Function and mechanism of polysaccharide on enhancing tolerance of Trichoderma asperellum under Pb2+ stress.

Trichoderma asperellum ZZY had good tolerance to Pb2+. The polysaccharide contains a functional group which can be effectively combined with metal ions. So in this manuscript, the function and mechanism of polysaccharide on enhancing tolerance of Trichoderma asperellum were further explored. The results indicated that the polysaccharide plays vital role in Pb2+ tolerance of Trichoderma asperellum. Most lead ions adsorbed on and transferred into mycelia were accumulated in the pure polysaccharide. The proportion of uronic acid and the ratio of main chain in pure polysaccharide were increased when the strain under Pb2+ stress. These changes increase the contact area of polysaccharides with Pb2+ and the ratio of carboxyl groups to provide more binding sites for Pb2+, which is beneficial to reduce the amount of free Pb2+ and slow down the toxicity. The response changes in surface morphology and advanced structure of polysaccharide also support the conclusion. The manuscript provided theoretical basis for the application on the remediation of lead pollution. It also had contributions to the remediation of heavy metal pollution in the environment and the environmental safety.