Study On The Aging Evaluation Indicators Of Auricularia Auricula Liquid Spawn

Aging of spawn has an adverse effect on the yield and quality of Auricularia auricula during the production of A.auricular spawn.However,there are few reports on the aging of liquid spawn of A.auricular currently,especially the lack of scientific indicators for judging the aging of liquid spawn of A.auricular,which can’t be effectively discovered and controlled.In view of this,the A.auricular variety"Hei29、Heiweibanjin and Heiweidanpian"was used as the test material to study the biological characteristics,relevant physiochemical indicators and metabolome of liquid spawn of A.auricular,in order to find a scientific indicators system for evaluating the aging of A.auricular spawn.The main findings are as follows:（1）Result of the biological characteristics on the aging of liquid spawn of A.auricular,showed that the p H value of nutrient solution increased continuously during the cultivation process;The color of the nutrient solution is clear and transparent at the beginning,and becomes darker in the later period,which is earthy yellow;The initial form of mycelium is floating small flocculent mycelium pellets,which are evenly distributed in nutrient solution.and later it gradually becomes larger smooth spherical or burr-like mycelium pellets,which are distributed on the bottom of the shaker bottle when standing;With the increase of mycelial ages,germination time increased continuously,while the growth rate and growth weight increased first and then decreased,indicating that mycelia vitality increased first and then decreased with the increase of culture time.After 12days,the sensory indicators of A.auricular obviously changed and mycelial viability begin to decline,and decrease of viability can be considered as the beginning of mycelium aging,it was determined that the mycelium begin to age at 12 days.（2）The research on physiochemical indicators related to aging of A.auricular hyphae shows that with the increase of mycelial age,the content of catalase,malondialdehyde content,production rate of ascorbic acid and superoxide anion free radicals increased constantly,indicating that catalase and ascorbic acid play a major role in the anti-oxidation of mycelium,while superoxide anionic free radicals increased constantly,the damage to mycelial cells continues to increase,and the degree of membrane lipid peroxidation continues to deepen;The activity of superoxide dismutase and proline content decreased constantly,the decline of superoxide dismutase activity is the main reason leading to the increasing rate of superoxide anion free radicals,the decrease of proline content will inevitably lead to the decrease of mycelial antioxidant capacity;The first increase and then the decrease of peroxidase indicates that it plays a major role in anti-oxidation in the early stage.hydrogen peroxide content first decreases and then increases,indicating that its scavenging ability decreases in the later stage,but the conductivity change has no obvious rules.（3）One-way analysis of variance of related physiochemical indicators shows that superoxide dismutase,catalase,ascorbic acid content,proline content,superoxide anion free radical production rate and malondialdehyde content have certain regularity with mycelial age.It is found that when catalase activity is less than 1.33 U/g、ascorbic acid content is less than 150 mg/100 g、superoxide anion free radical generation rate is less than 1.9 mol/g·min^-1、MDA content is less than 1.33μmol/L、superoxide dismutase activity is greater than 2.53 U/g or proline content is greater than 0.522μg/g,the mycelial vitality and metabolic capacity of liquid spawn of A.auricular begin to decline,and it can be considered that A.auricular is just beginning to age or has a low degree of aging.（4）Hierarchical cluster analysis of differential metabolites shows that there are a total of 73different metabolites,of which 19 are significantly different metabolites,the main categories are carboxylic acids and their derivatives,glycerophospholipids,fatty acyl groups and enol lipids,among them,the content of（+/-）isobutyl 3-methylthiobutyrate and 4-hydroxy-5-（2,4,5-trihydroxyphenyl）valeric acid increased significantly,the content of 3,5-dipentyl-2-hexylpyridine and 15-oxo-5S,6R-dihydroxy-7E,9E,11Z-eicosatrienoic acid has decreased significantly,it can be considered as a marker metabolite for judging aging.（5）KEGG annotation analysis of differential metabolites showed that there are a total of 10metabolic pathways involved in the aging process,including glycerophospholipid metabolic pathways,cysteine and methionine metabolic pathways,and phenylalanine,tyrosine and tryptophan biosynthesis.Glycerophospholipid is an important component in the formation of the lipid bilayer of the cell membrane,and it also participates in regulating oxidative stress.It indicates that the mycelium of A.auricular resists the cell membrane damage caused by membrane lipid peroxidation and the damage caused by aging through glycerophospholipid metabolism during the aging process,at the same time,amino acid metabolism is active,indicating that mycelial cells regulate mycelial cell metabolism by continuously producing and using relevant amino acids to counteract the damage produced by aging on mycelial cells,as well as for their own nutrient consumption and regulation of osmotic pressure.