species richness, while planting type, fertilization, and tillage did not have a significant impact on the species richness and diversity. Under the treatments of fertilization, non-tillage, and mix-planting, the response ratio of aboveground biomass to reseeding was positively correlated with the response ratio of species diversity to reseeding. Our results concluded that current reseeding practices can significantly improve plant biomass production and soil fertility but have minor effects on plant species diversity. These findings indicate that the preservation of biodiversity should receive greater attention from both researchers and practitioners in grassland remediation in China.

Changes of the bacterial and fungal populations present in organic dark leafy green vegetable juices during refrigerated storage

Dark leafy green vegetable juices (DLGVJs), prepared with vegetables such as kale and chard, have shown substantial market growth in the past decade due to its profound health benefits. Unfortunately, as an innovative product, there was limited research focusing on DLGVJs. This study aimed to bridge key critical knowledge gaps associated with the microbial quality and shelf life of DLGVJs and elucidate the changes in both physicochemical and microbial properties of different organic DLGVJs during refrigerated storage. Culture-dependent and culture-independent analytical methods were applied to profile the bacterial and fungal populations in three organic DLGVJs (kale, chard, and collard greens) during refrigeration. Plate count results showed that the initial total aerobic plate counts (APC) ranged from 6.49 ± 0.03 to 6.74 ± 0.08 Log CFU/mL, and the initial total fungal counts ranged from 5.19 ± 0.06 to 6.75 ± 0.04 Log CFU/mL in fresh DLGVJs. During refrigerated storage the pH of DLGVJs decreased as the storage time increased and the redness of the juices increased as well. The culture-dependent analysis revealed bacterial counts initially increased and then declined, while fungal counts showed an initial decrease followed by an increase. By the end of the storage, the highest APC and fungal population were observed in kale juice and chard juice (7.03 ± 0.05 and 6.70 ± 0.03 Log CFU/mL) respectively. 16S rRNA sequencing results showed that the dominant bacterial genera of spoiled DLGVJs at the end of storage included Serratia, Leuconostoc, and Hafnia-obesumbacterium, and the major spoilage fungal were composed of Mrakia, Filobasidium, and Vishniacozyma. Results of this study provide insights into the microbial populations present in DLGVJs and the dominant spoilage genera during refrigerated storage, laying the foundation for the development of intervention strategies in the future.

Organic carbon decomposition temperature sensitivity positively correlates with the relative abundance of copiotrophic microbial taxa in cropland soils

Revealing the relationships between the temperature sensitivity of soil organic matter decomposition (Q10) and microbial communities is critical to predict ecosystem feedbacks to global warming. However, the relationships are still far from well understood, especially within the low latitude regions. To address this knowledge gap, soil samples were collected from >100 cropland sites in Southwest China, a region with highly diverse climatic and environmental conditions. The results showed that Q10 values substantially varied across the region, ranging from 1.85 to 6.81, with an average value of 3.27. They were significantly positively correlated with the contents of soil organic carbon, while negatively correlated with the ratios of soil dissolved organic carbon to total organic carbon content. This indicates that soils with high organic carbon contents are more vulnerable to global warming. Further analysis suggested that Q10 values were positively correlated with soil microbial respiration rates, fungal abundance, prokaryotic diversity, and the relative abundance of copiotrophic microbial lineages, but negatively correlated with the proportions of oligotrophic microbes and microbial co-occurrence network degree. The structural equation modeling analysis suggested that soil organic carbon and its quality, as well as microbial attributes were the main factors explaining the variation in Q10 values. The findings in this study highlight the crucial and complex roles of soil microbiome in determining ecosystem feedbacks to global warming.

Primary productivity regulates rhizosphere soil organic carbon: Evidence from a chronosequence of subtropical Chinese fir (Cunninghamia lanceolata) plantation

Tree plantations worldwide are a large terrestrial carbon sink. Previous studies on the carbon sequestration capacity of plantations mainly focused on tree biomass carbon sequestration, but the importance of soil organic carbon (SOC) was relatively unclear. Living root carbon inputs influence SOC via plant-microbe interactions in the rhizosphere and play an essential role in nutrient cycling. Here, we compared SOC, including its fractions, microbial properties, and major nutrients in rhizosphere and bulk soils, and examined their relationships to net primary productivity (NPP) across three developmental stages of Chinese fir (Cunninghamia lanceolata) plantations (6, 18, and 42 years old) in subtropical China. Although NPP differed among the three plantations, SOC concentration in bulk soils did not vary significantly among them. However, SOC concentration and labile C pool I and recalcitrant C pool in rhizosphere soils were significantly (p < 0.05) higher in the young (6-year) and mature (42-year) plantations, both of which had lower (p < 0.05) NPP (−37.71 % and − 42.67 %) compared to the middle-aged (18-year) plantation, suggesting a decoupling of NPP from rhizosphere SOC in the plantations. The decoupling of NPP from rhizosphere SOC concentrations may be driven by nitrogen (N) and phosphorus (P) tree growth requirements, belowground C allocation, and resultant microbial activity in this highly weathered subtropical soil. Our study provides field-based evidence suggesting that rhizosphere SOC changes are primarily regulated by net primary production in subtropical forest plantations. We propose that accurate predictions of SOC dynamics in forest plantations require an improved understanding of rhizosphere processes during plantation development.

In vivo manipulation of human gut Bacteroides fitness by abiotic oligosaccharides.

Synthetic glycans (SGs) containing glycosidic linkages and structures not identified in nature offer a means for deliberately altering microbial community properties. Here pools of SG oligosaccharides were generated via polymerization of monosaccharides and screened for their ability to increase saccharolytic Bacteroides in ex vivo cultures of human fecal samples. A lead SG preparation was orally administered to gnotobiotic mice harboring a consortium of 56 cultured, phylogenetically diverse human gut bacteria and fed a Western diet. The abundances of 3 of 15 Bacteroides strains increased, most prominently B. intestinalis. Underlying mechanisms were characterized by analyzing in vivo expression of the carbohydrate utilization machinery, using retrievable microscopic paramagnetic particles with bound SG oligosaccharides and assaying SG degradation by individual purified B. intestinalis glycoside hydrolases. The results reveal that SGs can selectively co-opt carbohydrate utilization machinery in different human gut Bacteroides and demonstrate a means for identifying artificial carbohydrate structures for targeted bacterial manipulation.

Manufactured soil: A new use for bauxite residue

Bauxite processing residue produced at an Alumina refinery was used to produce manufactured soil. The residue was first acidified and then leached to remove excess salts. Green waste compost was added at rates of 5 and 10 % w/w, with or without the addition of 20 % w/w dune sand. The products were dried, crushed and sieved and the chemical, physical and microbial properties of the materials characterized. Products had an electrical conductivity and pH of 1.0–1.1 dS m−1 and 8.0–8.1 respectively in 1:5 soil:water extracts and corresponding values in saturation paste extracts were 5.4–5.7 dS m−1 and 7.4–7.5. The effective cation exchange capacity was 202–351 mmolc kg−1, exchangeable Na percentage was 41–46 %, Colwell-extractable P was 108–119 mg kg−1 and the Toxicity Characteristic Leaching Procedure showed that extractable metal concentrations were an order of magnitude below regulatory limits so the material can be considered as non-hazardous. Diethylenetriaminepentaacetic acid-extractable Cu, Zn and Mn were below reported critical levels. Addition of compost lowered concentrations of extractable Cr, As and V and drying the material further reduced extractable levels. When the material was dried it shrunk and solidified and the aggregates produced had a low macroporosity and high microporosity and water holding capacity compared with dune sand. Aggregates were very stable as measured by wet sieving. Compost addition increased organic C content, and the size (microbial biomass C) and activity (basal respiration and the activity of enzymes involved in C, N, S and P mineralization) of the soil microbial community. It was concluded that the materials produced had soil-like chemical, physical and microbial properties and could potentially be used as a soil substitute.

Akkermansia muciniphila Growth Promoted by Lychee Major Flavonoid through Bacteroides uniformis Metabolism.

Akkermansia muciniphila (A. muciniphila) possesses health-promoting properties. Nevertheless, A. muciniphila enrichment remains a challenging endeavor. Quercetin-3-O-rutinose-7-O-α-l-rhamnoside (QRR), a flavonoid found in lychee pulp, has a unique double-substituted glycosylated structure, requiring a specific intestinal microbiota for effective metabolism. Here, QRR was fermented using a coculture of Bacteroides uniformis and A. muciniphila, and the interactions between the two were elucidated in terms of QRR regulation of microbial growth changes and metabolic properties. The results demonstrated that QRR effectively promoted the proliferation of A. muciniphila based on the metabolic action of B. uniformis in vitro, which was evidenced by a notable increase in the number of viable bacteria. Furthermore, the coculture sample exhibited a significant increase in SCFAs. Qualitative analysis of metabolites by UPLC-ESI-Triple-TOF-MS/MS showed that B. uniformis could release sugars on QRR to produce quercetin-3-O-glucoside-7-O-α-rhamnoside and further quercetin. In the coculture and B. uniformis culture, quercetin was converted to taxifolin, which was identified as a crucial intermediate in the metabolism of QRR. Notably, the metabolite kaempferol was only detected in the coculture. The present study reveals the interaction between QRR and the coculture of A. muciniphila and B. uniformis, providing a practical basis for the potential prebiotic value of QRR.

Determining Some Chemical and Microbiological Changes in the Ripening Process of Kashar Cheese

In the present study, some microbial, chemical, and physicochemical characteristics occurring during ripening were observed in unpackaged and vacuum-packed Kashar cheese samples. Some microbial and chemical properties of Kashar cheese samples were studied Also, the free fatty acid ratio was determined with the SDS-Page Electrophoresis to determine proteolysis during the ripening period and with the High-Performance Thin Layer Chromatography (HPTLC) for lipolysis. Physical, chemical, and microbiological analyzes were made at 0, 15, 30, 45, 60, and 75 days of ripening during which the changes in the number of microbiologically total aerobic mesophilic bacteria (TAMB), Lactobacillus spp., Lactococcus spp., Pseudomonas spp., yeast-mold, lipolytic, and proteolytic bacteria were determined. In the present study, % lactic acid, pH, dry matter percentage, color parameters (L, a and b values) and water activity (aw) were analyzed during ripening and the changes during storage were defined. Lactobacillus spp., Lactococcus spp., TAMB, and proteolytic bacteria counts and % lactic acid ratios were higher in vacuum-packed Kashar cheeses. It was found that lipolysis and proteolysis were higher in cheese samples stored open during ripening.

Glucose addition in natural forest soils has higher biological nitrogen fixation capacity than other types of soils

Land use changes soil microbial and chemical properties, but the mechanism of biological nitrogen fixation under different land use patterns is rarely reported, so we used four types of soil: Natural forest soil (NS), healthy banana soil (HS), diseased banana soil (DS) and paddy soil (PS). Treatments included the control (CK), addition of glucose (G), addition of glucose and ammonium nitrate (GN), addition of banana straw (BS), addition of banana straw and ammonium nitrate (BSN), addition of banana root (BR), and addition of banana root and ammonium nitrate (BRN). The study found that the change of soil utilization types, glucose addition increased carbon dioxide emissions (Compared with the control, increased by 963.11%, 508.39%, 794.77% and 511.34%, respectively) and enhanced the ability of soil microbial nitrogen fixation. Importantly, natural forest soil microorganisms have a higher biological nitrogen fixation capacity compared to other types of soils. Glucose addition caused the accumulation of ammonium nitrogen (Compared with the control, increased by 426.08%, 934.21%, 420% and 1065.95%, respectively), indicating that microorganisms had higher utilization efficiency of soluble carbon and enhanced the biological nitrogen fixation capacity, and nitrogen addition caused the accumulation of ammonium nitrogen, thereby weakening the biological nitrogen fixation capacity. At the same time, glucose significantly increased the Fimicutes phylum (83.73%, 66.38%, 67.18% and 70.36%) and lowered the level of other bacterial phylums, thereby reducing the bacterial network structure, and the stability of the soil environment has decreased. Forest analysis showed that CO2 was an important factor in predicting the bacterial community structure of different soil types, an increase in CO2 content can predict drastic changes in the bacterial community. Bacteria at the Fimicutes phylum level preferred glucose, which may also have a negative effect on bacteria at the level of other phylums.

Sulfide addition accelerates anammox sludge granulation and promotes microbial cooperation

The granular anaerobic ammonium oxidation (anammox) system has attractive advantages in tolerance to environmental-stress and enhancement of nitrogen removal capacity. Sulfide addition can improve nitrogen removals in anammox systems via inducing sulfur denitrification, yet its function in the improvement of the property of anammox granular sludge remains unclear. Herein, we investigated the variations in the morphological and microbial properties of the anammox sludge response to different sulfide concentrations (Na2S: 10–100 mg/L) through a long-term experiment. By comparing the sludge diameter and heme c content, it comes that a relatively low sulfide (S/N [nitrate] molar ratio of 0.18–0.50) significantly promoted the average diameter and heme c concentration of sludge by 25–175 % and 75–95 %, respectively, compared to that of both without sulfide addition and a high sulfide addition (S/N > 0.85). This enhancement is primarily because a low amount of sulfide had stimulated the secretion of extracellular polymeric substance, induced slight biogenic sulfur accumulation as microbial nuclei, and facilitated the appropriate amount of filamentous bacteria proliferation. Microbial metabolism functions analyses revealed a robust granular anammox coupled with sulfur denitrification in the sulfide-mediated anammox reactor, and the assembled granules exhibited exceptional tolerance to environmental stress. Significantly, the anammox bacteria (Candidatus_Brocadia) dominating the granules displayed satisfactory anammox activity (21.8 ± 2.1 mg N/g VSS h), and their produced nitrate was efficiently removed by the sulfur-oxidizing bacteria (Thiobacillus) that predominantly occurred in the flocs. This collaboration ensured an efficient sulfide-mediated anammox granules system, achieving nitrogen removal efficiency exceeding 95 %. These results highlight the function of sulfide in improving the morphological property of anammox sludge as well as the creation of a favorable ecological niche for the functional microorganism, which is important to maintain the efficiency and robustness of the anammox process in treating wastewater.

Microbial Polysaccharides as Functional Components of Packaging and Drug Delivery Applications.

This review examines microbial polysaccharides' properties relevant to their use in packaging and pharmaceutical applications. Microbial polysaccharides are produced by enzymes found in the cell walls of microbes. Xanthan gum, curdlan gum, pullulan, and bacterial cellulose are high-molecular-weight substances consisting of sugar residues linked by glycoside bonds. These polysaccharides have linear or highly branched molecular structures. Packaging based on microbial polysaccharides is readily biodegradable and can be considered as a renewable energy source with the potential to reduce environmental impact. In addition, microbial polysaccharides have antioxidant and prebiotic properties. The physico-chemical properties of microbial polysaccharide-based films, including tensile strength and elongation at break, are also evaluated. These materials' potential as multifunctional packaging solutions in the food industry is demonstrated. In addition, their possible use in medicine as a drug delivery system is also considered.

Composted biochar versus compost with biochar: effects on soil properties and plant growth

Biochar is widely recognized as an amendment that enhances soil properties and sequesters carbon, particularly in degraded soils. However, biochar applied solely to soil may also hinder plant development due to toxic by-products generated during pyrolysis or nutrient retention. To mitigate these adverse effects, it has been suggested to either mix biochar with compost or to process it by composting with fresh organic materials. To date, there is a lack of comparative studies evaluating the performance of these two approaches. In this study, three types of biochar, differing in their initial feedstocks (beech wood, hornbeam/beech/oak mixture, and digestate/cereal straw mixture), were investigated. These biochars were applied solely, mixed with green waste compost, or processed as composted biochar in two soils of different fertility (a Luvisol and a gleyic Fluvisol). A pot experiment was conducted under controlled conditions where lettuce was grown for three months. After harvesting, plant biomass, and soil microbial and physicochemical properties were measured. Composted biochar and compost additives maintained a neutral soil pH, contrary to biochar applied solely or mixed with compost. The dissolved organic carbon and total nitrogen were higher in composted biochar treatments, leading to a higher proportion of humified material with a high degree of condensed aromatic groups compared to other treatments. Microbial activities were higher in the composted biochar treatments compared to those in the compost with biochar, and more specifically in the less fertile Luvisol. Finally, composted biochar increased plant growth by almost six times compared to the control without amendments, whereas the mix of biochar and compost increased it by only three times. Solely applied biochars did not affect lettuce growth. This study demonstrates that biochar composting is more beneficial than mixing biochar with compost in terms of improving soil fertility and mitigating the negative effects associated with pure biochar application.Graphical

Effect of 9-year water and nitrogen additions on microbial necromass carbon content at different soil depths and its main influencing factors

Microbial necromass carbon (MNC) is a major source of soil organic carbon (SOC) pool, significantly influencing soil carbon sequestration. The effects of long-term water and nitrogen addition on MNC in soils at different depths, as well as their interactions, remain poorly understood. In this study, we examined the influence of water addition (+51.67 mm), nitrogen addition (25, 50, 100 kg N ha−1 yr−1), and their interactions on MNC accumulation at different soil depths in temperate grasslands. The addition of water and nitrogen over nine years has been observed to exhibit a decreasing trend in the MNC at different soil depths. Notably, MNC in the topsoil layer (0–10 cm) decreased significantly by 18.56 % under low nitrogen addition treatment, while MNC in the subsoil layer (40–60 cm) declined significantly by 27.19 % under high nitrogen addition treatment. Fungal microbial necromass carbon (FNC) contributed 3.25 times more to SOC than bacterial microbial necromass carbon (BNC). In the 0–10 cm soil layer, MNC is primarily governed by both microbial attributes and the physicochemical properties of the soil, in the 20–40 cm soil layer, the physicochemical properties of the soil predominantly control MNC, in the 40–60 cm layer, microbial characteristics exert a more significant influence on MNC. Collectively, our observations suggest that soil MNC decreased with the addition of water and nitrogen in the 0–60 cm soil slope, which could enable the accurate prediction of global change impacts on the accumulation of soil carbon, thus facilitating the implementation of strategies to augment soil carbon sequestration.