Metabolic and microbial community dynamics during the anaerobic digestion of maize silage in a two-phase process

Abstract

Two-phasic anaerobic digestion processes (hydrolysis/acidogenesis separated from acetogenesis/methanogenesis) can be used for biogas production on demand or a combined chemicals/bioenergy production. For an effective process control, detailed knowledge about the microbial catalysts and their correlation to process conditions is crucial. In this study, maize silage was digested in a two-phase process and interrelationships between process parameters and microbial communities were revealed. In the first-phase reactor, alternating metabolic periods were observed which emerged independently from the feeding frequency. During the L-period, up to 11.8 g L(-1) lactic acid was produced which significantly correlated to lactic acid bacteria of the genus Lactobacillus as the most abundant community members. During the alternating G-period, the production of volatile fatty acids (up to 5.3, 4.0 and 3.1 g L(-1) for propionic, n-butyric and n-caproic acid, respectively) dominated accompanied by a high gas production containing up to 28 % hydrogen. The relative abundance of various Clostridiales increased during this metabolic period. In the second-phase reactor, the metabolic fluctuations of the first phase were smoothed out resulting in a stable biogas production as well as stable bacterial and methanogenic communities. However, the biogas composition followed the metabolic dynamics of the first phase: the hydrogen content increased during the L-period whereas highest CH4/CO2 ratios (up to 2.8) were reached during the G-period. Aceticlastic Methanosaeta as well as hydrogenotrophic Methanoculleus and Methanobacteriaceae were identified as dominant methanogens. Consequently, a directed control of the first-phase stabilizing desired metabolic states can lead to an enhanced productivity regarding chemicals and bioenergy.

Production of high-concentration n-caproic acid from lactate through fermentation using a newly isolated Ruminococcaceae bacterium CPB6

“…However, in none of the above cases for CA production from endogenous lactate [14, 18, 20], M. elsdenii was detected. So, M. elsdenii was not likely the main strain that is responsible for the lactate-to-CA conversion in these processes.…”

Carboxylic acid production from ensiled crops in anaerobic solid‐state fermentation ‐ trace elements as pH controlling agents support microbial chain elongation with lactic acid

“…Thereby, the production of bio‐based chemicals is achieved while energy carriers are gained from fermentation residues in a cascaded utilization process where biomass is degraded stepwise. Cascaded production of medium‐chain fatty acids (MCFA, herein defined as carboxylic acids with a carbon chain length of 5–6 C‐atoms) and biogas can be conducted by two‐phasic anaerobic digestion (AD) processes, where hydrolysis/acidogenesis and acetogenesis/methanogenesis occur in separate reactors . For the utilization of solid biomass, leach‐bed processes are state of the art.…”

Complete genome sequence of Ruminococcaceae bacterium CPB6: A newly isolated culture for efficient n -caproic acid production from lactate

“…Notably, Clostridium cluster IV is observed to be the most prominent population in the lactate-utilizing, CA-producing microbiome (Strauber et al, 2016;Zhu et al, 2015). This cluster belongs to the family Ruminococcaceae and is found to be abundant in gut microbiota, which plays an important role in host resistance against intestinal pathogens and promotion of systemic autoimmunity (Atarashi et al, 2011).…”