Screening And Identification Of Actinomyces From Soil And Analysis On Fermentation Products

Actinomycetes have provided many important bioactive compounds of high commercial value. These searches have been remarkably successful and approximately two third of naturally occurring antibiotics have been isolated from actinomycetes. The majority of the actinomycetes are widely distributed in the soil, so the development of actinomycetes in soil is of great importance. Screening and identificating the actinomycetes in the soil by several treatment and determinating the antibacterial acticity of the isolated strains,moreover, studying the fermentation condition and stability of the fermentation products. The detailed studies as follows:Nature drying and using three methods such as microwave irradiation, ultrasonic treatment and enrichment to pretreat the nine soil samples, which came from Guangdong Province, Liaoning Province,,ichuan Province,Zhejiang Province, Heilongjiang Province and Shandong Province. Using selective isolation medium starch-casein medium and humic acid medium wih50μg/mL potassium dichromate to isolation and screening of actinomycetes. A total of89strains were isolated from soils.Determining the antibacterial activity of89strains by plate method with the tested strains of Gram-positive bacteria.25strains showed great antibacterial activity against Bacillus subtilis and Micrococcus luteus, and the inhibition zone diameter were above15mm. Strain C1was showed strong activity for both of these pathogens of antibacterial diameter above25mm.Determining the antibacterial activity of89strains against seven pathogenic fungi by filter paper method, and using the disk diffusion method to re-screen the17strains which showed better activity in vitro.The results showed that the17actinomycetes showed high activity against at least four of the seven pathogenic fungi, including14strains which showed great actibacterial activity. Seven strains showed activity against five fungis, The strain C1showed activity against seven phytopathogenic fungis, and the inhibitory activity against Colletotrichum orbiculare and Fusarium oxysporum reached89.71%and74.63%respectively.Optimizing the fermentation medium and conditions of strain C1. The optimum fermentation condition of strain Cl was as follows:soybean meal20g, skim milk powder1g, sucrose80g, K2HPO41g, FeSO4·7H2O0.1g, CaCO33g, distilled water1000mL, initial pH value7.0,fermentation temperature28℃, fermentation time6days,50mL liquid medium in250mL fiake, shaked at200rpm. The fermentation metabolites of strain C1was studied by measuring the temperature and acidity-alkalinity stability. The results showed that it has a great stability between30-90℃. But the inhibitory rate of the fermentation was dropped by more than25%at pH3.0and11.0.Combined with classical taxonomy and molecular biology16S rDNA classification, the categories of strain C1was consistent with Streptomyces.Based on the morphology, culture, physiological and biochemical characteristics, the strain C1was preliminarily identified as Streptomyces sp.