Q: how to maintain pH value to culture Streptoccus mutans GS-5?

[Jinling Xie]

Hi, there,

    I'm trying to maintain pH value at 7.0 or 5.5 to culture
S.mutans GS-5. I used PBS. But it doesn't work. After o/n, the pH
value drops down too much. Anybody out there knows which buffer
I should use, please reply to this account. Thanks a lot in 
advance.

Jinling Xie