title: 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.
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research (UFZ), Permoserstr. 15, 04318, Leipzig, Germany. heike.straeuber@ufz.de.
authors.forename: Heike
authors.initials: H
authors.lastname: Sträuber
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research (UFZ), Permoserstr. 15, 04318, Leipzig, Germany.
authors.forename: Rico
authors.initials: R
authors.lastname: Lucas
authors.affiliation: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research (UFZ), Permoserstr. 15, 04318, Leipzig, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kleinsteuber
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000254:growth & development / Q000378:metabolism; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism; D056804:Biofuels; D058448:Biota; D019344:Lactic Acid / Q000378:metabolism; D008697:Methane / Q000378:metabolism*; D012820:Silage; D055549:Volatile Organic Compounds / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*
chemical_list: D056804:Biofuels; D055549:Volatile Organic Compounds; D019344:Lactic Acid; D008697:Methane
keywords: 454 Pyrosequencing; Acidogenesis; Anaerobic fermentation; Lactic acid; T-RFLP; Volatile fatty acids