Microbial Community Structure Under Various pH and Temperature Conditions During the Acidogenic Digestion of Duckweed

Duckweeds are efficient aquatic plants for wastewater treatment, due to their high nutrient uptake capabilities and resilience to severe environmental conditions. Combined with their rapid growth rates, high starch, and low lignin contents, duckweeds have also gained popularity as a biofuel feedstock for thermochemical conversion and alcohol fermentation. However, studies on the acidogenic anaerobic digestion of duckweed into carboxylic acids, another group of chemicals which are precursors of higher-value chemicals and biofuels, is lacking. In this study, a series of laboratory batch experiments were performed to determine the favorable operating conditions (i.e., temperature and pH) to maximize carboxylic acid production from wastewater-derived duckweed during acidogenic digestion. Batch reactors with 25 grams per liter solid loading were operated anaerobically for 21 days under mesophilic (35 C) or thermophilic (55 C) conditions at an acidic (5.3) or basic (9.2) pH. At the conclusion of the experiment, the dominant microbial communities under various operating conditions were characterized based on high-throughput sequencing of the V4 region of the 16S rRNA gene.