The Primary Study On Fungal Diversity And Enzyme Activities In Marine Sediments In The South China Sea

In recent years, with a lot of development and utilization of land resources, exploitationof marine resources, especially marine microbial resources, attracted more and more people’sattention. The special survival environment of the marine microorganisms made the uniquecommunity structures, genetic characteristics and physiological mechanisms, which lead tothe biological research of marine microorganisms become one of the world’s hotspots. Marinefungi, as one of the big group of marine microbial, was also paid attention to by manyresearchers.The materials were11marine sediment samples get from the South China Sea. Fungiwere isolated by a dilution-plate method, and their preliminary identification was studiedbased on fungal morphological characteristics and rDNA ITS (Internal Transcribed Spacer)sequences. In consideration of the important functional enzymes in industrial application,using six special selective medium screened by enzyme activity production of fungal, andstudied the enzyme production conditions of one of the fungal harboring comparativelyhigher enzyme production. The research methods and results are as follows:(1) Using salt Czapek Dox medium, YPD medium, cornmeal agar medium, MEAmedium, modified PDA medium, Sabouraud medium and bean sprouts medium withampicillin as antibacterial agents,1689strains of fungi were isolated from11marinesediment samples and initially classified as41fungi with eliminate duplicates. YPD mediumwas the optimal isolation medium. Morphology and ITS sequence analysis identified thesefungi belonged to15described genera: Acremonium, Acrodontium, Alternaria, Aspergillus,Bjerkandera, Chaetomium, Cladosporium, Dichotomomyces, Eurotium, Gibberella,Myrmecridium, Paecilomyces, Penicillium, Pseudozyma and Saccharomyces. Of whichAspergillus sp. and Penicillium sp. were the dominant populations. Among them8m,25mand95a only can be identified to genus; the rest38fungi were identified as25morphospecies.So species diversity of marine fungi in this region was more abundant.(2) Using transparent circle method, the fungi have been sequenced were screened on the special selective medium, each of the strains on the plate have three repeats,28°Ccultivation3-7d. Measuring the diameter of the transparent circles of different strains and thecolony diameter, the differences (D values) indicated the size of enzyme activities. Studied onenzyme activities of41sequenced strains showed that8strains produce cellulase,9strainsproduce amylase,5strains produce compound enzyme (Main including protease, amylaseand xylanase activities),16strains produce protease,3strains produce lipase and no strainproduce chitonsanase. Among which seven fungi strains produced three enzymes and fourfungi strains produced two enzymes. Penicillium sp.41m produced comparatively higherprotease, while Acrodontium sp.8m and Aspergillus sp.86b produced the most compoundenzymes.(3) Utilizing shake flask fermentation cultivated Aspergillus sp.86b, which producedcompound enzyme. The conditions of the enzyme production were culture temperature,culture time, initial pH value and inoculum size. Univariate tests and orthogonal test showedthat the primary and secondary order of the influencing factors ingredient for Aspergillus sp.86b produced enzyme rank as culture time, inoculum size, culture temperature and initial pHvalue. The opitial conditions for producing compound enzyme were culture temperature28°C,culture time3d, initial pH6.5and the inoculum size6%.There were abundant marine fungi resources from marine sediment samples in the SouthChina Sea. The marine fungi displayed a strong potential value of enzyme production strainsand more strains had enzyme activities. Therefore, the microbial resources of marinesediment samples in the South China Sea were worthy of further research.