Enhancement of emulsifier production by Curvularia lunata in cadmium, zinc and lead presence

Abstract

The influence of cadmium, zinc and lead on fungal emulsifier synthesis and on the growth of filamentous fungus Curvularia lunata has been studied. Tolerance to heavy metals established for C. lunata was additionally compared with the sensitivity exhibited by strains of Curvularia tuberculata and Paecilomyces marquandii-fungi which do not secrete compounds of emulsifying activity. Although C. lunata, as the only one out of all studied fungi, exhibited the lowest tolerance to heavy metals when grown on a solid medium (in conditions preventing emulsifier synthesis), it manifested the highest tolerance in liquid culture - in conditions allowing exopolymer production. Cadmium, zinc and lead presented in liquid medium up to a concentration of 15 mM had no negative effect on C. lunata growth and stimulated emulsifier synthesis. In the presence of 15 mM of heavy metals, both the emulsifier and 24-h-old growing mycelium exhibited maximum sorption capacities, which were determined as 18.2 +/- 2.67, 156.1 +/- 10.32 mg g(-1) for Cd2+, 22.2 +/- 3.40, 95.2 +/- 14.21 mg g(-1) for Zn2+ and 51.1 +/- 1.85, 230.0 +/- 28.47 mg g(-1) for Pb2+ respectively. The results obtained by us in this work indicate that the emulsifier acts as a protective compound increasing the ability of C. lunata to survive in heavy metal polluted environment. Enhancement of exopolymer synthesis in the presence of Cd2+, Zn2+ and Pb2+ may also suggest, at least to some extent, a metal-specific nature of emulsifier production in C. lunata. Due to accumulation capability and tolerance to heavy metals, C. lunata mycelium surrounded by the emulsifier could be applied for toxic metal removal.

Mn2+ modulates the expression of cellulase genes in Trichoderma reesei Rut-C30 via calcium signaling

“…For example, Ca 2+ plays an important role in the regulation of cellulase or hemicellulase in T. reesei [ 13 – 15 ]. Paraszkiewicz et al [ 37 ] reported Cd 2+ , Zn 2+ , and Pb 2+ as environmental stress factors, which increased the biosynthesis of fungal emulsifier in Curvularia lunata . Addition of Ca 2+ , Na + , and Mn 2+ enhanced ganoderic acid production in Ganoderma lucidum liquid cultures, through induction of the calcineurin signal pathway [ 17 , 29 , 38 ].…”

Mycogenic nanoparticles and their bio-prospective applications: current status and future challenges

“…A large number of fungi have been reported for the extracellular secretion of mucilaginous materials (ECMM or emulsifier) which also comprises excellent toxic metal binding capabilities. Paraszkiewicz et al [78] found that unlike other metal ions like (Cu II, Pb II and Zn II), Ni (II) did not stimulate ECMM production by Curvularia lunata. They also found that saturation of cellular fatty acids which is clearly characterized by Ni (II) triggered lipid peroxidation processes.…”

Characterization and mechanism of copper biosorption by a highly copper-resistant fungal strain isolated from copper-polluted acidic orchard soil

“…This may be because the heavy metal stress in liquid medium can stimulate mycelium to increase the secretion of extracellular mucilaginous material (ECMM). With polysaccharide and protein as the main components, ECMM can effectively protect the fungal cells, reduce the toxic effects of heavy metal ions on the cells, and increase the tolerance of mycelia to Cu ( Paraszkiewicz et al 2007;Vesentini et al 2007;Paraszkiewicz et al 2009;Sun et al 2009).…”