Furfural removal from liquid systems by actinobacteria

Abstract

Many industries such as petrochemical, pulp and paper, pharmaceutical, and food industries involve processes that use or produce furfural. Furfural is a heterocyclic aldehyde obtained by dehydrating at high temperatures of xylose; therefore, it is a characteristic compound present in acid hydrolyzates in which the furfural concentration can usually reach 2–3 g l−1. In the region Northeast of Argentina (NEA), furfural is produced from detanized quebracho sawdust. In NEA, wastewaters derived from furfural production contain around 800 mg l-1 of this compound, which can cause toxic effects on living systems if they are released into the environment without proper treatment. In the present work, the removal of different concentrations of furfural by actinobacteria from liquid systems was studied. Isolates of actinobacteria called L4, L6, L9 and L13 obtained from sediments of stabilization ponds of a furfural-producing plant in the NEA region, and Streptomyces sp. A5, A6, A12, A14 and M7, obtained from sites contaminated with other xenobiotic compounds, were selected on base of their tolerance to furfural in Starch Casein Agar medium. In order to select the most efficient actinobacteria with respect to their growth and furfural removal ability in liquid medium, Minimal Medium (MM) added with a furfural concentration of 418±1 mg l-1 as the only carbon and energy source was used. This selection was carried out by determining the minimum relationship between the concentration of residual furfural and the microbial growth. Streptomyces sp. A12 and M7 and strain L9 were selected because they showed the minimal relationship. Subsequently, the selected strains, as pure and mixed cultures, were inoculated in MM supplemented with furfural 807±10 mg l-1 as the only carbon and energy source. The results showed that the three pure cultures were able to grow and develop under these conditions; however, the culture for which the relationship mentioned above was minimal, was the consortium formed by the actinobacteria L9, A12 and M7. In order to evaluate the effectiveness of the bioremediation process, ecotoxicity tests were carried out using Raphanus sativus seeds (radish, Punta Blanca variety). The culture supernatants were evaluated before and after its treatment for each condition. In response, inhibition of germination and elongation of the radicle and hypocotyl were determined in the presence of furfural. Significant increases in these bioindicators (p < 0.05) were obtained when the treatment was carried out with the consortium formed by the actinobacteria L9, A12 and M7. The results obtained suggest that the selected actinobacteria consortium represents a promising bioremediation tool for the treatment of effluents containing furfural.