Isolation Of Marine Microbial Antagonists And Studies On Marine Actinomycete YT Against Yeasts

In this study,many kinds of samples,including seawater bubble,sea algae, seawater,sea mud,sea sand,decayed wood and sea invertebrata,were collected from Yellow Sea near Yantai and Qingdao region.128 strains marine-derived bacteria,36 strains marine-derived actinomycetes and 102 strains marine-fungi were isolated from the above samples.Their antibiotic activities against four microorganisms(Saccharomyces cerevisiae,Bacillus subtilis,Escherichia coli and Aspergillus niger)were assayed by paper diffusion method.It was found that the rate of marine bacteria producing antibiotic substance isolated from seawater bubble and sea mud to the total of bacteria isolated from different samples was high,respectively 63.6%and 55.0%and that the rate of marine actinomycetes producing antibiotic substance isolated from seawater and sea-animal rotted bodies was 50.0%and that the rate of marine fungi producing antibiotic substance isolated from decayed wood and seawater bubble was high, respectively 50.0%and 45.5%.The rate of the bacteria and actinomycetes against B.subtilis and S.cerevisiae was more than that against the other indication strains and the number of those microorganisms against B.subtilis was more than ones against E.coli,adversely,the number of fungi against B.subtilis was fewer than ones against E.coli.A marine-derived actinomycete YT isolated from sea invertebrata collected from Yantai was studied.According to morphological and cultural characteristics,this strain belonged to Albosporus of the genus Streptomyces sp. Strain YT in phylogenetic tree had low identity with other streptomyces,and the maximum identification was only 90%.The taxonomic status of this strain should be further studied.The spectrum of anti-microbes showed that this strain inhibited S.cerevisiae and Candida albicans strongly.In order to improve anti-yeast substance production,the compositions of medium and cultivation conditions were optimized.It showed the optimized carbon source was glucose;the optimized nitrogen resource was bean flour;Mg²⁺ and Ca²⁺improve antibiotic production.Glucose and bean flour and NaCI were the main factors that influenced anti-yeasts substance production by Plackett-Burman design;the optimized medium was composed of 0.83%glucose, 1.24%bean flour and 1.38%NaCl by center combination design.At the same time,several important fermentation conditions were optimized:the optimal inoculation quantity is 7%;the optimal volume of medium in 250mL flask was 50mL;the optimal temperature was 25℃.By the assay of physic-biochemical characteristics of anti-yeasts substance produced by strain YT,the substance was stable in different pH environment,but the anti-yeasts activity of fermentation liquid handled by high temperatures and UV reduced.The antibiotics were nonpolar,There were two anti-yeast substances in the fermentation liquid,but there existed only one in the intracellular substances.The method of chemical color reaction of the substances was obtained by chemical color reaction and biological footprint.Macroporous resin D101 adsorbed the substances in the fermentation liquid well,so the application of solid extraction by resin D101 was accepted.