Production of ligninolytic enzymes and some diffusible antifungal compounds by white-rot fungi using potato solid wastes as the sole nutrient source.

AIMS: The aim of this study was to evaluate the synthesis of ligninolytic enzymes and some diffusible antifungal compounds by white-rot fungi (WRF) using peels or discarded potato as the sole nutrient source. METHODS AND RESULTS: The strain Trametes hirsuta Ru-513 highlighted for its laccase activity (595 ± 33 U l-1 ), which is able to decolourize 87% of an anthraquinone dye using potato peels as the sole nutritional support. A native polyacrylamide gel of laccase proteins showed the presence of two isoenzymes, corresponding to proteins of 56 and 67 kDa, which were detected by SDS-PAGE. The antifungal activity of ethyl acetate extracts was evaluated by the agar diffusion method, where Anthracophyllum discolor Sp4 and Inonotus sp. Sp2 showed the highest inhibition zones of Mucor miehei. The fungal extracts also inhibited Fusarium oxysporum and Botrytis cinerea growth, with inhibition zones of up to 18 mm. The extract with the highest antifungal activity, from A. discolor Sp4 grown in discarded potato medium, was analysed using a gas chromatograph coupled to a mass spectrometer. Among the identified compounds, chlorinated aromatic compounds and veratryl alcohol were the most abundant compounds. CONCLUSIONS: The results revealed the relevance of potato waste valorization for the sustainable production of ligninolytic enzymes and antifungal compounds. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reports the synthesis of ligninolytic enzymes and diffusible antifungal compounds by WRF using potato wastes as the sole nutrient source and suggests a relationship between the enzymatic activity and the synthesis of antifungal compounds. These compounds and the synthesis of halogen compounds by WRF using agro-industrial wastes have been poorly studied before.

Increased diazinon hydrolysis to 2-isopropyl-6-methyl-4-pyrimidinol in liquid medium by a specific Streptomyces mixed culture.

Actinobacteria identified as Streptomyces spp. were evaluated for their ability to remove diazinon as the only carbon source from a liquid medium. Single cultures of Streptomyces strains were exposed to diazinon at a concentration of 50 mg L(-1). After 96 h incubation, six of the eight cultures grew and five strains showed an increase in their total protein concentrations and changes in their protein profile. Up to 32% of the diazinon was removed by the single Streptomyces cultures. A compatibility assay showed that the different Streptomyces species were not antagonistic. Twenty-six mixed cultures were then prepared. Diazinon removal was increased when mixed cultures were used, and maximum diazinon removal of 62% was observed when the Streptomyces spp. strains AC5, AC9, GA11 and ISP13 were mixed; this was defined as the selected mixed culture (SMC). Diazinon removal was positively influenced by the addition of glucose into the liquid medium. Our study showed a diazinon degradation rate of 0.025 h(-1), half-life of 28 h(-1) and 2-isopropyl-6-methyl-4-pyrimidinol (IMHP) production of 0.143 mg L h(-1). Rapid diazinon hydrolysis to IMHP was associated with a decrease in the pH of the medium as a consequence of microbial glucose metabolism and organic acid exudation. Moreover, the SMC of Streptomyces was able to remove IMHP. This work constitutes a new, if not the only, report on diazinon degradation by mixed cultures of Streptomyces spp. Given the high levels of diazinon removal, the SMC formed by four Streptomyces strains has the potential to be used to treat the diazinon present in environmental matrices.

Atrazine dissipation and its impact on the microbial communities and community level physiological profiles in a microcosm simulating the biomixture of on-farm biopurification system.

The effects of repeated atrazine application (40 mg a.i.kg(-1)) on its degradation, microbial communities and enzyme activities were studied in a peat based biomixture composed by straw, soil and peat in the volumetric proportions of 2:1:1 that can be used in on-farm biopurification system. Atrazine removal efficiency was high (96%, 78% and 96%) after each atrazine application and did not show a lag phase. Microbial enzyme activities were reduced significantly with atrazine application but rapidly recovered. Microbial diversity obtained by BiologEcoplate was similar after the first and second atrazine application. However, an inhibitory effect was observed after the third application. After each atrazine application, culturable fungi were reduced, but rapidly recovered without significant changes in culturable bacteria and actinomycetes compared to the control. Denaturing gradient gel electrophoresis (DGGE) patterns demonstrated that microbial community structure remained relatively stable in time when compared to the controls. In conclusion, our results demonstrated that after successive ATZ applications, the peat based biomixture had a good degradation capacity. Moreover, microbiological assays demonstrated the robustness of the peat based biomixture from a microbiological point of view to support pesticide degradation.

Carbendazim dissipation in the biomixture of on-farm biopurification systems and its effect on microbial communities.

The impact of repeated carbendazim (CARB) applications on the extent of CARB dissipation, the microbial diversity, the community level physiological profile (CLPP), and the enzymatic activity within the biomixture of an on-farm biopurification system was evaluated. After three successive CARB applications, the CARB dissipation efficiency was high; the efficiency of dissipation was 87%, 94% and 96% after each application, respectively. Although microbial enzymatic activity was affected significantly by CARB application, it could recover after each CARB pulse. Likewise, the numbers of cultivable bacteria, fungi and actinomycetes (as measured in CFUs) were slightly affected by the addition of CARB, but the inhibitory effect of the pesticide application was temporary. Denaturing gradient gel electrophoresis (DGGE) and Biolog Ecoplate assays demonstrated that the microbial populations remained relatively stable over time when compared to the control. The results obtained herein therefore demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system.

Using volatile organic compounds to enhance atrazine biodegradation in a biobed system.

The effect of the terpenes α-pinene, eucalyptol, and limonene, individually and as mixtures, on atrazine (ATZ) biodegradation and on biological activity in a biobed biomixture was evaluated. Additionally, terpenes emitted from the biomixture were captured using solid-phase microextraction. Terpenes added individually at relatively low concentrations (50 µg kg(-1)) significantly enhanced ATZ degradation and biological activity during the first incubation days. No significant effect on ATZ degradation was found from adding the terpene mixture, and, interestingly, an inhibitory effect on phenoloxidase activity was found during the first 20 days of incubation when mixed terpenes were present at 100 µg kg(-1). Capturing terpenes demonstrated that during the first hour of incubation a significant fraction of the terpenes was volatilized. These results are the first to demonstrate the feasibility of using terpenes to enhance the degradation of a pesticide. However, successive applications of terpenes or the addition of materials that slowly release terpenes could sustain the ATZ degradation enhancement.

The genus Hecabolus Curtis 1834 (Braconidae: Doryctinae) in South America, with description of six new species.

Six new species of the doryctinae wasp genus Hecabolus Curtis 1834 (Braconidae) are described from Brazil and Venezuela: H. assis sp. nov., H. julianoi sp. nov., H. robustus sp. nov., H. seniaridus sp. nov., H. shimborii sp. nov., and H. sulmatogrossensis sp. nov. A key to the nine described species of Hecabolus is provided.

Effect of cow slurry amendment on atrazine dissipation and bacterial community structure in an agricultural Andisol.

Atrazine is a commonly used herbicide for maize production in Chile, but it has recently been shown to be ineffective in soils that receive applications of cow slurries generated from the dairy industry. This effect may be caused either by the sorption of the pesticide to organic matter or more rapid degradation in slurry-amended soils. The objectives of this study were to evaluate the effects of cow slurry on atrazine dissipation, the formation of atrazine metabolites and the modification of bacterial community in Andisol. The cow slurry was applied at doses of 100,000-300,000 Lha(-1). After 4 weeks, atrazine was applied to the slurry-amended soils at concentrations of 1-3 mg kg(-1). The amounts of atrazine and its metabolites were determined by high performance liquid chromatography (HPLC). The soil microbial community was monitored by measurement of CO(2) evolution and changes in bacterial community using PCR-DGGE of 16S rRNA genes. The results show that cow slurry applications had no effect on atrazine dissipation, which had a half-life of 15-19 days. The atrazine metabolites were detected after 20 days and were significantly higher in soils amended with the slurry at both 20 and 40 days after application of the herbicide. Respiration rates were elevated after 10 days in all soils with atrazine addition. Both the atrazine and slurry amendments altered the bacterial community structures, indicated by the appearance of specific bands in the DGGE gels after 10 days. Cloning and sequencing of the 16S rRNA genes from the DGGE gels showed that the bands represented various genera of beta-proteobacteria that appeared in response to atrazine. According to our results, further field studies are required to explain the lower effectiveness of atrazine in weed control. These studies may include the effect of dissolved organic carbon on the atrazine mobility.

A combinatorial approach to materials discovery.

A method that combines thin film deposition and physical masking techniques has been used for the parallel synthesis of spatially addressable libraries of solid-state materials. Arrays containing different combinations, stoichiometries, and deposition sequences of BaCO(3), Bi(2)O(3), CaO, CuO, PbO, SrCO(3), and Y(2)O(3) were generated with a series of binary masks. The arrays were sintered and BiSrCaCuO and YBaCuO superconducting films were identified. Samples as small as 200 micrometers by 200 micrometers in size were generated, corresponding to library densities of 10,000 sites per square inch. The ability to generate and screen combinatorial libraries of solid-state compounds, when coupled with theory and empirical observations, may significantly increase the rate at which novel electronic, magnetic, and optical materials are discovered and theoretical predictions tested.

Synthesis and Electronic Transport of Single Crystal K3C60.

Sizable single crystals of C(6O) have been synthesized and doped with potassium. Above the superconducting transition temperature T(c), the electrical resistivity p(T) displays a classic metal-like temperature dependence. The transition to the superconducting state at T(c) = 19.8 K is extremely sharp, with a transition width DeltaT < 200 mK. In contrast to transport behavior of doped polycrystalline and granular thin films, no anomalous fluctuations are observed near T(c) in single crystal specimens.