Page 230 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 10. Co-culturing methanogens and methanotrophs in an MBR
Figure 1. Set-up of the 2 L membrane bioreactor (MBR) with a constant volume of 1.5 L. The inflow gas was a mixture of CH4, Argon and CO2, and compressed air of which the ratios could be modified. Medium and buffer (KHCO3) inflows and bleed and effluent outflows were controlled by calibrated medium pumps. Temperature, pH, and dissolved O2 were constantly monitored using in-liquid probes. Contents were mixed at 150 rpm with a stainless-steel rotor blade.
Co-cultivation. The methanotroph-only culture was grown to OD600 of 0.7 under oxygen limitation, which created anoxic conditions in the liquid. After at least a week of anoxia (O2 detection limit: 3 μM), the reactor was inoculated with M. barkeri. Fourteen days after inoculation with M. barkeri, a bleed cycle was introduced to select for methanogen- methanotroph aggregates and to remove excess methanotrophic biomass. The bleed cycle was set to 30 min pre-settling (no stirring) to minimize loss of aggregates followed by removal of
228