Bioavailability of pollutants in bacterial communities of Rodrigo de Freitas Lagoon, Rio de Janeiro, Brazil

Processes involving heavy metals and other contaminants continue to present unsolved environmental questions. To advance the understanding of geochemical processes that involve the bioavailability of contaminants, cores where collected in the Rodrigo de Freitas lagoon, and analyzed for bacterial activity and metal concentrations. Results would suggest an extremely reducing environment where organic substances seem to be the predominant agents responsible for this geochemical process. Analytical data showed sulphate reduction to be the main agent driving this process, since this kind of bacteria was found to be active in all of the samples analyzed. Esterase enzyme production did not signal the influence of heavy metals and hydrocarbon concentrations and heavy metals were found to be unavailable for biota. However, correlation between results for bacterial biomass and the potentially mobile percentage of the total Ni concentrations would suggest a negative impact.

Alternative methodology for isolation of biosurfactant-producing bacteria

Wide biosurfactant application on biorremediation is limited by its high production cost. The search for cheaper biossurfactant production alternatives has guided our study. The use of selective media containing sucrose (10 g.L-1) and Arabian Light oil (2 g.L-1) as carbon sources showed to be effective to screen and maintain biosurfactant-producing consortia isolated from mangrove hydrocarbon-contaminated sediment. The biosurfactant production was assayed by kerosene, gasoline and Arabian Light Emulsification activity and the bacterial growth curve was determined by bacterial quantification. The parameters analyzed for biosurfactant production were the growth curve, salinity concentration, flask shape and oxygenation. All bacteria consortia screened were able to emulsify the petroleum derivatives tested. Biosurfactant production increased according to the incubation time; however the type of emulsification (non-aqueous phase or aqueous phase) did not change with time but with the compound tested. The methodology was able to isolate biosurfactant-producing consortia from superficial mangrove sediment contaminated by petroleum hydrocarbons and was recommended for selection of biosurfactant producing bacteria in tropical countries with low financial resources.

A ampla aplicação de biossurfactantes em biorremediação é limitada pelo seu alto custo de produção. A procura de alternativas de produção mais baratas motivou nosso estudo. O uso de meio seletivo, contendo sacarose (10 g.L-1) e óleo Arabe Leve (2 g.L-1), mostrou-se eficiente na triagem e manutenção de consórcios bacterianos isolados de sedimento de mangue contaminado com hidrocarboneto. A produção de biossurfactante foi avaliada pela Atividade Emulsificante do querosene, gasolina e Arabe Leve e a curva de crescimento foi determinada pela quantificação bacteriana. Os parâmetros analisados para a produção de biossurfactante foram: curva de crescimento, concentração da salinidade, forma do frasco e oxigenação. Todos os consórcios bacterianos pesquisados foram capazes de emulsificar os derivados de petróleo testados. A produção de biossurfactante aumentou de acordo com o tempo de incubação, entretanto, o tipo de emulsificação aquosa e não-aquosa não mudou com o tempo, mas com o composto testado. A metodologia permitiu o isolamento de consórcios bacterianos produtores de biossurfactante de sedimento superficial de mangue contaminado com hidrocarbonetos do petróleo, sendo indicada para seleção de bactéria produtora de biossurfactante em países tropicais com baixos recursos financeiros.