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

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.

Performance of an Innovative Two-Stage Process Converting Food Waste to Hydrogen and Methane

“…Seed sludge [10% volume/volume (v/v)] is boiled for 15 min and then inoculated into the reactor. A heat-shock treatment is conducted to inhibit hydrogenotrophic bacteria and to harvest anaerobic 15 It was reported that cellulose degradation increased at high retention time 16 and protein degradation increased at both high retention time and neutral pH. 17 H 2 fermentation of 6 days is reasonable considering operation time and efficiency, 15 which is followed by post-treatment.…”

“…Figure 2 illustrates the variation of VFA, pH, and H 2 evolution during H 2 fermentation of food waste (error bars indicate the standard deviation of samples during repeat runs). Because of the various components of food waste, it is important to adjust the fermentation conditions 16 and protein degradation increased at both high retention time and neutral pH. 17 The production of VFA and H 2 was dramatically enhanced by reducing D from 4.5 to 2.3 days Ϫ1 .…”

An analysis of single and two stage, mesophilic and thermophilic high rate systems for anaerobic digestion of corn stalk

“…The only difference between the production processes for corn stalk and cellulose methane is that corn stalk methane production process requires the first step. Due to the resilient structure and composition of lignocellulosic biomass such as lignin that interlinks cellulose and hemicellulose layers, the conversion efficiency is limited [23,24]. The rate of hydrolysis of particulate organic matter is determined by the adsorption of hydrolytic enzymes onto the biodegradable surface sites [25,26].…”

Enhancing biogas quality of indigofera plant waste through co-digestion with cow dung

“…Unfortunately, the most indigofera wastes are stems containing much hemicellulose and lignocellulose. The subtrates with high content of cellulose and lignin that interlink each other [10], becomes difficult to hydrolyze, so that the yield of biogas is low. To overcome this, some researchers have proposed some pretreatment processes before processing in AD, such as thermo-chemical [12], thermal [2,1], mechanical-chemical-enzymatic [3], alkaline [7], and biological [9] pretreatments.…”