Potencial de cianobactérias para a biorremediação de águas e solos contaminados por arsênio

• Autor(a) principal: Souza, Eliane Aparecida de
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2500
• topic: Cianobactérias; Arsênio; Biorremediação; Cyanobacteria; Arsenic; Bioremediation; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

Environmental contamination by arsenic (As) is an increasingly present threat to aquatic ecosystems, in particular to those, which are close to mining areas. A number of researchers have been using the capacity of some microorganisms to tolerate and/or absorb contaminant ions from the polluted environments. Bioremediation techniques using microorganisms, such as cyanobacteria, consist on removing toxic ions from the environment using living organisms. The aim of this study was to evaluate the effect of As on the growth, absorption and toxic effects of Nostoc piscinale and Geitlerinema unigranulatum unicyanobacterial cultures. The growth was monitored by biomass content, using optical density (OD750nm) and cell number count (mL-1) associated with protein, total non protein thiols and chlorophyll a (Chl a). Morphological alterations on vegetative cells were also analyzed. Arsenic concentrations in the experiments were equivalent to: 0; 5; 50; 100; 150; 200; and 250 mg L-1 , in the form of sodium arsenate (Na2HAsO4. 7H2O). The analyses were carried out during 10 days. Data were examined by factorial analysis of variance (ANOVA p <0.05) and, when necessary, by Tukey's multiple comparison test (p <0.05). Both cyanobacteria N. piscinale and G. unigranulatum showed different behavior regard to As tolerance. The absorption was proportional to the increase of As concentration in the culture medium. Nostoc piscinale reached the maximum absorption peak at 150 mg L-1 As (As accumulation equal to 20.58 kg g-1 in the dry biomass). For G. unigranulatum, the largest As accumulation was 200 mg L-1 kg g-1, reaching 6.83 kg g-1 in the dry biomass. Maximum protein content determined in N. piscinale was 781.19 µg mL-1 when As concentration was 50 mg L-1 of As, approximately 12% higher than the control treatment. At 100 mg L-1 of As, G. unigranulatum produced 30,737.28µg mL-1 of protein, 42% higher than the control. The highest concentration of total non-protein thiols produced by N. piscinale was 0.0587 nmol g-1 and in G. unigranulatum was 0.0533 nmol g-1, both concentration was obtained at 150 mg L-1 of As. The highest Chl a contents was found in the control treatment, both for N. piscinale and equivalent to 2.66 µg ml-1 of Chl a. For G. unigranulatum the value was 4.25 µg ml-1 of Chl a. There was a reduction in Chl a content between treatments. Morphological and visual alterations were registered. It shows that As toxicity caused evident morphological alterations in vegetative cells of N. piscinale, whereas in G. unigranulatum no such significant changes were noticed between treatments and control. The results indicated that N. piscinale and G. unigranulatum could be indicated and used as potential alternatives for bioremediation of As impacted environments, in future laboratory experiments.