Hydrogen ions and organic acids secreted by ectomycorrhizal fungi, Pisolithus sp1, are involved in the efficient removal of hexavalent chromium from waste water

• Published in: Ecotoxicology and environmental safety 2018-10, Vol.161, p.430-436
• Main Authors: Shi, Liang, Xue, Jiawang, Liu, Binhao, Dong, Pengcheng, Wen, Zhugui, Shen, Zhenguo, Chen, Yahua
• Format: Article
• Language: English
• Subjects: Adsorption; Biodegradation, Environmental; Carboxylic Acids - metabolism; Chromium - isolation & purification; Chromium - metabolism; Cr(VI) reduction; EAOAs; ECM fungi; Hydrogen-Ion Concentration; Mycorrhizae - metabolism; Organic acids; Organic Chemicals; Oxidation-Reduction; Pisolithus sp1; Protons; Waste Water - chemistry; Water Pollutants, Chemical - isolation & purification; Water Pollutants, Chemical - metabolism
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2018.06.004

Pisolithus sp1 is an ectomycorrhizal (ECM) fungi that was chosen during a screening test of six strains of ECM fungi due to its ability to tolerate and remove hexavalent chromium (Cr(VI)). The physiological responses of Pisolithus sp1 to Cr(VI) exposure, the relationship between Pisolithus sp1 and exogenously added organic acids (EAOAs) or Na3VO4 (H+-ATPase inhibitor) and the ability of Pisolithus sp1 to reduce Cr(VI) in liquid culture were also investigated. Hydrogen ions (H+), which were produced directly by Pisolithus sp1, reduced the pH of the medium and played an important role in Cr(VI) reduction; however, Na3VO4 significantly inhibited this process and resulted in a decrease in the Cr(VI) reduction rates. Organic acids were secreted after the reduction in Cr(VI) by Pisolithus sp1, and EAOAs did not significantly affect Cr(VI) reduction; those results revealed the secondary role of organic acids in Cr(VI) reduction. The Cr(VI) removal rate of Pisolithus sp1 approached 99% after Cr(VI) treatment for 12 days. Overall, 75% of the Cr(VI) removal was due to extracellular reduction and 24% was due to adsorption. The results of this study provide a strong basis for using Cr(VI)-tolerant and Cr(VI)-reducing fungi, as well as ectomycorrhiza, in the remediation of Cr(VI)-contaminated sites. A Cr(VI)-tolerant ectomycorrhizal (ECM) fungi, Pisolithus sp1, with high Cr tolerance and removal ability was screened out from 6 strains. Pisolithus sp1 is the first reported ECM fungi, which can remove more than 99% Cr(VI) within 12 days. H+ which directly secreted by Pisolithus sp1 mainly involved in the Cr(VI) reduction, oxalic acid and malic acid played an secondary role in this process. The major physiological mechanism of Cr(VI) removal in Pisolithus sp1 is extracellular reduction and cell wall adsorption, which accounting for about 75% and 24% respectively. [Display omitted] •Pisolithus sp1 showed the strongest removal ability to Cr(VI) among six ECM fungi.•More than 99% Cr(VI) was removed by Pisolithus sp1 within 12 days.•Extracellular reduction is the main mechanism of Cr(VI) removal by Pisolithus sp1.•Secretion of H+ from Pisolithus. sp1 mainly involved in the Cr(VI) reduction.