Public defence, Bioproduct Technology, MSc Elisa Spönla

Title of the thesis: Enzymatic modification of lignocellulosic fibres and nanofibrils: From high-consistency fibre processing to laccase-aided hydrophobisation

Thesis defender: Elisa Spönla
Opponent: Professor emeritus Jack (John) Saddler, University of British Columbia, Canada
Custos: Professor Tiina Nypelö, Aalto University School of Chemical Engineering

Transition from fossil-based economy to bioeconomy requires resource-efficient utilisation of biomass. A significant proportion of the wood components, such as bark and parts of lignin and hemicellulose, currently end up in low-value applications, e.g., energy production. More efficient utilisation of these biomass fractions is becoming increasingly important from both economic and environmental perspectives. This doctoral thesis investigated enzymatic processing as a means of increasing the use of biomass in high-value products. Compared with chemical treatments, enzymes enable selective modification of biomass under mild conditions.

Traditionally, wood-based textile fibres are produced from dissolving pulp composed of highly purified cellulose. This thesis investigated how hemicellulose-rich paper-grade pulp could be used as a raw material for textile fibres through high-consistency enzymatic treatment, thereby retaining a larger proportion of wood components in the final product.  The results showed that enzymatic treatment enabled the use of paper-grade pulp in textile-fibre production and that high-consistency conditions significantly enhanced the enzymatic treatment. The results highlighted the importance of tailoring treatments to pulp properties. The process optimised for softwood pulp was less effective for eucalyptus pulp, but tailoring the enzyme mixture for eucalyptus significantly improved treatment efficiency. Pulp properties could be selectively modified by selecting enzyme combinations and coupling the enzymatic processing with chemical and hydrothermal treatments.

The thesis also investigated enzymatic modification of bark-based nanofibrils to make the material more hydrophobic and therefore better suited to applications such as coatings. The enzymatic treatment caused moderate changes in the surface chemistry of the samples, indicating increased hydrophobicity. Further research is needed to improve the treatment efficiency before the material can be used in practical applications.

The findings of this thesis support the development of more efficient and selectively targeted enzymatic treatments for wood-based materials. Beyond the applications studied, the work demonstrates that enzymatic processing offers versatile means of modifying wood-based materials, enabling more efficient utilisation of woody biomass and its side streams. Enzymatic modification may therefore increase the value derived from renewable natural resources and accelerate the transition towards a more resource-efficient bioeconomy.
 

Keywords: enzymatic modification, endoglucanase, xylanase, mannanase, laccase, cellulose, hemicellulose, high-consistency, regenerated fibre, lignocellulose nanofibril, functionalisation, side stream, carbohydrate binding module

Thesis available for public display 7 days prior to the defence at Aalto University's public display page.

Contact information: 
elisa.sponla@vtt.fi