Improvement Of Streptomyces Qinlingensis Sp.Nov.By Protoplast Techniques

Streptomyces qinlingensis sp.nov., an agricultural antibiotics producer, was isolated from a soil sample collected in Qinling mountains, Shaanxi Province, and identified as a new strain. Its fermentation broth exhibited potent antifungal and antibacterial activities. There are many kinds of bioactive compounds including streptothricins antibiotics with antifungal and antibacterial activities. To improve the antimicrobial activities and antibiotics production of S. qinlingensis, protoplast mutagenesis and protoplast fusion were applied in this study. The main results were as follows.The first method is protoplast regeneration combined with physical and chemical mutagenesis to select high-yielding strains. The results of bioassay showed that the antibacterial activities against Bacillus subtilis, Bacillus cereus, Staphylicoccus aureus, Pseudomonas aeruginosa and Escherichia coli and antifungal activities against plant pathogenic fungi Gibberella zeae, Colletotrichum gloesporioides, Botrytis cinerea, Fusarium oxysporum and Curvularia lunata of the fermentation broth from 3 strains, R-72 from protoplast regeneration, NTG-1 and H30-7 from NTG and heat mutagenesis of protoplast, respectively, were remarkable increased comparing with that of the parent strain, and the heredity characters of those strains were stable in successive ten generations. Of these, the toxicities of H30-7 against 5 species plant pathogenic fungi increased 3.16, 1.39, 1.16, 1.87, and 1.34 times compared to that of the starting strain. However, the results of HPLC detection revealed that the contents of streptothricin F of those 3 strains were 0.42 mg/mL,0.66 mg/mL and 0.76 mg/mL, respectively, which lower than that of parent strain, 0.82 mg/mL.The second method is the protoplast fusion between S. qinlingensis and Streptomycin producer Str2 because streptothricin and sreptomycin are both belong to aminoglycoside antibiotics. A fusant named F-47, with potent antifungal and antibacterial activities and stable heredity character, was screened from the fusants. Moreover, the culturing characteristics of F-47 have some clear differences from its parental strains. But, the result of HPLC detection showed that the content of streptothricin F dropped a lot from 0.82 mg/mL in the original strain S. qinlingensis to 0.19 mg/mL in the fusant F-47. This is possible because that there may be another antifungal agents are generated or contents of streptothricins are changed in the fermentation broth from fuant F-47 due to the effect of protoplast fusion.