The use of microbial fuel cell for efficient treatment of cauliflower waste and generation of electricity

Figures & data

Figure 1. Logical diagram of the research.

Table 1. List of abbreviations and symbols used in this manuscript.

Abbreviations and symbols	Meaning
MFC	Microbial fuel cell
COD	Chemical oxygen demand
SEM	Scanning electron microscopy
MWCNT	Multiwalled carbon nanotubules
PANI/MWCNT	Polyaniline multiwalled carbon nanotubules
LB	Lysogeny broth
CMC	Carboxymethyl cellulose
OCV	Open circuit voltage
PCR	Polymerase chain reaction
rRNA	Ribosomal ribonucleic acid
DNA	Deoxyribonucleic acid
BLAST	Basic Local Alignment Search Tool
NCBI	National Center for Biotechnology Information
g	Gram
mL	Millilitre
Mm	Millimetre
cm	Centimetre
mg/g	Milligram per gram
w/w	Weight by weight
w/v	Weight by volume
mW/m^3	Milliwatt per cubic metre
mg/L	Milligram per litre
v/v	Volume by volume
M	Molar
mV	Millivolt
H2SO4	Sulphuric acid
HNO3	Nitric acid
HCl	Hydrochloric acid
h	Hour
d	Day
°C	Degree celsius
H2O2	Hydrogen peroxide
Ω	Ohm
µL	Microlitre
µm^2	Square micrometre

Table 2. Physiochemical parameters of cauliflower waste sample.

Analytical parameters of cauliflower waste	Concentration
pH	7.0 ± 0.2
Ash content	9.51 ± 0.61%
Moisture	60.9%
Total reducing sugar (mg/g)	214.8
Soluble reducing sugar (mg/g)	0.53
Chemical oxygen demand (mg/g)	143.5 ± 5.60
Phosphorous (mg/g)	67.8
Ammoniacal nitrogen (mg/g)	0.90 ± 0.4

Figure 2. Open circuit voltage (OCV) observed during microbial fuel cell (MFC) operation at different time intervals. MFC was operated with normal graphite and polyaniline multiwalled carbon nanotubule (PANI/MWCNT)-coated graphite for analysis.

Table 3. OCV developed and power density during the MFC operation.

Substrate (anode/cathode)	Electrode (anode/cathode)	Open circuit voltage (mV)	Resistor (Ω)	Power density (W/m^3)	References
Cauliflower leaf waste/50 mM phosphate buffer	Graphite felt/ Graphite felt	200	–		This study
Cauliflower leaf waste/50 mM phosphate buffer	MWCNT-PANI-coated graphite/graphite	426	-		This study
Cauliflower leaf waste/50 mM phosphate buffer with K3[Fe(CN)6]	MWCNT-PANI-coated graphite/graphite	681	-		This study
Cauliflower leaf waste/50 mM phosphate buffer with K3[Fe(CN)6]	MWCNT-PANI-coated graphite/graphite	-	100	0.55	This study
Cauliflower leaf waste/50 mM phosphate buffer with K3[Fe(CN)6]	MWCNT-PANI- coated graphite/graphite	-	1000	10.1	This study
S. putrefacien- inoculated medium/ 0.05 M K3[Fe(CN)6]	MWCNT-PANI-coated graphite/graphite	342	1900	-	(Cui et al. 2015)

Note: K₃[Fe(CN)₆]: Potassium ferrocyanide.

Figure 3. Power generation in a microbial fuel cell using polyaniline multiwalled carbon nanotubule (PANI/MWCNT)-coated graphite fibre with the addition of potassium ferricyanide in catholyte and external resistance of 1000 and 100 Ω.

Table 4. Change in different chemical parameters of the substrate after MFC operation.

Electrode	Buffer	COD reduction (%)	Ammoniacal nitrogen reduction (%)	Phosphorus reduction (%)	Total reducing sugar reduction (%)
Normal graphite electrode	Phosphate buffer	10.75	50.5	10.4	36.5
PANI/MWCNT-coated graphite electrode with a resistor (1000 Ω)	Phosphate buffer with potassium ferricyanide	24.7	76.9	22.5	53.4

Note: COD: chemical oxygen demand; PANI/MWCNT: polyaniline multiwalled carbon nanotubules; MFC: microbial fuel cell.

Figure 4. Scanning electron microscopy (SEM) images of the graphite electrode. A: Normal graphite electrode; B: polyaniline multiwalled carbon nanotubule (PANI/ MWCNT)-coated graphite electrode and; C: PANI/MWCNT-coated graphite electrode after microbial fuel cell operation.

Figure 5. Holozone test for cellulolytic bacteria in carboxymethyl cellulose (CMC) agar plate by isolates R2, R3 and R4 (left to right) showing cellulolytic activity.

Figure 6. Gel electrophoresis of molecular amplification of 16S rRNA gene of bacterial DNA using a universal primer (1500 bp) in 1% agarose gel. L1: R2 bacteria, L2: R3 bacteria, L3: R4 bacteria and L4: ladder 100 bp.

Figure 7. Phylogenetic tree of R4 obtained by the neighbour-joining method using MEGA software. The efficiency of tree resolution was considered successful only when the clades have at least >50% bootstrap value. The allocated gene bank accession number of the R4 isolate is MT040749.

Cui, H. F., L. Du, P. B. Guo, B. Zhu, and J. H. T. Luong. 2015. “Controlled Modification of Carbon Nanotubes and Polyaniline on Macroporous Graphite Felt for High-Performance Microbial Fuel Cell Anode.” Journal of Power Sources 283: 46–53. doi:10.1016/j.jpowsour.2015.02.088.

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