From Microalgae to Sustainable Plastics: Preparing Protein Aggregates from Algal Biomass
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Authors
Wen, Yidan
Date
2025-02-07
Type
thesis
Language
eng
Keyword
Microalgae , Protein amyloid fibers , Bioplastics , Self-assembly , Protein extraction , Protein nanofibers
Alternative Title
Abstract
This thesis investigates the extraction and purification of proteins from microalgae, specifically spirulina and chlorella, and their self-assembly into amyloid-like aggregates as building blocks towards the development of sustainable bioplastic materials. In response to growing environmental concerns over traditional plastics, amyloid fibers – highly organized protein aggregates – offer a potential alternative due to their structural stability, functional versatility, and sustainability. Although amyloid fibers have been prepared from animal- and plant-based protein sources, microalgae protein-derived amyloid fibers remain largely unexplored. Given their high protein content and the current industrial production of microalgae, spirulina and chlorella present an untapped resource for the development of such materials.
Protein extraction and purification from spirulina and chlorella was performed using a pH shifting method, which is well-documented as an efficient, facile, and high-throughput protein extraction technique. Amyloid-like aggregation was induced under acidic conditions and elevated temperature, whereby spirulina proteins formed beta-sheet-rich structures with the typical fiber-like morphology, while chlorella proteins predominantly aggregated into non-fibrillar, spherical/annular structures. This difference in structural morphology underscores the importance of both protein purity and composition between sources. Protein aggregation is investigated in detail through Thioflavin T fluorescence, Fourier-Transform Infrared and circular dichroism spectroscopies, dynamic light scattering, zeta potential measurements, and atomic force microscopy imaging. Despite their morphological differences, both microalgal protein aggregates exhibit impressive stability across a wide pH range, persisting up to pH 11 before disassembly at pH 12, making them promising candidates for robust sustainable applications. Preliminary investigations incorporating model amyloid fibers into crude spirulina biomass revealed minimal improvement in mechanical strength, attributed to poor component mixing, underscoring the importance of processing in composite formation.
In short, this work underscores the feasibility of transforming microalgae proteins into stable aggregates with complex morphologies, and highlights the importance of biomass source, protein purity, and composition on the aggregation process. Our findings contribute to the growing and exceedingly important field of bio-based and biodegradable materials, and offer insights into the fundamental principles governing amyloid fiber formation. We anticipate that these efforts will lead to the formation of high-performance, tunable bioplastics which can be used for a variety of different applications.
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution-NonCommercial-NoDerivatives 4.0 International
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution-NonCommercial-NoDerivatives 4.0 International