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. 2019 Nov 22;10:2548. doi: 10.3389/fmicb.2019.02548

FIGURE 4.

FIGURE 4

(A) High levels of L-lactate can be detected in 3-week microbial cultures when both glucose and PLA are added. B. pumilus B12 was incubated for 3 weeks in minimal salt medium with PLA films and a primary carbon source of glucose was either absent (–) or present (+). Results were compared to PLA films incubated with Proteinase K for 4 h, and PLA incubated in MSM as a negative control. **** indicates ANOVA p-value ≤ 0.0001 and ns indicates ANOVA p-value ≥ 0.05 compared to PLA + MSM media only (–). These assays were performed with three biological and three technical replicates. (B) The addition of glucose significantly increases the release of L-lactate from PLA in microbial cultures. All microbial samples were incubated for 48 h in MSM supplemented with glucose (G). Supernatant samples that led to over saturation of the L-lactate detection assay were diluted 1:10 to ensure more accurate results. **** indicates ANOVA p-value ≤ 0.0001 compared to B. pumilus without PLA and ns indicates t-test p-value ≥ 0.05 comparing B. subtilis str.168 with and without PLA. These assays were performed with three biological and three technical replicates.