Bacterial communities involved in sulfur transformations in wastewater treatment plants.

The main sulfate-reducing (SRB) and sulfur-oxidizing bacteria (SOB) in six wastewater treatment plants (WWTPs) located at southern Brazil were described based on high-throughput sequencing of the 16S rDNA. Specific taxa of SRB and SOB were correlated with some abiotic factors, such as the source of the wastewater, oxygen content, sample type, and physical chemical attributes of these WWTPs. When the 22 families of SRB and SOB were clustered together, the samples presented a striking distribution, demonstrating grouping patterns according to the sample type. For SOB, the most abundant families were Spirochaetaceae, Chromatiaceae, Helicobacteriaceae, Rhodospirillaceae, and Neisseriaceae, whereas, for SRB, were Syntrophaceae, Desulfobacteraceae, Nitrospiraceae, and Desulfovibriaceae. The structure and composition of the major families related to the sulfur cycle were also influenced by six chemical attributes (sulfur, potassium, zinc, manganese, phosphorus, and nitrogen). Sulfur was the chemical attribute that most influenced the variation of bacterial communities in the WWTPs (λ = 0.14, p = 0.008). The OTUs affiliated to Syntrophus showed the highest response to the increase of total sulfur. All these findings can contribute to improve the understanding in relation to the sulfur-oxidizing and sulfate-reducing communities in WWTPs aiming to reduce H2S emissions.

Sulphate production by Paracoccus pantotrophus ATCC 35512 from different sulphur substrates: sodium thiosulphate, sulphite and sulphide.

One of the problems in waste water treatment plants (WWTPs) is the increase in emissions of hydrogen sulphide (H2S), which can cause damage to the health of human populations and ecosystems. To control emissions of this gas, sulphur-oxidizing bacteria can be used to convert H2S to sulphate. In this work, sulphate detection was performed by spectrophotometry, ion chromatography and atomic absorption spectrometry, using Paracoccus pantotrophus ATCC 35512 as a reference strain growing in an inorganic broth supplemented with sodium thiosulphate (Na2S2O3·5H2O), sodium sulphide (Na2S) or sodium sulphite (Na2SO3), separately. The strain was metabolically competent in sulphate production. However, it was only possible to observe significant differences in sulphate production compared to abiotic control when the inorganic medium was supplemented with sodium thiosulphate. The three methods for sulphate detection showed similar patterns, although the chromatographic method was the most sensitive for this study. This strain can be used as a reference for sulphate production in studies with sulphur-oxidizing bacteria originating from environmental samples of WWTPs.

Capability of a selected bacterial consortium for degrading diesel/biodiesel blends (B20): enzyme and biosurfactant production.

The search for alternative sources of energy, such as biodiesel, has been stimulated, since this biofuel is highly susceptible for biodegradation and has low toxicity, thus, reducing the impact in ecosystems. The objective of this study was to select a bacterial consortium with potential for degrading diesel/biodiesel blends (B20) obtained from areas contaminated with hydrocarbons/esters. In order to evaluate the biodegrability of the blend, six enzyme assays were conducted: alkane hydroxylase, Catechol 1,2-dioxygenase, Catechol 2,3-dioxygenase, Protocatechol 3,4-dioxygenase, ρ-NPA hydrolysis (esterase), and release of fatty acids through titration (lipase), with estimative of total protein and biosurfactant production (surface tension measurement and emulsifying index E(24)). The best results obtained allowed the selection of four bacteria isolates (Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia) for compiling a consortium, which will be used for bioaugmentation strategies in soils contaminated with these fuels. This consortium exhibited high potential for biodegradation of biodiesel, and might be an efficient alternative for cleaning up these contaminated environments.