Cr(VI) and lindane removal by streptomyces sp.M7 is improved by maize root exudate

Abstract

Environmental mixed pollution by both organic and inorganic compounds are detected worldwide. Phytoremediation techniques have been proposed as ecofriendly methods for cleaning up polluted sites. Several studies have demonstrated enhanced dissipation of contaminants at the root-soil interface through an increase in microbial activity caused by the release of plant root exudates (REs). The aim of this study was to evaluate the effectiveness for Cr(VI) and lindane removal by Streptomyces M7 cultured in a co-contaminated system in presence of maize REs. In order to evaluate the performance of Streptomyces M7 on lindane and chromium removal, fasks with minimal medium (MM) with 1 g L-1 glucose were arti- cially contaminated with 2 mg L–1 lindane and/or 25 mg L-1 of Cr(VI), and inoculated with Streptomyces M7. Then, in order to evaluate the effect of maize REs on lindane and chromium removal by Streptomyces M7, fasks with MM (without glucose) were supplemented with maize REs (0.4 gC L-1). Then, MM was contaminated with 2 mg L–1 lindane and/or 25 mg L-1 of Cr(VI) and inoculated with Streptomyces M7 .Flasks were incubated at 30 ºC, 150 rpm, ve days. Microbial growth and contaminants concentrations were determined. Our results showed when REs were added to the contaminated MM as the only carbon source, microbial removal of Cr(VI) and lindane increased signicantly in comparison to contaminant removal obtained in MM with glucose 1 g L-1. The maximum removal of 91% of lindane and 49% of Cr(VI) were obtained in the co-contaminated system. Streptomyces M7 showed plant growth promoting traits which could improve plant performance in contaminated soils. The results presented in this study provide evidence that maize REs improved growth of Streptomyces M7 when REs were used as a carbon source in comparison to glucose. Lindane and Cr(VI) removal was considerably enhanced making evident the phytoremediation potential of the actinobacteria-plant partnership.