Sampling procedure
Composition of gas samples was analysed using GC (Agilent 7890B gas
chromatograph customized with FID, TCD, Unibeads IS 60/80 mesh and
MolSieve 5A 60/80 SST columns). It is worth noting that the consumption
and production of various gases will result in changes in system
pressure (for batch operations) or off-gas flow rate (for continuous
operations). These changes would cause significant errors in the
estimated gas component uptake and production rates if they were not
accounted for. To address it, we have previously developed a protocol
(Stone, He, & Wang, 2019), which is followed in this work. The optical
density of each liquid sample was measured using a Beckman Coulter
DU® 730 UV/Vis spectrophotometer at OD750. To
determine the amount of the dissolved CO2 in the liquid
phase, we first removed cell mass through centrifugation, then measure
the total inorganic carbon (TIC) using a Shimadzu
TOC-VCSN Analyzer, also following the procedures
reported in (Stone et al., 2019).