Forty-two morphologically different fungal strains were isolated from different soil samples and agricultural wastes and screened for β-glucosidase activity under solid-state fermentation. Eight species were chosen as the most active β-glucosidase producers and were subjected to primary morphological identification. β-Glucosidase was highly produced by Aspergillus terreus, which showed the highest activity, and was subjected to full identification using scanning electron microscopy and molecular identification. Initial screening of different variables affecting β-glucosidase production was performed using Plackett-Burman design and the variables with statistically significant effects were identified. The optimal levels of the most significant variables with positive effect and the effect of their mutual interactions on β-glucosidase production were determined using Box-Behnken design. Fifteen variables including temperature, pH, incubation time, inoculum size, moisture content, substrate concentration, NaNO3, KH2PO4, MgSO4 · 7H2O, KCl, CaCl2, yeast extract, FeSO4 · 7H2O, Tween 80, and (NH4)2SO4 were screened in 20 experimental runs. Among the 15 variables, NaNO3, KH2PO4 and Tween 80 were found as the most significant factors with positive effect on β-glucosidase production. The Box-Behnken design was used for further optimization of these selected factors for better β-glucosidase production. The maximum β-glucosidase production was 4457.162 U g(-1).
The aid of beneficial microbes, which is a well-accepted strategy, may improve plant salt tolerance. However, the mechanisms that underpin it are unclear. In this study, seedling experiments were carried out to assess the effect of Bradyrhizobium and Enterobacter on the germination, growth, nonenzymatic and enzymatic content in soybean (Glycine max L.) under salt stress. Water was sprayed on the seeds as a control, and with 75 mM, 150 mM NaCl as salt stress. The findings demonstrate that salt stress (75, 150 mM) caused a significant decrease in germination, morphological criteria, and membrane stability index (MSI) when compared to control seeds but increased lipid peroxidation (MDA), electrolyte leakage (EL), osmotic pressure, proline, citric acid, sugar content, antioxidant enzymes. Furthermore, endophytic Bradyrhizobium and Enterobacter inoculation resulted in a significant rise in all of the above metrics.; however, these treatments resulted in significant reductions in ROS, EL, and MDA in stressed plants. Finally, the findings showed that combining Bradyrhizobium and Enterobacter was the most efficient in reducing the harmful effects of salt on soybean plants by boosting antioxidant up-regulation and lowering membrane leakage and ROS.
Microbial uricase is effective protein drug used to treat hyperuricemia and its complications, including chronic gout, also in prophylaxis and treatment of tumor lysis and organ transplants hyperuricemia. Uricase is commonly used as diagnostic reagent in clinical analysis for quantification of uric acid in blood and other biological fluids. Also, it can be used as an additive in formulations of hair coloring agents. A newly isolated strain, Aspergillus sp. 1–4, was able to produce extracellular uricase on a medium containing uric acid as inducer. Phylogenetic analysis based on ITS region sequence analysis and phenotypic characteristics showed that Aspergillus sp. strain 1–4 is closely related to Aspergillus welwitschiae and its nucleotide sequence was deposited in the GenBank database and assigned sequence accession number MG323529. Statistical screening using Plackett-Burman design with 20 runs was applied to screen fifteen factors for their significance on uricase production by Aspergillus welwitschiae. Results of statistical analysis indicated that incubation time has the most significant positive effect on uricase production followed by yeast extract and inoculum size with the highest effect values of 13.48, 5.26 and 4.75; respectively. The interaction effects and optimal levels of these factors were evaluated using central composite design. The maximum uricase production was achieved at incubation time (5 days), yeast extract (2 g/L) and inoculum size (4 mL/50 mL medium) are the optimum levels for maximum uricase production (60.03 U/mL). After optimization, uricase production increased by 3.02-folds as compared with that obtained from the unoptimized medium (19.87 U/mL).
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