Transcript
Strategic development for the mitigation of heavy metals in the surface water around coal mining
areas using native cyanobacterial strains
By,N. Arul Manikandan
Junior research fellowUnder the guidance of
Dr. K. PakshirajanDepartment of Biosciences and Bioengineering
Indian Institute of Technology Guwahati
Contents
• Introductiona) Heavy metal pollutionb) Robustness of cyanobacteria• Results and discussiona) Mechanism involved in N. muscorumb) Kinetics and isotherm of metal uptakec) Effect of heavy metals on lipid accumulation• Conclusions• References
Heavy metal pollution
Acid Mine drainage (AMD) Mines built as early as the 1800’s were developed in a manner which
utilized gravity drainage, to avoid excessive water accumulation in the mines.
As a result, water polluted by acid, iron, sulfur and aluminum drained away from the mines and into streams
2FeS2(s) + 7O2(g) + 2H2O(l) 2Fe2+(aq) + 4SO42−(aq) + 4H+(aq)
Iron pyrites
Iron Sulfuric acid
The acid runoff further dissolves heavy metals such as copper, lead, mercury into ground or surface water.
Methods to remove heavy metals
Coa
gula
tion
2
Extra
ctio
n
3
Bio
sorp
tion
4
Phyt
orem
edia
tion
5
Phyc
orem
edia
tion
6
Conventional chemical methods
Novel biological methods
1
Prec
ipita
tion
Robustness of cyanobacteria
The oxygen atmosphere that we depend on was generated by numerous
cyanobacteria photosynthesizing during the Archaean and Proterozoic Era.
Many species are filamentous, forming long, straight chains of cells or many
branching chains.
There is growing interest in the field of application of cyanobacteria as
bioremedial agents to overcome the heavy metal-related environmental
problems:
a) They offer in situ remediation of contaminants without input of energy and
materials for their growth and biomass production.
b) They also require no organics for their growth, which is a major drawback
with other microorganisms, such as bacteria and fungi.
S. No Components Quantity/ L
1 citric acid 0.006 g
2 ferric citrate 0.006 g
3 EDTA (disodium salt)
0.001 g
4 Na2CO3 0.02 g
5 MgSO4 · 7H2O 0.075 g
6 CaCl2 · 2H2O 0.036 g
7 K2HPO4 0.04 g
8 Trace minerals
BG-110 media for N. muscorum cultivation
Materials and methods
Syiem et al. 2015
Hwang et al. 2014
Heavy metal removal mechanism by cyanobacterium
N. muscorum
Four key aspects in heavy metal removal by N. muscorum
1
23
4Initial Passive
biosorption
Biosorption following Ion-
exchange
Active intracellular uptake
Metal assimilation by Redox reactions
Intracellular redox reaction
Exopolysaccharides and Proteins
Outer membrane yielding to
sorption
Periplasmic membrane to
transport metal ions
Export
Components involved in heavy metal removal by cyanobacteria
FTIR image showing polysaccharide and protein present in cell wall of N. muscorum
Generally, the various functional groups such as hydroxyl, amino, carboxyl, sulfhydryl etc., present on the cell surface confer negative charge to the cell surface (Chojnacka et al. 2005).
Cu
Cu
Cu
Cu
Cu
Cu
Pb
Pb
Pb
PbPb
CdCd
Cd
Zn
Cd
Cd
Zn
Zn
Zn
Zn
Zn
Zn
Redox reactions
Metal removal by quick sorption and slow intracellular uptake
During the passive uptake, metal ions are adsorbed onto the cell surface within a relatively short span of time.
Time (min.)
0 50 100 150 200 250
Cu(
II) re
mov
al (m
g/g)
0
2
4
6
8
10
Experimental observation of metal removal by quick biosorption followed by slow
bioaccumulation
Biosorption of heavy metals
Slow intracellular uptake
Metal removal by Ion-exchange mechanism
Cu
Cu
Cu
Cu
Cu
Cu
Pb
Pb
Pb
PbPb
CdCd
Cd
Zn
Cd
Cd
Zn
Zn
Zn
Zn
Zn
Zn
Redox reactionsC
CC
C
C
C
C
C
N
N
N
N
N
N
N
Metals are likely to bind the adsorption sites on biomass by displacing other cations linked through energetically weaker bonds.
NC
EDX image showing metal removal by N. muscorum through Ion-exchange mechanism
Virgin biomass
Heavy metal treated biomass
The metabolic activities in live species possibly help in higher uptake of metal ions, and also, more binding sites are available in live biomass as compared to dead biomass.
Comparison of biosorption and bioaccumulation
0 10 20 30 40 50 60 700
20
40
60
80
100
120
140(a)
Run 1 Run 2 Run 3 Run 4Run 5 Run 6 Run 7 Run 8Run 9 Run 10 Run 11 Run 12
Time (h)
Cu(
II) r
emov
al (%
)
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S. No Cu
(mg/L)
Pb (mg/L) Cd
(mg/L)
Fe
(mg/L)
Zn
(mg/L)
Ca
(mg/L)
(%)Cu
Removal
(%)Pb
Removal
(%)Cd
Removal
1 10 15 10 5 5 10 56.72 99.19 61.22
2 10 20 10 1 10 10 62.04 54.60 74.91
3 5 20 10 1 10 5 93.64 99.05 78.89
4 10 20 5 5 10 5 89.55 99.50 79.02
5 5 15 10 5 10 5 96.46 99.30 83.68
6 10 20 5 5 5 5 95.07 99.07 73.01
7 10 15 5 1 10 10 92.90 52.40 66.96
8 5 15 5 1 5 5 95.89 99.18 88.52
9 10 15 10 1 5 5 53.23 90.00 52.34
10 5 20 10 5 5 10 94.69 87.93 86.00
11 5 15 5 5 10 10 96.88 99.29 86.60
12 5 20 5 1 5 10 89.19 82.50 76.06
Plackett- Burmann designResults
It has been suggested that different metals have preference for binding with different ligands
Specific functional group present in biomass
Kinetic studySingle and multi metal system
A BHeavy metal
removal
A B Heavy metal removal
Study on effect of co-ions
A – Ligands present in the N. muscorum; B – Heavy metals present in the solution
Pseudo-second order
Pseudo-first order
when one of the reactants concentration is in excess (10 to 100 times) of the other reactant, then the reaction follows a first order kinetics and such a reaction is called pseudo-first order reaction.
Isotherm study
Cu
Cu
Cu
Cu
Cu
Cu
Pb
Pb
Pb
PbPb
CdCd
Cd
Zn
Cd
Cd
Zn
Zn
Zn
Zn
Zn
Zn
Redox reactions
Langmuir isotherm Freundlich isotherm Temkin isotherm
qm
(mg/g)
KL
(L/m
g)
R2 n
g/L
KF
(mg/g)
R2 kTm
(L/m
g)
bTm
(kJ/
mol)
R2
0.063 7.298 0.923 1.66 1.533 0.99 0.00
70
6.196 0.92
Biosorption Bioaccumulation
0 50 100 150 200 250 300 3500
1
2
3
4
5
6
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8
Biomass concentration ( g /L )
pH
Cultivation time (hours)
Bio
mas
s con
cent
ratio
n (g
/L)
pH
Reactor study
Photo bioreactor
Among the different heavy metals examined for their bioremoval by N. muscorum in this multicomponent study, Pb(II) was removed with a high efficiency followed by Cu(II) and Cd(II).
However, the time required for maximum metal removal was prolonged to 72 hrs due to the presence of co-ions.
The metal removal by EDX analysis simply suggested ion-exchange as a possible mechanism for binding of metal ions onto the biomass surface for their uptake, and this is attributed to the presence of N-H and C=O functional groups by FTIR analysis.
The metal removal by N. muscorum followed the pseudo first-order kinetics with very high estimated sorption capacity values for all these metals.
Overall, this study proved a very good potential of the cyanobacterium N. muscorum in the removal of heavy metals from a complex mixture containing metals and other co-ions.
Conclusions
References Roy, A. S., Hazarika, J., Manikandan, N. A., Pakshirajan, K., & Syiem, M. B. (2015).
Heavy Metal Removal from Multicomponent System by the Cyanobacterium Nostoc muscorum: Kinetics and Interaction Study. Applied biochemistry and biotechnology, 175(8), 3863-3874.
Manikandan, N. A., Pakshirajan, K., & Syiem, M. B. (2014). Cu(II) removal by biosorption using chemically modified biomass of Nostoc muscorum–a cyanobacterium isolated from a coal mining site. International Journal of Chemtech Research, 07(1), 80-92.
Hazarika, J., Pakshirajan, K., Sinharoy, A., & Syiem, M. B. (2014). Bioremoval of Cu (II), Zn (II), Pb (II) and Cd (II) by Nostoc muscorum isolated from a coal mining site. Journal of Applied Phycology, 1-10.
Syiem, M. B., Goswami, S., Diengdoh, O. L., Pakshirajan, K., & Kiran, M. G. Zn (II) and Cu (II) removal by Nostoc muscorum: a cyanobacterium isolated from a coal mining pit in Chiehruphi, Meghalaya, India. Canadian Journal of Microbiology.
Hwang, J. H., Kim, H. C., Choi, J. A., Abou-Shanab, R. A. I., Dempsey, B. A., Regan, J. M., ... & Jeon, B. H. (2014). Photoautotrophic hydrogen production by eukaryotic microalgae under aerobic conditions. Nature communications, 5.
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The Critical Micelle Concentration（ CMC） of Sophorolipids is 10～ 40mg/L, and γ-CMC is 30～ 40mN/m, has very high efficiency as surfactants. This figure is 5 to 20 times better than Sodium Dodecyl Sulfate(SDS), being considered due to its balky structure. However, Sophorolipids generate only less foam, contributing to easy rinsing and lower skin stimulus.
High Degradability Sophorolipids has high degradability as same as Lauric Acid Sodium Salt, far better Eco-Friendliness comparing to existing synthetic surfactants.
Properties
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Mulligan, C.N., Yong, R.N. and Gibbs, B.F., 2001. Surfactant-enhanced remediation of contaminated soil: a review. Engineering Geology, 60(1), pp.371-380.
Chaprão, M.J., Ferreira, I.N., Correa, P.F., Rufino, R.D., Luna, J.M., Silva, E.J. and Sarubbo, L.A., 2015. Application of bacterial and yeast biosurfactants for enhanced removal and biodegradation of motor oil from contaminated sand. Electronic Journal of Biotechnology, 18(6), pp.471-479.
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solubilization ratio (SR)
Emulsification activity and stability
Minimum surface tension, CMC and interfacial tension determination
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The results suggested that the longer hydrophobic chain in SL gives less CMC.
CMC of SLs ranges between 40 to 100 mg/l andthe value depends on the substrate used for its production.
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Emulsification
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n
Acidic sophorolipid Lactonic sophorolipid
n
OOH
OOH
OH
O
CH2OR2
CH2OR2CH3
OO CH
C = O
CH2
O
n
OH
OOH
OH
O
CH2OR2
CH2OR2CH3
O CH
C = O
CH2
O
OOH
OOH
OH
OH
O
CH2OR2
CH2OR2CH3
O CH
COOH
CH2
OOH
OOH
OH
OH
O
CH2OR2
CH2OR2CH3
O CH
CH2
SLs synthesis is associated with nitrogen starvation.
Overall, it can be concluded that the physiological role of SLs synthesis is extracellular carbon source storage, combined with dealing with a high-sugar niche and defending it against other competing microorganisms (Van Bogaert et al., 2007).
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SLs and their derivatives have also shown promise as surfactants, emulsifiers, antimicrobials, and a source of specialty chemicals such as sophorose and hydroxylated fatty acids ( Rau et al., 2001 and Solaiman et al., 2007).
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Factors influencing the sophorolipids production
Operation conditions
Physical parameters
Medium composition
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23
4Agitation
pHAeration
TemperatureN
itrog
en
sour
ce21
Car
bon
sour
ce
11
23
4
Fed-batchSelf cyclingfermentation
Resting cellmethod
Batch
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But compared to chemical surfactants biosurfactants can be considered environmentally safer, and besides this, they have several advantages over chemical or synthetic surfactants, such as high ionic strength tolerance, high temperature tolerance, higher biodegradability and lower toxicity, lower critical micelle concentration and higher surface activity (Bognolo, 1999).
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Classical commercial fermentation processes for the production of non-growth associatedproducts can be subdivided into three phases (Omstead et al., 1985) and SLs is noexception: (1) the first stage is inoculum development; (2) the second phase is the stagein which SLs are microbiologically synthesized and (3) the third phase is recovery ofSLs.
India has approximately 90 different vegetable oil refineries located in different states of the country.
Industrial wastewater treatment using sophorolipids
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Process Timeline Flow
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