Bananas can thrive in a relatively high-pH environment, which is one of the reasons I grow them. The pH in my aquaponic system runs pretty high (around 7.5-8), so rather than battling to lower it, I just chose to grow plants that could tolerate those conditions.
BTW, here's an info page from the wiki that covers pH as it pertains to bananas:
Info:Soil - Bananas Wiki (says ideal is 5.5-7.5)