To find out whether higher amounts of PAM could be degraded
by the two strains, another experiment was carried out using liquid
cultures of theMSMPsupplemented with various concentrations of
glucose. The initial PAM concentration was 100mgL−1. The results
shown in Fig. 5 indicated that the degradation of PAM by the two
strains could both be improved when a low concentration of glucose
(less than 200mgL−1) was present in the cultures. With higher
levels of glucose, the removal efficiency decreased. The improved
PAMdegradation showed that low concentrations of glucose can be
used as co-metabolism substrate with PAM by both of the strains.
This is because conventional carbon sources at low concentrations
stimulate microbial growth, which lead to higher levels of
enzymes available for the degradation of toxic compounds [23].
However, if too much conventional carbon sources are present,
the microorganisms will use the conventional carbon sources in
priority instead of toxic compounds to satisfy their growth and
metabolism, consequently lead to the decrease of the biodegradation.