| The biological characteristics and related active bio-products of Cordyceps bassiana were studied by using fungi isolation and purification, PCR, HPLC and so on. The contents of this thesis were focus on strain identification of Cordyceps bassiana, life history confirmation, optimization of culture conditions for liquid fermentation and artificial cultivation, and the study on the related active bio-products, including polysaccharides and low molecular compounds. The results were showed below:1.Identification of Cordyceps bassian and its life history confirmation: Beauveria bassiana was identified by means of morphology and 16S rRNA sequencing. Results of the life history confirmation of Cordyceps bassiana showed that Cordyceps bassiana and Beauveria bassiana were the same species during the different growth stages. In another word, Cordyceps bassiana was the teleomorph of Beauveria bassiana.2.Optimization of culture conditions for liquid fermentation and artificial cultivation: The liquid fermentation medium and its corresponding culture conditions were firstly optimized according to the one-at-a-time method. The optimum concentration of medium components was then following and determined by orthogonal matrix method. The results of the optimum fermentation medium was as follows: sucrose 25‰(w/v), peptone 3‰, (NH4)2SO4 1.5‰, K2HPO4 1.5‰and MgSO4 0.5‰. The optimum fermentation conditions were as follows: initial pH 7.0, temperature 26℃,medium volume 75mL/ 250mL, inoculums volume 5% (v/v), culture duration 3 days. Under the above optimum nutrition and environmental conditions, the corresponding maximal mycelia yield could obtain 2.135g/100mL, maximal water-soluble exo-polysaccharides production could reach 1.827g/L after 3 day's fermentation. With the same procedure, the artificial cultivation conditions of Cordyceps bassiana were optimized and results showed below: wheat was chosen as the major nutrition for culture under the moisture 70%, culture temperature 22～24℃, and pH 7.0.3.Study of Cordyceps bassiana on its related active bio-products: Results showed that the total contents of protein in sporophore and mycelium were 35.32% and 24.05% respectively, which were lower than that of Cordyceps sinensis. While the content of amino acid in sporohore and mycelium were significant higher than that of Cordyceps sinensis, which were 25.96%and 16.521% respectively. The content of mannitol in mycelium was 12.05%, which was also higher than that in sporophore and wild Cordyceps sinensis.The composition of polysaccharide and identification of nucleosides type were analyzed by GC and HPLC respectively. The results showed that EPS was composed of mannose and galactose in molar ratio of 1.2:1.0, IPS was composed of mannose and galactose and glucose in molar ratio of 5.4:4.0:1.0. There were three kinds of nucleosides, guanosine, uredine and adenosine. The content of every kind of nucleosides in mycelium was higher than that in sporophore or Cordyceps sinensis. The study in this thesis provides a certain scientific basis for further evaluating the Cordyceps bassiana quality and exploiting its potential values.4.Activity assay: Further investigation was focus on antioxidant activities in vitro. The results showed that IPS could exhibit the radical scavenging activities on DPPH, hydroxyl radical, and superoxide radical; moreover, it also showed the ability of chelating Fe2+. In another aspect, EPS could only scavenge hydroxyl radical and chelate Fe2+. Both EPS and IPS had the ability to inhibit the growth of gram-positive bacteria, but had no effects on gram-negative bacteria. Low molecular compounds extracted from ethyl acetate or n-butanol could significantly inhibit the growth of both gram-positive bacteria and gram-negative bacteria. |
