The Influence Of Hemin And VitaminK₂ On Growth And Metabolism Of Aerobic Cultured Lactobacillus Casei

Lactobacillus casei was one of the most important probiotic bacterias and was generally used in fermentation and food industry. L.casei was mainly used to produce lactic acid in fermentation industry and added into dairy food as prebiotics in food industry. L.casei would get poor survival when the food was stored in low temperature, transported and sold for there are many stress condition such as oxygen, cold, other organism and so on. Besides, it would also lose activity when in the digestive tract of human for the acid in stomach and bile in intestinal tract. Consequently, high activity and tolerance to stress environment were needed in the use of L.casei. It had been found that some facultative lactic acid bacterias got improved survival and more flavor component production when growth under respiration.Aerobic growth of L.casei ATCC393 was studied to discover the condition of its respiration. It was found in the single factor experiments that when cultured aerobic with the addition of hemin and vitaminK₂, L.casei would keep a high level of survival to 10⁹cfu/mL for a long time while no control comparable. So we defined aerobic with hemin and vitaminK₂ as respiratory condition and growth, metabolites, survival, cell surface and enzyme activity were further analyzed for aerobic, respiratory and Fermentative cultures.Study on the growth curve of three L.casei strains cultured in different conditions got the result that the pH changing was the same among the cultures, respiration and fermentation cells got the same growth curve but the agitated one got optical density decreased when enter into late stationary phase. All cells had the same glucose utilization rate and respiratory cells got lactic acid produced decreased but acetic and formic acid increased, this was accounted for the same pH of three cultures. Mesostate pyruvate was not fully used by aerobic cells; more pyruvate was found in aerobic cultures. A new flavor component acetoin was found in respiratory cultures.There were notable differences between the three cultures for survival and stress tolerance. Fermentative and aerobic cell got poor tolerance to cold, heat, bile, and acid stress except freeze-dry. In contrast, respiratory cells were more tolerated in these stresses than the other two conditions. It was found by transmission electron microscope oxygen made the cells wall components changed and got a thinner and smoother cell wall. Malformation and autolysis was found in aerobic cells, and this would be the reason for its poor survival and decreasing in optical density. The high activity of respiratory cells to environment stress was attributed to the rigid cell wall.L.casei was able to grow aerobically, and this in because its NADH oxidase. The NADH oxidase activity of aerobic cells was two fold more than the other two conditions. Respiratory cells use oxygen in a different way from aerobic cells for respiration and fermentation got the same NADH oxidase activity.In this study, the influence of oxygen on the growth, metabolism and activity of L.casei were analyzed, on the other hand, we got the conclusions that respiration got high activity cells and make the cells produced more flavor component. These results not only provided a reference to keep activity in utilization of L.casei, but also improved the survival of probiotic cells in diary foods and got better probiotic effect.