Abstract
Granulated sludge from anaerobic reactors is constituted by the microbial consortia responsible for the degradation of different substrate present in wastewaters. This study characterized anaerobic microorganisms in a granular sludge from a Uasb reactor (Upflow Anaerobic Sludge Blanket) by Most Probable Number (MPN) technique and method of cloning and sequencing the 16S rDNA gene. The main objective of this study was to quantify and to identify the microorganisms in two different culture media containing sulfate (Posgate C [6.0 sodium lactate and 3.13 g L-1 sodium sulfate] and Zinder [2.24 sodium lactate and 0.96 g L-1 sodium sulfate]). Microorganisms quantified by Postgate C and Zinder media were: 9.30x1010 and 7.50x1011 MPN mL-1 for general anaerobic bacteria; 4.30x108 and 2.10x108 MPN mL-1 for sulfate reducing bacteria; and 1.20x108 and 1.5x108 MPN mL-1 for methane producing archaea, respectively. Bacteria identified by 16S rDNA gene sequencing from the MPN in both culture media were related to the phyla Firmicutes and Proteobacteria. The conditions of Postgate C culture medium favored the sulfate-reducing bacteria and the Zinder culture medium favored the general anaerobic bacteria.
Highlights
Most Probable Number (MPN) estimates were used to determine the abundance of anaerobic microorganisms in two culture media
The MPN of sulfate reducing bacteria (SRB) was slightly higher In Postgate C culture medium (4.30 x108 MPN mL-1) than in Zinder medium (2.10x108 MPN mL-1)
SRB were favored in the first nutritional requirement (Postgate C) due to the greater amount of sodium lactate (6.0 g L-1) and sulfate (3.13 g L-1) when compared with the second condition (Zinder medium, sodium lactate 2.24 and sulfate 0.96 g L-1)
Summary
The microbial consortia from granular sludge UASB reactor showed predominance of methanogenic archaea in previous studies by FISH (Fluorescent in situ hybridization) technique (Del Nery et al, 2008; Hirasawa, Sarti, Del Aguila, & Varesche, 2008). It was verified a relative abundance greater than 84% microorganisms belonging to Bacteria Domain by the large-scale sequencing technique using the Illumina MiSeq platform (Delforno et al, 2017). The sulfur metabolism has been assigned to organic and inorganic sulfur assimilation, alkanesulfonate assimilation, sulfur oxidation, and sulfate reduction-associated complexes by the large-scale sequencing technique using the Illumina HiSeq platform (Delforno et al, 2017)
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