Developing cellulose-based opacifiers through enzymatic treatment of microcrystalline cellulose

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School of Chemical Engineering | Master's thesis
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Date

2025-10-27

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Major/Subject

Biotechnology

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Degree programme

Master's Programme in Chemical, Biochemical and Materials Engineering
Kemian-, bio- ja materiaalitekniikan maisteriohjelma
Magisterprogrammet i kemi-, bio- och materialteknik

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en

Pages

102

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Abstract

The growing demand for sustainable materials has driven efforts to reduce dependence on titanium dioxide, the dominant opacifier in paints, coatings and cosmetics. Although TiO2 is highly efficient, its production has a significant carbon footprint and raises health and environmental concerns, motivating the search for bio-based alternatives. Light scattering in biopolymers like cellulose is influenced by porosity, offering a model for designing sustainable opacifiers from low-refractive-index materials. This thesis investigates enzymatic modification of microcrystalline cellulose to develop cellulose-based opacifiers. Porosity was introduced using cellulase, with the aim of producing pores in the 200-350 nm range, roughly half the wavelength of visible light, to maximize multiple scattering and thereby improve opacity. Some samples also received ultrasonication pretreatment to assess its effect on enzymatic efficiency. Reaction parameters including enzyme dose, hydrolysis time, reaction temperature, and suspension consistency were varied to optimize porosity formation. Untreated MCC and TiO2 were used as a reference and porosity, pore size distribution, and optical properties were measured to evaluate the effect of treatments on light scattering and whiteness. Enzymatically treated MCC, including samples pretreated with ultrasonication, developed porosity in the 200-350 nm range, enhancing light scattering and opacity. Low enzyme dose at 3% consistency yielded better optical performance than higher doses at 5% consistency and surface roughness also contributed to improved light scattering. Ultrasonication likely enhanced enzyme efficiency. A clear correlation between increased porosity and higher opacity was observed. Although opacity remained below that of TiO2, treated MCC showed promise as a sustainable, bio-based opacifier and provides foundation for further optimization and exploration of alternative pretreatments and cellulose sources.

Description

Supervisor

Lipponen, Juha

Thesis advisor

Al-Ogaili, Ahmed

Keywords

microcrystalline cellulose, porosity, light scattering, cellulase, enzymatic treatment, opacifiers, MCC

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https://urn.fi/URN:NBN:fi:aalto-202512179386

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[dipl] Kemian tekniikan korkeakoulu / CHEM