Production and Characterization of Phospholipases C from some Bacillus thuringiensis Isolates Recovered from Egyptian Soil
Pages 10-24
Nooran Sherif Elleboudy, Walid Faisal ElKhatib, Mohammad Mabrouk Aboulwafa and Nadia Abdel-Haleem Hassouna

DOI: http://dx.doi.org/10.6000/1927-3037.2016.05.01.3

Published: 02 March 2016

Abstract: Two hundred and thirty one isolates, with the characteristic morphology of Genus Bacillus, were recovered from 100 soil samples collected from 7 different Egyptian governorates, and were screened for phospholipase C (PLC) production by egg-yolk plate method. Sixty isolates have shown very high PLC production and were further assessed using chromogenic assay method. The highest five producers, identified by 16S rRNA gene sequencing as Bacillus thuringiensis, were selected and their PLCs were purified to homogeneity using ammonium sulfate precipitation and Sephadex G-75 gel filtration chromatography. PLCs had molecular masses of 28.5 kDa as indicated by SDS-PAGE. The characteristics of the studied five PLCs were having maximal activities at 35-45°C and pH 7.2. The enzymes could retain more than half of their maximum activities at 30-60°C and pH 7-8. Equivalent activities were recorded at low water tension. PLC from B. thuringiensis KT159186 was relatively thermostable with a maximum activity at 40°C. The half-inactivation temperature was above 50°C, which compared favorably to that of other enzymes. Activity at the wide temperature range (20-80°C) was high (about 50% of maximum),. This PLC could tolerate pH as high as 12 with only 30% loss of activity. Specificity pattern of PLC from the same isolate showed equivalent activities toward phosphatidylcholine and phosphatidylinositol in addition to marked activity toward phosphatidylethanolamine, which makes it a typical non-specific PLC for industrial purposes. In conclusion, these characteristics of PLC from the test isolate make it attractive for various industrial applications.

Sorbed Anthracene Degradation by Sophorolipid Producing Yeasts
Pages 1-5
M. Cristina Romero, Juan C. Chiaravalli and Enso H. Reinoso

DOI: http://dx.doi.org/10.6000/1927-3037.2016.05.01.4

Published: 02 March 2016

Abstract: The organic pollutan adsorption/desorption process by microbial degradation had been less studied than metal ones. The sorption assays alone did not predict desorption, due to hysteresis, irreversibility, fixed compounds in different sites, with diverse desorption rates. Most of the studies dealt with bacteria rather than filamentous fungi and yeasts. So, our aims were to isolate yeasts from polluted sediments, to quantify its potential to uptake anthracene (An) and to evaluate the bioavailability by a desorption model. Yeasts were isolated from hydrocarbon-polluted samples, 40-isolates grew in anthracene-plates. Molecular characterization was achieved by sequence analysis of the ITS1-5.8S rRNA-ITS4 and 26S rRNA regions; morphological and physiological determination were also done. Candida parasilopsis, Pichia anomala and Rhodothorula mucilaginosa were the prevalent yeasts. An-degradation was assessed in soil-systems with 0, 50, 100, 150, 200 and 250 μg An/l, 3 differentes sorbens types, organic carbon, organic nitrogen, PAHs, sand:silt:clay, pH and cation exchange capacity. Sophorolipids excretion were confirmed by HPLC, UV-detector with active fraction at 9.669 min (RT 9.646 min = sophorolipid-standard). A desorption model with equilibrium, nonequilibrium and nondesorption areas, was applied to explain the experimental data, An-transformation was greater in the organic liquid-phase than in the soil-sorbed ones; the desorption-coefficients and soil components were negatively correlated with the kinetic parameters. The An-release depended on the sophorolipid excretion, soil matrix and particles sizes. Desorption parameters significantly fitted the yeast uptake, with R² = 0.97, R² = 0.90 and R² = 0.97 for C. parasilopsis, P. anomalaand R. mucilaginosa, respectively.