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Evaluation of anionic surfactant removal in anaerobic reactor with Fe(III) supplementation

ABSTRACT: The objective of this study was to evaluate the removal of linear alkylbenzene sulfonate (LAS) associated with Fe(III) supplementation using an expanded granular sludge bed (EGSB) reactor. The reactor was inoculated with a granular sludge obtained from a full scale UASB plant that treated effluent from a poultry slaughterhouse and fed with synthetic wastewater containing a specific LAS loading rate (SLLR) of 1.5 mg.gVS-1.d-1 (~ 16.4 mgLAS L-1 influent) and supplied with 7.276 µMol L-1 (~ 410 mgFe L-1) of Fe(III). The biomasses from the inoculum and at the end of the EGSB-Fe operation (127 days) were characterized using 16S rRNA Ion Tag sequencing. An increase of 20 % in the removal efficiency was observed compared to reactors without Fe(III) supplementation that was reported in the literature, and the LAS removal was approximately 84 %. The Fe(III) reduction was dissimilatory (the total iron concentration in the influent and effluent were similar) and reached approximately 64 %. The higher Fe(III) reduction and LAS removal were corroborated by the enrichment of genera, such as Shewanella (only EGSB-Fe - 0.5 %) and Geobacter (1 % - inoculum 18 % - EGSB-Fe). Furthermore, the enrichment of genera that degrade LAS and/or aromatic compounds (3.8 % - inoculum 29.6 % – EGSB-Fe of relative abundance) was observed for a total of 20 different genera.

PROVIDER: PRJEB15116 | ENA |

REPOSITORIES: ENA

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			Action	DRS
	ERR1578862.fastq.gz	Fastqsanger.gz
	ERR1578863.fastq.gz	Fastqsanger.gz

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Project description:Previous studies demonstrated that an outer membrane c-type cytochrome, OmcB (GSU_2737), was involved in Fe(III) reduction in Geobacter sulfurreducens. An OmcB-deficient mutant was greatly impaired in its ability to reduce both soluble and insoluble Fe(III). Reintroducing omcB restored the capacity for Fe(III) reduction at a level proportional to the level of OmcB production. Here, we report that the OmcB-deficient mutant gradually adapted to grow on soluble Fe(III) but not insoluble Fe(III). The adapted OmcB-deficient mutant reduced soluble Fe(III) at a rate comparable to that of the wild type, but the cell yield of the mutant was only ca. 60% of that of the wild type under steady-state culturing conditions. Analysis of proteins and transcript levels demonstrated that expression of several membrane-associated cytochromes was higher in the adapted mutant than in the wild type. Further comparison of transcript levels during steady-state growth on Fe(III) citrate with a whole-genome DNA microarray revealed a significant shift in gene expression in an apparent attempt to adapt metabolism to the impaired electron transport to Fe(III). These results demonstrate that, although there are many other membrane-bound c-type cytochromes in G. sulfurreducens, increased expression of these cytochromes cannot completely compensate for the loss of OmcB. The concept that outer membrane cytochromes are promiscuous reductases that are interchangeable in function appears to be incorrect. Furthermore, the results indicate that there may be different mechanisms for electron transfer to soluble Fe(III) and insoluble Fe(III) oxides in G. sulfurreducens, which emphasizes the importance of studying electron transport to the environmentally relevant Fe(III) oxides. (From Leang C, Adams LA, Chin KJ, Nevin KP, Methé BA, Webster J, Sharma ML, Lovley DR. Adaptation to disruption of the electron transfer pathway for Fe(III) reduction in Geobacter sulfurreducens. J Bacteriol. 2005 Sep;187(17):5918-26.) Keywords: Geobacter, gene expression, genetic modification

Project description:Whole-genome DNA microarray analysis of Geobacter sulfurreducens cells grown on Fe(III)-oxide or Mn(IV)-oxide versus cells grown on soluble Fe(III) citrate indicated that there were significant differences in transcription patterns during growth on the insoluble metal oxides compared to growth on soluble Fe(III). Many of the genes that appeared to be up-regulated during growth on the metal hydroxides were involved in electron transport. The most highly up-regulated genes for both conditions were omcS and omcT, which encode co-transcribed c-type cytochromes exposed on the outer surface of the cell that are known to be required for Fe(III) and Mn(IV)-oxide reduction. Other electron transport genes that were up-regulated on both insoluble metals included the gene coding for the outer membrane c-type cytochrome, OmcG, genes for the outer membrane proteins, OmpB and OmpC, and the gene that codes for the structural protein of electrically conductive pili, PilA. Genes that were up-regulated in cells grown on Fe(III)-oxide but not Mn(IV)-oxide, included outer membrane c-type cytochromes including OmcE, a putative DMSO reductase protein, and proteins from the cytochrome bc1 complex. Electron transport genes that were only up-regulated in Mn(IV)-oxide grown cells included the genes that code for the outer membrane c-type cytochromes, OmcZ and OmcB, the periplasmic c-type cytochrome, MacA, and fumarate reductase. Genetic studies indicated that the c-type cytochrome proteins, PpcH, OmcJ, OmcM, OmcV, MacA, OmcF, OmcI, and OmcQ, and the iron sulfur subunit of the cytochrome b/b6 complex, QcrA, are important for reduction of insoluble Fe(III)-oxides but do not appear to be important for Mn(IV) reduction. These results demonstrate that the physiology of Fe(III) reducing bacteria differ significantly during growth on insoluble electron and soluble electron acceptors and emphasizes the importance of c-type cytochromes in extracellular electron transfer in G. sulfurreducens. Geobacter sulfurreducens cells were grown with acetate (5 mM) provided as the electron donor and either Fe(III) oxide or Fe(III) citrate provided as the electron acceptor. Cells were harvested at mid-log and total RNA was extracted. Total RNA (0.5 μg) was amplified using the MessageAmp II-Bacteria Kit (Ambion, Foster City, CA) according to the manufacturers instructions. Ten micrograms of amplified RNA (aRNA) was chemically labeled with Cy3 (for the control or soluble electron acceptor condition) or Cy5 (for the experimental or insoluble electron acceptor condition) dye using the MicroMax ASAP RNA Labeling Kit (Perkin Elmer, Wellesley, MA) according to the manufacturer’s instructions.

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Evaluation of anionic surfactant removal in anaerobic reactor with Fe(III) supplementation

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