Carbohydrate storage in anaerobic sequencing batch reactors

This study demonstrates the accumulation and degradation of trehalose as a storage compound in a glucose-fed anaerobic sequencing batch reactor (ASBR). One hour after substrate addition, only 40% of the added organic matter (as chemical oxygen demand, COD) was accounted for by the cumulative methane production and soluble COD remaining in the reactor. All influent COD was accounted for by methane and biomass production by the end of the 24-h ASBR cycle. These dynamics can be explained by the production of an intracellular storage product. Total carbohydrate analysis showed that 26% of the glucose added to the reactor transiently accumulated within the biomass. Based on 13C-nuclear magnetic resonance (NMR) analysis, trehalose (α-d-glucopyranosyl-(d-glucopyranoside)) was identified as the main carbohydrate produced. Mathematical modeling was performed and the IWA Anaerobic Digestion Model No. 1 (ADM1) was modified to include microbial storage. The modified model adequately described the ASBR dynamics during a 24-h cycle.