Bioremediation of Heavy Metals from Aquatic Environments 229

Table 13.1. Bioremediations of various heavy metals by fungi.

Sr. No.

Metal

Fungi

References

1

Hg

Aspergillus niger

Acosta-Rodríguez et al. 2018

Aspergillus flavus

Kurniati et al. 2014

P. canescens

Say et al. 2004

R. arrhizus

Tobin et al. 1984

2

Cr

A. niger

Acosta-Rodríguez et al. 2018

Rhizopus nigricans

Bai and Abraham 2001

3

Pb

Penicillium sp.

Siegel et al. 1983

Rhizopus arrhizus

Fourest and Roux 1992

4

Cd

Aspergillus niger

Das et al. 2013

Penicillium spinulosum

Townslcy and Ross 1986

5

Zn

A. niger

Acosta-Rodríguez et al. 2018

6

As

Aspergillus nidulans

Maheshwari and Murugesan 2009

Aspergillus niger

Acosta-Rodríguez et al. 2018

7

Co

Trichoderma, Apecilomyces

Townslcy and Ross 1986

Penicillium, Pythium, Rhizopus, Aspergillus niger

Acosta-Rodríguez et al. 2018

and the second method involves the absorption of metals by the metabolism called bioaccumulation

(Kadukova and Vircikova 2005). Some of the studies that are based on the biosorption process are

detailed in Table 13.1.

These methods are surface binding, the complexion by various functional groups including

hydroxyl, phosphate, carboxyl, and amine groups and ion exchange reaction (Wang and Chen

2009). The fungus cell wall makes a connection with ions of metals (Figure 13.3). The extracellular

methods use cell wall binding, precipitation and chelation (Bellion et al. 2006). The recycling of

fungi in bioremediation is an expensive process (Tsezos 1984). Living cells of fungi are killed by

various methods like chemical drying, mechanical drying, autoclaving and vacuum drying.

Factors Affecting the Fungal Biosorption: The removal of ‘heavy metals’ by fungi depends on

various environmental factors and types of metals (Hassen et al. 1998). Different parameters such

as oxygen level and glucose affect the absorption of metals (Javaid et al. 2011). The parameters like

concentration, contact time, initial metal ion concentration, temperature, pH and biomass have been

noted to affect the fungal biosorption process (Kapoor and Viraraghavan 1995).

Fungal Bioleaching: Fungal bioleaching has been used in mining areas and for the treatment of

waste material containing metals (Bosecker 2001). Fungi can also be used for sorting of heavy

metals from low-grade ores (Chaudhary et al. 2014). Penicillium verruculosum and Aspergillus

were used to solubilize iron Penicillium and Aspergillus leached Ni, Fe and Co (Valix et al. 2001).

Fungal Bio-immobilization: The interaction between metals and fungus causes a notable decrease

in the mobility of heavy metals. This immobility has been achieved by different methods such as

bio-precipitation, bio-reduction/bio-oxidation, biosorption and bioaccumulation. The fungus,

Rhizopus arrhizus can be used for the elimination of Cu²⁺, Fe³⁺ and Cd²⁺ by the fungal

bio-immobilization process (Lewis and Kiff 1998).

Fungal Biomineralization: Biologically Controlled Mineralization (BCM) and Biologically

Induced Mineralization (BIM) are types of biomineralization. In BCM, the microorganisms are

used to control the growth and nucleation of the biominerals, however in BIM organisms modify

the native environment to produce optimum conditions for the mineral’s precipitation (Gadd 2010).