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).