title: New steady-state microbial community compositions and process performances in biogas reactors induced by temperature disturbances.
abstract: BACKGROUND
  The microbial community in a biogas reactor greatly influences the process performance. However, only the effects of deterministic factors (such as temperature and hydraulic retention time (HRT)) on the microbial community and performance have been investigated in biogas reactors. Little is known about the manner in which stochastic factors (for example, stochastic birth, death, colonization, and extinction) and disturbance affect the stable-state microbial community and reactor performances.
  
  
  RESULTS
  In the present study, three replicate biogas reactors treating cattle manure were run to examine the role of stochastic factors and disturbance in shaping microbial communities. In the triplicate biogas reactors with the same inoculum and operational conditions, similar process performances and microbial community profiles were observed under steady-state conditions. This indicated that stochastic factors had a minor role in shaping the profile of the microbial community composition and activity in biogas reactors. On the contrary, temperature disturbance was found to play an important role in the microbial community composition as well as process performance for biogas reactors. Although three different temperature disturbances were applied to each biogas reactor, the increased methane yields (around 10% higher) and decreased volatile fatty acids (VFAs) concentrations at steady state were found in all three reactors after the temperature disturbances. After the temperature disturbance, the biogas reactors were brought back to the original operational conditions; however, new steady-state microbial community profiles were observed in all the biogas reactors.
  
  
  CONCLUSIONS
  The present study demonstrated that temperature disturbance, but not stochastic factors, played an important role in shaping the profile of the microbial community composition and activity in biogas reactors. New steady-state microbial community profiles and reactor performances were observed in all the biogas reactors after the temperature disturbance.
authors.affiliation: Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, 200433 Shanghai, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Luo
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800 Kgs Lyngby Copenhagen, Denmark.
authors.forename: Davide
authors.initials: D
authors.lastname: De Francisci
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800 Kgs Lyngby Copenhagen, Denmark.
authors.forename: Panagiotis G
authors.initials: PG
authors.lastname: Kougias
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800 Kgs Lyngby Copenhagen, Denmark.
authors.forename: Treu
authors.initials: T
authors.lastname: Laura
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800 Kgs Lyngby Copenhagen, Denmark.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800 Kgs Lyngby Copenhagen, Denmark.
authors.forename: Irini
authors.initials: I
authors.lastname: Angelidaki
keywords: Anaerobic digestion; Microbial community composition; Process performance; Temperature disturbance