4.4 Metal Ion Biosorption Enhancement Using Molecular
Tools
Investigating biological mechanisms at the molecular level to produce bioengineered
organism with higher biosorption capacity can be used for effective bio-removal of
heavy metal. The high cost of conventional technologies to reduce toxic metal ion
concentrations in industrial wastewater to acceptable regulatory standards has
prompted exploitation of genetic and protein engineering approaches to produce
cost-effective “green” biosorbents (Valls and de Lorenzo 2002). Another emerging
area of research is the design and development of novel algal strains with increased
affinity, capacity, and selectivity for biosorption of heavy metal ions (Zvinowanda
et al. 2009; Karthikeyan et al. 2007). Many genes are involved in metal uptake,
detoxification, or tolerance (Ayansina and Olubukola 2017). Cysteine-rich peptides
such as glutathione (GSH), some lipopolysaccharides, phytochelatins (PCs), and
metallothioneins (MTs) bind metal ions (Cd, Cu, Hg, etc.) and enhance metal ion
bioaccumulation (Zhang et al. 2015).
Based on the above said technologies (AAB, PAB, immobilized algal cell,
molecular tools), various efforts have been made to commercialize the algal-based
Table 3.6 HM removal efficiency by immobilized algal biomass
Metal
species
Algae
pH Immobilized
Maximum metal
uptake (mg/g)
References
Cd
2+
Chlamydomonas
reinhardtii
6
–
79.7
Bayramoğlu
et al. (2006)
Chlorella
sorokiniana
5
–
192
Akhtar et al.
(2004)
Spirulina platensis
TISTR 8217
6
Alginate
70.92
Rangsayatorn
et al. (2004)
Spirulina platensis
TISTR 8217
4–7 Silica
36.63
Rangsayatorn
et al. (2004)
Cu
2+
Chlorella sp.
7
–
33.4
Maznah et al.
(2012)
Chlorella vulgaris
4.5 –
63.08
Mehta and Gaur
(2001)
Hg
2+
Chlamydomonas
reinhardtii
6
Ca-alginate
35.9
Bayramoğlu
et al. (2006)
Chlamydomonas
reinhardtii
6
Ca-alginate
106.6
Bayramoğlu
et al. (2006)
Ni
2+
Chlorella vulgaris
4.5 –
111.41
Mehta and Gaur
(2001)
Pb
2+
Chlamydomonas
reinhardtii
6
Ca-alginate
230.5
Bayramoğlu
et al. (2006)
Chlamydomonas
reinhardtii
6
Ca-alginate
380.7
Bayramoğlu
et al. (2006)
Zn
2+
Chlorella sp.
7
–
28.5
Maznah et al.
(2012)
70
S. Ahmad et al.
Tools
Investigating biological mechanisms at the molecular level to produce bioengineered
organism with higher biosorption capacity can be used for effective bio-removal of
heavy metal. The high cost of conventional technologies to reduce toxic metal ion
concentrations in industrial wastewater to acceptable regulatory standards has
prompted exploitation of genetic and protein engineering approaches to produce
cost-effective “green” biosorbents (Valls and de Lorenzo 2002). Another emerging
area of research is the design and development of novel algal strains with increased
affinity, capacity, and selectivity for biosorption of heavy metal ions (Zvinowanda
et al. 2009; Karthikeyan et al. 2007). Many genes are involved in metal uptake,
detoxification, or tolerance (Ayansina and Olubukola 2017). Cysteine-rich peptides
such as glutathione (GSH), some lipopolysaccharides, phytochelatins (PCs), and
metallothioneins (MTs) bind metal ions (Cd, Cu, Hg, etc.) and enhance metal ion
bioaccumulation (Zhang et al. 2015).
Based on the above said technologies (AAB, PAB, immobilized algal cell,
molecular tools), various efforts have been made to commercialize the algal-based
Table 3.6 HM removal efficiency by immobilized algal biomass
Metal
species
Algae
pH Immobilized
Maximum metal
uptake (mg/g)
References
Cd
2+
Chlamydomonas
reinhardtii
6
–
79.7
Bayramoğlu
et al. (2006)
Chlorella
sorokiniana
5
–
192
Akhtar et al.
(2004)
Spirulina platensis
TISTR 8217
6
Alginate
70.92
Rangsayatorn
et al. (2004)
Spirulina platensis
TISTR 8217
4–7 Silica
36.63
Rangsayatorn
et al. (2004)
Cu
2+
Chlorella sp.
7
–
33.4
Maznah et al.
(2012)
Chlorella vulgaris
4.5 –
63.08
Mehta and Gaur
(2001)
Hg
2+
Chlamydomonas
reinhardtii
6
Ca-alginate
35.9
Bayramoğlu
et al. (2006)
Chlamydomonas
reinhardtii
6
Ca-alginate
106.6
Bayramoğlu
et al. (2006)
Ni
2+
Chlorella vulgaris
4.5 –
111.41
Mehta and Gaur
(2001)
Pb
2+
Chlamydomonas
reinhardtii
6
Ca-alginate
230.5
Bayramoğlu
et al. (2006)
Chlamydomonas
reinhardtii
6
Ca-alginate
380.7
Bayramoğlu
et al. (2006)
Zn
2+
Chlorella sp.
7
–
28.5
Maznah et al.
(2012)
70
S. Ahmad et al.