The effects of iron-free lactoferrin (apo-LF) and several metal-bound forms of this protein (Fe-LF, Cu-LF, Zn-LF) on the growth of Bifidobacterium strains, Escherichia coli and Staphylococcus aureus were investigated. Apo-LF, Cu-LF and Zn-LF inhibited the growth of E. coli and S. aureus. The growth inhibitory effect of Cu-LF and Zu-LF was much stronger than that of apo-LF, while Fe-LF was ineffective or only slightly effective. On the other hand, apo-LF, Cu-LF and Fe-LF promoted the growth of Bifidobacterium strains, as indicated by both an increase in culture OD and an increase in the number of viable cells. This growth-promoting effect disappeared when LF was hydrolyzed by pancreatin.
Bifidobacteriumlo ngumR O23 was immobilized in calcium alginate gels and freeze-dried. The effects of immobilization, storage temperature and composition of the protective solution were studied. High mortality (two log reduction in viable count) was observed when a concentrated culture was immobilized and immediately freeze-dried. Such and immobilization procedure also reduced stability during storage at 20° C. This feature was strain/species related, as immobilization in alginate beads was not detrimental to the survival of Lactococculsa ctisR O58 and Lactobacillusrh amnosus RO11 to freeze-drying, but influenced negatively Streptococctuhse r mophiluRsO 57. Alginateand calcium chloride, used in the immobilization process, were not responsible for the high mortality of immobilized B. longum RO23. Bifidobacteria grown in the alginate beads did not produce high post-lyophilization mortality, suggesting that freeze-drying the culture immediately following immobilization was the cause of the high mortality, and exposing the cells to a growth medium between immobilization and freeze-drying may allow recovery. Whey-based protective solutions that are mixed to the alginate beads were more effective than milk-based solutions in protecting the immobilized cells against mortality during freeze-drying.
The inhibitory effects of seven human-derived Bifidobacterium strains on pathogenic Escherichia coli serotype O-111 were examined in co-cultivation. All of the Bifidobacterium strains tested inhibited the growth of E. coli and limited the increase in the ammonia concentration in the co-cultures. Also, in each instance, the pH of the culture medium decreased due to their production of acetic and lactic acids. From the results of pH-controlled fermentation, the growth inhibition of E. coli was attributed mainly to the decrease in the pH of the culture medium. The possibility that some unidentified inhibitory substances derived from Bifidobacterium strains were present was little thought. In mono-cultures of Bifidobacterium strains, the ammonia concentration in the culture medium decreased to a level below that initially present in the medium prior to inoculation. Enzymatic assays showed that the activity of an enzyme involved in ammonia production (L-asparagine deaminase) was much weaker in each of the Bifidobacterium strains than in E. coli, whereas the activities of enzymes involved in ammonia assimilation (glutamine synthetase, glutamate synthase and glutamate dehydrogenase) were much higher in bifidobacteria. The decrease in the ammonia concentration in the co-culture appears to be related not only to the number of colonyforming units of bifidobacteria but also to the differences among the bacteria examined in enzymatic activities which are concerned with utilization and production of ammonia.
The resistance of bifidobacteria to six kinds of antibiotics was examined. Bifidobacteria were isolated from the feces of healthy individuals (12 cases) and patients (11 cases) administered an antibiotic-resistant Bifidobacterium preparation (LacBR ®). These patients were given antibiotic drugs etc. Only a few of the healthy individuals had the bifidobacteria resistant to ampicillin, cefazolin, erythromycin, minocycline and ofloxacin. However, many of the LacB-R ®-administered individuals had the bifidobacteria resistant to the antibiotics except minocycline and ofloxacin. All persons in both group showed resistance to amikacin. The administration of LacBR ® was useful to maintain the number of intestinal Bifidobacterium because administered Bifidobacterium was recovered with the healthy control level in some of the patients receiving therapy with many kinds of antibiotics.
Wistar rats fed apurified diet containing 5% corn oil, butter, or beef tallow for 4 weeks were examined for cecal microflora and cecal short-chain fatty acids. Bifidobacteria and proteus showed remarkable decreases in viable numbers in the cecum of rats fed a butter-containing diet compared with animals fed corn oil-or beef tallow-containing diets. Clostridia showed a significantly decreased number in the beef tallow and butter groups compared with the corn oil group. The concentrations of acetate, propionate, and butyrate and the total concentrations of short-chain fatty acids in the cecum of rats were significantly lower in the rats given butter or beef tallow compared with the animals given corn oil. The cecal pH was higher in the butter and beef tallow groups. The results indicate that butter and beef tallow as dietary fat are unfavorable for bacterial fermentation in the cecum of rats.