Bio-removal of toxic metals by metal resistant anaerobic bacteria: molecular characterization and performance studies

Tese de dout., Ciências Biotecnológicas (Biotecnologia Ambiental), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2010

The objective of the research described in this thesis was the identification and characterization of anaerobic bacterial communities with high metal resistance and ability for metal removal, thus with potential for application in bioremediation processes. A sulphate-reducing bacteria (SRB) consortium resistant to high concentrations of heavy metals (Fe, Cu, Zn), similar to those typically present in acid mine drainage (AMD), was obtained from a wastewater treatment plant. Moreover, this consortium showed ability to use wine wastes as carbon and electron source. The phylogenetic analysis of the dsr gene sequence revealed that this consortium contains species of SRB affiliated to Desulfovibrio fructosovorans, Desulfovibrio aminophilus and Desulfovibrio desulfuricans. Wine wastes as carbon source for SRB activity were applied with success in a bioremediation process for the treatment of artificial AMD. TGGE fingerprinting and phylogenetic analysis showed that the composition of the community in the bioreactor fed with wine wastes remained stable during the whole time of operation and its bacterial diversity was higher than the community in the bioreactor fed with ethanol. Several microbial communities were investigated for their ability to remove uranium (VI) and additionally the impact of U(VI) on SRB communities was explored. Although the original communities were mainly composed by SRB, after uranium exposure these bacteria were not detected in the communities. The highest efficiency for U(VI) removal was observed with a consortium from a soil collected in Monchique thermal place. Moreover this community also showed ability to remove Cr(VI). However when U(VI) was replaced by Cr(VI) several differences in the structure of the bacterial community were observed. The mechanism of U(VI) removal by this consortium was also investigated and was found that U(VI) removal occurred by enzymatic reduction and bioaccumulation. Phylogenetic analysis of 16S rRNA showed that this community was mainly composed by bacteria closely related to Sporotalea genus and Rhodocyclaceae family.

Fundação para a Ciência e a Tecnologia(FCT)