Research Of The Forming And Influence Of Biofilm Of Thermoduric Bacteria In Wet Milk Powder Process

The formation of thermoduric bacteria biofilm in wet milk powder process makes the thermoduric bacteria have a stronger ability resistance to the external stress environment,meanwhile,causes the risk of secondary pollution.Hence,research of thermoduric bacteria biofilm will be contributed to control the thermoduric bacteria in milk powder process,which can improve the rate of qualified products and make assurance.Firstly,thermoduric bacteria had been separated and identified with the method of microbial culture GB4789.2 and 16 S rDNA full sequence detection.The research was aimed to investigate to the distribution of thermoduric bacteria in milk powder production of raw materials and study its physiological and biochemical characteristics.The growth characteristics and differences among from isolated strains were analyzed by determined each microbial growth curve and pulsed-field gel electrophoresis.Secondly,the regularity of microbial spread from thermoduric bacteria biofilm in milk powder process was studied in different factors e.g.temperature,milk concentration,metal ions and strains.Finally,microorganisms diversity and dynamic changes in thermoduric bacteria biofilm had been studied by means of scanning electron microscopy and the technology of metagenome to clear its microstructure and forming mechanism.The main contents and achievements of this article are as follows:1.A total of 18 strains of spore formation have been isolated and identified that belong to 4 species.B.cereus,B.lincheniformis and B.subtilis are in the range of central spore and A.flavithermus is in the ranger of terminal spore.2.5 isolated model strains were grown vigorously in the temperature of 37±1?.Other strains could grow in the temperature of 55±1?,apart from A.flavithermus and B.cereus.Range from 25 to 34 DNA fragments of PFGE patterns were generated from 5 isolated model strains,which mainly concentrated in the length of 10-200 kb.3.Biofilm has an ability to spread microorganism that will to be new source of pollution in milk powder process.There is a key point about microbial spread of biofilm at 4.5h in the temperature of 55±1?;The temperature of 65±1? will be beneficial to the formation of spores,meanwhile inhibiting the formation of biofilm;Metal ions will play a catalytic role in microbial growth and microbial spread.The experiment result about the formation of biofilm by single strain revealed that the quantity of microbial spread showed a growing trend within 12.5h and made microorganism possess a stronger ability to thermophilic.4.The formation of thermoduric bacteria biofilm caused the thermoduric bacteria being wrapped and formed a stable structure so that can provide them from external stress environment.5.Microoganisms are higher diversity in milk powder production of raw materials,while gradually decrease along with the formation of biofilm.In the process of the formation of thermoduric bacteria biofilm,AnoxyBacillus and Enterococcus gradually decrease.GeoBacillus will be more easier to adhere to the inner wall of stainless steel tube as an earlier stage colonization,forming primary biofilm.And Bacillus,as a later stage colonization,will be dominant strains in the later period,gradually form a top-level thermoduric bacteria biofilm.The main content of this article included biological characteristics of thermoduric bacteria,the regularity of microbial spreaded from thermoduric bacteria biofilm,microstructure and microorganisms diversity.Research found that the formation of thermoduric bacteria biofilm would increase production costs and reduce the quality of production of milk powder.Hence,research of control the formation of biofilm would be emphasis and direction in milk powder process in the future.