Isolation, identification and antibacterial characteristics of broad-spectrum antagonistic strains in soils of garbage accumulation

Abstract:

[Objective] A broad-spectrum antagonistic strain with high antibacterial ability was screened from the garbage heap soil and its antibacterial properties were studied for pollution control of township garbage accumulation sites. [Methods] Antagonistic fungi were isolated from the soil of garbage accumulation sites in townships by plate dilution method and cylinder-plate method, and the antagonistic strains were identified by morphological observation, physiological and biochemical characteristics and molecular biological identification. Suitable organic reagents were selected to extract mycelia and fermentation broth of antagonistic fungi, by measuring the polarity of antibacterial active substances. The TLC-Bioautography method was used to analyze the bacteriostatic active components in the fermentation broth and mycelia. Determination of antibacterial spectrum of ethyl acetate extract of mycelium used 23 indicator bacteria. The high-temperature tolerance, acid-base tolerance, ultraviolet stability, natural light stability of the crude extract and the minimum inhibitory concentration against Escherichia coli and Candida albicans were determined. [Results] A passaging stable broad-spectrum antagonistic fungus DAZ-2 was isolated and identified as Aspergillus fumigatus by morphological observation, physiological and biochemical characteristics, and ITS sequence analysis. Selecting ethyl acetate reagent to extract methanol extract and fermentation broth of Aspergillus fumigatus DAZ-2 fermentation mycelium. The TLC-Bioautography method showed that the antibacterial active substances in the two were not the same component, and the multi-component substances cooperated to produce a bacteriostatic effect. The crude ethyl acetate extract of fermenting mycelium (200 μg/mL) has antibacterial effect on 11 indicator bacteria, and the MIC of Escherichia coli and Candida albicans is 7.50 and 15 μg/mL, and the antibacterial ability was stable, tolerated to temperature, light, ultraviolet, acid, and alkali. [Conclusion] A wide-spectrum antagonistic strain, Aspergillus fumigatus DAZ-2 with high antibacterial activity and stable passage was isolated, which is expected to provide a scientific basis for the development of microbial drugs and the pollution control of garbage accumulation sites in villages.