Effect Of Oxidation-reduction Potential On The Biomass Of Lactobacillus Casei Zhang In Culture System

In this experiment,the changes of oxidation-reduction potential and biomass of Lactobacillus casei Zhang in static culture system were monitored,and the oxidation-reduction potential of Lactobacillus casei Zhang in high density culture environment was treated by injecting sterile air and adding oxidant potassium ferricyanide solution respectively.To explore the effects of culture systems with different ORP values created by two ORP control methods on the biomass of Lactobacillus casei Zhang,the experimental results are as follows:（1）In the static culture process of Lactobacillus casei Zhang,three ventilation strategies were set for the experimental group:whole-process sterile air of 2.0 L/min,tank top air pressure preservation and tank top nitrogen pressure preservation.The experimental results showed that three different ventilation strategies formed three different ORP environments.ORP is always in oxidation state in the culture environment through 2.0 L/min air;ORP is always in reduction state in the culture mode of nitrogen pressure holding on top of tank;ORP is in a trend of first decreasing and then rising in the culture mode of air pressure holding on top of tank;ORP is only in oxidation state for a little time during the culture process.As static culture would be inhibited by acid,ORP changes under the three different ventilation strategies were all correlated with acid production rate,which could indirectly reflect the activity of bacteria.At the end of logarithmic growth,the number of viable bacteria in the three groups of experiments was:Through 2.0 L/min air group（1.52±0.021）×10⁹CFU/m L,tank top air pressure holding group（1.76±0.033）×10⁹CFU/m L,tank top nitrogen pressure holding group（1.95±0.035）×10⁹CFU/m L,due to acid inhibition,The number of viable bacteria still increased a little after entering the stable period,and the maximum number of viable bacteria in the three groups reached（2.02±0.028）×10⁹CFU/m L.At the end of logarithmic growth,the density OD_600nmof the three groups were as follows:the whole-pass 2.0 L/min air group OD_600nm=2.729±0.021,the tank top nitrogen pressure holding group OD_600nm=3.1795±0.018,and the tank top air pressure holding group OD_600nm=3.102±0.011.（2）In the constant pH batch culture high density culture system,through sampling of viable bacteria number,OD_600nm,wet and dry bacteria yield of Lactobacillus casei Zhang during the culture process,the results showed that different ORP in the culture system had significant differences on the biomass of Lactobacillus casei Zhang（P<0.05）.The number of viable bacteria,OD_600nm,and the yield of wet and dry bacteria were significantly higher than those in the other groups（P<0.05）in the-300m V control group with potassium ferricyanide solution.Under-300 m V ORP condition controlled by potassium ferricyanide,the number of viable bacteria in the medium could reach（2.38±0.46）×10¹⁰CFU/m L,which was 1.15 times that of nitrogen pressure holding group under the control of potassium ferricyanide,1.32 times that of-200 m V,1.37 times that of-100 m V,and 1.45 times that of 0 m V,is 1.74 times+100 m V;At the same time,it is higher than the ventilation control of all experimental groups,which is 1.35 times of air pressure holding tank top,2.38 times of-250m V,2.52 times of-200m V,2.54 times of-100m V,2.56 times of the whole-pass 2.0 L/min air group.（3）By drawing static growth curves of Lactobacillus casei Zhang under different concentrations of potassium ferricyanide,it can be seen that adding 1～5 g/L potassium ferricyanide in MRS Medium will not have toxic effects on Lactobacillus casei Zhang.In conclusion,it is screened out in this experiment that when ORP of-300 m V is regulated by adding potassium ferricyanide solution,the maximum microbial biomass can be obtained at the end of Lactobacillus casei Zhang logarithmic growth.Under this ORP condition,the number of viable bacteria is the highest,the concentration of bacterial bodies is the highest,the yield of wet bacterial bodies is the highest,and the yield of dry bacterial bodies is the highest.This study provides a new method and a new idea for optimizing the high density culture of lactic acid bacteria and provides basic data for the development of lactic acid bacteria resources in the later stage.