Doctoral Dissertation: Improving enzymatic conversion of lignocellulose to platform sugars
The doctoral dissertation entitled "Improving enzymatic conversion of lignocellulose to platform sugars" of Anikó Várnai, M.Sc. in Bioengineering, was examined in the Faculty of Agriculture and Forestry, University of Helsinki, on 9 November.
Increasing demand and uncertain availability of fossil fuels urge us to find alternative resources available in large quantities especially for the petrol-based transportation sector.
Lignocellulosic biomass, available worldwide in plant cell walls, is a promising alternative feedstock. It can be depolymerised to sugar monomers, which provide potential raw material for sugar platform-based production of fuels and chemicals. However, the enzymatic saccharification of lignocellulose to platform sugars is hindered primarily by the complexity of lignocellulosic substrates as well as by the performance of the hydrolytic enzymes involved.
This study focuses on various rate limiting factors such as the decrease in the reactivity and accessibility of the substrates which slow down the hydrolysis, on auxiliary enzymes needed for the efficient solubilisation of cellulose, as well as on the adsorption of enzymes. Consequently, solutions to these limitations were sought to improve the efficiency of biomass conversion processes.
This study showed for the first time that increasing substrate concentration could compensate for the absence of carbohydrate binding modules (CBMs) in hydrolytic enzymes (Paper V). The performance of cellulases lacking CBMs was comparable to that of cellulases comprising CBM at 20% substrate concentration.At the same time, over 60% of the enzymes without CBMs could be recovered at the end of the hydrolysis. Thus, the major part of hydrolytic enzymes without CBMs could potentially be recovered in industrial high consistency processes.
Professor Jack N Saddler, University of British Columbia, served as the opponent, and Professor Annele Hatakka as the custos.
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