Mixed-culture fermentor for simulating methanogenic digestors

Area of Science:

• * Anaerobic Digestion
• * Biogeochemical Cycles
• * Microbial Ecology

Background:

• * Propionate is a key intermediate in anaerobic digestion, influencing methane (CH4) yield.
• * Understanding propionate degradation kinetics is vital for optimizing biogas production from animal waste.

Purpose of the Study:

• * To quantify propionate degradation rates in an animal waste anaerobic digester.
• * To investigate the factors affecting propionate degradation, particularly hydrogen (H2) turnover.
• * To explore the role of microenvironments in regulating propionate metabolism.

Main Methods:

• * Measurement of propionate degradation using [2-13C]propionate in an anaerobic digester.
• * Development of a continuous, mixed-culture fermentor to simulate digester conditions.
• * Manipulation of hydrogen (H2) levels and turnover rates in the fermentor.

Main Results:

• * Propionate degradation rate was determined to be 0.304 mM/h, contributing significantly to total CH4 production.
• * Propionate degradation was inhibited when methanogenic precursor degradation rates matched digester conditions.
• * Reducing H2 turnover rate in a model fermentor restored propionate degradation, indicating H2 accumulation as an inhibitory factor.

Conclusions:

• * High hydrogen turnover rates can inhibit propionate degradation in anaerobic digesters.
• * Localized microenvironments associated with particles may create distinct H2 concentrations, influencing overall degradation rates.
• * Managing H2 dynamics is critical for efficient propionate conversion and methane generation.