| Strawberry（Fragaria ananassa）is delicious and nutritious,but it is vulnerable to microbial infection in harvesting and storage because of its high water content and delicate organization.Gray mold is the most common disease of postharvest strawberry,causing serious economic losses.However,most fungicides are chemical synthesis,which are highly polluted,residual and easily resistant to pesticides.It leads to serious food safety problems.Therefore,it is urgent to develop natural,non-toxic and healthy fungicides,which have important application significance for maintaining the quality of strawberry commodities,prolonging shelf life and reducing the loss of storage,transportation and marketing.Glucose oxidase（GOX）is an oxidoreductase that catalyzes glucose to product hydrogen peroxide（H2O2）and gluconic acid.As a safe and efficient additive,GOX has been widely used in the food industry.It has the characteristics of glucose removal,deoxidization and sterilization.However,little research has been done on the preservation of fruits and vegetables.In this study,the effects of GOX on the growth of Botrytis cinerea were determined by the determination of spore germination,integrity of spore cell membrane and transmission electron microscopy observation in vitro.The GOX system was optimized and its products were determined.The mechanism of controlling the resistance of B.cinerea was studied by means of electron microscopy and transcriptome analysis after GOX treatment.The time kinetics of strawberry gray mould resistance regulation was studied.The strawberry decay index,active oxygen level,CAT enzyme activity,POD enzyme activity,PAL enzyme activity and flavonoid content were determined to study the mechanism of GOX system on strawberry gray mould resistance regulation.In this paper,the antimicrobial and fresh-keeping mechanism of GOX on postharvest strawberry gray mold was discussed in order to provide theoretical basis and new technical methods for postharvest strawberry fresh-keeping.The main results are as follows:（1）The antifungal effect of GOX on spore germination and cell structure of B.cinerea was clarified.GOX inhibits the spore germination of B.cinerea by destroying the integrity of spore cell membrane and the morphology of spore cells.（2）The GOX-glucose treatment system was optimized and its mechanism of inhibiting the growth of B.cinerea was revealed.The inhibition rate of 10 g/L glucose treatment was higher than that of others.The content of glucose and pH in medium decreased with the increase of GOX concentration,while gluconic acid and hydrogen peroxide increased.After GOX treatment,the mycelium of B.cinerea was deformed,and the surface of mycelium was rough and shrunken.Besides,the cell vacuolated,and the mitochondria were absent.Transcriptionomic analysis revealed that differential genes were involved in tyrosine metabolism,biosynthesis of phenylalanine,tyrosine and tryptophan,glycine,and serine and threonine metabolism.The results showed that metabolites of GOX-glucose system inhibited the growth of B.cinerea,and destroyed the mycelial structure of B.cinerea.Besides,it changed the overall distribution of Botrytis cinerea genes,and led to changes in the related metabolic pathways.（3）The antimicrobial and fresh-keeping effects of GOX-glucose system on postharvest strawberries were clarified,and the mechanism of its inhibition on the occurrence of gray mold of strawberries was revealed.The metabolite content of GOX-glucose system increased with time.The GOX-10 g/L glucose system was selected to treat strawberries after 24 h,and the related resistance indexes were determined.It was found that the content of reactive oxygen species（H2O2）and related enzyme activities（CAT,POD）,along with the key enzyme activity of phenylpropane metabolism（PAL）and its products（flavonoids）were higher than those of the control group to some extent.The results showed that GOX-glucose treatment increased the level of reactive oxygen species,and the activity of key enzymes in phenylpropane metabolism and the content of products in strawberry,thus inhibiting the occurrence of gray mildew during storage. |
