Multimodal, quantitative analysis enables process management of productive, mixotrophic biofilms

Area of Science:

• Biotechnology and Bioengineering
• Microbial Ecology
• Sustainable Energy Production

Background:

• Biofilms are promising for continuous biotechnological production but understanding their biomass dynamics and electron fluxes is crucial for optimization.
• Nitrogenase-driven hydrogen production in dual-species biofilms presents challenges in maintaining stability and maximizing yield.

Purpose of the Study:

• To investigate biofilm dynamics and hydrogen production in a dual-species consortium of Pseudomonas taiwanensis and Rhodopseudomonas palustris.
• To optimize hydrogen production by managing biofilm structure, biomass dispersion, and reactor gas composition.

Main Methods:

• Utilized a segmented-flow tubular capillary biofilm reactor with a dual-species consortium.
• Employed a novel flow cytometry-based pipeline to monitor biofilm development and biomass dispersion.
• Analyzed hydrogen production under varying gas compositions and implemented controlled nutrient interruption for biofilm dispersion.

Main Results:

• Mature biofilms reached semi-steady-state with stable species composition and continuous erosive dispersion.
• Addition of low oxygen levels (≤1%) significantly enhanced hydrogen production, contrary to expectations of anaerobic operation.
• Controlled biofilm dispersion via nutrient interruption restored high hydrogen production rates, enabling cyclical production.

Conclusions:

• Biofilm management strategies, including controlled dispersion and microoxic conditions, are essential for enhancing productivity in biofilm-based systems.
• Significant unaccounted electron fluxes indicate substantial maintenance energy demands in biofilms.
• This study provides insights into optimizing continuous hydrogen production using engineered microbial consortia.