Six agricultural organic wastes and three inorganic matrices were selected for rhodococci whole cells immobilization. The degree of immobilization of rhodococci cells varied from 6.20% to 34.30% on organic matrices. A high level of Rhodococcus rhodochrous CNMN-Ac-05 cells immobilization was demonstrated on inorganic matrices, it was from 69.25% to 97.30%. After the contact with support the strain dissociated, forming, in addition to original S type, rough (R) and altercolour smooth (S) types. Immobilization of rhodococci cells on organic supports led to the appearance of phenotypic heterogeneity from 0.34% to 3.26%. On inorganic matrices the variability of rhodococci was 0.88-1.05%.
Introduction. In recent years, due to wide applications of nanotechnologies in various fields, the safety of nanomaterials has become a pressing issue. Fullerene C60 is not an exception. Research on the activity of microorganisms and their interaction with nanoparticles is of major importance, both for microorganisms and for the ecosystem as a whole.
Material and methods. Fullerene C60 powder was purchased from Sigma-Aldrich. The object of study was R. rhodochrous CNMN-Ac-05 strain. The number of viable bacterial cells was estimated by colony-forming units (CFU). The morphological features of the rhodococci colonies have been described according to the usual microbiological method.
Results. It was established that fullerene C60 in concentrations of 1-25 mg/L fullerene C60 stimulated the growth of R. rhodochrous by 2.4-2.8 times. As the concentration of fullerene C60 increased up to 50-100 mg/L, the multiplication and growth of rhodococci decreased by 29.5% and 38% respectively. In the presence of 1-10 mg/L fullerene C60 the rhodococci population remained homogeneous, being composed of 100% S type colonies. The increase of fullerene C60 concentration led both to the decrease in the CFU number and to the appearance of R type colonies, up to 1.3% of population.
Conclusions. Fullerene C60 in concentrations 1-100 mg/L had no obvious toxic effect on the rhodococci strain. The optimum concentration is 10 mg/L. The concentrations higher than 25 mg/L led to the dissociation of rhodococcal population and diminution in the CFU counts, but not to the total inhibition.
The paper’s aim was to select the optimal mineral medium for LDPE biodegradation by the strain Penicillium verrucosum CNM-FP-02. It was selected 5 mineral salt media (MSM), which differed in salt content and N/P ratio. After 40 days of submerged cultivation, the following parameters were determined: catalase activity and pH of cultural media, biomass accumulation, rate of LDPE degradation, optical microscopy and the tensile testing of polyethylene. It was observed that catalase activity on all media, except MSM 4, was higher in the presence of LDPE. The addition of polyethylene to the growth media stimulated the fungal biomass accumulation by 19.3-93.1% (4 media out of 5 tested). The percentage of degradation of LDPE films was different, depending on the culture medium, from 0.41% to 0.92%. The most active LDPE films were degraded on medium MSM 2. Visualization of plastic strips under an optical microscope revealed the immobilization of the microorganism and the damage on the polyethylene surface. The tensile test showed increased elasticity of the plastic in the variants treated with fungal strain. In conclusion, in order to stimulate the biodegradation of LDPE by the strain P. verrucosum CNM-FP-02, the medium MSM 2 (N/P ratio 1:1) was selected.
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