京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21157号 / 農博第2283号 / 新制||農||1059(附属図書館) / 学位論文||H30||N5131(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 吉村 剛, 教授 髙野 俊幸, 教授 梅澤 俊明 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

There is a growing global energy demand and the society is forced to shift towards renewable energy sources due to the depletion of fossil fuels. Lignocellulosic biomass is a renewable resource available in vast amounts and could therefore have the potential to become a primary source for fuel production. Lignin, as a substantial part of the biomass, is underutilized due to its complex structure which can limit the potential of applying lignin towards value- adding products. However, one way to promote lignin valorization is to produce lignin nanoparticles (LNPs) that are considered valuable in the biomedical field. The aim of this report was to investigate if different botanical origins will affect the properties of LNPs, such as size, polydispersity index, 𝜁-potential and morphology. LNPs from Miscanthus sinensis grass lignin, obtained by the organosolv process, was successfully produced via solvent exchange and compared with LNPs from spruce organosolv lignin. The experimental part resulted in Miscanthus LNPs ranging from 133.7 to 377.4 nm, where a higher initial concentration yielded larger particles, and the average ζ- potential was -38.7 mV. This work has shown that the botanical origin will affect both size and shape of LNPs produced with the same method. Miscanthus LNPs were larger in size and ellipsoidal in shape compared to the spherical spruce LNPs. The lignin concentration influenced the particle size for both origins and the difference in LNP size became more significant as the concentration increased. However, to only explore two different types of plant origins is not sufficient enough to reach a general conclusion. Also, there are many influential steps from plant origin to LNP and to reach a more generalized conclusion, it is arguable that there is a necessity to explore and determine both the applied pulping method, the process to isolate the lignin and the method used to produce the LNPs. / Det globala energibehovet ökar och samhället tvingas därmed att växla till förnybara resurser eftersom de fossila bränslena kan ta slut. Biomassa är en förnybar resurs som finns tillgänglig i stora mängder och kan därför bli en potentiell primär energikälla. Lignin, som är en väsentlig del av biomassan, används inte i lika stor utsträckning på grund av dess komplexa struktur. Komplexiteten begränsar därför användandet av lignin i värdeskapande produkter. Men en väg för att ta tillvara på lignins värdefulla egenskaper kan vara framställandet av nanopartiklar (NP), vilket öppnar upp för användning av lignin inom det biomedicinska fältet. Syftet med den här rapporten är att undersöka om lignin från olika botaniska ursprung påverkar nanopartiklarnas egenskaper, som exempelvis storlek, polydispersitet, 𝜁-potential och morfologi. NP av lignin från gräsarten Miscanthus sinensis framställdes genom solvent exchange och jämfördes sedan med NP från granlignin. Både miscanthus- och granligninet var isolerat genom organosolvprocessen. Den experimentella delen av arbetet visade att NP from miscanthuslignin gav partiklar inom intervallet 133.7 to 377.4 nm, där högre koncentration gav större partiklar, och medelvärdet för 𝜁-potentialen var -38.7 mV. Resultatet från arbetet visade att det botaniskt ursprunget påverkar både storleken och formen på NP av lignin som framställts med samma metod. NP från miscanthuslignin var större och hade en mer elliptisk form, i jämförelse med de mer sfäriska partiklarna från granlignin. Ligninkoncentrationen påverkade partikelstorleken för båda typerna av lignin, dessutom blev skillnaden i partikelstorlek större när koncentrationen ökade. Däremot var det svårt att dra någon generell slutsats genom att bara undersöka två olika ursprung. Eftersom det finns flera steg i processen från växters ursprung till NP av lignin som kan påverka partiklarnas egenskaper kan det vara nödvändigt att utforska både den tillämpade massaprocessen, isoleringsmetoden och metoden som används för att framställa NP av lignin.

Sweetpotato is an important staple crop, and a supplementary source of nutrients; minerals, carbohydrates, and vitamins, for the food industry. Quality of sweetpotatoes depends on cultivar, preharvest management practices, and harvest equipment causing skinning. Information on morph-physiological characteristics of storage roots is needed for preharvest management decisions, cultivar selection, and application of harvest aids and harvesting procedures for postharvest storage durability of sweetpotatoes. Also, devices to measure skinning properties of storage roots are needed. This research was conducted to measure skin toughness of various sweetpotato cultivars. The number of skin layers was determined using fluorescent microscopy, and lignin content was determined with the Near Infrared System. Preharvest cultural practices, such as devining to enhance skin set and lignin content, were applied 1, 3, 7 days preharvest, and Ethephon at the rate of 1.68 ha-and 0.84 kg ha-1 applied at 1, 3, and 7 days preharvest. In addition, curing to enhance skin healing and lignin content was evaluated. This research was conducted in the field and in the greenhouse environments. The force gauge and the torquometer were the most accurate and precise devices to measure the force needed to break the skin of the various sweetpotato cultivars. The cultivars, “L07-6R”, “L07-146”, and “Beauregard-14” had the toughest skin compared to the other cultivars. However, “Covington” and “Hatteras” had the highest lignin content. Fluorescent microscopy showed that the cultivars “L07-6R” and “L07-146” had 12 and 10 cell layers, respectively, and the treatment of Ethephon at 1.68 Kg∙ha-1 3 days and 7 days before harvest resulted in the highest lignin content in the skin. Divining 3 days preharvest, and applying Ethephon at 0.84 kg∙ha-1 at 1day and 3days preharvest resulted in the highest lignin content. In addition, the treatments with Ethephon at 1.68 Kg∙ha-1 applied at 3 days and 7 days preharvest resulted in the hardest skin as indicated by torquometer and the force gauge. Curing for 7 days resulted in higher lignin content compared to the others pretreatments. When wounded and cured for 7 days, the healing process was enhanced greatly, resulting in rapid skin set of sweetpotato storage roots.

The main objective of this research was to develop a catalytic thermal conversion process for production of carbon-based nanomaterials (CNs) from kraft lignin. Four specific objectives were to: (1) understand the structural evolution of kraft lignin during its thermal treatment process; (2) investigate effects of temperature, and iron catalyst loading and morphology on the catalytic thermal conversion of kraft lignin to CNs, understand lignin catalytic thermal conversion mechanism; (3) explore potential applications of CNs synthesized from kraft lignin as an adsorbent for lead removing from contaminated water; (4) and propose effective methods for graphene material characterization. Experimental results indicated that the crystallinity of CNs from non-catalytic thermal conversion of kraft lignin increased and amorphous potion in CNs decreased with increased temperature. Specifically, as temperature increased from 500 to 1000 °C, CNs had its lateral crystallite size (La) increased from 6.97 to 13.96 angstrom, its lattice space (d002) decreased from 3.56 to 3.49 angstrom, and its crystallite (Lc) thickness was between 8 to 9 angstrom. The process of catalytic thermal conversion of kraft lignin yielded graphene-based nanomaterials such as multilayer graphene-encapsulated iron nanoparticles (MLGEINs), multilayer graphene (MLG) sheets, and MLG nanoribbons. Producing MLGEINs required a minimum temperature of 750 °C. The minimum temperature for producing MLG sheets and MLG nanoribbons was found to be 600 °C. It was found that carbonous gases from kraft lignin decomposition acted as the carbon source for MLG sheets and MLG nanoribbons formation, and solid carbon from carbonized lignin acted as the carbon source for the formation of MLGEINs. The yield of CNs increased with increased iron loading. Solid iron nanoparticles as a catalyst favor to form MLG nanoribbons, while iron nitrate favors to form MLGEINs. MLGEINs showed a good sorption capacity for aqueous Pb2+. The adsorption mechanism was mainly dominated by ion-exchange reaction. The final lead contains MLGEINs can be rapidly separated from solution through a magnet. FTIR, Raman, and HRTEM techniques are effective tools for characterizing defects in graphene-based materials. XRD technique is useful to evaluate the average structure parameters of graphene-based materials. SEM technique can be used to characterize morphology of graphene-based materials.

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Renewable materials have been put into the spotlight as the demand for environmentally responsible feedstocks grows yearly. Lignin, an abundant and renewable aromatic polymer, which can source a diverse cast of derivative structures, has yet to rise to the potential it possesses as a material in high technological applications. The expansion of studies and growing interest in its versatility has brought forth materials such as lignin nanoparticles, coatings, films, second generation alcohols, phenolic building blocks for drug synthesis, and many others. Among the many valorization methods thus far pursued, photochemical methods have received relatively low representation, incurring several challenges stemming from less desirable interactions of lignin as a substrate directly with light. As the search for clean, low-emissive processes with high scale-up potential for lignin valorization continued, advances and studies on the benefits and challenges on the use of photochemistry with this class of compounds became the focus of this work. This thesis will primarily aim to highlight our efforts to find photocatalytic materials and systems to achieve lignin valorization, discuss its limitations and benefits, and provide a pathway towards potential applications of these reactions. Our core values were to find conditions that worked well, but also translating that success into systems that could be greener and less dangerous or environmentally impactful. We can report to have achieved single-product yields of over 2% in protolignin valorization reactions using Pd and Au based nanoparticles, supported on niobium-based materials. We have also reached up to 2% yields in visible-light reactions using CdSe quantum dots. While literature reports tend to overwhelmingly focus on lignin models, we have kept ours on real lignin, which while more complex and challenging, does present more relevant results in the long run for this field. These results, in addition to molecular model valorization experiments, present a promising prospect for the application of photocatalysis in lignin valorization for the future.