EPS Glycoconjugate Profiles Shift as Adaptive Response in Anaerobic Microbial Granulation at High Salinity.

Maria C Gagliano,Ute Kuhlicke,Thomas R Neu,Hardy Temmink,Caroline M Plugge,Dainis Sudmalis

doi:10.3389/fmicb.2018.01423

Maria C Gagliano, Ute Kuhlicke + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2018.01423

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Abstract

Anaerobic granulation at elevated salinities has been discussed in several analytical and engineering based studies. They report either enhanced or decreased efficiencies in relation to different Na+ levels. To evaluate this discrepancy, we focused on the microbial and structural dynamics of granules formed in two upflow anaerobic sludge blanket (UASB) reactors treating synthetic wastewater at low (5 g/L Na+) and high (20 g/L Na+) salinity conditions. Granules were successfully formed in both conditions, but at high salinity, the start-up inoculum quickly formed larger granules having a thicker gel layer in comparison to granules developed at low salinity. Granules retained high concentrations of sodium without any negative effect on biomass activity and structure. 16S rRNA gene analysis and Fluorescence in Situ Hybridization (FISH) identified the acetotrophic Methanosaeta harundinacea as the dominant microorganism at both salinities. Fluorescence lectin bar coding (FLBC) screening highlighted a significant shift in the glycoconjugate pattern between granules grown at 5 and 20 g/L of Na+, and the presence of different extracellular domains. The excretion of a Mannose-rich cloud-like glycoconjugate matrix, which seems to form a protective layer for some methanogenic cells clusters, was found to be the main distinctive feature of the microbial community grown at high salinity conditions.

Highlights

The upflow anaerobic sludge blanket (UASB) reactor, designed in 1970s by Lettinga et al (1980), is commonly applied to treat high-strength industrial wastewaters (Van Lier et al, 2015)
The results indicate a key role of Methanosaeta in aggregation and in shaping extracellular polymeric substances (EPS) glycoconjugate patterns with the bacterial partners in response to salinity stress
Operation and performance of the low salinity reactor (LS) and high salinity (HS) UASB reactors, working at 5 and 20 g/L Na+ respectively, are presented in detail by Sudmalis et al (2018). Both reactors produced methane throughout the 217 days operation regardless of the salinity level and this was accompanied by an efficient Chemical Oxygen Demand (COD) removal at increasing organic loading rate (OLR) (Table 1)

Summary

Introduction

The upflow anaerobic sludge blanket (UASB) reactor, designed in 1970s by Lettinga et al (1980), is commonly applied to treat high-strength industrial wastewaters (Van Lier et al, 2015). In such reactors microbial biomass spontaneously aggregates into granules with a characteristic structure (Sekiguchi et al, 1999), and this enables high organic removal and methane production rates (Seghezzo et al, 1998; Hulshoff Pol et al, 2004). The acetotrophic methanogenic archaeon Methanosaeta, which shows filamentous growth, can play an important role in biomass auto-aggregation (Wiegant, 1988; Tay et al, 2010; Li et al, 2015).

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