Toward Real-Time Determination of Yield Coefficients of Early-Stage Electroactive Biofilms by Optical Microscopy

Physiological cellular parameters, such as latency times ( lagt ), cell production rates (CPR), doubling times ( t d ), relative growth rates (RGR), and yield coefficients ( Y Ne ), are only known as endpoint measurements for electroactive microorganisms (EAM). Here we show that these can be gained non-invasively and in real-time for early-stage biofilm formation at electrodes using a microfluidic electrochemical flow-cell (EFC) allowing in vivo optical microscopy. Parameters obtained for early-stage mixed culture biofilm anodes formed at +150 mV vs. Ag/AgCl sat. KCl have lagt of 2.31–4.58 days, CPR of 0.72–1.20 × 10 5 cells h −1 , t d of 176.54–1838.65 min, RGR of 0.02–0.27 h −1 , and Y Ne of 5.99–7.94 × 10 12 cells mol e- −1 . However, oxygen permeation into the EFC was the main problem that remained unsolved during the study that provides interesting lessons for future improvements.