Screening Of AEC-resistant Strain Of Flammulina Velutipes

Improving amino acids quality is major work of agricultural plants breeding.Threonine, lysine, methionine, and Isoleusine which are biosynthesized through the aspartate family pathway are 4 of 8 essential amino acids for humans and monogastric animals and usually lysine is the first limiting amounts amino acids in many agricultural products. S-(2-aminoethyl)-L-cysteine which is lysine analogue plays a vital role in the study of metobolism of asparate-derived amino acids and elevations of these amino acid content. Edible fungi are abundant in nutritions such as amino acids. Firstly, in this thesis, .inhibitions of lysine analogue S-2-Aminoethyl-L-Cysteine(AEC) on mycelial growth of Agrocybe chaxingufwhitej , Pleurotus citrinopileatus, Pleurotus eryngii, Plewrotus tuber-regium, Agaricus blazi and Flammulina velutipes(IM02)were tested and the relativity of inhibitions effect and amino acids content of above edible fungi was also established. Secondly, a selection scheme based on AEC inhibition was applied to isolating AEC resistant strains from UV-irradiated oidida of Flammulina velutipes and comparision of free and total amino acids content was conducted. The work was expected to be the theoretical and practical basis of the study of breeding of aspartate family amino acids-rich strain of edible fungi and metobolism of amino acids. 1 .Mycelial growth rate of Agrocybe chaxingufwhite) , Pleurotus citrinopileatus, Pleurotus tuber-regium, Pleurotus eryngii, Agaricus blazei and Flammulina velutipes (IMQ2) was measured when they grow in the minimal medium and complete medium which comprised different concentrations of AEC and ICso of inhibition of AEC on mycelial growth rate were calculated .2.The death rates of UV-irradiated and Co60 -irradiated oidida of Flammulina velutipes were tested.3.A selection scheme based on AEC inhibition was applied to isolating AEC resistant strains from UV-irradiated oidida of Flammulina velutipes and free and total amino acids content were determined.4.The hybridation of AEC-resistant strains and the wild strains with IS02 were conducted to examine the authenticity of these strains.1 .The results showed that ICso of inhibition of AEC on mycelial growth rate of Agrocybe chaxingufwhite) , Pleurotus citrinopileatus, Pleurotus tuber-regium, Pleurotus eryngii, Agaricus blazei and Flammulina velutipes (IMQ2) in the minimal medium was 5754.1 ? 159.4, 21.7, 1158.8, 361.8 and 24.8mg.L~1 respectively and IC50 of inhibition of AEC on mycelial growth rate of Agrocybe chaxingufwhite , Pleurotus citrinopileatus, Pleurotus tuber-regium, Pleurotus eryngii and Flammulina velutipes(lM02) in the complete medium was 379751.1, 402.2, 244.9,1576.7 and 2792.3mg.L~1, respectively .which were different significantly.2.The death rates of UV-irradiated and Co60 -irradiated oidida of Flammulina velutipes were in conformity with the quadratic equation Y=3.7833+7.7874X-0.1481X2 and Y=0.4315+ 0.5768X-0.0008X2 through curve estimation.3. One AEC resistant strain was isolated by screening UV-irradiated oidida of Flammulina velutipes and were confirmed after five replicates. The resistant strain contained much higher concentrations of free threonine, methionine and alanine than the wild strain of IM02.4.The authenticity of the mutant strain was confirmed by the hybridation test. [Conclusions]It was estimated that sensitivity of enzymes on end products in the feedback pathway of aspartate family amino acids biosynthesis were different significantly in the edible fungi. The results would cast a promising perspectives on strain improvement work of edible fungi to high aspartate family amino acids.