Engineering of lignin and lignin-carbohydrate complexes for high-value applications
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School of Chemical Engineering |
Doctoral thesis (article-based)
| Defence date: 2026-01-23
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en
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129 + app. 62
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Aalto University publication series Doctoral Theses, 8/2026
Abstract
Industrial development has led to a dramatic increase in fossil fuel consumption. These nonrenewable energy sources, while currently accessible and cost-effective, contribute heavily to greenhouse gas emissions, therefore accelerating anthropogenic climate change. Addressing this global environmental challenge requires a transition toward sustainable, low-carbon energy alternatives. Within this paradigm, lignocellulosic biomass has emerged as a promising solution, offering a renewable, carbon-neutral feedstock that can be converted into biofuels and bioproducts. Its valorization not only supports the reduction of fossil fuel dependence but also contributes to the mitigation of climate change by harnessing a circular bio-based economy. However, despite its high availability and low cost, lignocellulosic biomass exhibits significant resistance to degradation, presenting substantial challenges for its effective valorization. While considerable progress has been made in the efficient conversion and application of cellulose, lignin remains a challenging component of lignocellulosic biomass, often assigned to combustion or disposal, thus extremely underestimating its unique chemical potential. To address the challenges in lignin utilization, a novel strategy was developed based on structure–property–performance correlation, representing a first step toward efficient lignin engineering. The approach involves selective modification of targeted functional groups while keeping others unchanged, followed by comprehensive property and performance evaluation. It was particularly useful for investigating how specific functional groups affect the physicochemical behavior of lignin and its performance in methylene blue adsorption. For instance, benzylic −OH groups were found to contribute approximately 3 and 2.3 times more than phenolic and aliphatic −OH groups, respectively. Overall, this work established a robust framework for tailoring lignin properties to meet the demands of high-value applications. Following that, a recently developed green biorefinery concept (AqSO Omni) was advanced using the power of artificial intelligence (AI) to provide simultaneous maximization of both lignincarbohydrate complexes (LCCs) yield and content in acetone-extracted lignin as LCCs hold great potential for high-value applications, yet achieving high yields remains challenging. Using Bayesian Optimization, optimal processing conditions were identified, achieving LCC yields of 8–15 wt% and carbohydrate contents up to 60/100 Ar. Importantly, LCCs with higher carbohydrate content showed lower glass transition (Tg) and surface tension, highlighting a significant step toward scalable production of tailor-made LCCs with tuned properties. Based on the previous outcomes, lignin demonstrated strong radical scavenging potential, that marked the urgent need for the development of a reliable and fast screening method for quantitative evaluation of the antioxidant properties of lignin. It was achieved by assessing the impact of the solvent, time, and the type of substrate on the antioxidant activity using a well-established 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. This work unveiled the importance of appropriate solvent choice as it predetermines the DPPH scavenging mechanism, steady state establishment, and the DPPH stability with 90 vol% acetone (aq.) exhibiting the greatest suitability for the antioxidant evaluation. While a small-scale and rapid performance evaluation method for lignin engineering is concerned, the concluding stage of the study involved the development of the UV-shielding lignocellulosic film, where a small addition of lignin into the formulation allowed to block over 90% of the UV rays.Description
Supervising professor
Hummel, Michael, Prof., Aalto University, Department of Bioproducts and Biosystems, FinlandThesis advisor
Balakshin, Mikhail, Prof., Aalto University, Department of Bioproducts and Biosystems, FinlandRigo, Davide, Doctor of Science, Institut Català d'Investigació Química (ICIQ), Spain
Other note
Parts
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[Publication 1]: Diment, Daryna; Tkachenko, Oleg; Schlee, Philipp; Kohlhuber, Nadine; Potthast, Antje; Budnyak, M. Tetyana; Rigo, Davide; Balakshin, Mikhail. 2023. Study toward a More Reliable Approach to Elucidate the Lignin Structure–Property–Performance Correlation. Biomacromolecules, 25(1), pp.200-212.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202401171529DOI: 10.1021/acs.biomac.3c00906 View at publisher
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[Publication 2]: Diment, Daryna; Löfgren, Joakim; Stosiek, Matthias; Alopaeus, Marie; Cho, Mijung; Xu, Chunlin; Hummel, Michael; Rigo, Davide; Rinke, Patrick; Balakshin, Mikhail. 2024. Enhancing Lignin‐Carbohydrate Complexes Production and Properties with Machine Learning. ChemSusChem, p.e202401711.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202505143651DOI: 10.1002/cssc.202401711 View at publisher
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[Publication 3]: Diment, Daryna; Musl, Oliver; Balakshin, Mikhail; Rigo, Davide. 2025. Guidelines for Evaluating the Antioxidant Activity of Lignin via the 2, 2‐diphenyl‐1‐picrylhydrazyl (DPPH) Assay. ChemSusChem, p. e202402383.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202507045552DOI: 10.1002/cssc.202402383 View at publisher
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[Publication 4]: Diment, Daryna; Cho, Mijung; Rigo, Davide; Hummel, Michael. 2025. Fractionation of AqSO biorefinery lignins and their application in antioxidant and UVprotective films. ChemSusChem, p. e202501985.
DOI: 10.1002/cssc.202501985 View at publisher