Selection of Type I and Type II methanotrophic proteobacteria in a fluidized bed reactor under non-sterile conditions

► Type II methanotrophs produce PHB but Type I do not. ► Selection factors for Type II versus Type I were investigated using a laboratory-scale fluidized bed reactor. ► Elevated levels of dissolved oxygen (DO, 9 mg/L) and pH of 6.2-6.5 with nitrate as the N-source resulted in Type I methanotrophic biomass. ► Type II methanotrophic biomass was developed with dissolved N2 as the N-source at low influent DO (2.0 mg/L).