Biomass-specific rates as key performance indicators: A nitrogen balancing method for biofilm-based electrochemical...

Area of Science:

• Microbial electrochemistry
• Biotechnology
• Environmental engineering

Background:

• Microbial electrochemical technologies (METs) utilize microorganisms and electrodes for reactions like microbial electrosynthesis (MES).
• Traditional rate normalization in METs (electrode dimensions, electrolyte volume) overlooks biomass quantity.
• Accurate biomass quantification is crucial for understanding biofilm-based METs, especially in continuous, 3D electrode systems.

Purpose of the Study:

• To develop a non-destructive method for determining microbial biomass in biofilm-based METs.
• To enable biomass-specific rate calculations for improved performance assessment.
• To compare the performance of MES reactors using biomass-specific rates.

Main Methods:

• Developed a simple method combining nitrogen balance and optical density for biomass determination.
• Applied the method to four MES reactors converting CO2 to carboxylates.
• Monitored biomass distribution (biofilm vs. suspension) over 100 days.

Main Results:

• >99% of biomass formed a biofilm within 69 days in the MES reactors.
• Biomass-specific growth rates ranged from 0.12-0.16 days⁻¹, with growth becoming insignificant after 100 days.
• Biomass-specific carboxylate production rates varied from 0.08-0.37 molC molX⁻¹d⁻¹.

Conclusions:

• The developed method provides accurate, non-destructive biomass quantification in biofilm-based METs.
• Biomass-specific rates offer a more effective way to evaluate MES performance, identify limitations, and compare with other technologies.
• This approach enhances the assessment and optimization of microbial electrosynthesis systems.