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Open Access Research

Towards a metagenomic understanding on enhanced biomethane production from waste activated sludge after pH 10 pretreatment

Mabel Ting Wong1, Dong Zhang2, Jun Li1, Raymond Kin Hi Hui1, Hein Min Tun1, Manreetpal Singh Brar1, Tae-Jin Park1, Yinguang Chen2* and Frederick C Leung13*

Author Affiliations

1 5 N01, Kadoorie Biological Sciences Building, School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, Hong Kong

2 State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China

3 Bioinformatics Center, Nanjing Agricultural University, Nanjing, China

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Biotechnology for Biofuels 2013, 6:38  doi:10.1186/1754-6834-6-38

Published: 19 March 2013

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.

Keywords:
Wastewater treatment plant; Sludge; Pretreatment; Renewable energy; Biomethane; Pyrosequencing; Metagenomic