How do bacteria maintain their internal ph despite the ph of the environment in which they grow?

The answer to this question would be: by producing buffer

The pH of optimal growth of bacteria might be different. Some bacteria can grow in an acid condition called acidophile, other live in base condition called alkaliphiles and the rest live in neutral pH condition called neutrophiles. The bacteria can maintain their internal pH by producing acid, base or buffer. If the surrounding pH is too acid, the bacteria can reduce the H + concentration by producing base. If the condition is too alkali/base, the bacteria can produce acid by doing fermentation.