Effects Of Microbial Fermentation Broth On The Growth Of Red Tide Algae

In recent years,the frequent outbreak of red tide and the expansion of its impact scale have brought serious threats to coastal areas.Among all kinds of methods to prevent red tide,microbial control of red tide has become a key research direction.Firstly,this study determined the effects of five microbial fermentation broths on the growth of two species of red tide algae.Ba3 strain fermentation broth with obvious algae inhibition effect was selected to further study for algae inhibition effect of different dosages.Secondly,the active components were separated by organic solvent extraction and macroporous resin,and the molecular weight of the active components was analyzed by LC-MS.Finally,the composition of the interalgal bacterial community of five species of red tide algae,Prorocentrum donghaiense,Alexandrium tamarense,Alexandrium catenella,Skeletonema costatum and Scrippsiella trochoidea was analyzed by high-throughput analysis.The main results are as follows.1.Inhibitory effect of fermentation broth of Bacillus spp.and Saccharomyces cerevisiae on the growth of red tide algaeBa1 strain,Ba2 strain,Ba3 strain,Bacillus subtilis and Saccharomyces cerevisiae fermentation broth at different fermentation time had significant inhibitory effects on the growth of two kinds of red tide algae,and the inhibitory rate of Prorocentrum donghaiense(>91%)was higher than that of Alexandrium tamarense(>80%).The density of algae cells in four different Ba3 strain fermentation broth treatments showed that the more the Ba3 strain was added,the more obvious the algae inhibition effect was.Molecular biological identification showed that Ba3 strains belonged to Firmicutes,Bacilli,Bacillales,Bacillaceae and Bacillus.2.Isolation and Activity of Algae Inhibiting Components from Ba3 Fermentation BrothThe results of crude extraction with organic solvents showed that the algae-inhibiting active ingredients of Ba3 fermentation broth mainly existed in the ethanol extraction phase,and in the aqueous phase of petroleum ether,ethyl acetate andn-butanol.Preliminary analysis by dialysis bag showed that the molecular weight of algae inhibitor was less than 8000.The crude extract of Ba3 strain fermentation broth was adsorbed with HZ830 macroporous resin and gradient eluted with 10%~100% ethanol.The eluting components with algae-inhibiting activity of 10%~50% ethanol were obtained.Among them,the 30% eluting components had the best algae-inhibiting effect.The peak appeared in 5.39 min and 6.20 min and the molecular weight of the two compounds were 537 by LC-MC.It was presumed that they were isomers.3.Structural analysis of the interalgal bacteria in the culture medium of five red tide algae.By means of high throughput sequencing analysis,it was found that the interalgal bacterial community of Prorocentrum donghaiense contains 6 phyla,9 classes,20 orders,24 families and 28 genera.The dominant genera was Marivita(91.33%)and the proportion of unidentified genera was 5.15%.There are 4 phyla,7 classes,19 orders,25 families and 26 genera in the algal bacterial community of Alexandrium tamarense.The dominant genera are Marivita(83.65%),and the proportion of unidentified genera is9.37%.There are 7 phyla,10 classes,22 orders,28 families and 33 genera in the algal bacterial community of Alexandrium catenella.The dominant genera are Marivita(68.07%),and the proportion of unidentified genera is 9.83%.There are 5 phyla,8 classes,17 orders,21 families and 25 genera in the algal bacterial community of Skeletonema costatum.The dominant genera are Altererythrobacter(48.38%),and the proportion of unidentified genera is 34.95%.There are 6 phyla,8 classes,16 orders,21 families and 28 genera in the interalgal bacterial community of Scrippsiella trochoidea.The dominant genera are Balneola(19.68%)and the proportion of unidentified genera is 38.04%.There are 10 genera in the composition of the interalgal bacterial community of the five cultures of red tide algae,4 endemic genera of Prorocentrum donghaiense,2endemic genera of Alexandrium tamarense,8 endemic genera of Alexandrium catenella,3 endemic genera of Skeletonema costatum and 4 endemic genera of Scrippsiella trochoidea.