The effect of combined quinone reductase (QR) and lignin peroxidase (LiP) on the depolymerization of technical lignins isolated from soda-anthraquinone (SAQ), steam explosion (S-E), and two sulfite processes (NaE and NaPE) was... more
The effect of combined quinone reductase (QR) and lignin peroxidase (LiP) on the depolymerization of technical lignins isolated from soda-anthraquinone (SAQ), steam explosion (S-E), and two sulfite processes (NaE and NaPE) was investigated. While LiP is best known for its ability to degrade lignins, it may also cause lignin re-polymerization due to the random coupling of phenoxy radicals and quinoid intermediates. This study evidenced that the addition of the bioreactor produced QR can to some extent limit the lignin re-polymerization by LiP. The synergistic application of QR and LiP lowered the molecular weights (Mw) of SAQ, NaE, S-E, and NaPE lignins by 31%, 34%, 41%, and 52%, respectively. The thermogravimetric analysis also showed that the thermal stability of the four lignins was reduced, whereas gas chromatography-mass spectrometry analysis showed that the degradation products included monomeric phenols. Therefore, the combined QR and LiP system is a promising approach for lignin valorization.
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This study aims to investigate the potential of using lignin sourced from South African black liquor as a total phenol substitute in phenol-formaldehyde resins (PFRs), with a particular focus on bonding strength and curing properties.... more
This study aims to investigate the potential of using lignin sourced from South African black liquor as a total phenol substitute in phenol-formaldehyde resins (PFRs), with a particular focus on bonding strength and curing properties. Four South African pulping-based lignins were used to synthesize these lignin-phenol formaldehyde resins (LPF100 resins), namely Eucalyptus Kraft lignin, Pine Kraft lignin, Bagasse Soda lignin, and Bagasse Steam Exploded lignin. Fourier-transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry were used to determine structural and curing properties. These resins were then used directly (unmodified) as adhesives to test shear bonding strength (R0 LPF100 adhesives). To improve the bonding properties of the unmodified LPF100 adhesives, the LPF100 resins were modified via the addition of a crosslinker (hexamine) as well as a hardener (either glyoxal, R1, or epichlorohydrin, R2). All R0 LPF100 adhesives fell below th...
Research Interests:
The effect of combined quinone reductase (QR) and lignin peroxidase (LiP) on the depolymerization of technical lignins isolated from soda-anthraquinone (SAQ), steam explosion (S-E), and two sulfite processes (NaE and NaPE) was... more
The effect of combined quinone reductase (QR) and lignin peroxidase (LiP) on the depolymerization of technical lignins isolated from soda-anthraquinone (SAQ), steam explosion (S-E), and two sulfite processes (NaE and NaPE) was investigated. While LiP is best known for its ability to degrade lignins, it may also cause lignin re-polymerization due to the random coupling of phenoxy radicals and quinoid intermediates. This study evidenced that the addition of the bioreactor produced QR can to some extent limit the lignin re-polymerization by LiP. The synergistic application of QR and LiP lowered the molecular weights (Mw) of SAQ, NaE, S-E, and NaPE lignins by 31%, 34%, 41%, and 52%, respectively. The thermogravimetric analysis also showed that the thermal stability of the four lignins was reduced, whereas gas chromatography-mass spectrometry analysis showed that the degradation products were mostly phenols. Therefore, the combined QR and LiP system is a promising approach for lignin val...
Research Interests:
Exploring indigenous microalgae capable of producing significant amounts of neutral lipids through high-throughput screening is crucial for sustainable biodiesel production. In this study, 31 indigenous microalgal strains were isolated... more
Exploring indigenous microalgae capable of producing significant amounts of neutral lipids through high-throughput screening is crucial for sustainable biodiesel production. In this study, 31 indigenous microalgal strains were isolated from diverse aquatic habitats in KwaZulu-Natal, South Africa. Eight superior lipid-producing strains were selected for further analysis, based on Nile red fluorescence microscopy screening. The microalgal isolates were identified to belong to the genera Chlorella, Neochloris and Chlamydomonas via morpho-taxonomic and molecular approach by 18S rRNA gene sequencing. Chlorella vulgaris PH2 had the highest specific growth rate (μ) and lowest doubling time of 0.24 day−1 and 2.89 ± 0.05 day−1, respectively. Chlorella vulgaris T4 had the highest biomass productivity of 35.71 ± 0.03 mg L−1day−1. Chlorella vulgaris PH2 had the highest lipid content of 34.28 ± 0.47 and 38 ± 9.2% (dcw) as determined by gravimetric analysis and the sulfo-phospho-vanillin (SPV) method, respectively. Chlorella vulgaris PH2 exhibited a high content of saturated fatty acids, while Chlorella sp. T4 exhibited a high total content of saturated and monounsaturated fatty acids with a low content of polyunsaturated fatty acids. The preponderance of neutral lipids suggests that Chlorella sp. T4 is a suitable candidate for biomass feedstock for biodiesel production.
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The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could... more
The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could improve the profitability of these processes and their environmental performance. In this study, an original strategy involving the sequential application of enzymes and pyrolysis was explored for the conversion (i.e., valorization) of lignins to bio-oil rich in phenols. Methods Four technical lignins from different processes were pretreated for 24 h using the concerted depolymerization action of lignin peroxidase and quinone reductase enzymes. Pyrolysis was then performed on the pretreated and untreated (control) samples using a bench-scale tubular reactor at 550 ℃ for 30 min. Results Enzymatic pretreatment could contribute to a 17.5-82.3% increase in the bio-oil mass yield during subsequent pyrolysis. In some cases, enzymatic pretreatment also imp...
Research Interests:
The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could... more
The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could improve the profitability of these processes and their environmental performance. In this study, an original strategy involving the sequential application of enzymes and pyrolysis was explored for the conversion (i.e., valorization) of lignins to bio-oil rich in phenols. Methods Four technical lignins from different processes were pretreated for 24 h using the concerted depolymerization action of lignin peroxidase and quinone reductase enzymes. Pyrolysis was then performed on the pretreated and untreated (control) samples using a bench-scale tubular reactor at 550 ℃ for 30 min. Results Enzymatic pretreatment could contribute to a 17.5-82.3% increase in the bio-oil mass yield during subsequent pyrolysis. In some cases, enzymatic pretreatment also improved the production of total phenols in bio-oils by a maximum of 43%, with steam explosion (S-E) lignin showing the best performance. Of the four technical lignins, S-E and sodaanthraquinone lignins gave the highest production of monomeric phenols whereas the sulfite lignins were more challenging to valorize due to their high inorganic contents. Conclusion Enzymatic pretreatment could contribute to the valorization of some technical lignins to phenols during subsequent pyrolysis.
Research Interests:
This study aims to investigate the potential of using lignin sourced from South African black liquor as a total phenol substitute in phenol-formaldehyde resins (PFRs), with a particular focus on bonding strength and curing properties.... more
This study aims to investigate the potential of using lignin sourced from South African black liquor as a total phenol substitute in phenol-formaldehyde resins (PFRs), with a particular focus on bonding strength and curing properties. Four South African pulping-based lignins were used to synthesize these lignin-phenol formaldehyde resins (LPF100 resins), namely Eucalyptus Kraft lignin, Pine Kraft lignin, Bagasse Soda lignin, and Bagasse Steam Exploded lignin. Fouriertransform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry were used to determine structural and curing properties. These resins were then used directly (unmodified) as adhesives to test shear bonding strength (R 0 LPF100 adhesives). To improve the bonding properties of the unmodified LPF100 adhesives, the LPF100 resins were modified via the addition of a crosslinker (hexamine) as well as a hardener (either glyoxal, R 1 , or epichlorohydrin, R 2). All R 0 LPF100 adhesives fell below the GB/T 17657-2013 plywood standard of 0.7 MPa, with the Bagasse Soda LPF100 adhesive recording the highest bonding performance of 0.5 MPa, and the lowest curing temperature of 688C. From the modified adhesives, the best performing were the Pine Kraft (R 1) and the Eucalyptus Kraft (R 2) LPF100 adhesives, recording 1.4 and 1.3 MPa, respectively. The curing temperatures of both these resins were 718C and 808C, respectively. Ultimately, the results of this study indicated that favorable adhesive properties may be obtained with the use of South African pulping-based lignins as a 100 percent phenol substitute in PFRs.
Research Interests:
The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could... more
The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could improve the profitability of these processes and their environmental performance. In this study, an original strategy involving the sequential application of enzymes and pyrolysis was explored for the conversion (i.e., valorization) of lignins to bio-oil rich in phenols. Methods Four technical lignins from different processes were pretreated for 24 h using the concerted depolymerization action of lignin peroxidase and quinone reductase enzymes. Pyrolysis was then performed on the pretreated and untreated (control) samples using a bench-scale tubular reactor at 550 ℃ for 30 min. Results Enzymatic pretreatment could contribute to a 17.5-82.3% increase in the bio-oil mass yield during subsequent pyrolysis. In some cases, enzymatic pretreatment also improved the production of total phenols in bio-oils by a maximum of 43%, with steam explosion (S-E) lignin showing the best performance. Of the four technical lignins, S-E and sodaanthraquinone lignins gave the highest production of monomeric phenols whereas the sulfite lignins were more challenging to valorize due to their high inorganic contents. Conclusion Enzymatic pretreatment could contribute to the valorization of some technical lignins to phenols during subsequent pyrolysis.