Study On The Biocontrol Medicament Of Yeast And Its Effect On Preservation Of Winter Jujubes

Winter jujube is easily infected during storage after harvest,accelerate the decay of the fruit,causing unpredictable economic losses.The chemical methods is the main control methods of postharvest diseases of winter jujube in the past,however,winter jujubes are best eaten fresh,During its short storage period,agricultural residues are not easy to be degraded and removed,and the effect is not ideal,which may cause harm to human health and the environment.Therefore,alternative methods which is safe,effective,green and pollution-free is urgently demanded in the storage of winter jujube.Antagonistic yeast biocontrol agents have shown great potential as an alternative to fungicides for the control of postharvest decay of fruits and vegetables,becoming a new research field.Biocontrol medicament of yeast replaces chemical fungicides to prevent and control postharvest diseases of winter jujube,which is of great significance for reducing the use of chemical agents,protecting the environment and ensuring the edible safety of winter jujube.In this study,Rhodotorula mucilaginosa(TY-1)which had antagonistic effect on postharvest diseases of winter jujube was used as experimental materials.Experiments were carried out in aspects of optimization of medium and cultivation conditions,isolation and concentration of yeast cells from the culture,optimization of complex protective agents and preparing the liquid and solid biocontrol agents.Its activity was analyzed,and the inhibition effect of yeast biocontrol preparation on postharvest disease of winter jujube was studied.The main research results were as follows.(1)Optimization of medium and cultivation conditions of Rhodotorula mucilaginosa was based on NYDB basal culture medium.The optimal proliferation medium was 7.00 g fructose,12.00 g peptone,5.00 g yeast powder,3.00 g sodium chloride and 1000 m L water.The concentration of the optimized medium could reach 2.683×10~8cells/m L,which was 4 times before optimization;The single factor test and orthogonal test were carried out on the factors affecting the growth of Rhodotorula mucilaginosa:p H,temperature,inoculum volume and bottling amount.The optimum culture conditions were determined by the range analysis method was 27℃,p H4,and loaded.The bottle volume was 50m L,the inoculum volume was 5%,and the yeast cells concentration could reach 3.49×10~8cells/m L,which is 1.3 times that before the condition optimization.(2)The survival rate of yeast for different protective agent at 4℃,the 5%trehalose+Vc was the best protective agent,the compound protectant combined with trehalose and Vc had a positive protective effect on the survival rate and the maintenance of biocontrol efficacy during the storage period.The liquid biocontrol preparation had a mortality rate of 9%after 15 days.The live yeast cells of the solid biocontrol preparations were subjected to vacuum freeze-drying after centrifugation,causing a certain loss to the number of viable yeast,but the mortality of viable bacteria after 15 days was only 4.6%.(3)The fresh-keeping effect of biocontrol preparations on winter jujube showed that both biocontrol medicament could inhibit the growth of Penicillium citrinum,and the incidence of winter jujube in the liquid control group was about 40%,and that in the solid control group was about30%,and both could reduce the diameter of disease spot in the"live"test of winter jujube.The liquid and solid biocontrol preparations could reduce the decaying rate of winter jujube,maintain the moisture,hardness and soluble solid content of jujube,delaying the degradation of Vc,and inhibiting the increase of titratable acid content,and playing a certain positive effect in PPO enzyme,POD enzyme and PAL enzyme activity,in the experiment of storage and preservation of winter jujube.