Elina Heikkilä

Topochemistry of alkaline, alkaline-peroxide and hydrotropic pretreatments of common reed to enhance enzymatic hydrolysis efficiency.

Common reed was studied as raw material for sugar bioconversion. The low temperature alkaline, alkaline-peroxide and hydrotropic pretreatments were employed to overcome the recalcitrance of reed before enzymatic hydrolysis. After pretreatments, lignin was efficiently decreased from the fiber cell wall. Xylan was significantly reduced by hydrotropic pretreatment as well. The surface chemical compositions of reed before and after pretreatments were investigated by X-ray spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Reed had a high surface coverage by lignin. Hydrotropic pretreatment was outstanding to decrease the surface coverage by lignin and expose the polysaccharides to fiber surface. The surface lignin reduction was also supported by attenuated total reflectance (ATR)-FTIR results. Furthermore, the topochemical modification of the fiber wall by hydrotropic pretreatment could improve the fiber digestibility, and thus the maximum glucan and xylan yields with the cellulase dosage of 20 FPU/g raised to 93.1% and 25.5%, respectively.

Topochemistry of Environmentally Friendly Pretreatments To Enhance Enzymatic Hydrolysis of Sugar Cane Bagasse to Fermentable Sugar

In this work, dilute alkaline and alkaline peroxide pretreatments were conducted in comparison with hydrotropic pretreatment to improve the delignification of bagasse prior to enzymatic hydrolysis. The surface chemical composition of bagasse after pretreatments was investigated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The surface distribution of lignin and extractives on the bagasse fiber was significantly changed by dilute alkaline, alkaline peroxide, and hydrotropic pretreatments. Hydrotropic pretreatment typically showed, other than the decrease of surface coverage by lignin and extractives, dramatic removal of xylan, thereby leading to more cellulose exposed on the fiber surface after pretreatment. Fiber morphology after pretreatments was more favorable for enzyme hydrolysis as well. However, the hydrotropic treatment had clear advantages because the enzymatic hydrolysis yields of glucan and xylan of pretreated bagasse were 83.9 and 14.3%, respectively.

Charge-Directed Fiber Surface Modification by Molecular Assemblies of Functional Polysaccharides

Molecular assemblies, namely, polyelectrolyte complexes (PECs) composed of negatively charged xylan-based derivatives and a novel positively charged cellulose derivative (CN(+)), were used for interfacial modification of wood fibers by charge directed self-assembly. The adsorption process was studied using polyelectrolyte titration and elemental analysis. X-ray spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used as advanced techniques for the characterization of the modified fiber surfaces. The measurements revealed an intense interaction between the pulp fibers and PECs, and provided essential information for a better understanding of the adsorption process. The information gathered on this paper might contribute to the basis for the development of new value added products by the use of underutilized biomass.

Photoresponsive cellulose fibers by surface modification with multifunctional cellulose derivatives

Eucalyptus bleached kraft pulp fibers were modified by adsorption of novel bio-based multifunctional cellulose derivatives in order to generate light responsive surfaces. The cellulose derivatives used were decorated with both cationic groups (degree of substitution, DS of 0.34) and photoactive groups (DS of 0.11 and 0.37). The adsorption was studied by UV-vis spectroscopy, surface plasmon resonance (SPR) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The adsorption isotherms followed the Freundlich model and it turned out that the main driving force for the adsorption was electrostatic interaction. Moreover, strong indications for hydrophobic interactions between the fibers and the derivatives and the derivatives themselves were found. ToF-SIMS imaging revealed an even distribution of the derivatives on the fiber surfaces. The modified fibers underwent fast photocrosslinking under UV-irradiation as demonstrated by light absorbance and fluorescence measurements. Thus, our results proved that the modified fibers exhibited light-responsive properties and can potentially be used for the manufacture of smart bio-based materials.

Modification of pine pulp during oxygen delignification by xylan self-assembly

Self-assembly is a technique of preparing functional materials based on targeted intermolecular interactions involving different macromolecules. In this work, hardwood xylan was disassembled from wood and birch bleached kraft pulp using pressurized hot water extraction (HWX) and cold alkali extraction (CAX), respectively. The extracted biopolymers were characterized using gas chromatography (GC), size exclusion chromatography (SEC) and Fourier transform infrared spectroscopy (FTIR), and subsequently added into an oxygen delignification reactor containing pine kraft pulp. The assembly of xylan-pulp fiber was characterized using advanced time-of-flight secondary ion mass spectrometry (ToF-SIMS) and imaging. The xylan-pine pulp assembly was not significantly removed during the whole elemental chlorine free bleaching sequence or during low consistency refining. Modified fibers had superior mechanical properties compared to the reference pulp. Our concept can be easily applied in the pulp and paper industry, and it opens new possibilities for the utilization of fully bio-based fibers in new materials.