Abstract
Nickel contamination is a serious environmental issue that requires immediate action. In this study, 23 strains of Trichoderma were isolated from terrestrial and marine environments and identified using a polyphasic approach of morphological characterization and ITS gene sequence analysis. The Trichoderma strains were tested for their tolerance and biosorption of nickel. Our results showed the growth of all Trichoderma strains on Trichoderma Selective Medium (TSM) with 50–1200-ppm nickel, indicating their tolerance of this heavy metal even at a relatively high concentration. Six Trichoderma strains (three isolated from terrestrial substrates and three from marine substates) had the highest radial growth on TSM with 50-ppm Ni. Among these fungal isolates, Trichoderma asperellum (S03) isolated from soil exhibited the best growth after 2 days of incubation. For the biosorption of nickel, the accumulation or uptake efficiency by the six selected Trichoderma was determined in Potato Dextrose Broth (PDB) supplemented with 50-ppm Ni using a Flame Atomic Absorption Spectrophotometer (AAS). The percent uptake efficiency of the three strains of T. asperellum (S03, S08, and LL14) was computed to be up to 66%, while Trichoderma virens (SG18 and SF22) and Trichoderma inhamatum (MW25) achieved up to 68% uptake efficiency. Observation of the Trichoderma strains with Scanning Electron Microscopy (SEM) before and after the absorption of nickel showed very minimal damage on the hyphal and conidial surface morphology, but changes in the colonial characteristics were observed. Our study highlighted the potential of terrestrial and marine strains of Trichoderma for the bioremediation of nickel pollution.
Highlights
Heavy metals may cause damage by moving up the food chain to accrue in humans [1]
Terrestrial and marine substrates were used for the isolation of Trichoderma
While strains isolated from marine substrates almost grow comparatively well in the presence and absence of marine salts in their culture media, their growth under saline conditions showed the adaptability of Trichoderma in the marine environment
Summary
Heavy metals may cause damage by moving up the food chain to accrue in humans [1]. Due to their chemical stability, they persist in the environment. Several methods have been devised for the treatment and removal of heavy metals in contaminated sites [2]. These traditional physicochemical processes for the remediation of polluted soils are expensive and often do not permanently alleviate the pollution hazard. The inhalation of nickel can cause cancer of the lungs, nose, and sinuses [4] These all necessitate the removal of heavy metal contamination, nickel, from contaminated sites. Even fungus-like protists such as slime molds or myxomycetes could be involved in the biosorption of heavy metals [10]
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