Ldo10101

The DO content and temperature of water containing BMNBs were measured simultaneously using a portable dissolved oxygen meter (HQ30d, Hach, USA) equipped with a luminescent dissolved oxygen sensor (LDO10101). The sensor was calibrated before leaving factory and conducting the experiments. The experimental data was recorded during each measurement every 10 s.

To maintain anaerobic conditions in the opti‐MFC and opti‐BES, the minimal medium was purged with 100% nitrogen for 10 h prior to use and the purging continued during the experiment. This conventionally prepared anaerobic minimal medium still contained trace amount of DO (∼0.08 mg/L), which is sufficient for GFP maturation (Fig. S3) (Hansen et al., 2001). For experiments requiring controlled DO concentrations, highly purified air and nitrogen were both purged into the medium reservoir, while their respective pressures were adjusted separately until the target DO value was reached and stable for 1 h. The DO value of the minimal medium before entering the opti‐MFC or opti‐BES was continuously monitored using a DO probe (LDO10101, Hach Company, Loveland, CO). The DO probe was sterilized with 70% aqueous ethanol solution and rinsed with sterilized deionized water before use.

AB62 solution (0.05 mL, 68.2 mM, final dye concentration 113.6 μM) was added to the enzyme solution in 0.1 M phosphate-citrate buffer (30 mL, 3 U_AB62 mL⁻¹). The absorbance decrease (637 nm, 30 °C) was measured to control the decolorization process. The reaction was monitored (20-s intervals) up to the substrate depletion (the stable absorbance level). The activity of laccase was calculated on the base of initial linear dependence of absorbance vs time. The value obtained in the first process was set as 100 %. Next, five consecutive portions of the substrate were added after substrate depletion.
The influence of oxygen consumption on the enzyme activity was checked by monitoring the oxygen concentration using a luminescent dissolved oxygen probe (LDO10101, Hach Lange).