Investigation Of Bacillus Licheniformis And Bacillus Pumilus In Milk Powder Production Process And Genome Analysis Of Bacillus Licheniformis

Bacillus licheniformis and Bacillus pumilus are both Gram-positive bacteria,belonging to the genus Bacillus.These two kinds of bacillus are widely used in animal and plant disease control,environmental management and feed addition,they are also often detected in dairy products,but has not been given enough attention.In the early stage of the laboratory,Bacillus licheniformis and Bacillus pumilus were isolated and identified from a batch of unqualified whole milk powder produced by a dairy company in southern Xinjiang,and through the tie-back test confirmed that these two kinds of bacillus do affect the quality of dairy products.Therefore,investigate the contamination distribution of Bacillus licheniformis and Bacillus pumilus in the milk powder production process,infer its potential pollution path,find the critical control point is essential to guide the prevention and control of microbial contamination of the milk powder production line and the improvement of the production process.At the same time,due to the relatively serious contamination of Bacillus licheniformis,the study conducted whole-genome sequencing of the isolated Bacillus licheniformis and mastered the whole gene data of milk-derived Bacillus licheniformis,laying the foundation for revealing the mechanism of dairy products deterioration.First,50 samples were collected in 10 batches from five key links of the whole milk powder production line(raw milk,concentrated milk,spray drying workshop,fluidized bed and packaging workshop)of a dairy company in southern Xinjiang.The samples were screened by Bacillus thermophilus,and the Bacillus licheniformis ker A specific gene PCR identification,Bacillus pumilus LC01 specific gene PCR identification and 16S rRNA gene sequence analysis were performed to understand the contamination distribution of Bacillus licheniformis and Bacillus pumilus in milk powder production.The results showed that the contamination rates of Bacillus licheniformis and Bacillus pumilus were8% and 4%,respectively.The contamination mainly occurred in the samples of raw milk,concentrated milk and fluidized bed milk powder.Therefore,to prevent and control the pollution of Bacillus licheniformis and Bacillus pumilus,it is necessary to start with the above three key links,all of them,raw milk is the source of pollution,the most important thing is keeping the breeding environment clean and the disinfection of milking,transporting and storing tools,as well as the prevention and treatment of latent mastitis in dairy cows,at the same time,it is suggested to optimize the CIP cleaning technology to remove the biofilm formed by Bacillus in the production line.;We then sequenced the whole genome of Bacillus licheniformis YCRF-2 isolated from milk powder,and analyze its virulence factor,drug resistance gene,metabolite protease and lipase.The whole genome sequencing showed Bacillus licheniformis YCRF-2 contains 27 virulence factors,multiple drug resistance genes,37 protease genes,14 lipase genes and the metabolites contain multiple antibiotics.These results indicate that Bacillus licheniformis does pose a threat to the quality of dairy products,and its safety needs to be reassessed,this study laid a foundation for revealing the mechanism of Bacillus licheniformis effect on the quality of dairy products.