Experiments were designed to establish the method for viable cell counts of
bifidobacteria in the fermented milk. Results obtained are as follows:
1) The solution containing 0.1% of yeast extract or corn steap liquor was superior for the viable cell counts of
bifidobacteria as the diluents of samples for the serial dilution to the physiological saline usually used in the enumeration of lactic acid bacteria.
2) Modified Rogosa's and BL agar were demonstrated to be the best media for the viable cell counts of both
bifidobacteria and lactic acid bacteria in the fermented milk, but B. C. P. plate count agar which were generally used for the enumeration of the latter, was not suitable for the determination of
bifidobacteria.
3) Anaerobic cultivations are essential for the measurement of viable cells of
bifidobacteria and either of anaerobic jar method, Gas Pak anaerobic jar or Pouch method is adapted for this purpose.
However, there was little difference in superiority among them.
4)
Bifidobacterium formed colonies 0.5 to 3.0mm in diameter after the cultivations at 37°C for 48 to 72hr under the conditions described above.
5) Differential calculation of viable cells of
bifidobacteria and lactic acid bacteria was completely established from the mixed cultures of the two or three species using modified Rogosa's selective agar together with B. C. P. plate counts agar.
Because
Bifidobacterium could grow on the Rogosa's selective agar, but the growth of lactic acid bacteria was inhibited.
6) The detection of
bifidobacterial colony decreased remarkably, when both of the Gas Pak anaerobic jar and Pouch method generally used as the simple techniques for anaerobic cultivations, were applied to their viable cell counts with the modified Rogosa's selective agar.
View full abstract