Descoloração do corante verde de malaquita por isolado bacteriano

Abstract

Malachite green (VM) is a triphenylmethane dye widely used in the textile industry, aquaculture and has also been reported as toxic to living things. When discarded in effluents, they cause bioaccumulation in the local biota, in addition to preventing the transmission of light in the receiving body due to strong colorings reducing photosynthesis and causing damage to the environment. Various physical and chemical methods are used to discolor this dye. However, biological methods are economically viable in addition to being eco-friendly. Therefore, this work aimed to isolate bacteria from the environment of water bodies with potential degradation of VM. The strain denominated LAMBA 3.8 was selected because it presented degradation greater than 90 % in medium containing 50, 100 and 150 mg.L -1 of dye. Degradation was also evaluated at pH 7 and 8 and at two incubation temperatures, 30 and 37 ºC, at times 24 and 48 h. The decolorization efficiency was higher at pH 7 and 8 at both temperatures, in 48 h of incubation. The concentration of the dye did not affect the rate of discoloration. The laccase enzyme was measured at 1.66 U.L -1 . The degraded dye was evaluated by UV-Vis and FTIR. The UV-Vis spectrum showed change in the absorbance of the VM, while the peaks in the FTIR showed changes in the functional groups. In the phytotoxicity test, the treated solution continued to present toxicity in Vigna radiata seed, whereas the microtoxicity test showed that the treated solution no longer inhibited the Enterococcus sp isolate, sensitive to the VM dye. We concluded that the LAMBA 3.8 isolate effectively degraded the VM in addition to losing toxicity after treatment, showing that it is a viable isolate for the bioremediation process.