title: Towards a metagenomic understanding on enhanced biomethane production from waste activated sludge after pH 10 pretreatment.
abstract: BACKGROUND
  Understanding the effects of pretreatment on anaerobic digestion of sludge waste from wastewater treatment plants is becoming increasingly important, as impetus moves towards the utilization of sludge for renewable energy production. Although the field of sludge pretreatment has progressed significantly over the past decade, critical questions concerning the underlying microbial interactions remain unanswered. In this study, a metagenomic approach was adopted to investigate the microbial composition and gene content contributing to enhanced biogas production from sludge subjected to a novel pretreatment method (maintaining pH at 10 for 8 days) compared to other documented methods (ultrasonic, thermal and thermal-alkaline).
  
  
  RESULTS
  Our results showed that pretreated sludge attained a maximum methane yield approximately 4-fold higher than that of the blank un-pretreated sludge set-up at day 17. Both the microbial and metabolic consortium shifted extensively towards enhanced biodegradation subsequent to pretreatment, providing insight for the enhanced methane yield. The prevalence of Methanosaeta thermophila and Methanothermobacter thermautotrophicus, together with the functional affiliation of enzymes-encoding genes suggested an acetoclastic and hydrogenotrophic methanogenesis pathway. Additionally, an alternative enzymology in Methanosaeta was observed.
  
  
  CONCLUSIONS
  This study is the first to provide a microbiological understanding of improved biogas production subsequent to a novel waste sludge pretreatment method. The knowledge garnered will assist the design of more efficient pretreatment methods for biogas production in the future.
authors.affiliation: 5 N01, Kadoorie Biological Sciences Building, School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, Hong Kong. yg2chen@yahoo.com.
authors.forename: Mabel Ting
authors.initials: MT
authors.lastname: Wong
authors.forename: Dong
authors.initials: D
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Raymond Kin Hi
authors.initials: RK
authors.lastname: Hui
authors.forename: Hein Min
authors.initials: HM
authors.lastname: Tun
authors.forename: Manreetpal Singh
authors.initials: MS
authors.lastname: Brar
authors.forename: Tae-Jin
authors.initials: TJ
authors.lastname: Park
authors.forename: Yinguang
authors.initials: Y
authors.lastname: Chen
authors.forename: Frederick C
authors.initials: FC
authors.lastname: Leung