Under anaerobic conditions, the rates of lactic acid degradation
by L. buchneri and spoilage cultures from reduced NaCl and commercial
sources were similar, and both D- and L- forms of lactic acid
were metabolized (Data not shown. Information available online in
Supplemental Fig. 2). D- and L-lactic acid that were produced during
normal cucumber fermentation (55 mM and 45 mM, respectively)
were simultaneously metabolized by this L. buchneri spoilage
isolate, indicating that the isomeric form is not a limiting factor for
lactic acid utilization in fermented cucumbers. Furthermore, the
rise in pH that was observed during anaerobic lactic acid utilization
in fermented cucumber media was strongly correlated with the
decrease in lactic acid concentration for mixed spoilage cultures
(R2 ¼ 0.912) and pure cultures of L. buchneri (R2 ¼ 0.975) across
multiple independent experiments with varying NaCl concentrations
and initial pH (Fig. 3).