Effects Of Different Oscillating Methods On Bacterial Biofilms

In the process of food production and transportation,food raw materials often exposed to various food processing equipment,such as vibrating screens,conveyor belts,mixers,fermenters.Vibrio parahaemolyticus(VP)and Listeria monocytogenes(LM)are common foodborne pathogens that can adhere to the surface of food processing equipment to form biofilms.At present,the research on the growth process of food-borne pathogenic bacteria biofilm mainly focuse on the formation process of the biofilm under static environment.However,the formation process of the biofilm growth under vibration conditions in the food production environment.This study mainly simulated different vibration culture conditions,and initially explored the effects of vibration on the biofilm formation,and structure.This study provides a theoretical reference for the selection of different vibration processing equipment in the food industry and food safety risk assessment.This paper mainly studies the formation of biofilms of two common foodborne pathogens,VP and LM.In the food production environment,the bacteria are diverse,and the biofilm may be formed by various mixed bacteria.Therefore,this study first explored the formation process of mixed biofilm of Vibrio parahaemolyticus and Listeria monocytogenes on the surface of glass and stainless steel;then explored the effects of different vibration modes on the growth of bacterial biofilm;explored the structure characteristics of the biofilm under vibration.and explored the influence of vibration on the uniformity of the biofilm from the macroscopic to the microscopic aspect.The main research contents and research results are as follows:1.Formation of Vibrio parahaemolyticus-L.monocytogenes mixed biofilmIn this study,we use crystal violet staining method to detect the formation of VP,LM and Mix on the surface of glass and stainless steel,the amount of single bacteria culture and mixed biofilm,the biovolum and the growth variability during biofilm formation were analyzed.The formation of the biofilm was observed by confoeal laser scanning microscopy The change in biovolum during the growth of the biofilm was analyzed.As a result,it was found that the formation ability of the mixed biofilm was between VP and LM.Biofilm formation ability: VP>Mix>LM in the early stage of biofilm development,Biofilm formation ability: LM>Mix>VP in late development of the biofilm.VP,LM and mixed biofilms show similar growth trends: rising at first and then falling.At 48 h,the amount of VP and mixed biofilm formation get to peak time,and the amount of LM biofilm formation was the highest at 60 h.The biofilm formation process is mainly divided into three stages,the initial adhesion period,the development maturity period and the dispersion period.VP and LM adhere to the surface of glass and stainless steel,and continue to grow,covering the surface of the material gradually.The structure of the biofilm become complex,and the fluorescence intensity is gradually enhanced,eventually forming a mature biofilm with a three-dimensional structure.With the incubation time increasing,the biofilm enters the dispersion phase,and the amount of biofilm begins to decrease gradually,We can find gap appears on the surface of the material.There are differences in the amount of bacterial biofilm formation between glass(GS)and stainless steel surface(SS),VP(GS)> VP(SS);Mix(GS)<Mix(SS);During 36 h,LM(GS)<LM(SS).Through the analysis of coefficient of variation,it was found that the variability of the biofilm growth on the surface of the glass: Mix> LM> VP,the variability of the biofilm growth on the surface of the stainless steel: VP> LM> Mix.2.Effects of different vibration cultures on the growth of biofilmIn this paper,crystal violet staining and laser confocal microscopy were used to detect the formation of biofilm under horizontal rotating vibration,bevel vibration and vertical rotary vibration.The biofilm growth trend is rising first and then falling;the biofilm formation peak time is 48-60 h;on the stainless steel surface: VP,LM and Mix biofilm formation ability: static > horizontal rotary vibration >bevel vibration > Vertical rotary vibration;vibration culture conditions have the same growth trend as static culture biofilm on glass surface.Compared with static culture,VP,LM and Mix biofilms showed different degrees of reduction.The amount of biofilm reduction in some time periods exceeded 90%.Vibration causes a significant difference in biofilm growth.Vibration culture has little effect on the growth of VP biofilm,and has a great influence on Mix.Direct observation of the growth of the biofilm by confoeal laser scanning microscopy revealed that the fluorescence intensity was positively correlated with the film growth.The vibration causes the initial aggregation of VP and LM less on the surface of the material,the formation of the biofilm is slow,and it is impossible to cover the entire surface of the material,and there is a gap between the biofilm and the surface of the material.The fluorescence intensity is significantly weaker than the biofilm of the stationary culture..3.Effects of different vibration culture methods on the structure of biofilmThe change of the structural properties of the biofilm under vibration conditions was analyzed by ISA.Furthermore,the influence of vibration on the heterogeneity of VP biofilm was analyzed from macro to micro.The results show that the general trend of the influence of vibration on the biofilm is the porosity,homogeneity and the biofilm roughness increase,the structure entropy decreases.The vibration causes inhomogeneity of the VP biofilm at different positions,the biofilm at the center point is higher than the average biofilm thickness of the biofilm at the peripheral site,the structure is relatively dense,and the porosity are smaller.Different vibration modes lead to different interactions between the medium and the biofilm on the surface of the material,and the growth of the biofilm is different.Bevel vibration culture: The biofilm located at the vibration axis compared with the outer side of the shaft: the biovolume of the biofilm is high,the porosity is low,and the average biofilm thickness is high.,the biofilm growth is relatively uniform under rotary vibration culture and static culture.