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Glycerol : a versatile renewable feedstock for the chemical industry
\"This book is aimed at providing a concise discussion on the use of glycerol as a renewable raw material for the chemical industry. With the increasing use of biodiesel produced from oils and fats, there is a surplus of glycerol in the world. This abundant and rather cheap raw material can be transformed in commodities and specialty chemicals, as well as in fuels. The book describes the main processes of chemical transformation of glycerol, highlighting those that are currently in commercial use and pointing out potential processes to be used in the future. The first chapter introduces the concept of biofuel and briefly describes the production of biodiesel. It also highlights glycerol as the main byproduct of biodiesel synthesis and presents some numbers regarding the world production of glycerol. The second chapter shows the common uses of glycerol and addresses the point whether or not they can drain the large amounts of glycerol produced from biodiesel. The chapter addresses pros and cons of each use. The third chapter covers the main biotechnological processes of glycerol transformation. The fourth chapter thoroughly describes the main thermochemical processes to transform glycerol into commodities, products that will be further used in the chemical industry to produce polymers, for instance. The fifth chapter covers the production of glycerol derivatives of high added-value. The sixth chapter addresses the use of glycerol in the context of a biorefinery. The main idea is to show that many of the processes described in the previous chapters could be entirely green, using exclusively renewable raw materials.\"--Publisher's description.
BOOK
Correction: Polyhydroxyalkanoate production in Priestia megaterium strains from glycerol feedstock
[This corrects the article DOI: 10.1371/journal.pone.0322838.].
Journal Article
Optimising environmental factors for maximal lactate productivity in Synechocystis sp. PCC 6803 through a design of experiments approach
Genetic and metabolic engineering of Synechocystis sp. PCC 6803 has given rise to strains that produce a variety of bio-chemicals. Despite these successes, improvements in productivity metrics are required to achieve economically viable bio-production of carbon dioxide-derived compounds. Previously, environmental factors have been leveraged to increase product yields. Here, we optimise multiple environmental factors simultaneously using Design of Experiments (DOE) principles and find conditions that maximise L-lactate production. Light intensity, glycerol concentration, and light-dark cycle were found to be significant factors. Optimising these conditions resulted in a 6.3- and 7.4-fold increase in titre and yield. The results detailed here could have implications for metabolic engineering of, and bioprocesses using, Synechocystis sp. PCC 6803. In the future, DOE-mediated optimisation of environmental conditions could effectively maximise product titres from different production strains, or the enhanced conditions described here could be directly implemented in other metabolic engineering projects.
Journal Article
Novel Hydroxyl-Functional Aliphatic COsub.2-Based Polycarbonates: Synthesis and Properties
A series of novel functional polycarbonates, specifically poly(solketal glycidyl ether carbonate-co-propylene carbonate)s with varying compositions, were synthesized through the ring-opening copolymerization of solketal glycidyl ether, propylene oxide, and carbon dioxide. The reaction was catalyzed by rac-(salcy)Co[sup.III]X complexes with bis(triphenylphosphine)iminium salts as co-catalysts, achieving high selectivity. The resulting terpolymers exhibited number-average molecular weights ranging from 2 × 10[sup.4] to 1 × 10[sup.5] and a narrow, bimodal molecular weight distribution, with dispersities of 1.02–1.07 for each mode. Interestingly, the addition of a small amount of water to the reaction mixture yielded a terpolymer with a unimodal molecular weight distribution and a dispersity of 1.11. Subsequent acidic hydrolysis of the solketal protective groups produced poly(glyceryl glycerol carbonate-co-propylene carbonate). All terpolymers were amorphous, with Tg near or below room temperature. The hydroxyl-functional polycarbonates underwent cyclodepolymerization under milder conditions compared to polycarbonates with protected hydroxyl groups.
Journal Article
WVO.sub.x Supported on Industrial Al.sub.2O.sub.3, SiO.sub.2, AC, TiO.sub.2-Al.sub.2O.sub.3 for Catalytic Dehydration of Gas-Glycerol to Acrolein
WVO.sub.x bi-metal oxides supported on the cost-effective industrial mesoprous Al.sub.2O.sub.3, SiO.sub.2, active carbon (AC), and TiO.sub.2-Al.sub.2O.sub.3 with different specific surface areas (WVO/Al.sub.2O.sub.3, WVO/SiO.sub.2, WVO/AC, and WVO/TiO.sub.2-Al.sub.2O.sub.3) were designed and prepared through co-impregnation method for large-scale bio-glycerol dehydration to acrolein. The XRD, BET, SEM-EDS, XPS, and NH.sub.3-TPD characterization results revealed the WO.sub.3-VO.sub.x (V.sup.4+/V.sup.5+) species existed with better dispersion, lower molar ratio of V.sup.4+/V.sup.5+, and enhanced strength of surface acid sites on the developed mesoporous TiO.sub.2-Al.sub.2O.sub.3 in comparison with that on the mesoporous Al.sub.2O.sub.3, SiO.sub.2, and AC, demonstrating strong interaction of WO.sub.3-VO.sub.x species with the TiO.sub.2-Al.sub.2O.sub.3 support and accounting for the acrolein selectivity over catalysts following the order of WVO/TiO.sub.2-Al.sub.2O.sub.3 (75.8%) > WVO/AC (71.2%) > WVO/SiO.sub.2 (55.3%) > WVO/Al.sub.2O.sub.3 (42.8%). Over the WVO/TiO.sub.2-Al.sub.2O.sub.3, gas-glycerol conversion reached above 97.0% with acrolein selectivity of about 75.0% under the gas hourly space velocity (GHSV) of 120-360 h.sup.-1, and maintained an improved catalytic stability.
Journal Article
The Time-Resolved Salt Stress Response of IDunaliella tertiolecta/I—A Comprehensive System Biology Perspective
Algae-driven processes, such as direct CO[sub.2] fixation into glycerol, provide new routes for sustainable chemical production in synergy with greenhouse gas mitigation. The marine microalgae Dunaliella tertiolecta is reported to accumulate high amounts of intracellular glycerol upon exposure to high salt concentrations. We have conducted a comprehensive, time-resolved systems biology study to decipher the metabolic response of D. tertiolecta up to 24 h under continuous light conditions. Initially, due to a lack of reference sequences required for MS/MS-based protein identification, a high-quality draft genome of D. tertiolecta was generated. Subsequently, a database was designed by combining the genome with transcriptome data obtained before and after salt stress. This database allowed for detection of differentially expressed proteins and identification of phosphorylated proteins, which are involved in the short- and long-term adaptation to salt stress, respectively. Specifically, in the rapid salt adaptation response, proteins linked to the Ca[sup.2+] signaling pathway and ion channel proteins were significantly increased. While phosphorylation is key in maintaining ion homeostasis during the rapid adaptation to salt stress, phosphofructokinase is required for long-term adaption. Lacking β-carotene, synthesis under salt stress conditions might be substituted by the redox-sensitive protein CP12. Furthermore, salt stress induces upregulation of Calvin–Benson cycle-related proteins.
Journal Article
Itaconate Production from Crude Substrates with U. maydis: Scale-up of an Industrially Relevant Bioprocess
Industrial by-products accrue in most agricultural or food-related production processes, but additional value chains have already been established for many of them. Crude glycerol has a 60% lower market value than commercial glucose, as large quantities are produced in the biodiesel industry, but its valorisation is still underutilized. Due to its high carbon content and the natural ability of many microorganisms to metabolise it, microbial upcycling is a suitable option for this waste product. In this work, the use of crude glycerol for the production of the value-added compound itaconate is demonstrated using the smut fungus Ustilago maydis. Starting with a highly engineered strain, itaconate production from an industrial glycerol waste stream was quickly established on a small scale, and the resulting yields were already competitive with processes using commercial sugars. Adaptive laboratory evolution resulted in an evolved strain with a 72% increased growth rate on glycerol. In the subsequent development and optimisation of a fed-batch process on a 1.5-2 L scale, the use of molasses, a side stream of sugar beet processing, eliminated the need for other expensive media components such as nitrogen or vitamins for biomass growth. The optimised process was scaled up to 150 L, achieving an overall titre of 72 g L.sup.- 1, a yield of 0.34 g g.sup.- 1, and a productivity of 0.54 g L.sup.- 1 h.sup.- 1. Pilot-scale itaconate production from the complementary waste streams molasses and glycerol has been successfully established. In addition to achieving competitive performance indicators, the proposed dual feedstock strategy offers lower process costs and carbon footprint for the production of bio-based itaconate.
Journal Article
The Effect of Acyl Chain Position on the 2D Monolayer Formation of Monoacyl-Isn/I-Glycerol at the Air/Water Interface: Quantum Chemical Modeling
This paper deals with the results of quantum chemical modeling of the monoacyl-sn-glycerol 2D cluster formation at the air/water interface using a semi-empirical PM3 method. The impact of the 2 or 3 positions of the acyl substituent on the thermodynamics of the monolayer formation is assessed for surfactants with an acyl substituent CnH[sub.2n+1]COO chain length of n = 6–17 carbon atoms. The calculation shows a significant change in the spontaneous clusterization threshold for isomeric compounds, which differs only in the position of the acyl substituent with respect to the glycerol backbone. This change is almost equal to substituent shortening by approximately two methylene fragments. At the same time, the geometric parameters of the unit cell for resulting monolayers are not affected so drastically. The 2D films in question possess an oblique or orthorhombic unit cell with parameters for 2 and 3-monoacyl-sn-glycerol monolayers, as follows: a = 4.91 Å and 4.82 Å and b = 5.00 Å and 4.92 Å, with hydrocarbon chains tilted at t = 23.0° and 23.5°. The calculated results are in accordance with existing experimental data obtained using grazing incidence X-ray diffraction measurements and the π-A isotherm technique.
Journal Article
Influence of Ni Addition on Au/CeOsub.2 Photocatalysts for Solar Photocatalytic Hsub.2 Production by Glycerol Photoreforming
Solar glycerol photoreforming was investigated on Au-Ni/CeO[sub.2] photocatalysts with an overall metal content equal to 1wt% and different Au/Ni weight ratios. The deposition of gold over ceria was performed by two different methods, deposition–precipitation and photoreduction. Deposition–precipitation was the best method to deposit gold on CeO[sub.2] with the formation of small Au nanoparticles (around 4 nm). The most active sample (0.9 wt% Au-0.1 Ni wt%/CeO[sub.2]) provided a H[sub.2] production rate of 350 µmol/gcat∙h, much higher than the corresponding monometallic samples. A higher amount of Ni led to detrimental effects in H[sub.2] production, likely due to the covering of the gold surface active sites by Ni. On the contrary, the presence of a small amount of Ni (0.1 wt%) allowed a remarkable improvement of the Au/CeO[sub.2] photocatalytic stability after consecutive runs of simulated solar irradiation. This finding, as well as the activation of synergistic effects, the improved charge carrier separation, and the exploitation of the localized surface plasmon resonance property of gold, led to the proposal of an alternative photocatalytic system to the most investigated TiO[sub.2]-based photocatalysts for H[sub.2] production. The enhanced stability is promising to further foster the investigation of these photocatalysts applied to sustainable H[sub.2] production.
Journal Article
Effect of different finishing and polishing procedures on color stability of Ormocer- and methacrylate-based composites
The optical properties of composite restorations are influenced by composite's surface conditions and polishing techniques, which can affect stain resistance. This study examined how surface condition and polishing techniques affect the color stability of two composite restorative materials. A total of 150 composite discs were divided into 30 experimental groups (n = 5) based on composite material (ormocer-based composite, Admira Fusion, and methacrylate-based composite' Grandio), surface condition (against matrix, air, or glycerin), and polishing technique (No polishing, 1-step, 2-step, abrasive + one-step, and abrasive + two-step). Color measurements were taken using a spectrophotometer before immersion (baseline) and after 3 months of immersion in a coffee solution. Data were analyzed using ANOVA and Tukey HSD test ([alpha] = 0.05). Composite type, surface condition, and polishing technique all had a significant effect on [DELA]E (P < 0.001). Admira Fusion and Grandio exhibited the lowest [DELA]Ð value (3.26 ± 0.15, 3.43 ± 0.08 respectively) when polished with abrasives and a 2-step technique (P < 0.05). Grandio showed the highest [DELA]Ð value (19.66 ± 0.37) when light cured in air and without exposure to any polishing technique (P < 0.05). The color stability of composites was enhanced by applying glycerin coatings prior to light curing and polishing.
Journal Article