Study On Diversity Of Microbial Community Structure Of Edible Fungi During Storage And Modified Atmosphere Preservation Of Panus Giganteus

Edible fungus are favored by consumers because of their delicious taste and rich nutrition.In recent years,the edible fungi industry has developed on a large scale as a poverty alleviation project.Edible fungus have high water content and maintain metabolic activities by consuming their own nutrients after harvest.Because edible fungi have no epidermis protective tissue.They are easily infected by exogenous microorganisms in the process of storage,transportation and circulation,resulting in corruption and loss of commodity value,which restricted the development of the edible fungus industry.In this study,Panus giganteus,Agrocybe cylindracea,hypsizygus marmoreus and Lentinus edodes were taken as the research objects,and the surface microbial community structure diversity and dominant rot-causing bacteria of four kinds of edible fungi stored at4?were comprehensively analyzed by high-throughput sequencing technique.Secondly,the changes of total bacterial count,storage quality and enzyme activity on the surface of Panus giganteus under three different modified atmosphere packaging conditions were further studied,and the best gas proportion condition of modified atmosphere packaging was determined.The purpose of this study is to provide theoretical basis and feasible reference for the study of Panus giganteus fresh-keeping technology.The main results are as follows:1.In this paper,16S r DNA high-throughput sequencing technique was used to detect the diversity of microbial community structure in four kinds of edible fungi,including Panus giganteus,Agrocybe cylindracea,hypsizygus marmoreus and Lentinus edodes,16S r DNA high-throughput sequencing results show that:(1)A total of 250731 high-quality and effective sequences were obtained from 4edible fungi samples of Panus giganteus,Agrocybe cylindracea,hypsizygus marmoreus and Lentinus edodes,covering 7 phyla,14 classes,24 orders,48 families,106 genera of microorganisms.(2)The diversity of microbial community structure is the most abundant in hypsizygus marmoreus,followed by Agrocybe cylindracea and Shiitake,and Panus giganteus have the lowest microbial community structure diversity.(3)Proteobacteria is the dominant phyla of Panus giganteus,Agrocybe cylindracea,hypsizygus marmoreus and Lentinus edodes.(4)Pseudomonas is the dominant genus on the surface of Panus giganteus,Agrocybe cylindracea and hypsizygus marmoreus;the dominant genus of Lentinus edodes are Serratia and Ewingella.2.The effects of modified atmosphere preservation on Panus giganteus were studied with three gas ratios of 5%O₂+15%CO₂+80%N₂,10%O₂+10%CO₂+80%N₂ and15%O₂+5%CO₂+80%N₂ respectively.The results showed that:(1)Modified atmosphere packaging with 5%O₂+15%CO₂+80%N₂ can effectively inhibit the growth and reproduction of microorganisms on the surface of the fruit body of Panus giganteus.The total number of microorganisms on the surface of the fruit body is still less than 5.0 Lg CFU/g when stored to the 15th day.The total number of microorganisms in the control treatment group was close to 5.0 Lg CFU/g on the 9th day.Modified atmosphere preservation of 5%O₂+15%CO₂+80%N₂ can extend the shelf life of Panus giganteus by 6 days.(2)5%O₂+15%CO₂+80%N₂ modified atmosphere packaging treatment can delay the softening of Panus giganteus,reduce weight loss and respiratory intensity,keep reducing sugar content at a higher level.On the 15th day of storage,the hardness of the 5%O₂+15%CO₂+80%N₂ modified atmosphere packaging group of Panus giganteus is 18 g higher than the control group,and the weight loss rate is 3.6%lower than the control group,the maximum respiratory intensity is about 265 CO₂ mg·(kg·h)^-1,which is 495 CO₂mg·(kg·h)^-1 lower than the control group.The reducing sugar content is 13%higher than the control group.(3)Compared with the control,5%O₂+15%CO₂+80%N₂ modified atmosphere packaging treatment of Panus giganteus can significantly increase POD activity and CAT activity,and delay the aging process of Panus giganteus,reduce the browning degree of Panus giganteus.3.The 16S r DNA high-throughput sequencing technology was used to analyze the microbial community structure diversity of the air control group Panus giganteus under4?storage conditions,and to determine the total number of colonies,hardness,weight loss,enzyme activity and other quality indicators during storage.Study the correlation between the total number of colonies and quality characteristics.The results showed that:(1)During the storage process of the air control group Panus giganteus at 4?.Proteobacteria are the dominant bacteria phylum in the early and mid-late stages of storage of Panus giganteus.Pseudomonas are the dominant bacteria genus in the early and mid-late stages of the storage of Panus giganteus.(2)There is a significant correlation between the total number of colonies and quality characteristics.In summary,the change in the total number of colonies during storage of Panus giganteus at 4°C can be used as a key factor in evaluating the quality deterioration of Panus giganteus.The determination of the total number of colonies during the storage of Panus giganteus can provide a reference for predicting the shelf life of Panus giganteus.Modified atmosphere packaging with 5%O₂+15%CO₂+80%N₂ can effectively control the growth and reproduction of microorganisms and keep the Panus giganteus with better storage quality.Compared with the air control group,the shelf life is extended by 6 days and extended its shelf life to 15 days.