Mixed-acid fermentation and polysaccharide production by Lactobacillus helveticus in milk cultures

Abstract

Lactobacillus helveticus grown in milk with pH control at 6.2 had a slower growth rate (μ = 0.27 h-1) and produced less exopolysaccharide (49 mg 1-1) but increased lactic acid production (425 mM) compared to cultures without pH control (μ = 0.5 h-1, 380 mg exopolysaccharide 1-1, and 210 mM lactate), respectively. Both cultures displayed a mixed-acid fermentation with formation of acetate, which is linked not only to citrate metabolism, but also to alternative pathways from pyruvate.