The Screening, Identification And Component Analysis Of The Antarctic Fungi Against Aquatic Pathogens

China is the largest country of fish production,consumption,processing and exporting.However,the spread of fish diseases affects the sustainable development,wherein,Aeromonas hydrophila is among common fish pathogens.According to the number and species analysis,Antarctic fungi may be the species with widest biodiversity in the region.The development of active substances from polar microbes is in the ascendant,wherein the antimicrobial activity may act through its secondary metabolites which are therefore potential drug sources.Based on Antarctic fungi as the main object,this paper firstly screened Antarctic fungi containing secondary metabolites antagonism aquatic pathogenic bacteria,including fungal culture behavior observation,product separation and screening.Then we identified this fungal by morphology and molecular method,and recorded the characteristics during fungal fermentation process.Finally we performed active tracking and structure identification of antimicrobial component.The main results are as follows:23 strains of Antarctic fungi were fermented for 10 days and extracted separately,wherein extract content was 28-190 mg per 1L fermentation liquor.By kirby-bauer method,the fermented product of strain B-7 was proved to be highly sensitive to Aeromonas hydrophila ATCC 7966,Vibrio anguillarum HLPF and Streptococcus agalactiae.The strain B-7 conformed to the common features of basidiomycete through morphology and microscopic observation.After comparison and evolutionary tree analysis by 18 S rDNA and ITS sequence,strain B-7 was most likely to belong to Bjerkandera spp.of Meruliaceae.During fermentation process,the pH value of B-7strain increased after decrement,while the residual sugar curve decreased.After batch fermentation,total 20 g extract was obtained from 160 bottles of fermented liquid.Active component was separated and purified from fermented product through active tracking method.Among active component two compounds were identified by nuclear magnetic resonance spectrum and mass spectrum,named veratric acid and erythro-1-(3,5-dichloro-4-methoxy phenyl)-1,2-propanediol wherein the former was isolated from fungus for the first time.Furthermore,3-chloro-2-methoxy benzoic acid and 4-chloro-2-methoxy benzoic acid were identified by GC-MS.The non-active component hellebore aldehyde was also identified by nuclear magnetic resonance spectrum.It was indicated that the antibacterial activity of fermented product dispersed and reduced with the continuous separation,and there were more than one active product.In this experiment,three typical bacteriostatic models were used to screen and validate the in vivo and in vitro antimicrobial activity of fermentation extract of Bjerkandera spp.from the Antarctic Pole for the first time.Then two compounds with development potential of antimicrobial agents were identified using active tracking method,wherein one was the first time to isolate from fungus.This research provides a reference for the development of new drugs antagonism aquatic pathogenic bacteria.