Bioprospecção de bactérias em efluentes de indústrias de papel e celulose com potencial de descoloração de azo corantes

Abstract

At the height of industrialization, effluents produced by large industries, containing toxic waste in their composition, are commonly dumped in irregular locations, causing contamination. Many compounds present in these effluents are toxic and carcinogenic. A good example are synthetic dyes, such as azo dyes, most abundant synthetic dye produced, used in large scale in the textile, pharmaceutical, food and pulp and paper industries. The effluent from the pulp and paper industry presents residual synthetic dyes, in addition to many lignolytic compounds, which have a molecular structure similar to that of synthetic dyes, so the present study had the objective of bioprospecting effluent bacteria from the pulp and paper industry ( Eldorado, located in Três Lagoas-MS), which had the potential to discolor and reduce the azo dyes janus B (VJ-B) and methyl orange (AM), for laboratory use, given the structural similarity between them. For this purpose using the ATZ-R selective medium containing the dye as the only source of carbon, bacteria were isolated and purified from the industrial effluent. A total of 8 bacteria were isolated for study (4 in each of the 2 dyes), all classified as gram-negative rods, oxidase positive. The isolates were subjected to a discoloration test under microaerophilic conditions for 144 hours to evaluate the ability to the dyes discoloration. For the orange methyl dye, yeast extract was used as a source of nitrogen to ascertain the influence that this causes of the discoloration process. Samples had measured OD (624 or 625 m VJ and 460 nm AM) every 24 hours (0 to 144 h). At the initial and final time of the test, the chemical oxygen demand test (COD) was performed to verify the oxygen consumption by the bacteria to perform the biodiscoloration process. Samples of VJ-B had the reduction shown by the change in coloration, turning from blue to purple purple, isolates J2 and J3 demonstrated a better reduction in less time, with 91.21% and 91.79%, respectively. However, the COD reduction did not exceed 15%. For the AM dye, the isolates presented good performance, with visible removal of the orange color, the yeast extract showed to be effective to increase the bacteria's ability to discolor the dye, reducing the time of discoloration, the isolates L1 and L2, demonstrated good capacity, in the discoloration and reduction of COD. However, when using yeast extract, discoloration increased by up to 20%, whereas for COD reduction there was no statistical difference, reinforcing the theory that discoloration and reduction of COD are independent events. The two isolates that presented the best results for each dye had the RNAr 16S gene sequenced and identified as belonging to the genus Pseudomonas, well described in the literature on the ability of discoloration, but not yet described as discoloration of VJ-B dye. Thus, the results of the present work were very promising, since the isolated bacteria showed the ability to reduce the dyes studied under microaerophilic conditions.