A Poptosis Of Sweet Cherry Rot-causing Mould Induced By Phenyllactic Acid And Its Application In Sweet Cherry Preservation

Sweet cherries are very popular with consumers,but are highly susceptible to microbial decay,which causes untold economic losses every year.Phenyllactic acid(PLA)is a new natural organic acid that has been discovered in recent years and has a broad spectrum of fungal inhibition without toxic effects.Mucoraceae is an extremely common pathogenic fungus on sweet cherries,causing spoilage and posing a risk to humans.In this study,the indicator fungus Mucoraceae reesei was selected to study the inhibitory effect and mode of action of PLA on Mucoraceae reesei and to apply PLA to the preservation of sweet cherries.The main findings of the study are as follows:1.PLA played a significant inhibitory effect on the growth of Mucoraceae reesei,where the minimum inhibitory concentration(MIC)was 12 mmol/L.The growth of Mucoraceae reesei could be better inhibited at this concentration,and the mycelium of Mucoraceae reesei acting on PLA was observed by scanning electron microscopy and transmission electron microscopy.The results showed that the mycelium of Mucoraceae reesei did not show any obvious rupture or breakage,but there was obvious deformation within the mycelium,presumably targeting the inner spores.2.PLA caused the death of Mucoraceae reesei spores by apoptosis: DAPI(4’,6-diamidino-2-phenylindole)staining of Mucoraceae reesei spores 4 h after the action of PLA showed that the structural integrity of PLA-treated Mucoraceae reesei spores was damaged;Hoechst/PI double staining of Mucoraceae reesei spores 4 h after the action of PLA showed that the spores treated with PLA had undergone apoptosis.The results of the TUNEL staining of Mucoraceae reesei spores 4 h after the action of PLA showed that the number of Mucoraceae reesei spores with damaged DNA was increasing after the action of PLA;the results of the reactive oxygen species(ROS)assay of Mucoraceae reesei spores 4 h after the action of PLA showed that PLA significantly increased the accumulation of ROS in Mucoraceae reesei spores.The results of the Caspase-3 enzyme activity assay showed that PLA increased the accumulation of ROS in Mucoraceae reesei spores after 4 h of PLA action,which directly confirms that PLA can cause apoptosis in Mucoraceae reesei.The results show that PLA can cause apoptosis in Mucoraceae reesei.The above can confirm that there is apoptosis in Mucoraceae reesei,and as the concentration of PLA increases,the proportion of apoptosis increases,and apoptosis is its main mode of death.3.The appropriate concentration of PLA can play a role in preserving the freshness of sweet cherries: when the concentration of PLA is 12 mmol/L with low temperature storage and air conditioning packaging can better maintain the gas composition of the package,maintain the brightness,colour and hardness of sweet cherries,delay decay,maintain good aromatic smell,but when the concentration is low(< 3 mmol/L)can not play a role in preserving freshness,higher concentrations of PLA(24 The higher concentrations of PLA(24 mmol/L),although better at maintaining hardness and delaying decay,had a negative effect on the colour and brightness of sweet cherries and damaged the surface gloss.The above experiments showed that PLA could inhibit the growth of Mucoraceae reesei,and the main mode of action was to induce apoptosis of spores,which laid the foundation for the later study of the specific molecular mechanism of PLA-induced Mucoraceae reesei;PLA was applied to the preservation of sweet cherries,and it was confirmed that 12 mmol/L of PLA could maintain the quality of sweet cherries better,which was a new exploration for the development of new biological preservatives.