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

Abstract

BackgroundUnderstanding 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).ResultsOur 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.ConclusionsThis 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.

Accelerating the sludge disintegration potential of a novel bacterial strain Planococcus jake 01 by CaCl2 induced deflocculation

“…Anaerobic digestion (AD) is the more frequently used method for sludge stabilization (Wong et al, 2013). To accelerate the degradation and to enhance the production of biogas various pretreatment methods can be employed (Appels et al, 2008).…”

How to use molecular biology tools for the study of the anaerobic digestion process?

“…6). Enzymes necessary for catalyzing CO 2 conversion to methane were all found within the metagenomes of the bioreactor sludges treating cellulosic materials and waste activated sludge (Rademacher et al 2012;Wong et al 2013). Acetate kinase and phosphotransacetylase, involved in the first step of acetoclastic methanogenesis, were not detected in these studies.…”

“…Extracting a representative protein fraction for analysis is complicated due to the complex microbial communities involved, the presence of interfering compounds, and the heterogeneity of natural environments. Nevertheless, metaproteomics Wong et al (2013); in red, genes that could not be detected in those studies. Dotted lines represent an alternative pathway for the activation of acetate to acetyl-CoA, as suggested by Wong et al (2013).…”

“…Nevertheless, metaproteomics Wong et al (2013); in red, genes that could not be detected in those studies. Dotted lines represent an alternative pathway for the activation of acetate to acetyl-CoA, as suggested by Wong et al (2013). MF-methanofuran, MPT-methanopterin, CoM-coenzyme M, CoB-coenzyme B, CoA-coenzyme A, F 420 -coenzyme F 420 , Fd-ferredoxin.…”

“…Acetate kinase and phosphotransacetylase, involved in the first step of acetoclastic methanogenesis, were not detected in these studies. Wong et al (2013) proposed an alternative route in which an acetate transporter coupled to acetyl-CoA synthetase and the hydrolysis of pyrophosphate by inorganic pyrophosphatase drives this reaction forward, similar to the pathway present in Methanosaeta thermophila (Smith and Ingram-Smith 2007).…”