Discrepant hexavalent chromium tolerance and detoxification by two strains of Trichoderma asperellum with high homology

• Significant different Cr(VI) tolerance by two fungal strains with 99% homology.
• Cr(VI) reduction by extracellular enzyme prevented Cr getting into the fungal cells.
• Intracellular matter could complex with Cr in the cell and reduced chromium toxicity.
• Intracellular Cr discharged from cells reduced potential damage.

The tolerance and detoxification of Cr(VI) by eukaryotic microorganisms are of fundamental importance to the treatment of Cr contaminated wastewater. This study presents various significant tolerance and detoxification of hexavalent chromium [Cr(VI)] performed by two strains of PTN7 and PTN10, identified as Trichoderma asperellum with 99% homology. This difference demonstrated by the two similar fungal strains was interpreted based on series Cr(VI) reduction experiments, including those by fungi strain, extracellular polymeric substances (EPS), extracellular and intracellular enzyme in addition to analysis of Cr(VI) and total Cr in the fungal cells. Here, it was confirmed that the higher Cr(VI) tolerance performance by the preferable strain was attributed to stronger extracellular enzyme reduction ability, higher intracellular organic matter absorption capacity and higher intracellular Cr discharge rate from the cell, which could prevent Cr(VI) from getting into the cells, thus reducing potential damage of Cr(VI) to the cells.