Microbial Diversity Of Four Natural Forages Silage In Hainan Island And Screening Of Excellent Lactic Acid Bacteria

To analyze the microbial diversity of tropical natural forage,as well as the impact of environmental factors on it,select excellent lactic acid bacteria strains suitable for tropical silage,natural herbaceous forage plants such as Saccharum arundinaceum,Microstegium vagans,and woody forage plants such as Leucaena leucocephala and Broussonetia papyrifera were collected from different climatic regions in Hainan Island and ensiled using vacuum bag method,The third generation of high-throughput sequencing(Pac Bio II)was used to analyze the bacterial diversity in raw materials and silage;At the same time,excellent lactic acid bacteria in silage were screened and validated for king grass silage.By analyzing the chemical composition,fermentation quality,and microbial diversity of silage,the effects of environmental factors and plant species on microbial diversity of silage were systematically studied,as well as the effect of selected excellent lactic acid bacteria on silage of king grass,in order to provide a theoretical basis for developing lactic acid bacteria preparations suitable for tropical forage silage,The results are as follows:1.There are differences in microbial community on the different climatic regions and different types of plants.The abundance of harmful bacteria is high,mainly including Enterobacter cancerogenus,Pantoea ananatis,and Cenchrus americanu.The abundance of lactic acid bacteria is relatively low,mainly including Weissella cibaria、Lactococcus lactis、Leuconostoc lactis.Lactic acid bacteria are mainly distributed in Qiongzhong,Haikou,and Sanya;There are abundant lactic acid bacteria attached to the surface of Microstegium vagans in plants.There is a certain correlation between the microbial composition on the surface of forage and environmental factors.There is a significant correlation between harmful bacteria such as Pantoea and longitude,latitude,and rainfall.There is a significant correlation between Weissella cibaria and rainfall,average temperature2.There are significant differences in the fermentation quality and silage microorganisms of tropical natural forage in different climatic regions and types of plant.The fermentation quality of silage in Sanya is the best among regions,while Qiongzhong is the worst;Among plants,Leucaena leucocephala has the best fermentation quality,while Broussonetia papyrifera has the worst.Climate regions and plant species has a significant impact on α diversity of silage microorganisms,with Sanya being the highest and Changjiang being the lowest among regions;Among the plants,the Broussonetia papyrifera is the highest,and Leucaena leucocephala is the lowest.After silage,the types and abundance of lactic acid bacteria have significantly increased.The main lactic acid bacteria are Pediococcus pentosaceus,Lactobacillus plantarum,Weissella paramesenteroides,Leuconostoc pseudosenteroides,and Paucilatobacillus vaccinostercus;The relative abundance of lactic acid bacteria is higher in Changjiang and Sanya,and lowest in Wanning;The lactic acid bacteria in the silage of Saccharum arundinaceum、Microstegium vagans and Leucaena leucocephala are relatively abundant,while the lowest is in the Broussonetia papyrifera.There is a significant correlation between longitude,latitude,rainfall,and average temperature in environmental factors and silage microorganisms,while there is no significant correlation between altitude and silage microorganisms.3.In this study,a total of 98 strains of lactic acid bacteria were isolated and 4 dominant strains were selected.After identification through 16 S rDNA sequencing,10 D,13C,and 14 B are Lactiplantibacillus plantarum,and 15 B is Pediococcus acidilactic.Among the four representative strains,13 C grows well and has fast acid production rate,while 10 D has strong acid production ability.14 B grows well when pH=3.0 and it has good acid resistance;All strains grow well at 50℃ and have strong high-temperature resistance.4.Adding 4 excellent strains and 3 commercial strains to the king grass silage cannot significantly improve the silage quality compared to the control,all treatments have pH value between 4.6 and 4.8.But they have an impact on the diversity of the microbial community in the king grass silage.The 10 D and 15 B significantly increase the relative abundance of beneficial bacteria,including Weissella cibaria and Leuconostoc lactis;LPLB has increased the abundance of Leuconostoc buchneri.