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PhD Defense: Isolation,characterization and applications of nanocellulose produced by ancestral enzymes

Asteartea, Apirilak 30, 2019 - 11:00
CFM Auditorium
Borja Alonso, nanobiomechanics group, nanoGUNE
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Nanocellulose has been described as a new wonder material that can be isolated from cellulose. Nanocellulose has a myriad of applications. However, efficient, controlled and sustainable nanocellulose isolation is still a challenge with current methodologies. Enzyme hydrolysis shows up as a novel alternative, but yields are lower in comparison with chemical methods. To improve this process, we need new enzymes with higher performances. Here we propose the use of ancestral enzymes developed with ancestral sequence reconstruction (ASR); these had shown higher activity, stability and promiscuity than the extant ones, demonstrating then ideal for biotechnology application. Here, we present a method based on the utilization of ancestranl endoglucanase. This method allows controlling nanocellulose size and maintains the native cellulose structure where the chemical or mechanical methods fail. This enzymatic nanocellulose shows higher crystallinity and thermostability than a commercial nanocellulose sample produced by acid sulfuric treatment. The optimized protocol was used to isolate nanocellulose from lignocellulosic substrates. In this case we used treatments with addition of different ancestral enzymes such as xylanase and lytic polysaccharide monooxygenase (LPMO), to help ancestral endoglucanase hydrolysis. We achieved nanocellulose isolation from two lignocellulosic pulps with different properties. Also, we observed how LPMO produced nanocellulose oxidation. Here, we propose LPMO as substitution of chemical oxidation of cellulose, demonstrating that the enzymatic method can substitute both nanocellulose isolation and modification by chemical methods. 
The enzymatic nanocellulose can be used in high performance tailored materials. In this thesis, we studied our nanocellulose in two different applications. The first one was as reinforcement for thermoplastic materials, in our case waterborne polyurethane (WBPU). As control we used commercial nanocellulose produced by sulfuric acid. We observed that small nanocellulose addition produced nanocomposites with higher thermal and mechanical properties. Nanocomposites with our nanocellulose had better properties than the ones prepared with the acid hydrolyzed nanocellulose. Moreover, we introduced the enzymatic nanocellulose to manufacture conductive nanopapers with graphene addition by two different strategies. We produced nanopapers with high thermal, mechanical and conductive properties by mixing enzymatic nanocellulose with different concentration of reduced graphene. Moreover, by graphene chemical vapor deposition (CVD) over a nanocellulose film we manufactured transparent conductive films, as substitution of plastic or metal substrates. Overall this thesis represent one of the very first report in wich succefull production of nanocellulose is achieved by using these enzymes. This nanocelluloses has properties that make it ideal for medical applications in biotechnology.

Supervisor: R. Pérez-Jiménez / María Aranzazu Eceiza

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