Characteristics of carbohydrate degradation and the rate‐limiting step in anaerobic digestion

TLDR

The study examined how cellulose, soluble starch, and glucose degrade during the acidogenic phase and how substrate loading rate and solids retention time affect the methanogenic phase of anaerobic digestion. Continuous chemostat experiments revealed that cellulose hydrolysis is the rate‑limiting step, with substrate utilization rates decreasing in the order glucose > soluble starch > acetic acid > cellulose; Methanosarcina outperformed Methanothrix, and the methanogenic phase can tolerate up to 11.2 g acetic acid L⁻¹ day⁻¹.

Abstract

Abstract The characteristics of the degradation of cellulose, soluble starch, and glucose in the acidogenic phase and the effects of the substrate loading rate and biological solids retention time on the methanogenic phase of anaerobic digestion were investigated. The results obtained from continuous experiments using laboratory‐scale anaerobic chemostat reactors elucidated the true rate‐limiting step of anaerobic digestion. The specific rate of substrate utilization decreased in the following order: glucose, soluble starch, acetic acid, and cellulose. The rate of the hydrolysis of cellulose was so low that this was shown to be the rate‐limiting step in overall anaerobic digestion. Among methanogenic bacteria Methanosarcina would provide a higher substrate utilization rate than Methanothrix , and the maximum allowable substrate loading rate in the methanogenic phase was 11.2 g acetic acid/L day.