Lactobacillus panis PM1 is a novel microorganism isolated from thin stillage (TS), a major by-product resulting from bioethanol fermentation, and was selected as the focus of this thesis due to its ability to produce 1,3-propanediol (1,3-PDO) from glycerol. The purpose of this thesis was to understand the central and auxiliary metabolic pathways of L. panis PM1 and to metabolically-engineer strain PM1 based on the improved metabolic knowledge for industrial applications. The 16S rRNA sequence and carbohydrate fermentation pattern were used to classify L. panis PM1 as belonging to the group III lactobacilli; thus, strain PM1 exclusively fermented glucose to lactate, acetate, and/or ethanol, clearly suggesting that its primary metabolism occurred via the 6-phosphogluconate/phosphoketolase (6-PG/PK) pathway. In contrast to typical group III lactobacilli, for fructose fermentation, L. panis PM1 utilized both the 6-PG/PK and the Embden-Meyerhof pathways, showing distinct strain-specific characteristics (more lactate, less acetate, no mannitol, and sporadic growth). In the PM1 strain, auxiliary metabolic pathways governed end-product formation patterns along with central metabolism. Under aerobic conditions, a coupled NADH oxidase-NADH peroxidase system was a determinant for NAD+ regeneration and was regulated by oxygen availability; however, the accumulation of its major end-product, hydrogen peroxide, eventually resulted in oxidative stress. The citrate-to-succinate route was another important auxiliary pathway in L. panis PM1. This route was directly connected to central energy metabolism, producing extra ATP for survival during the stationary phase, and was regulated by the presence of citrate, acetate, and succinate and a transcriptional repressor (PocR). Lactobacilli panis PM1 produced 1,3-PDO via the glycerol reductive route; however, the absence of the glycerol oxidative route restricted the utilization of glycerol to solely that of electron acceptor. Lower ratio of glucose to glycerol, in combination with PocR, repressed the glycerol reductive route, resulting in less 1,3-PDO production. In an effort to metabolically engineer L. panis PM1, an artificial glycerol oxidative pathway was introduced, and the engineered PM1 strain successfully produced a significant amount of important platform chemicals, including 1,3-PDO, lactate, and ethanol, solely from TS. Overall, this thesis reveals the significant feasibility of utilizing L. panis PM1 for industrial fermentative applications.

Master of Science / Department of Grain Science and Industry / Praveen V. Vadlani / Large quantities of byproducts are generated during the biomass processing, which leads to under-utilization of resources and concomitant waste disposal problem. Typically, these byproducts still contain considerable amounts of high-value compounds that have important industrial applications. However, in current time, most of these byproducts are used for low-value applications, including as boiler fuel. These byproducts are potential sources for many valuable chemicals such as antioxidants, flavors, colorants, preservatives, and biocides. Therefore, the reuse and recycle of these biomass residues is very important for the bioeconomy. By some additional and necessary processing steps, we can transfer those biomass residues from a low-value level to a higher value status and apply the final products to various fields such as food industry, and pharmaceutical industry, etc. Till date, limited research has been reported in the production of important specialty chemicals from biomass residues. This thesis is focused on the solvent extraction and isolation of valuable chemicals from bioprocessing byproducts. While choosing different solvents and techniques, “environmental friendly” green solvents were also evaluated. Also some new techniques, such as thin-layer chromatography plates making and laboratory-made lignin are developed to make the research more economically feasible. Even though conventional extraction method such as solid-liquid extraction was evaluated, we tried to minimize the solvent/biomass ratio and also augmented additional processes to the conventional process to obtain higher yield of compounds of interest (COI). In this research, different biomass resources were evaluated for valuable specialty chemicals. These resources include: lignocellulosic biomass and raw biomass. Lignocellulosic biomass is a sustainable feedstock for the production of biofuels and chemicals. The potential chemicals from the resources were extracted using various organic solvents and analyzed by gas chromatography-mass spectrometry (GC-MS). The results indicated that the selected biomass residues contain relatively higher amounts of three valuable compounds: vanillin, apocynin, and phytol. Different types of organic solvents and extraction techniques were tested to optimize the extraction process. Ultra-sonication was considered as an efficient extraction method and ethanol was chosen as the final solvent. Commercially viable isolation methods such as thin-layer chromatography (TLC) and column chromatography were also studied in this research. A solvent system of hexane, dichloromethane, ethyl acetate, and chloroform with 1:1:1:0.1 v/v ratio gave us a good separation of the COI. Biomass-derived lignin was made in the laboratory to compare with commercially available lignin. The results show that the laboratory-made lignin contains similar bioactive compounds and gives us a good quantity of target compounds. In conclusion, instead of letting the byproducts being discarded or used as low-value applications or become a threat to the environment, the decision to select them as raw materials to produce valuable specialty targeted compounds for industries has been demonstrated in our research. The future research will focus on optimization and scale-up study of the extraction process. In addition, the application and production of bioactive compounds will be further evaluated.

La valorisation chimique des espèces condensables issues de la torréfaction de biomasse ainsi que l'utilisation d'un gaz vecteur à faible coût, tels que les gaz de combustion, peuvent constituer des étapes importantes pour le développement du procédé de torréfaction à l'échelle industrielle. Les rendements des espèces condensables varient selon la composition de la biomasse, notamment par la présence de certains minéraux, et varient aussi en fonction de conditions opératoires telles que le gaz vecteur utilisé. Afin d'étudier l'effet du potassium sur la perte de masse de la biomasse et sur le rendement des espèces condensables, trois biomasses déminéralisées ont été imprégnées avec différentes concentrations de K2CO3 puis torréfiées à 275°C jusqu'à l'obtention d'une perte de masse cible (25 ou 30%). La torréfaction a été effectuée à la fois dans un instrument d'analyse thermogravimétrique (ATG) et dans un réacteur à l'échelle laboratoire sous azote et en présence de gaz de combustion. Des analyses ATG des biopolymères (cellulose, xylane et lignine) bruts et imprégnés avec du K ont été réalisées pour faciliter l'interprétation des résultats. La perte de masse augmente lorsque la teneur en K des biomasses augmente et, par conséquent, des temps de séjour plus courts sont suffisants pour obtenir la perte de masse cible. Cela semble être principalement le résultat du décalage de la décomposition de la cellulose vers des températures plus faibles. Les vitesses de réaction maximales sont bien plus élevées en présence de gaz de combustion car la biomasse subit des réactions d'oxydation en plus de la décomposition classique. Quelle que soit l'atmosphère, K inhibe la production d’anhydrosaccharides (levoglucosan, LAC et DGP) et de furanes (à l'exception du 2-furanmethanol). En parallèle, une augmentation substantielle du rendement en acétol est constatée. La rupture du cycle pyranose de la cellulose qui entraine la formation des produits légers est favorisée en présence de K au détriment de la dépolymérisation qui produit du levoglucosan. Le K favorise la production de 2-furanmethanol, syringol et guaiacol surtout en présence de gaz de combustion. En revanche, la production de vanilline et de syringaldéhyde est défavorisée en présence de K tandis qu'elle est fortement favorisée en présence de gaz de combustion quand la biomasse est libre de K. L'effet du K sur les rendements des espèces condensables lors de la torréfaction de la biomasse est démontré quelle que soit la nature de l'atmosphère. De plus, dans les conditions testées, l'oxygène présent dans l'atmosphère intensifie, dans une mesure plus ou moins grande, la tendance imposée par le K / The chemical valorization of condensable species from biomass torrefaction as well as the use of a low-cost carrier gas such as flue gas may be important steps for industrial-scale implementation of torrefaction. The condensable species yield varies according to the biomass composition, in particular by the presence of certain minerals, and also changes according to the operating conditions such as the gas atmosphere. In this context, to investigate the effect of potassium on mass loss of biomass during torrefaction and in the yield of condensable species, three demineralized biomasses were impregnated with different concentrations of K2CO3 and then torrefied at 275°C up to a target mass loss (25 or 30%). Torrefaction was carried out in both a thermogravimetric analysis (TGA) instrument and a laboratory fixed-bed reactor under nitrogen and flue gas atmospheres. TGA of raw and K-impregnated biopolymers (cellulose, xylan and lignin) were performed to facilitate interpretation of the results. When K content increased in the biomass, shorter torrefaction times were sufficient to obtain the targeted mass loss. This behavior seems to be a result of shifting the cellulose decomposition to lower temperatures. The maximum reaction rates are much higher under flue gas because the biomass undergoes oxidation reactions in addition to the ordinary decomposition. Regardless of the gas atmosphere employed, K inhibits the production of anhydrosugars (levoglucosan, LAC and DGP) and furans (except 2-furanmethanol). This suppression is accompanied by a substantial increase in acetol yield. The cleavage of pyranose rings in cellulose which results in the formation of low molecular weight compounds is favored in the presence of K to the detriment of the depolymerization which delivers levoglucosan. K promotes the production of 2- furanmethanol, syringol and guaiacol especially under flue gas atmosphere. However, the yields of vanillin and syringaldehyde decreased in the presence of K whereas they are strongly favored under flue gas atmosphere when the biomass does not contain K. The effect of K on the yields of condensable species from biomass torrefaction is demonstrated whatever the gas atmosphere. Moreover, under the conditions tested, the oxygen present in the atmosphere intensifies, to a greater or lesser extent, the tendency imposed by the K

Over the last several decades, there have been a tremendous developments and greatinnovations in photocatalysis process along with the development of efficient nanosized catalysts for simple approach and economic viability. In this study, magnetic core@doubleshell nanomaterials were investigated and synthesized in lab with three-step innovative approach where Fe3O4 nanoparticles (NPs) were produced first to act as cores without using any surfactants. The magnetite/silica core–shell structure was then prepared by hydrolysis of tetraethoxysilane (TEOS) in the presence of core particles under alkaline conditions. And the outermost shell, the α-Fe2O3/TiO2 nanoparticles, were grown over magnetic core of Fe3O4@SiO2 using coprecipitation and calcination method. Furthermore, the Fe3O4@SiO2@α-Fe2O3/TiO2 NPs were then loaded on the reduced graphene oxide (r-GO) using hydrothermal method and are also mixed by kneading with the layered double hydroxides (LDH) of Mg2+ and Al3+. These nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), and energy dispersive X-ray spectroscopy (EDS). Different model compounds like microcrystalline cellulose (90 μm), D-xylose, and sodium lignosulfonate representing cellulose, hemicellulose, and lignin, respectively, were converted to valuable chemicals with different NPs under visible light for different time periods. For example, valeric acid (VA) and vanillylmandelic acid (VMA) were produced when cellulose was used for the conversion with core-double shell NPS which were quantified using high performance liquid chromatography (HPLC). Similar approach was adopted for the conversion of brewers’ spent grain (BSG), a lignocellulosic biomass, without oxygen under visible light, which yielded ethanol as the main product along with other sugars and acids of very low concentrations. The magnetic property of the nanomaterials made it easy for recycle and reuse. From a sustainability point of view, this study will fill a large need in the biomass photocatalysis field by developing core-shell multi-functional photocatalysts for direct transformation of lignocellulose into valuable chemicals under low temperatures, atmospheric pressure, and visible light from the sun.