Strength of Flocs Formed by the Complexation of Lysozyme with Leonardite Humic Acid
1
Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8572, Ibaraki, Japan
2
Department of Soil Science, University of Chittagong, Chittagong 4331, Bangladesh
3
Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8572, Ibaraki, Japan
*
Author to whom correspondence should be addressed.
Polymers 2020, 12(8), 1770; https://doi.org/10.3390/polym12081770
Received: 14 July 2020 / Revised: 2 August 2020 / Accepted: 5 August 2020 / Published: 7 August 2020
(This article belongs to the Special Issue Polymers and Nanomaterials: Interactions and Applications)
Aggregation and aggregates properties of natural organic and nanosized macromolecules such as humic substances and proteins are crucial to explore so-called colloid-mediated transport and the fate of substances in soil and water environments. Therefore, the aggregation and dispersion, charging, and floc strength of lysozyme (LSZ)–leonardite humic acid (LHA) flocs were experimentally investigated. The experiments were performed in different salt concentrations and LSZ to LHA mass ratios as a function of pH. We obtained the stronger flocs at pH 4.4, where the isoelectric point (IEP) of the complex with the mass ratio 2.5 was confirmed. Thus, the aggregation of LSZ–LHA flocs is mainly caused by charge neutralization. We obtained the floc strength of 4.7 nN around IEP at low salt concentration of 3 mM, which was stronger than 2.8 nN in high salt concentration of 50 mM. The effect of salt concentration can be rationalized by charge-patch attraction at low salt concentration. With increasing mass ratio, the IEP shifted to higher pH. This is due to the increase in positive charge from LSZ in the mixture. The effect of the LSZ to LHA mass ratio on the maximum strength was weak in the range studied.
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Keywords:
floc breakage; humic substance; protein; aggregation
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MDPI and ACS Style
Wan Abdul Khodir, W.K.; Hakim, A.; Kobayashi, M. Strength of Flocs Formed by the Complexation of Lysozyme with Leonardite Humic Acid. Polymers 2020, 12, 1770. https://doi.org/10.3390/polym12081770
AMA Style
Wan Abdul Khodir WK, Hakim A, Kobayashi M. Strength of Flocs Formed by the Complexation of Lysozyme with Leonardite Humic Acid. Polymers. 2020; 12(8):1770. https://doi.org/10.3390/polym12081770
Chicago/Turabian StyleWan Abdul Khodir, Wan K.; Hakim, Azizul; Kobayashi, Motoyoshi. 2020. "Strength of Flocs Formed by the Complexation of Lysozyme with Leonardite Humic Acid" Polymers 12, no. 8: 1770. https://doi.org/10.3390/polym12081770
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