Nature Of The Filamentous Marine Fungi Nematicidal Metabolites And Fermentation Conditions

Marine fungi were now highly concerned about for their potential bioactive substances based on their variety and genetic background, as well as their special habitat. Three marine filamentous fungal strains of MTJ5-3-1, MTJ4-2-1, MTJ5-1-4 from Bohai Gulf were sought for the nematicide. Among them, MTJ5-3-1 was proved the most efficiency of nematicidal effect. Based on this, its optimum condition including pH, temperature and nutrition were evaluated. Moreover, physico-chemical properties of the nematicidal components from the metabolites were detected based on lethal rate on pinewood nematode (Bursaphelenchus xylophilus). The results were summarized as follows:a. Nematicidal effects of MTJ5-3-1,MTJ4-2-1,MTJ5-1-4Preliminary studied of the nematieidal bioactive substances obtained from MTJ5-3-1 MTJ4-2-1 MTJ5-1-4 showed that all the three filamentous strains were strong efficiency in against pinewood nematode separately with 93.85% 85.37% and 92.25%. Among them, MTJ5-3-1 was the most efficiency of nematicidal effect (level A, lethal rate=90%). b. Optimum condition for the fermentation of MTJ5-3-1 strainAccording to the results of single factor and statistical analysis, the optimum marine aquatic medium was composed of glucose 10g/L, peeled potato 150g/L and yeast extract 2g/L, sea-water 500-600ml/L with nature pH. The optimum inoculate quantity was 2×106 spores. Fermentation was performed under the conditions of 120r/min,26℃for 4 days. c. Qualitative analysis of MTJ5-3-1 nematicidal activity metabolitesFirst of all, the fermentation broth of MTJ5-3-1 was hyper-filtrated in order to remove the macromolecules that over 6000 dalton, substances remained were extracted subsequently by water-saturated ethyl acetate and water-saturated n-butanol. The water-soluble component was then collected and determined with a lethal rate of 97.85% in nematicidal activity. Instrumental analysis including spectro-comparator and chromatography shown the product was characterized by nitrogenous saccharides or its derivants, involving 4 heat-stable components and neutral properties. d. Identification and classification of MTJ5-3-1 strainMorphological characteristics of MTJ5-3-1 strain suggest that the MTJ5-3-1 strain might belong to the genus Acremonium. The results of molecular biological assay on ITS sequences showed 100% homology with Acremonium sp. NJM 0672 and Acremonium sp. NJM 0567. According to the results, MTJ5-3-1 strain should be Acremonium sp MTJ5-3-1.