Study On Antibacterial Substances Produced By The Marine Streptomyces Parvus DY2741

In this study, many kinds of samples including seawater, sea sand and seashells etc, were collected from Xiamen sea area. Fifty seven strains marine-derived bacteria, seventeen strains marine-derived actinomycetes and 128 strains fungi were isolated from the above samples. Their antibacterial activities against four microorganisms (Staphylococcus aureus, Escherichia coli, Saccharomyces cerevisiae and Aspergillus niger) were assayed by paper diffusion method. It was found that the rate of marine bacteria producing antibacterial substances isolated from seawater and seashells to the total of bacteria isolated from different samples was higher, respectively 69.2% and 45.5%. The rate of marine actinomycetes producing antibacterial substances isolated from seawater, sea sand and seashells was higher, respectively 75.0%, 80.0% and 80.0% and that the rate of marine fungi producing antibacterial substances isolated from sea sand and seashells was higher, respectively 54.5% and 57.1%. The rate of the bacteria and actinomycetes against two kinds of bacteria was more than that against the other indication strains and the rate of the fugi against all these indicaiton strians was on average.A marine-derived actinomycete DY2741 isolated from sea invertebrata collected from Xiamen intertidal zone was studied. According to morphological, cultural characteristics and physiology and biochemistry, this strain belonged to Flavus of the genus Streptomyces sp. 16S rDNA compared with the genebank and its phylogenetic tree showed that homology of gene order between DY2741 and Streptomyces parvus strain NRRL B-1455T was 99%.In order to increase yield of antibacterial substances, the compositions of medium and fermentation conditions were optimized. It showed the optimized carbon source was starch; the optimized nitrogen source was ammonium chloride. Acrooding to the design of Box-Behnken central composite, the optimum medium composition: starch 2.035%, ammonium chloride 0.4425% and NaCl 2.000%. Optimization of fermentation showed that initial pH was 7.0, seed age was 48h, inoculation quantity was 6%, the optimum volume of medium in 250mL flask was 70mL, the optimum temperature was 28℃and fermentation time was 5d.The antibacterial substances in the fermented broth was stable to the pH and ultraviolet. The antibacterial activity started to deline at 100℃.By determination, it was deduced that the antibacterial substances in DY2741 broth had lipid solubility property with middle polarity. On the basis of separation of the Sephadex LH-20, two peaks with antibacterial activity appeared, and the second peak showed the stronger inhibition activity against S.aureus and E.coli. In order to analyze thefraction, TLC was analyzed to choose the tube which had a clear and single spot. Gas chromatography-mass spectrometry (GC-MS) analysis was performed to this tube. While TIC showed it was relatively pure. According to comparison of MS spectrum and the standard spectral library and FTIR analysis, it was preliminarily inferred as dibutyl phthalate (DBP).