Protective Effect of an Exopolysaccharide Produced by Lactiplantibacillus plantarum BGAN8 Against Cadmium-Induced Toxicity in Caco-2 Cells

Mechanistic and future prospects in rhizospheric engineering for agricultural contaminants removal, soil health restoration, and management of climate change stress

Climate change, food insecurity, and agricultural pollution are all serious challenges in the twenty-first century, impacting plant growth, soil quality, and food security. Innovative techniques are required to mitigate these negative outcomes. Toxic heavy metals (THMs), organic pollutants (OPs), and emerging contaminants (ECs), as well as other biotic and abiotic stressors, can all affect nutrient availability, plant metabolic pathways, agricultural productivity, and soil-fertility. Comprehending the interactions between root exudates, microorganisms, and modified biochar can aid in the fight against environmental problems such as the accumulation of pollutants and the stressful effects of climate change. Microbes can inhibit THMs uptake, degrade organic pollutants, releases biomolecules that regulate crop development under drought, salinity, pathogenic attack and other stresses. However, these microbial abilities are primarily demonstrated in research facilities rather than in contaminated or stressed habitats. Despite not being a perfect solution, biochar can remove THMs, OPs, and ECs from contaminated areas and reduce the impact of climate change on plants. We hypothesized that combining microorganisms with biochar to address the problems of contaminated soil and climate change stress would be effective in the field. Despite the fact that root exudates have the potential to attract selected microorganisms and biochar, there has been little attention paid to these areas, considering that this work addresses a critical knowledge gap of rhizospheric engineering mediated root exudates to foster microbial and biochar adaptation. Reducing the detrimental impacts of THMs, OPs, ECs, as well as abiotic and biotic stress, requires identifying the best root-associated microbes and biochar adaptation mechanisms.

The Next-Generation Probiotic E. coli 1917-pSK18a-MT Ameliorates Cadmium-Induced Liver Injury by Surface Display of Metallothionein and Modulation of Gut Microbiota

Cadmium (Cd) is recognized as being linked to several liver diseases. Currently, due to the limited spectrum of drugs available for the treatment of Cd intoxication, developing and designing antidotes with superior detoxification capacity and revealing their underlying mechanisms remains a major challenge. Therefore, we developed the first next-generation probiotic E. coli 1917-pSK18a-MT that delivers metallothionein (MT) to overcome Cd-induced liver injury in C57BL/6 mice by utilizing bacterial surface display technology. The results demonstrate that E. coli 1917-pSK18a-MT could efficiently express MT without altering the growth and probiotic properties of the strain. Moreover, we found that E. coli 1917-pSK18a-MT ameliorated Cd contamination-induced hepatic steatosis, inflammatory cell infiltration, and liver fibrosis by decreasing the expression of aminotransferases along with inflammatory factors. Activation of the Nrf2-Keap1 signaling pathway also further illustrated the hepatoprotective effects of the engineered bacteria. Finally, we showed that E. coli 1917-pSK18a-MT improved the colonic barrier function impaired by Cd induction and ameliorated intestinal flora dysbiosis in Cd-poisoned mice by increasing the relative abundance of the Verrucomicrobiota. These data revealed that the combination of E. coli 1917 and MT both alleviated Cd-induced liver injury to a greater extent and restored the integrity of colonic epithelial tissues and bacterial dysbiosis.

Guardians of the Gut: Harnessing the Power of Probiotic Microbiota and Their Exopolysaccharides to Mitigate Heavy Metal Toxicity in Human for Better Health

Heavy metal pollution is a significant global health concern, posing risks to both the environment and human health. Exposure to heavy metals happens through various channels like contaminated water, food, air, and workplaces, resulting in severe health implications. Heavy metals also disrupt the gut's microbial balance, leading to dysbiosis characterized by a decrease in beneficial microorganisms and proliferation in harmful ones, ultimately exacerbating health problems. Probiotic microorganisms have demonstrated their ability to adsorb and sequester heavy metals, while their exopolysaccharides (EPS) exhibit chelating properties, aiding in mitigating heavy metal toxicity. These beneficial microorganisms aid in restoring gut integrity through processes like biosorption, bioaccumulation, and biotransformation of heavy metals. Incorporating probiotic strains with high affinity for heavy metals into functional foods and supplements presents a practical approach to mitigating heavy metal toxicity while enhancing gut health. Utilizing probiotic microbiota and their exopolysaccharides to address heavy metal toxicity offers a novel method for improving human health through modulation of the gut microbiome. By combining probiotics and exopolysaccharides, a distinctive strategy emerges for mitigating heavy metal toxicity, highlighting promising avenues for therapeutic interventions and health improvements. Further exploration in this domain could lead to groundbreaking therapies and preventive measures, underscoring probiotic microbiota and exopolysaccharides as natural and environmentally friendly solutions to heavy metal toxicity. This, in turn, could enhance public health by safeguarding the gut from environmental contaminants.

The Involvement of Lactic Acid Bacteria and Their Exopolysaccharides in the Biosorption and Detoxication of Heavy Metals in the Gut

Heavy metal pollution has become one of the most important global environmental issues. The human health risk posed by heavy metals encountered through the food chain and occupational and environmental exposure is increasing, resulting in a series of serious diseases. Ingested heavy metals might disturb the function of the gut barrier and cause toxicity to organs or tissues in other sites of the body. Probiotics, including some lactic acid bacteria (LAB), can be used as an alternative strategy to detoxify heavy metals in the host body due to their safety and effectiveness. Exopolysaccharides (EPS) produced by LAB possess varied chemical structures and functional properties and take part in the adsorption of heavy metals via keeping the producing cells vigorous. The main objective of this paper was to summarize the roles of LAB and their EPS in the adsorption and detoxification of heavy metals in the gut. Accumulated evidence has demonstrated that microbial EPS play a pivotal role in heavy metal biosorption. Specifically, EPS-producing LAB have been reported to show superior absorption, tolerance, and efficient abatement of the toxicity of heavy metals in vitro and/or in vivo to non-EPS-producing species. The mechanisms underlying EPS-metal binding are mainly related to the negatively charged acidic groups and unique steric structure on the surface of EPS. However, whether the enriched heavy metals on the bacterial cell surface increase toxicity to local mammal cells or tissues in the intestine and whether they are released during excretion remain to be elucidated.

Effect of lactic acid bacteria by different concentrations of copper based on non-target metabolomic analysis

Copper (Cu) is an essential element for mammals, but excess intake can have detrimental health consequences. However, Cu is no longer present in the "Limit of Contaminants in Foods" promulgated in 2022. The potential impact of different Cu (II) concentrations on human health remains unclear. In this study, a strain of lactic acid bacteria (LAB), namely, Lactiplantibacillus plantarum CICC 23121 (L23121), was selected as a prebiotic indicator strain to indirectly assess the effects of food-limited Cu (II) concentrations (issued by Tolerance limit of copper in foods in 1994) on the functions of intestinal microbes. We used non-target metabolomics, automatic growth curve detector, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) to investigate the effects of Cu (II) on L23121. The study revealed shows that the 50% minimum inhibitory concentration (MIC50) of Cu (II) for most lactic acid bacteria was 4 mg/L. At low Cu (II) concentrations (≤ 4 mg/L), the pentose phosphate pathway and pyrimidine metabolism of the lactic acid bacteria were affected, resulting in a decrease in the content of beneficial secondary metabolites and a significant decrease in the cell activity. As Cu (II) concentrations increase (≥ 6 mg/L), the key amino acid and lipid metabolisms were affected, leading to the inhibition of growth and primary metabolite production of the bacteria. Under high concentration of Cu (II) (6 mg/L), the surface adhesion of the bacteria was distorted and covered with significantly large particles, and the functional groups of the cells were significantly shifted. As a probiotic, the abundance of lactic acid bacteria in the intestine is significantly reduced, which will inevitably seriously damage intestinal homeostasis. Thus, to protect human intestinal microbes' health, it is recommended to limit the concentration of Cu in food to less than 4 mg/L.

Comparative Studies on the Structure and Biological Activities of Two New Polysaccharides from Tricholoma sinoportentosum (TS-P) and Termitomyces albuminosus (TA-P)

Polysaccharides are important active ingredients of living organisms. In this study, two new polysaccharides, Tricholoma sinoportentosum polysaccharide (TS-P) and Termitomyces albuminosus (TA-P), were extracted and purified using anion exchange column chromatography. The structure of each polysaccharide was identified by HPGPC, FT-IR, HPLC, GC-MS and NMR, and the biological activities were also investigated. The results of the structure identification showed that TS-P was composed of arabinose, mannose, glucose and galactose at a ratio of 1:1:3:2 and its main chain was composed of (1→4)-Arap residues, (1→4,6)-D-Manp residues and two (1→6)-Galp residues. The TA-P was composed of arabinose, glucose and galactose at a ratio of 2:4:8. Its main chain was composed of two (1→4)-β-L-Arap residues, one (1→4)-Glcp residues, three (1→2,6)-Galp residues and five (1→6)-Galp residues. The immunoassay showed that TS-P and TA-P could significantly promote the proliferation of T cells, B cells and RAW264.7 cells. The cell cycle results showed that for B cells and macrophages, TS-P and TA-P mainly affected the G0/G1 phases of the cell cycle; for T cells, TS-P affected G2/M phase, while TA-P mainly affected the G0/G1 phases. TS-P could significantly promote B cells to secrete IgA, IgG and IgD (p < 0.01), while TA-P could significantly promote the secretion of IgA and IgG (p < 0.01). The chemical structure and biological activity of TS-P and TA-P were first studied and compared to lay a theoretical foundation for the application of fungal polysaccharide.

Orally Administrated Lactiplantibacillus plantarum BGAN8-Derived EPS-AN8 Ameliorates Cd Hazards in Rats

Cadmium (Cd) is a highly toxic metal that is distributed worldwide. Exposure to it is correlated with a vast number of diseases and organism malfunctions. Exopolysaccharides (EPS) derived from Lactiplantibacillus plantarum BGAN8, EPS-AN8, previously showed great potential for the in vitro protection of intestinal cells from this metal. Here, we investigated the potential of food supplemented with EPS-AN8 to protect rats from the hazardous effects of Cd exposure. After thirty days of exposure to lower (5 ppm) and higher (50 ppm)-Cd doses, the administration of EPS-AN8 led to decreased Cd content in the kidneys, liver, and blood compared to only Cd-treated groups, whereas the fecal Cd content was strongly enriched. In addition, EPS-AN8 reversed Cd-provoked effects on the most significant parameters of oxidative stress (MDA, CAT, GST, and GSH) and inflammation (IL-1β, TNF-α, and IFN-γ) in the duodenum. Moreover, micrographs of the duodenum were in line with these findings. As the gut microbiota has an important role in maintaining homeostasis, we used 16S rRNA amplicon sequencing and investigated the effects of Cd and EPS-AN8 on one part of the microbiota presented in the duodenum. Although Cd decreased the growth of lactobacilli and mostly favored the blooming of opportunistic pathogen bacteria, parallel intake of EPS-AN8 reversed those changes. Therefore, our results imply that EPS-AN8 might be extremely noteworthy in combatting this toxic environmental pollutant.

Bacterial Exopolysaccharides as Emerging Bioactive Macromolecules: From Fundamentals to Applications

Microbial exopolysaccharides (EPS) are extracellular carbohydrate polymers forming capsules or slimy coating around the cells. EPS can be secreted by various bacterial genera that can help bacterial cells in attachment, environmental adaptation, stress tolerance and are an integral part of microbial biofilms. Several gut commensals (e.g., Lactobacillus, Bifidobacterium) produce EPS that possess diverse bioactivities. Bacterial EPS also has extensive commercial applications in the pharmaceutical and food industries. Owing to the structural and functional diversity, genetic and metabolic engineering strategies are currently employed to increase EPS production. Therefore, the current review provides a comprehensive overview of the fundamentals of bacterial exopolysaccharides, including their classification, source, biosynthetic pathways, and functions in the microbial community. The review also provides an overview of the diverse bioactivities of microbial EPS, including immunomodulatory, anti-diabetic, anti-obesity, and anti-cancer properties. Since several gut microbes are EPS producers and gut microbiota helps maintain a functional gut barrier, emphasis has been given to the intestinal-level bioactivities of the gut microbial EPS. Collectively, the review provides a comprehensive overview of microbial bioactive exopolysaccharides.

Prospects of Biogenic Xanthan and Gellan in Removal of Heavy Metals from Contaminated Waters

Biosorption is considered an effective technique for the treatment of heavy-metal-bearing wastewaters. In recent years, various biogenic products, including native and functionalized biopolymers, have been successfully employed in technologies aiming for the environmentally sustainable immobilization and removal of heavy metals at contaminated sites, including two commercially available heteropolysaccharides-xanthan and gellan. As biodegradable and non-toxic fermentation products, xanthan and gellan have been successfully tested in various remediation techniques. Here, to highlight their prospects as green adsorbents for water decontamination, we have reviewed their biosynthesis machinery and chemical properties that are linked to their sorptive interactions, as well as their actual performance in the remediation of heavy metal contaminated waters. Their sorptive performance in native and modified forms is promising; thus, both xanthan and gellan are emerging as new green-based materials for the cost-effective and efficient remediation of heavy metal-contaminated waters.

Serum klotho and its associations with blood and urine cadmium and lead across various stages of glomerular function: data for US adults aged 40-79 years

Exposures to cadmium and lead can cause oxidative stress, leading to tissue damage resulting in kidney and cardiovascular diseases. The antiaging protein klotho, on the other hand, is known to act as an anti-oxidative agent. How klotho homeostasis interacts with exposure to cadmium and lead has not been reported. Thus, this study was carried to investigate associations of serum klotho with blood and urine cadmium and lead in US adults aged 40-79 years across stages of eGFR-based kidney function and albuminuria defined as urinary albumin/creatinine ratio of > 30 mg/g creatinine. As long as the kidney function was normal (eGFR ≥ 90 mL/min/1.73 m²) or near normal (60 ≤ eGFR < 90 mL/min/1.73 m²), there was no evidence of an association between cadmium exposure and klotho concentrations irrespective of the presence/absence of albuminuria. During kidney dysfunction (15 ≤ eGFR < 60 mL/min/1.73 m²), 10% increases in blood cadmium concentrations resulted in decreases in klotho concentrations between 0.27 and 0.84%. In addition, during severe kidney dysfunction (15 ≤ eGFR < 45 mL/min/1.73 m²), a positive association between urine cadmium and serum klotho concentrations was observed. In the absence of albuminuria and when kidney function was normal or near normal, 10% increases in blood lead concentrations were observed to be associated with modest decreases between 0.28% and 0.37% in serum klotho concentrations. Similar results were observed between the concentrations of urine lead and serum klotho during kidney dysfunction.

Bacterial Biosorbents, an Efficient Heavy Metals Green Clean-Up Strategy: Prospects, Challenges, and Opportunities

Rapid industrialization has led to the pollution of soil and water by various types of contaminants. Heavy metals (HMs) are considered the most reactive toxic contaminants, even at low concentrations, which cause health problems through accumulation in the food chain and water. Remediation using conventional methods, including physical and chemical techniques, is a costly treatment process and generates toxic by-products, which may negatively affect the surrounding environment. Therefore, biosorption has attracted significant research interest in the recent decades. In contrast to existing methods, bacterial biomass offers a potential alternative for recovering toxic/persistent HMs from the environment through different mechanisms for metal ion uptake. This review provides an outlook of the advantages and disadvantages of the current bioremediation technologies and describes bacterial groups, especially extremophiles with biosorbent potential for heavy metal removal with relevant examples and perspectives.