Isolation And Identification Of Extracellular Active Substances From An Algae-lysing Bacterium Which Was Purified By Sephadex

In the present, harmful algal blooms become a global environmental disaster asthe global economical development and the destruction of marine environment. Themicrobial methods by algicidal microorganisms as economic, environmental,alternative approaches are applied to control algal blooms, because the effects of thetraditional methods were limited by high cost, repeated pollution and so on.On the basis of which a algicidal strain B1screened from red tide water inXiangzhou Shipside of Zhuhai, the algae-lytic mechanism and the identification,separation of the B1extracellular active substances were studied in the growth ofPhaeocystis globosa. The main results were as follows:Through the preliminary analysis of the active substances, The results showed thealgae-lysing components probably included aromatic aldehyde and phosphorus groups,but not protein.In order to further investigate the algae-lytic effect of the Bacillus sp. B1, thealgae-lytic influences of different contents of B1bacteria-free filtrate on the contentof chlorophyll a and malondialdehyde (MDA), superoxide dismutase (SOD) andcatalase (CAT) activity were studied in the growth of Phaeocystis globosa. Whenmore than1mL bacteria-free filtrate was added into100mL Phaeocystis globosa, theeffect of algae-lying was the best without extra-interference and the removal rate was83%. MDA content also increased and reached the maximum153%after48hour. Theactivity of SOD and CAT always kept decreasing, and reached the minimum of27%and33%after96and48hour, respectively. The results showed that algicidalsubstances of B1was mainly attributed to the decreased activity of SOD, CAT andperoxidation enhancement of the cellular membrane which resulted in the growthinhibition of Phaeocystis globosa.To obtain the algicidal components of strain B1, a series of purified techniquesincluding ethanol precipitation, organic solvents extraction, dialysis, rotaryevaporation, gel filtration chromatography and HPLC were used. And five of thesealgicidal components were purified. Through the series of techniques about structureidentification involved UV and infrared spectroscopy, the results showed the extracellular active substances were soluble in water with high polarity, and themolecular weight was less than3.5kD. The purified techniques of ethanolprecipitation and organic solvents extraction could not enrich effectively algicidalcomponents. All of the results showed that the active substances were belong toaliphatic amide class and contained different chemical groups.