Chromate reduction by Burkholderia cepacia immobilized in sol-gel silica matrices

G. ALVAREZ; FOGLIA, M.L.; CAMPOROTONDI DANIELA; DEGROSSI, JOSÉ; DESIMONE, MARTÍN F.; DIAZ L.

Tucuman

Congreso; SAIB XLV Reunión Anual; 2009

SAIB

Cr (VI) is highly soluble and bioavailable, its carcinogenic and teratogenic potential is well known. Cr (III) on the contrary is less soluble and less toxic. Cr (VI) pollution mainly results from industrial activities. Chemical methods for the reduction of chromate are expensive thus recently biological treatments arouse great interest. In this work we proposed the use of sol-gel silica matrices obtained from sodium silicate to immobilize a chromate reducing bacteria. The advantages of  bacteria immobilization are the possibility to recycle the beads, protect bacteria and reduce their presence in the resulting product. Bacteria were cultured aerobically at 35 ºC in different media amended with chromate concentrations from 25 to 500 ppm. Cr (VI) was estimated by the diphenyl carbazide method. Experiments were performed in the presence of various electron donors such as glucose and in LB media. Best results were obtained with LB media. No difference was observed for pH 7 and pH 9. B. cepacia was resistant to 1000 ppm of Cr (VI) and reduced more than 98% of Cr (VI) within 48 hs when 50 or 100 ppm were added. After 8 days, bacteria reduced more than 89% and 60% of 400 and 500 ppm respectively. No differences were observed between bacteria in suspension and the immobilized ones. Further studies are being performed with real samples obtained from metal plating waste and contaminated soils.