Bacillus phytases: Current status and future prospects

Phytases catalyze the hydrolysis of phytic acid in a stepwise manner to lower inositol phosphates, myo-inositol (having important role in metabolism and signal transduction pathways), and inorganic phosphate. These enzymes have been widely used in animal feed in order to improve phosphorus nutrition and to decrease pollution in animal waste. Compared to previously described phytases, the phytase (PhyL) from Bacillus licheniformis ATCC 14580 has attractive biochemical properties which can increase the profitability of several biotechnological procedures (animal nutrition, human health…etc). Due to its amino acid sequence with critical substitutions, the PhyL could be a model to enhance other phytases features, in terms of thermal stability and high activity. Otherwise, an engineered PhyL, with low pH optimum, will represent a challenge within the class of β- propeller phytases

Involvement of cysteine 306 and alanine 63 in the thermostability and oligomeric organization of glucose isomerase from <em>Streptomyces</em> sp. SK

International audienceThe implication of the original alanine 63 (Ala63) and the unique cysteine 306 (Cys306) residues in the thermostability of the Streptomyces sp. SK glucose isomerase (SKGI) were investigated by site-directed mutagenesis and homology modelling. The Cys306 to Ala mutation within SKGI dramatically affected its thermal stability by decreasing the half-life from 80 to 15 min at 90A degrees C while the Ala63 to Ser replacement shifted this half-life to 65 min. The electrophoretic analysis proves that the residue Cys306 participates in oligomerization of the SKGI. Its stabilizing role is materialized by hydrogen bonds established with arginines at positions 284 and 259, as deduced from the constructed three-dimensional model. We have also shown that the presence of an Ala63 instead of Ser63 seems to be more suitable for enzyme thermostability by maintaining hydrophobic pocket that contributes to the protection of the enzyme active site

The Impact of Greenhouse and Field Growth Conditions on <i>Chenopodium quinoa</i> Willd Accessions’ Response to Salt Stress: A Comparative Approach

Quinoa’s exceptional capacity to tolerate high salt levels presents a promising solution to the agricultural challenges posed by salt stress. This study aimed to explore salt stress effects on three quinoa accessions (18 GR, R-132, and DE-1) and to compare the influence of greenhouse and field growing conditions on their salinity tolerance. The plants were irrigated by 50, 100, 150, and 200 mM NaCl concentrations. The results showed that quinoa plants’ response to morphological, physiological, biochemical, and enzymatic parameters was influenced by NaCl concentration, accession, growing conditions, and their interactions. As salinity irrigation increased, aerial part length and leaf area decreased significantly (p −2·s−1 for greenhouse and open field conditions, respectively. NaCl stimulated MDA and H2O2 in both conditions for all accessions, and the DE-1 accession displayed the lowest levels. Proteins, sugars, proline, peroxidase, ascorbate peroxidase, and catalase were stimulated by salt stress, except in the R-132 accession. Field cultivation resulted in a more severe salinity response. Greenhouse conditions may enhance quinoa’s salt tolerance due to the less demanding growth conditions. DE-1 exhibited the highest salt tolerance, while R-132 showed the lowest. This study sets the stage for further research into the genetic basis of salt tolerance in various quinoa accessions, optimizing growth in salty regions through farming practices, and confirming the obtained results in real-world conditions for sustainable agriculture

Assessment of Liver Toxicity in Wistar Rats after Chronic Exposure to Phosphate-Processing Wastewaters from Gafsa-Metlaoui Laundry in Tunisia

In the mining basin of the Gafsa region in southwestern Tunisia, environmental exposure to randomly discharged phosphate-processing wastewaters (PPWW) presents a serious threat to health and the surrounding ecosystems. Thus, the contaminated areas are in continuous deterioration over time. There is a paucity of information on the deleterious effects of this kind of effluent. In the current work, the PPWW characterization showed the presence of high contents of Pb (0.90 ± 0.02 mg/L), Cd (0.35 ± 0.27 mg/L), Cr (0.43 ± 0.1 mg/L) and Fe (215.1 ± 2.41 mg/L), exceeding the permissible limits. To assess the chronic toxicity of the effluent in mammalians, two doses of PPWW (50% and 100%) were administered by gavage to Wistar rats for 28 consecutive days. The results revealed that the two PPWW concentrations significantly increased the plasma biochemical markers (bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH)), compared to untreated animals. Moreover, PPWW treatment severely altered the lipid profile by increasing the contents of triglycerides, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-cholesterol) by 143%, 114%, and 91%, respectively, and significantly reduced the high-density lipoprotein cholesterol (HDL-cholesterol) level by 46%, compared to the control animals. In addition to the significant decrease in activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in the liver of intoxicated rats, the malondialdehyde (MDA) level was remarkably altered. All of these were associated with deep histopathological damages, materialized by dilatation of sinusoids, congestion of the centrilobular vein, and inflammatory cell infiltration. These disturbances were accompanied by metal detection in the liver and blood. Additionally, DNA fragmentation detected in hepatic tissues highlighted the genotoxic effects of PPWW. All of the aforementioned effects occurred in a PPWW dose-dependent manner. These findings evidenced, for the first time, the in vivo-deleterious impacts of this type of effluent on mammalians inhabiting the mining basin area and therefore showed the real threats to which humans, as consumers, could be exposed. Accordingly, there is a dire need to pay special attention to PPWW before being discharged into environmental ecosystems without any prior treatments.This research was funded by the Ministry of Higher Education and Scientific Research of Tunisia (Fund allocated to LR21ES26).Peer reviewe

Cytotoxic effects of seven Tunisian hospital wastewaters on the proliferation of human breast cancer cell line MDA-231: correlation with their chemical characterization

International audienceHospital wastewaters contain large amounts of pharmaceutical residues, which may eventually be discharged into the aquatic environment through wastewater treatment plants, raising the question of their impact on human and environmental health. This has prompted the launch of several monitoring studies into the most commonly administered compounds in urban wastewater. The aim of this study was, therefore, to explore the cytotoxic potential of wastewaters samples collected from seven hospitals in Tunisia. The physicochemical analyses showed a large fluctuation of certain parameters in the collected samples, such as chemical oxygen demand (ranged from 860 to 1720 mg L-1), biochemical oxygen demand (ranged from 385 to 747 mg L-1), total organic carbon (ranged from 256 to 562 g L-1), total suspended solids (ranged from 905 to 1450 mg L-1), conductivity (ranged from 3.31 to 7.14 mu sm/cm), and turbidity (ranged from 100 to 480 NTU). The analysis using inductively coupled plasma mass spectrometry (ICP-MS) also showed that hospital wastewater contains high concentrations of Hg (ranged from 0.0024 to 0.019 mg L-1). This could be explained by the variation of the activity and the services in certain hospitals compared to others. All hospital wastewater samples induced the proliferation of human breast cancer cell line MDA-231, even at low concentrations (20 mu L/assay). Moreover, the maximum induction reached at the concentration of 60 mu L/assay in wastewater samples from hospitals located in Monastir, Sidi Bouzid, Mahdia, and Sfax with percentages of induction up to 42.33, 14, 7.61, and 5.42%, respectively. These observations could be due to the presence of endocrine disrupting compounds (EDCs) in these wastewaters. Given this, our results evidenced the potential risk of these hospital effluents to environmental and public health

Domestic Environment and Gut Microbiota: Lessons from Pet Dogs

Accumulating data show the involvement of intestinal microbiota in the development and maintenance of numerous diseases. Many environmental factors influence the composition and function of the gut microbiota. An animal model subjected to the same environmental constraints that will allow better characterization of the microbiota&ndash;host dialogue is awaited. The domestic dog has physiological, dietary and pathological characteristics similar to those of humans and shares the domestic environment and lifestyle of its owner. This review exposes how the domestication of dogs has brought them closer to humans based on their intrinsic and extrinsic similarities which were discerned through examining and comparing the current knowledge and data on the intestinal microbiota of humans and canines in the context of several spontaneous pathologies, including inflammatory bowel disease, obesity and diabetes mellitus