Fate of trace metals in anaerobic digestion

© Springer International Publishing Switzerland 2015. A challenging, and largely uncharted, area of research in the field of anaerobic digestion science and technology is in understanding the roles of trace metals in enabling biogas production. This is a major knowledge gap and a multifaceted problem involving metal chemistry; physical interactions of metal and solids; microbiology; and technology optimization. Moreover, the fate of trace metals, and the chemical speciation and transport of trace metals in environments— often agricultural lands receiving discharge waters from anaerobic digestion processes— simultaneously represents challenges for environmental protection and opportunities to close process loops in anaerobic digestion.The authors acknowledge funding within the framework of the COST Action 1302 (‘European Network on Ecological Roles of Trace Metals in Anaerobic Biotechnologies’). GC is supported by a European Research Council Starting Grant (‘3C-BIOTECH; No. 261330).Peer Reviewe

Molecular dynamics unlocks atomic level self-assembly of the exopolysaccharide matrix of water-treatment granular biofilms

Biofilm formation, in which bacteria are embedded within an extracellular matrix, is the default form of microbial life in most natural and engineered habitats. In this work, atomistic molecular dynamics simulations were employed to examine the self-assembly of the polysaccharide Granulan to provide insight into the molecular interactions that lead to biofilm formation. Granulan is a major gel forming matrix component of granular microbial biofilms found in used-water treatment systems. Molecular dynamics simulations showed that Granulan forms an antiparallel double helix stabilized by complementary hydrogen bonds between the beta-glucosamine of one strand and the N-acetyl-beta-galactosamine-2-acetoamido-2-deoxy-alpha-galactopyranuronic pair of the other in both the presence and absence of Ca2+. It is shown that Ca2+ binds primarily to the carboxyl group of the terminal hexuronic acid of the sugar branch and that interactions between branches mediated by Ca2+ suggest a possible mechanism for strengthening gels by facilitating interhelical bridging

Characterization of the protein fraction of the extracellular polymeric substances of three anaerobic granular sludges

Extracellular polymeric substances (EPS) play major roles in the efficacy of biofilms such as anaerobic granules, ranging from structural stability to more specific functions. The EPS of three granular anaerobic sludges of different origins were studied and compared. Particularly, the peptides from the protein fraction were identified by mass spectrometry. Desulfoglaeba and Treponema bacterial genera and Methanosaeta and Methanobacterium archaeal genera were prominent in all three sludges. Methanosaeta concilii proteins were the most represented in EPS of all three sludges studied. Principally, four proteins found in the three sludges, the S-layer protein, the CO-methylating acetyl-CoA synthase, an ABC transporter substrate-binding protein and the methyl-coenzyme M reductase, were expressed by Methanosaeta concilii. Mainly catabolic enzymes were found from the 45 proteins identified in the protein fraction of EPS. This suggests that EPS may have a role in allowing extracellular catabolic reactions.Peer reviewed: YesNRC publication: Ye