I work with Clostridia to produce ABE solvents anaerobically. They always produce foam during exponential growth phase due to high CO2 output. Then, the foam sort of dissolves itself and the fermentation proceeds just fine. I don't even need to add anti-foam if there is enough head space in the fermenter.
To my knowledge and experience, foaming is more of a technical/operational issue other than having an impact on the microbes.