Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-21

Effect of lignin-degrading enzymes on the decomposition of large aromatic hydrocarbons:
Coronene as a surrogate for powdered activated carbon (PAC).
Kojo Twum Konadu 1, Keiko Sasaki 1*, Kwadwo Osseo-Asare 2, Takashi Kaneta 3.
1. Kyushu University, Department of Earth Resources Engineering, Fukuoka, Japan.
2. Penn State University, Department of Materials Science & Engineering and Department of Energy &Mineral Engineering, Pennsylvania, USA.
3. Okayama University, Department of Chemistry, Okayama, Japan.
Abstract
Coronene was decomposed by the cell-free spent medium (CFSM) of Phanerocheate chrysosporium, whichcontained 1.12 mU/mL and 20.61 mU/mL of lignin peroxidase (LiP) and manganese peroxidase (MnP) respectively.
The reaction was completed in three days, during which, about 13.6% of the initial 10 mg of coronene had been
converted into primarily aliphatic compounds. The changes effected by lignin-degrading enzymes on the chemicalbonds in the coronene and PAC residues were similar, which indicated that the coronene can function as surrogate
for studying larger hydrocarbons.
collected by filtration through a 0.2 µm filter and the1. Introduction
Lignin-degrading

enzymessuchasligninactivities of MnP [5] and LiP [1] were determined

peroxidase (LiP), manganese peroxidase (MnP) andbefore being used for coronene degradation.

laccase, are known to degrade aromatic hydrocarbons

2.2 Coronene degradation

by cleaving the C=C and C=O bonds in materials like

20 mL samples of CFSM were contacted with 10

coal and powdered activated carbon (PAC) which aremg of coronene (97%) at initial pH of 4.0 and 30ºC.

sometimes used as surrogates for the carbonaceous

The mixture was shaken at 120 rpm for 7 days andmatter in refractory gold ores [1-3]. However, thesesamples were taken periodically for analysis. The

substrates have complex molecular sizes andsolid residue was washed with ultra-pure water before

structures, making it difficult to adequately quantify

being dried under vacuum at room temperature.

the effects of the enzymes. Accordingly, coronene

Afterwards, the dried solid was characterized by(C24H12) was selected as a surrogate for some larger

fluorescence spectrometry, SEM, XRD, FTIR andhydrocarbons because it represents the smallest

1

approximation to graphene sheets [4]. It was

3. Results and discussion

H-NMR.

anticipated that by using this simpler aromatic carbon,
it would be easier to characterize and make inferences
about the effect of biodegradation on materials likePAC
2. Experimental
2.1 Fungal growth and enzyme secretionP.

chrysosporium

wasusedforenzyme

production in a liquid culture with the same
composition as Tien [1]. The fungus was cultured in
500 mL of the medium in a 2000 mL sterilized flasks
for 3 days at pH 4.0, 37ºC and no agitation. Following

Fig. 1 Changes in residual coronene mass over bio-that, the cell-free spent medium (CFSM) wasdegradation time. Initial coronene mass 10 mg.

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Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-21
Fluorescence spectrometry was used to quantify

4. Conclusions

the amount of degraded coronene by the CFSM overFurther tests on the suitability of coronene as athe 7-day period. The findings in Fig. 1 appear tosurrogate for PAC will be conducted includingshow that the reaction was completed around the 3rdAu(CN)2- uptake, but, based on the currently

day, with about 1.36 mg of the coronene being

available data, coronene can serve as an easierconverted into other substances by 22.4 mU of LiP

characterization tool for larger, insoluble aromaticand 414.4 mU of MnP. 3D fluorescence analysis ofhydrocarbons.

the solid residue did not show any other compounds
mixed with coronene. Thus, indicating that theoxidized products formed by the enzymes were either
fluorescent inactive or released into solution. Anobserved increase in acidity of the residual liquidsupernatant illustratesd the formation of some watersoluble compounds.
FTIR and 1H-NMR showed an increase in thealiphatic functional groups C-H, C=C-H and carbonyl
C=O relative to the C=C in the solid residue.
Comparatively, the coronene residues and PAC
residues from our earlier work [3] exhibited similarchanges in chemical bonding after CFSM treatment,with the exception of the pH change, indicating thatboth substances might have followed C=C bondcleavage pathway for aromatic carbon degradation bylignin-degrading enzymes.
The physical structure of PAC and coronene

Fig. 2 XRD patterns of the fresh coronene and the bio-residues were also analyzed, focusing on the poretreated residues in the regions of 8.9-9.6° for the 001

structure of the solids. N2 adsorption experiments

peak.

conducted on the PAC residue showed that theReference

specific surface area was significantly decreased after[1] Ofori-Sarpong, G., Tien, M., Osseo-Asare, K.

the treatment. This change was ascribed to theHydrometallurgy, 102, (2010), 66-72.

destruction of the microporous structure to form

[2] Tien, M., Kirk, T. K. Meth. Enzymol. 161, (1988),

larger pores, however, analysis of the coronene

238-299.

residue by XRD (Fig. 2) showed that the layer[3] Konadu, K. T., Sasaki, K., Osseo-Asare, K.,

structure was progressively compressed, resulting in

Kaneta, T. Hydrometallurgy, 168, (2017), 76–83.

a decrease in the d-spacing of the slits. This

[4] Bartolomei, M., Pirani, F., Marques, J.M.C. J.

observation illustrates that it is possible that not allPhys.

the micropores in the PAC residue were enlarged but[5] Wariishi, H., Valli, K., Gold, M. H. J. Biol. Chem.,that some might have become inaccessible through267, (1992), 23688-2369.

compression.

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Chem. C, 121, (2017), 14330–14338.