Antimicrobial Mechanisms Of Air Disdischarge Against Spoilage Organism On Lotus Root Postharvest

Lotus root is a kind of high moisture content, crispness of aquatic vegetables, but rot caused economic losses in the process of storage. Currently, a lot of measures preventing lotus root brown stain, including chemical methods and physical methods, can not effectively inhibit the growth of microorganisms during storage and transportation, chemical anti-rot methods usually cause a safety hazard, air discharge is a kind of green、 safety anti-rot methods. In this paper, pathogenic bacteria isolated from lotus root rot has been treated by air discharge, and the antibacterial action was reaserched by cellular level and molecular level, related enzyme activity and respiratory metabolism aspect and so on, to reveal antibacterial mechanism of spoilage organisms from lotus root postharvest rot by air discharge.The main research contents are as follows:(1) Lotus root postharvest pathogens was identified by morphology and molecular biology, Fusarium tricinctum was determined as lotus root postharvest pathogens, which is different from Fusarium.oxysporum f.sp.nelumbicola isolated from Lotus root preharvest.(2) Cross crossover、hollow glass and headspace gas analyzer method were used to determine the effect of hypha growth, spore germination, and hypha breathing by air discharge. The mycelium growth, spore germination, mycelium breathing of F. tricinctum were inhibited significantly. The longer the processing time, the stronger the inhibition. Ozone+NAI treatment on hypha growth, spore germination, respiratory inhibition was superior to the individual treatment of Ozone and NAI.(3) Conductivity method、digestion method、spectrophotometry and thiobarbituric acid method were used to determined the effect of f. tricinctum cell wall、cell membrane permeability and related enzymes by air discharge. Scanning electron microscope found that the surface of the hyphae was strongly deformed and concaved by Ozone treatment; Mycelium surfaces appear shrink by NAI treatment; hyphae surface was badly damaged, strongly deformed、shrinked、depressed by Ozone+NAI treatment. Transmission electron microscope found that hyphae cell became not clear, decreased in the number of mitochondria, and leaked a large inclusions, cell wall became thin obviously compared with control hyphae cell. Apoptosis detection test found that air discharge can significantly induce F.tricinctum spores apoptosis, lead to the accumulation of mitochondrial ROS, prompting the mitochondrial membrane potential hyperpolarization, cause apoptosis.(4) F.tricinctum was treatment by air discharge, with the extension of processing time, the cell wall and cell membrane permeability increased gradually. The cell membrane lipid peroxided deeply, the accumulation of MDA increased gradually. F. tricinctum cell wall and cell membrane under the Ozone + NAI treatment were damaged than the condition of the same treatment time Ozone, NAI alone significantly(P<0.05). Three different processing conditions can make the cell wall degradated enzymes of galacturonic acid enzyme, polymer β-D- glycosidase enzymes were significantly reduced, the Ozone + NAI treatment on inhibition of two enzymes activity is superior to Ozone, NAI treated separately(P<0.05).(5) The effect of F. tricinctum mitochondria compound enzyme and ATP enzyme activity by air discharge in vitro, living condition. The results showed that air discharge can not significantly inhibit mitochondria enzymes and the ATP enzyme activity. In living conditions, F.tricinctum was treatment by air discharge for 24 h, mitochondria composite enzymeⅠ、Ⅱ、Ⅳ and ATP enzyme activity significantly increased, but mitochondrial activity of compound enzyme Ⅲ significantly reduced after 3 days, but mitochondria composite enzyme and ATP enzyme activity significantly increased after 6 days.