Despite the bactericidal effects of ethanol, acidifying effects of fermentation, and low oxygen conditions of industrial alcohol production, bacteria that undergo lactic acid fermentation can contaminate such facilities because lactic acid has a low pKa of 3.86 to avoid decoupling the pH membrane gradient that supports regulated transport.
In spite of ethanol's antibacterial effects, the acidic byproducts of fermentation, and the low oxygen conditions in industrial alcohol production, bacteria that employ lactic acid fermentation can still contaminate these facilities because lactic acid has a low pKa value to maintain the pH gradient necessary for regulated transport.