2.5 Sampling and biomass measurements
Samples were routinely taken by opening the sampling assembly that was
connected to a pre-sterile collecting bottle. After that, a clean
magnetic stir bar was put in the collecting bottle to homogenously stir
the culture, and then four ~10 mL cultures were
separately aliquoted into four centrifugal tubes. The actual culture
volume and settled cell volume were recorded prior to centrifugation at
3,200 x g (GS 6KR, Beckman Coulter, Inc., Brea, CA) for 20 mins. The
packed cell volume of each tube was recorded, and the supernatant was
collected and stored at 4˚C for further analyses. One tube was saved for
protein quantifications, while the other three tubes were used for
determining fresh weight (FW) and dry weight (DW) as described (Corbin
et al., 2016) using pre-weighed 1.6 µm Binder-Free Glass Microfiber
filters (Whatman GF/A 4.7 cm, GE Healthcare Life Sciences, Pittsburgh,
PA). To quantify DW, the biomass was dried in an oven at 65˚C for 24 h
and weighed and reweighed until a stable value was obtained.