Fungal-bacterial biofilm mediated heavy metal rhizo-remediation

Abstract

Heavy metal pollution due to excessive use of chemical fertilizers (CF) causes a major damage to the environment. Microbial consortia, closely associated with the rhizosphere are able to remediate heavy metal-contaminated soil by reducing plant toxicity. Thus, this study was undertaken to examine the remedial effects of microbial biofilms against contaminated heavy metals. Fungi and bacteria isolated from soil were screened for their tolerance against Cd2+, Pb2+ and Zn2+. Fungal-bacterial biofilms (FBBs) were developed with the highest tolerant isolates and were further screened for their bioremediation capabilities against heavy metals. The best biofilm was evaluated for its rhizoremediation capability with different CF combinations using a pot experiment conducted under greenhouse conditions with potato. Three bacterial and two fungal isolates were selected to develop FBBs upon the tolerance index (TI) percentage. Significantly (P < 0.05) the highest metal removal percentage was observed in Trichoderma harzianum and Bacillus subtilis biofilm under in situ condition. The biofilm with 50% of recommended CF (50CB) significantly (P < 0.05) reduced the soil available Pb2+ by 77%, Cd2+ by 78% and Zn2+ by 62% compared to 100% recommended CF (100C). In comparison to initial soil, it was 73%, 76% and 57% lower of Pb2+, Cd2+ and Zn2+, respectively. In addition, 50CB treatment significantly (P < 0.05) reduced the metal penetration into the tuber tissues in comparison with 100C. Thus, it is concluded that T. harzianum–B. subtilis biofilm is an ideal combination to remediate soil contaminated with Cd2+, Pb2+ and Zn2+.

Evaluation of cellulolytic fungal-bacterial biofilms for the enhancement of bioethanol production

“…Filamentous fungi can be considered as biofilm-forming organisms as they naturally adapted to grow on surfaces [37]. The production of EPS by fungal mycelium has the potential to increase EPS production in FBBs [24,8]. In the current study, microscopic observation indicated high EPS secretion by FBBs (Fig.…”