Following the worsening energy crisis of unreliable electricity and unaffordable petroleum products coupled with the increase number of poverty-stricken people in Nigeria, the populace is desperately in need of cheap alternative energy supplies that will replace or complement the existing energy sources. Previous efforts by the government in tackling the challenge by citizenship sensitization of the need for introduction of biofuel into the country’s energy mix have not yielded the expected results because of a lack of sustained government effort. In light of the shortcomings, this study assesses the current potential of available biomass feedstock for biogas production in Nigeria, and further proposes appropriate biogas plants, depending on feedstock type and quantity, for the six geopolitical zones in Nigeria. Besides, the study proposes government-driven biogas development systems that could be effectively used to harness, using biogas technology, the estimated 270 TWh of potential electrical energy from 181 million tonnes of available biomass, in the advancement of electricity generation and consequent improvement of welfare in Nigeria.

Agricultural residues are constantly increasing with increased farming processes, and improper disposal is detrimental to the environment. Majority of these waste residues are rich in lignocellulose, which makes them suitable substrate for bacterial fermentation in the production of valueadded products. In this study, bacterial cellulose (BC), a purer and better form of cellulose, was produced by two Komagataeibacter sp. isolated from rotten banana and kombucha drink using corncob (CC) and sugarcane bagasse (SCB) enzymatic hydrolyzate, under different fermentation conditions, that is, static, continuous, and intermittent agitation. The physicochemical and mechanical properties of the BC films were then investigated by Fourier Transformed Infrared Spectroscopy (FTIR), Thermogravimetry analysis, Field Emission Scanning Electron Microscopy (FESEM), and Dynamic mechanical analysis. Agitation gave a higher BC yield, with Komagataeibacter sp. CCUG73629 producing BC from CC with a dry weight of 1.6 g/L and 1.4 g/L under continuous and intermittent agitation, respectively, compared with that of 0.9 g/L in HS medium. While BC yield of dry weight up to 1.2 g/L was obtained from SCB by Komagataeibacter sp. CCUG73630 under continuous agitation compared to that of 0.3 g/L in HS medium. FTIR analysis showed BC bands associated with cellulose I, with high thermal stability. The FE-SEM analysis showed that BC fibers were highly ordered and densely packed. Although the BC produced by both strains showed similar physicochemical and morphological properties, the BC produced by the Komagataeibacter sp. CCUG73630 in CC under intermittent agitation had the best modulus of elasticity, 10.8 GPa and tensile strength, 70.9 MPa. [GRAPHICS]

This study was dedicated to techno-economic analysis of an integrated 1st and 2nd generation biorefinery, where the organosolv pretreated oat husk and thin stillage is valorized through filamentous fungi and baker yeast. By this strategy, process economy can benefit from multiple value-added products including lignin (80% purity), and protein-rich biomass as feed/food ingredients. Ethanol recovery of organosolv pretreatment benefits the already existing equipment in 1st generation ethanol plant. The best results shows that the integration of 10 tons/h oat husk into a process using 18.8 tons/h grains results in increasing ethanol production from 5.2 to 7.5 tons/h, in addition to 1.6 tons/h lignin (80% purity) and 7.6 tons/h fungal biomass. Integrated process is beneficial not only for 2nd but also for 1st generation ethanol production. Selling the fungal biomass as feed and food increased the net present value (NPV) in comparison to conventional ethanol plant by 71% and 7.9-fold, respectively. © 2021 The Authors

Nature has designed a few biobased molecules that are responsible for bioluminescence and photoluminescence in some living species. In this thesis, the potential use of luminescence phenomena existing in nature toward the attainment of luminescent textiles was explored.

The primary focus of the thesis was to create a biomimetic design method to obtain luminescent textiles using biobased products. In the first part of the thesis, a detailed literature study on luminescence phenomena seen in nature was reviewed and the results allowed to form the selection of luminous bacteria reaction system depending upon the availability, regeneration of the substrate, and cost. Eco technologies such as air atmospheric plasma and cold remote plasma treatment were used for textile activation and enzyme immobilization. Primarily, the catalytic activity and luminescence efficiency of the luminous bacteria system were evaluated and optimized in the aqueous phase, by intensity measurements using a luminometer. Furthermore, the optimized reaction system was incorporated onto textiles to evaluate the bioluminescence effect. The evaluation of the bioluminescent system on textiles showed that the relative light intensity (RLU) as high as 60,000 RLU equivalent to that of LED light could be achieved. The study revealed its first successful attempt to utilize a biomimetic strategy for immobilization of enzyme(s) involved in the luminous bacteria reaction system onto a plasma-activated microfibrous nonwoven textile to attain biomimetic/bio luminescent materials that can be used for various applications such as biosensors, biomedical, safety and aesthetic use.

Furthermore, the inherent photoluminescence property of biobased molecules riboflavin (RF) and flavin mononucleotide (FMN) were explored with the aim to obtain multifunctional photoluminescent textiles. Cellulosic, polyester, silk, and wool-based photoluminescent textiles with UV protection, coloration properties were obtained using traditional methods such as diffusion, screen printing, coating, and use of resource-efficient digital printing techniques allowed to obtain antibacterial properties along with photoluminescence effect.

Luminescent textiles are being increasingly used in apparel and sportswear aswell as in buildings, agriculture and automotives, for safety alert or forillumination or as a design feature[1]. Till now these luminescent textiles havebeen based on technologies such as LED, luminescent particles (rare earthmetals and metal oxides), which are not so eco‐friendly[2].Bio‐inspired strategies can provide efficient methods to achieve eco friendlybioluminescent textiles. Research projects have explored ways which aremainly based on culture of bioluminescent algae[3] or bacteria on textiles.Here we present another approach to achieve bioluminesence using biobasedproducts from various living organisms such as fireflies, fungi, earthwormsthat are found in land and in jelly fishes, shrimps, dinoflagellates, corals inmarine environment [4]. In order to mimic the luminescence effect seen innature, reaction mechanisms in various bioluminescent living organisms arestudied and the components or molecules responsible for luminescence areidentified [5‐10]. Most of the time, these involve enzymatic reactions.However the main challenge is to reproduce the bioluminescent mechanismand to adapt it to new materials which can yield some eco efficient bioinspired luminescent textiles.

Limited feed ingredients hinder aquaculture’s rapid growth. Current unsustainable fish feeding practices use ingredients like fishmeal and soybean meal, which could be directly consumed for as human food. This demands novel alternatives for fish nutrition. While studies have explored plant/animal-based protein sources, they have not fully met fish feed nutritional needs. Single-cell proteins like bacteria, algae, and fungi are gaining attention as sustainable alternatives to traditional fish feed protein sources. Filamentous fungal biomass stands out with its high protein content, essential amino acids, and functional amino acids like lysine and arginine. This biomass also provides other nutrients that fish commonly require, such as essential fatty acids (linoleic acid, linolenic acid, arachidonic acid), minerals (phosphorus, potassium, calcium), vitamins (B, C, E), and pigments. Incorporating cell wall components like chitin, chitosan, and beta-glucans makes fungal biomass a functional feed ingredient that enhances fish immune systems. When applied to rainbow trout diets, fungal-based feed is highly digestible, comparable to fishmeal-based feed, and positively impacts gut microbiomes. The increase of lactic acid bacteria (Lactococcus lactis) after consuming fungal-based feed suggests its potential as a fish feed prebiotic. 

While fungal biomass holds promise as a nutrient-rich fish feed source, its large-scale production on synthetic substrates poses economic challenges. To optimize production, organic-rich waste like Distiller's Dried Grains with Solubles (DDGS) and thin stillage from ethanol production are explored as substrates. Thin stillage, previously considered for fungal biomass production, faces difficulties due to its high solid content. Optimizing thin stillage's suspended solids for cultivating different filamentous fungi from Ascomycetes and Zygomycetes is necessary. Submerged cultivation of Aspergillus oryzae, Rhizopus delemar, and Neurospora intermedia was tested using various thin stillage dilutions. Cultivating these species in 75% diluted thin stillage yielded the highest biomass. The harvested fungal biomass contained around 50% protein and 45% essential amino acids, with ash content below 10%, enhancing fish digestibility. Notably, when 75% diluted thin stillage was used, the washing step could be skipped without compromising final biomass quality, streamlining production processes. Using fungal-based feed in fish nutrition presents a sustainable alternative to traditional fishmeal-based feed. It goes beyond protein and amino acids, providing other essential nutrients such as fatty acids, minerals, pigments etc. High digestibility and positive effects on fish health through gut microbiome modulation make it a valuable substitute for common protein sources. To enhance sustainability, scaling up fungal biomass production using diluted thin stillage as a substrate is a promising avenue. 

Brewer’s spent grain (BSG) constitutes 85% of brewing byproducts and 30% of initial malt. In 2021, BSG production reached approximately 37.2 million tons. Owing to its high moisture and nutritional content, BSG is prone to biological deterioration, causing environmental issues when discarded as waste. It has limited application as low-quality animal feed owing to its high fiber and low protein content, making landfilling the primary disposal method. However, BSG's abundance of starch, cellulose, hemicellulose, lignin, and protein make it ideal for value-added product generation in a biorefinery. The aim of this research was to investigate BSG fractionation and identify valuable products from each fraction, ultimately establishing a BSG-based biorefinery for sustainable valorization. 

Fungal cultivation, anaerobic digestion, hydrothermal, and organosolv pretreatments were employed to establish a BSG-based biorefinery. Edible filamentous fungi (Aspergillus oryzae, Neurospora intermedia, and Rhizopus delemar) were cultivated on crude BSG to produce food and feed-grade biomass. Fungal growth increased the protein content of the BSG by up to 47%. However, entangled solids with fungal filaments negatively affected product digestibility, limiting its incorporation in food and feed. This problem was resolved by recovering a solid-free, starch- and protein-rich stream from BSG via hydrothermal pretreatment. 

Hydrothermal pretreatment effectively separated BSG's starch and protein components, with solubilizations reaching 82% and 48% of the initial content, respectively. Fungal assimilation of the liquid stream produced pure, high-protein biomass and high ethanol yield. However, most of the BSG cellulose and lignin remained in the solid fraction. Organosolv pretreatment was applied to further separate BSG polymers into valorizable fractions efficiently, yielding a cellulose-rich solid stream, polysaccharide-rich organosolv liquor, and high-purity lignin (~95%). This pure lignin product can enhance the biorefinery’s economy and be sold or converted into platform chemicals. 

Direct fungal cultivation on cellulose-rich pulp and liquor fractions from organosolv revealed that the liquor fraction was suitable for producing pure, high-protein fungal biomass, while the pulp fraction required further processing. Moreover, anaerobic digestion was employed to produce a diverse array of products improving the product flexibility of the biorefinery. Organosolv liquor produced biohydrogen and volatile fatty acids (VFAs) without methanogen inhibition, while BSG and BSG organosolv solid fractions generated biogas. Inhibiting methanogens shifted the BSG process towards VFAs production, while organosolv solid fractions showed limited potential for VFAs generation. 

These results illustrate that BSG can serve as the foundation for a multi-product biorefinery that generates food-grade fungal biomass and valuable co-products, including high-purity lignin, bioethanol, biogas, biohydrogen, and VFAs. This flexibility allows the biorefinery to adapt to market changes and ensure its economic viability. 

Aims

Biodesulfurization of fossil fuels is a promising technology for deep desulfurization. Previously, we have shown that Paenibacillus strains 32O-W and 32O-Y can desulfurize dibenzothiophene (DBT) and DBT sulfone (DBTS) effectively. In this work, improvements in DBT and DBTS desulfurization by these strains were investigated through immobilization and nanoparticle coating of cells.

Methods and Results

Paenibacillus strains 32O-W and 32O-Y immobilized in alginate gel beads or coated with Fe3O4 magnetite nanoparticles were grown at various concentrations (0.1–2 mmol l−1) of DBT or DBTS for 96 h. The production of 2-hydroxybiphenyl (2-HBP) from the 4S pathway biotransformation of DBT or DBTS was measured. The highest amounts of 2-HBP production occurred at concentrations of 0.1 and 0.5 mmol l−1. Compared to planktonic cultures maximum 2-HBP production increased by 54% for DBT and 90% for DBTS desulfurization with immobilized strains, and 44% for DBT and 66% for DBTS desulfurization by nanoparticle-coated strains.

Conclusions

Nanoparticle-coated and immobilized cells may be of use in efforts to increase the efficiency of biodesulfurization.

Significance and Impact of the Study

Alginate immobilization or nanoparticle coating of bacterial cells may be useful approaches for the enhancement of biodesulfurization for eventual use on an industrial scale.

Efforts are made to change from 1st to 2nd generation bioethanol production, using lignocellulosics as raw materials rather than using raw materials that alternatively can be used as food sources. An issue with lignocellulosics is that a harsh pretreatment step is required in the process of converting them into fermentable sugars. In this step, inhibitory compounds such as furan aldehydes and carboxylic acids are formed, leading to suboptimal fermentation rates. Another issue is that lignocellulosics may contain a large portion of pentoses, which cannot be fermented simultaneously with glucose by Saccharomyces cerevisiae. In this thesis, high local cell density has been investigated as a means of overcoming these two issues. Encapsulation of yeast in semi-permeable alginate-chitosan capsules increased the tolerance towards furan aldehydes, but not towards carboxylic acids. The selective tolerance can be explained by differences in the concentration of compounds radially through the cell pellet inside the capsule. For inhibitors, gradients will only be formed if the compounds are readily convertible, like the furan aldehydes. Conversion of inhibitors by cells close to the membrane leads to decreased concentrations radially through the cell pellet. Thus, cells closer to the core experience subinhibitory levels of inhibitors and can ferment sugars. Carbohydrate gradients also give rise to nutrient limitations, which in turn trigger a stress response in the yeast, as was observed on mRNA and protein level. The stress response is believed to increase the robustness of the yeast and lead to improved tolerance towards additional stress. Glucose and xylose co-consumption by a recombinant strain, CEN.PK XXX, was also improved by encapsulation. Differences in affinity of the sugar transporters normally result in that glucose is taken up preferentially to xylose. However, when encapsulated, cells in different parts of the capsule experienced high and low glucose concentrations simultaneously. Xylose and glucose could thus be taken up concurrently. This improved the co-utilisation of the sugars by the system and led to 50% higher xylose consumption and 15% higher final ethanol titres. A protective effect by the capsule membrane itself could not be shown. Hence, the interest in flocculation was triggered, as a more convenient way to keep the cells together. To investigate whether flocculation increases the tolerance, like encapsulation, recombinant flocculating yeast strains were constructed and compared with the non-flocculating parental strain. Experiments showed that strong flocculation did not increase the tolerance towards carboxylic acids. However, the tolerance towards a spruce hydrolysate and especially against furfural was indeed increased. The results of this thesis show that high local cell density yeast cultures have the potential to aid against two of the major problems for 2nd generation bioethanol production: inhibitors and simultaneous hexose and pentose utilisation.

Lignocellulosic biomass is a potential feedstock for production of sugars, which can be fermented into ethanol. The work presented in this thesis proposes some solutions to overcome problems with suboptimal process performance due to elevated cultivation temperatures and inhibitors present during ethanol production from lignocellulosic materials. In particular, continuous processes operated at high dilution rates with high sugar utilisation are attractive for ethanol fermentation, as this can result in higher ethanol productivity. Both encapsulation and membrane bioreactors were studied and developed to achieve rapid fermentation at high yeast cell density. My studies showed that encapsulated yeast is more thermotolerant than suspended yeast. The encapsulated yeast could successfully ferment all glucose during five consecutive batches, 12 h each at 42 °C. In contrast, freely suspended yeast was inactivated already in the second or third batch. One problem with encapsulation is, however, the mechanical robustness of the capsule membrane. If the capsules are exposed to e.g. high shear forces, the capsule membrane may break. Therefore, a method was developed to produce more robust capsules by treating alginate-chitosan-alginate (ACA) capsules with 3-aminopropyltriethoxysilane (APTES) to get polysiloxane-ACA capsules. Of the ACA-capsules treated with 1.5% APTES, only 0–2% of the capsules broke, while 25% of the untreated capsules ruptured within 6 h in a shear test. In this thesis membrane bioreactors (MBR), using either a cross-flow or a submerged membrane, could successfully be applied to retain the yeast inside the reactor. The cross-flow membrane was operated at a dilution rate of 0.5 h-1 whereas the submerged membrane was tested at several dilution rates, from 0.2 up to 0.8 h-1. Cultivations at high cell densities demonstrated an efficient in situ detoxification of very high furfural levels of up to 17 g L-1 in the feed medium when using a MBR. The maximum yeast density achieved in the MBR was more than 200 g L-1. Additionally, ethanol fermentation of nondetoxified spruce hydrolysate was possible at a high feeding rate of 0.8 h-1 by applying a submerged membrane bioreactor, resulting in ethanol productivities of up to 8 g L-1 h-1. In conclusion, this study suggests methods for rapid continuous ethanol production even at stressful elevated cultivation temperatures or inhibitory conditions by using encapsulation or membrane bioreactors and high cell density cultivations.