Selection of sulfur oxidizing bacterium for sulfide removal in sulfate rich wastewater to enhance biogas production

Sulfur oxidizing bacteria (SOB) were isolated and tested in order to remove sulfide from high sulfate wastewater to reduce the amount of hydrogen sulfide (H2S) in the produced biogas. A promising SOB isolate, designated as isolate T307, was selected due to its best sulfide removal (86.7 percent) in the effluent of a sulfate reduction reactor (SRR) over a 24 hrs incubation. The bacterium was able to grow better as a mixotroph (yeast extract as a carbon source) than as a chemolithoautotroph. In addition, as a heterotroph, the bacterium grew well with yeast extract and peptone. Based on partial 16S rRNA gene sequence, the isolated T307 was an Alcaligenes sp. and was able to convert most of sulfide species (total sulfide: TS; dissolved sulfide: DS and H2S) into elemental sulfur or sulfate over a 20 hrs period of cultivation by controlling the speed of shaking. In a biogas reactor set, after pre-treating a sulfide medium with Alcaligenes sp. T307 there was a much higher specific yield of CH4 (238 ml CH4 g-1COD removed) and more biogas (154 ml L-1 d-1) was produced with the biogas containing more methane (48.1 percent CH4, 51.5 percent CO2 and 0.41 percent H2S) in comparison to a control with a specific yield of CH4, (72 ml CH4 g-1COD removed) 86 ml L-1 d-1 biogas produced with a composition of 35.5 percent CH4, 63.7 percent CO2 and 0.86 percent H2S.

Isolation of Thiobacillus sp from aerobic sludge of distillery and dairy effluent treatment plants and its sulfide oxidation activity at different concentrations.

In the present study two strains of Thiobacillus sp were isolated from aerobic sludge of distillery and dairy effluent treatment plant using standard methods of isolation and enrichment. Experiments were conducted using isolated cultures in batch bioreactor with initial sulfide concentration of 75 and 150 mg/l. The effect of initial sulfide concentration on the activity of isolated Thiobacillus sp was studied. Sulfide oxidizing capacity was also determined at different initial sulfide concentrations. The results from the study indicate the possible isolation of Thiobacillus cultures from native source and application in the full-scale reactor

Evidência sugerindo dois mecanismos de resistência ao arsenato em Thiobacillus ferrooxidans / Evidence for two arsenate resistance mechanisms in Thiobacillus ferrooxidans

Thiobacillus ferrooxidans é capaz de crescer na presença dos altos níveis de arsênio livre que säo gerados durante a recuperaçäo de ouro a partir de arsenopirita por lixiviaçäo. Os mecanismos dessa resistência näo säo conhecidos nessa bactéria. Uma cepa desta bactéria, isolada na Mina Morro Velho (Nova Lima, MG), foi cultivada em meio inorgânico 9K com concentraçöes de 0, 2, 4, 6 ou 8g.L-1 de arsenato de sódio em culturas semi-contínuas em fermentador de 10 litros. O crescimento celular foi pouco alterado por teores de arsenato inferiores a 4g.L-1. Para essa concentraçäo, o tempo de cultura foi consideralmente prolongado em funçäo de uma fase latente de cerca de 30h. Quando níveis de arsenato entre 4g.L-1 e 8g.L-1 foram utilizados, o perfise de cresciemtno das células adaptadas foi melhor. Este fenômeno näo foi observado nas culturas em frascos de 500mL (velocidade de agitaçäo: 150rpm). A comparaçäo dos perfis eletroforéticos (PAGE-SDS) dos extratos livres de células obtidos das bactérias cultuvadas sem ou na presença de 8g.L-1 de arsenato destacou, no último caso, quatro bandas maiores com peso molecular aparente de cerca de 16.500, 22.500, 24.000 e 33.500. Da, respectivamente. Esses resultados sugerem que há dois mecanismos de resistência em T. ferrooxidans para baixo e alto níveis de arsenato, respectivamente.