3.1 Glutarate tolerance and degradation test
It has generally been believed that glutarate was toxic to any
microorganism, and different strains had different tolerances to
toxicity(J. Adkins, J. Jordan, & D. R.
Nielsen, 2013; W. Li et al., 2019;
Rohles et al., 2018). Although many
studies have been done on its physiological
roles(J. Adkins, J. Jordan, & D. R.
Nielsen, 2013; W. Li et al., 2019;
Rohles et al., 2018), glutarate tolerance
remained unclear. Thus, glutarate tolerance was first performed before
production. The tolerance examination was conducted in an optimized SOB
medium(Zhao, Li, & Deng, 2018) with
Bgl4146 at 37 °C, which was also
used in glutarate production. The cells in exponential growth were
placed into increasing glutarate concentrations (Fig. 2A). After
cultivating to 30 g/L glutarate, cells grew well although the growth
curve was lower than the control (no glutarate). When the concentration
of glutaric acid reached 50 g/L, the cells still grew slowly. However,
the cells hardly grew and even some cell lysis was discovered when the
glutarate concentration increasing to 100 or 150 g/L. Therefore, at
least 50 g/L glutarate was able to be tolerated by Bgl4146, this was
verified in fermentation production of glutaric
acid(W. Li et al., 2019).
Then we also tested the glutarate degradation in Bgl4146 because of theCsiD and YgaF in E. coli involving in the
utilization of glutarate(Zhang, Gao, Guo,
Guo, Kang, Xiao, Yan, Tao, Zhang, & Dong, 2018). The Bgl4146 was
detected in M9 with 5 g/L glutarate as the single carbon source for
glutarate degradation (Fig. 2B). However, the strain hardly grew and
consumed only 0.1% glutarate in 96 h (Fig. 2B). Therefore, we would not
consider the degradation of glutaric acid in the next study.