Actinobacteria useful in co-contamination bioremediation process

SIMÓN ZOLÁ MZ; APARICIO JD; POLTI MA; ALVAREZ A; BENIMELI C.S.; AMOROSO M.J.

La Falda

Workshop; 2do Workshop lationoamericano sobre bacterias rizosféricas promotoras del crecimiento vegetal (PGPR-Latinoamerica 2014); 2014

Introduction Mixed pollution caused by organic and inorganic compounds is a widespread problem that tends to concentrate in soils and sediments. Bioremediation technologies with microorganisms and/or plants have become the focus of interest. In the last ten years a stronger emphasis has been placed on the study of microbial bioremediation of environments with heavy metals and pesticides. Actinobacteria is an important group of microorganisms, able to remove oil, pesticides, and heavy metals, among other substances. There have been previous studies on biotransformation of organoclhorine pesticides or heavy metals by actinobacteria. The use of a single population involves many metabolic limitations, which could be avoided by using bacterial consortium. The aim of this work was to evaluate the use of actinobacteria to remediate soil co-contaminated with lindane and Cr(VI). Materials and methods Actinobacteria were used to remediate soil co-contaminated with Cr(VI) and lindane. Four actinobacteria, tolerant to Cr(VI) and lindane mixture were selected: Streptomyces spp. A5, M7, and MC1, and Amycolatopsis tucumanensis DSM 45259. Sterilized soil samples (SSS) were inoculated with actinobacteria strains, either individually or as a consortium, and contaminated with Cr(VI) and lindane, either immediately or after 7 days of growth, and incubated at 30 ºC during 14 days. Also, inoculated SSS without toxics and non-inoculated SSS with both toxics were used as controls. The actinobacteria showing better performance in the SSS were selected to carry out studies in non-SSS, in order to evaluate the influence of the native microbial flora on their ability to remove Cr(VI) and lindane. Results This study was conducted to determine the ability of actinobacteria to grow and remove Cr(VI) and lindane in SSS. Lindane was used at a concentration of 25 mg kg_1, (2.5 times its acceptable level in soils). In control flasks, bioavailable chromium was reduced from 50 to 12 mg kg_1 considering that a fraction of chromium was adsorbed by soil compounds. Over time, this concentration was kept constant considering 12 mg kg_1 as 100% to further calculations. No variations of lindane concentrations in both control series were observed, so, there was no evidence of noticeable contribution of abiotic processes to the pesticide removal. All actinobacteria were able to grow and remove both contaminants, the consortium showed the highest Cr(VI) removal, while Streptomyces sp. M7 produced the maximum lindane removal. In non-SSS, Streptomyces sp. M7 and the consortium removed more than 40% of the lindane, while Streptomyces sp. M7 demonstrated the greatest Cr(VI) removal. The most appropriate strategy for bioremediation of Cr(VI) and lindane co-contaminated soils would be the inoculation with Streptomyces sp. M7. Conclusion Streptomyces sp. M7 and the consortium tested could be useful for bioremediation of soils co-contaminated with Cr(VI) and lindane. There are two strategies, either inoculation of a portion of non-sterilized soil with actinobacteria and then using this to inoculate a contaminated environment, or else using actinobacteria grown in a synthetic medium. This latter approach reduces operational time in the laboratory and therefore reduces costs as well. Areas temáticas propuestas: Aplicaciones ambientales y Bio-remediación [6] y Biotecnología [4]