Highlights ► Glycerol is an abundant and inexpensive carbon source generated as a by-product of biofuel production. ► High degree of reduction of glycerol enables increased yields of fuels and ...reduced chemicals. ► Current efforts exploit glycerol for the microbial production of numerous compounds. ► Future research efforts will expand the portfolio of available products.
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•LTA zeolites exhibited remarkable efficiency in glycerol transesterification with DMC.•The tested reaction exclusively yielded glycerol carbonate as the sole product.•The reaction ...between glycerol and DMC over LTA zeolites took place on the surface.•Catalytic mechanism involving basic and conjugated acidic/base sites can be suggested.•Methanol was identified as the potential agent for potassium ion removal.
The objective of this study was to investigate the use of LTA-structured zeolites as catalysts for synthesizing glycerol carbonate through the transesterification of glycerol with dimethyl carbonate, under mild reaction conditions. To evaluate the catalysts, a range of characterization techniques, including XRD, AES, SEM, TPD-NH3, TPD-CO2, and FT-IR with probe molecules like pyridine and pyrrole, along with elemental analysis, were employed. The investigation focused on various forms of LTA-structured zeolites (with K, Na, and Ca cations) to assess their impact on transesterification activity, with particular attention to the type of ion utilized and their basicity. Among these zeolites, K-Na-LTA (3A) zeolites demonstrated the most promising performance, achieving glycerol conversion rates ranging from 55 % to 77 %. Moreover, increasing basicity in the 3A zeolites led to higher glycerol conversion and glycerol carbonate yield. Encouragingly, all tested samples exhibited 100 % selectivity, exclusively producing the desired glycerol carbonate. However, during catalyst recycling, the decrease in glycerol conversion was observed, likely due to the leaching of active sites from the catalyst into the reaction medium. Methanol, being a one of the products, was identified as a potential agent responsible for the removal of potassium ions, during this process.
Summary
Dunaliella has been extensively studied due to its intriguing adaptation to high salinity. Its di‐domain glycerol‐3‐phosphate dehydrogenase (GPDH) isoform is likely to underlie the rapid ...production of the osmoprotectant glycerol. Here, we report the structure of the chimeric Dunaliella salina GPDH (DsGPDH) protein featuring a phosphoserine phosphatase‐like domain fused to the canonical glycerol‐3‐phosphate (G3P) dehydrogenase domain. Biochemical assays confirm that DsGPDH can convert dihydroxyacetone phosphate (DHAP) directly to glycerol, whereas a separate phosphatase protein is required for this conversion process in most organisms. The structure of DsGPDH in complex with its substrate DHAP and co‐factor nicotinamide adenine dinucleotide (NAD) allows the identification of the residues that form the active sites. Furthermore, the structure reveals an intriguing homotetramer form that likely contributes to the rapid biosynthesis of glycerol.
Significance Statement
Green alga Dunaliella has a remarkable ability to thrive at high salinity environments. Structural and biochemical characterization of the glycerol‐3‐phosphatase fused glycerol‐3‐phosphate dehydrogenase protein boosts our understanding of the glycerol‐mediated salt‐resistance mechanism that can potentially benefit industrial and agricultural applications.
Waste glycerol can be subjected to various processing operations, including purification and refining, to obtain glycerol of an appropriate purity. Alternative methods for utilising waste glycerol ...are also being sought, e.g., by converting it into other valuable chemical products or biofuels. Therefore, various technologies are being developed to ensure effective and sustainable utilisation of this type of waste. The production of value-added products from waste glycerol strongly determines the improvement of the economic viability of biofuel production and corresponds to the model of a waste-free and emission-free circular economy. This paper characterises the mechanisms and evaluates the efficiency of existing methods for microbiological utilisation of waste glycerol into liquid biofuels, including biodiesel, bioethanol and biobutanol, and identifies further production avenues of value-added products. In addition, it presents the results of a bibliographical analysis of publications related to the production of liquid fuels and economically valuable products from glycerol, assesses the progress of research and application work and, finally, identifies areas for future research.
Pseudomonas aeruginosa is an important opportunistic pathogen that is lethal to cystic fibrosis (CF) patients. Glycerol generated during the degradation of phosphatidylcholine, the major lung ...surfactant in CF patients, could be utilized by P. aeruginosa. Previous studies have indicated that metabolism of glycerol by this bacterium contributes to its adaptation to and persistence in the CF lung environment. Here, we investigated the metabolic mechanisms of glycerol and its important metabolic intermediate glycerol 3-phosphate (G3P) in P. aeruginosa PAO1. We found that G3P homeostasis plays an important role in the growth and virulence factor production of P. aeruginosa PAO1. The G3P accumulation caused by the mutation of G3P dehydrogenase (GlpD) and exogenous glycerol led to impaired growth and reductions in pyocyanin synthesis, motilities, tolerance to oxidative stress, and resistance to kanamycin. Transcriptomic analysis indicates that the growth retardation caused by G3P stress is associated with reduced glycolysis and adenosine triphosphate (ATP) generation. Furthermore, two haloacid dehalogenase-like phosphatases (PA0562 and PA3172) that play roles in the dephosphorylation of G3P in strain PAO1 were identified, and their enzymatic properties were characterized. Our findings reveal the importance of G3P homeostasis and indicate that GlpD, the key enzyme for G3P catabolism, is a potential therapeutic target for the prevention and treatment of infections by this pathogen.
In view of the intrinsic resistance of Pseudomonas aeruginosa to antibiotics and its potential to acquire resistance to current antibiotics, there is an urgent need to develop novel therapeutic options for the treatment of infections caused by this bacterium. Bacterial metabolic pathways have recently become a focus of interest as potential targets for the development of new antibiotics. In this study, we describe the mechanism of glycerol utilization in P. aeruginosa PAO1, which is an available carbon source in the lung environment. Our results reveal that the homeostasis of glycerol 3-phosphate (G3P), a pivotal intermediate in glycerol catabolism, is important for the growth and virulence factor production of P. aeruginosa PAO1. The mutation of G3P dehydrogenase (GlpD) and the addition of glycerol were found to reduce the tolerance of P. aeruginosa PAO1 to oxidative stress and to kanamycin. The findings highlight the importance of G3P homeostasis and suggest that GlpD is a potential drug target for the treatment of P. aeruginosa infections.
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Mechanical load influences bone structure and mass. Arguing the importance of load-transduction, we investigated the mechanisms inducing bone formation using an elastomeric substrate. ...We characterized Poly (glycerol sebacate) (PGS) in vitro for its mechanical properties, compatibility with osteoprogenitor cells regarding adhesion, proliferation, differentiation under compression versus static cultures and in vivo for the regeneration of a rabbit ulna critical size defect. The load-transducing properties of PGS were compared in vitro to a stiffer poly lactic-co-glycolic-acid (PLA/PGA) scaffold of similar porosity and interconnectivity. Under cyclic compression for 7days, we report focal adhesion kinase overexpression on the less stiff PGS and upregulation of the transcription factor Runx2 and late osteogenic markers osteocalcin and bone sialoprotein (1.7, 4.0 and 10.0 folds increase respectively). Upon implanting PGS in the rabbit ulna defect, histology and micro-computed tomography analysis showed complete gap bridging with new bone by the PGS elastomer by 8weeks while minimal bone formation was seen in empty controls. Immunohistochemical analysis demonstrated the new bone to be primarily regenerated by recruited osteoprogenitors cells expressing periostin protein during early phase of maturation similar to physiological endochondral bone development. This study confirms PGS to be osteoconductive contributing to bone regeneration by recruiting host progenitor/stem cell populations and as a load-transducing substrate, transmits mechanical signals to the populated cells promoting differentiation and matrix maturation toward proper bone remodeling. We hence conclude that the material properties of PGS being closer to osteoid tissue rather than to mineralized bone, allows bone maturation on a substrate mechanically closer to where osteoprogenitor/stem cells differentiate to develop mature load-bearing bone.
The development of effective therapies for bone and craniofacial regeneration is a foremost clinical priority in the mineralized tissue engineering field. Currently at risk are patients seeking treatment for craniofacial diseases, traumas and disorders including birth defects such as cleft lip and palate, (1 in 525 to 714 live births), craniosynostosis (300–500 per 1,000,000 live births), injuries to the head and face (20 million ER visits per year), and devastating head and neck cancers (8000 deaths and over 30,000 new cases per year). In addition, approximately 6.2 million fractures occur annually in the United States, of which 5–10% fail to heal properly, due to delayed or non-union 1, and nearly half of adults aged 45–65 have moderate to advanced periodontitis with associated alveolar bone loss, which, if not reversed, will lead to the loss of approximately 6.5 teeth/individual 2.
The strategies currently available for bone loss treatment largely suffer from limitations in efficacy or feasibility, necessitating further development and material innovation. Contemporary materials systems themselves are indeed limited in their ability to facilitate mechanical stimuli and provide an appropriate microenvironment for the cells they are designed to support.
We propose a strategy which aims to leverage biocompatibility, biodegradability and material elasticity in the creation of a cellular niche. Within this niche, cells are mechanically stimulated to produce their own extracellular matrix. The hypothesis that mechanical stimuli will enhance bone regeneration is supported by a wealth of literature showing the effect of mechanical stimuli on bone cell differentiation and matrix formation. Using mechanical stimuli, to our knowledge, has not been explored in vivo in bone tissue engineering applications. We thus propose to use an elastomeric platform, based on poly(glycerol sebacate (PGS), to mimic the natural biochemical environment of bone while enabling the transmission of mechanical forces.
In this study we report the material’s load-transducing ability as well as falling mechanically closer to bone marrow and osteoid tissue rather than to mature bone, allowed osteogenesis and bone maturation. Defying the notion of selecting bone regeneration scaffolds based on their relative mechanical comparability to mature bone, we consider our results in part novel for the new application of this elastomer and in another fostering for reassessment of the current selection criteria for bone scaffolds.
100 Years Later, What Is New in Glycerol Bioproduction? Semkiv, Marta V.; Ruchala, Justyna; Dmytruk, Kostyantyn V. ...
Trends in biotechnology (Regular ed.),
August 2020, 2020-08-00, 20200801, Volume:
38, Issue:
8
Journal Article
Peer reviewed
Industrial production of glycerol by yeast, which began during WWI in the so-called Neuberg fermentation, was the first example of metabolic engineering. However, this process, based on bisulfite ...addition to fermentation liquid, has many drawbacks and was replaced by other methods of glycerol production. Osmotolerant yeasts and other microorganisms that do not require addition of bisulfite to steer cellular metabolism towards glycerol synthesis have been discovered or engineered. Because the glycerol market is expected to reach 5 billion US$ by 2024, microbial fermentation may again become a promising way to produce glycerol. This review summarizes some problems and perspectives on the production of glycerol by natural or engineered eukaryotic and prokaryotic microorganisms.
Glycerol is an important feedstock for the food, pharmaceutical, and other industries.Wild-type Saccharomyces cerevisiae produces significant amounts of glycerol from glucose after the addition of steering agents (Neuberg fermentation), whereas genetically modified S. cerevisiae strains can synthesize glycerol without steering agents under either aerobic or anaerobic conditions.Osmotolerant yeasts produce significant amounts of glycerol aerobically under hyperosmotic conditions, and can be used for industrial glycerol production.Microalgae and cyanobacteria can produce glycerol directly from atmospheric CO2, but this process has not yet been implemented industrially.
•Versatility of glycerol monolaurate (GML) with application in various industries.•Effect of support material on stability of catalysts and reaction performance.•Critical analysis of reaction ...parameters for higher yield of GML.•Valuable insights on future directions in glycerol monolaurate production.
Glycerol monolaurate (GML) is a versatile green chemical with wide industrial applicability, including in the food, pharmaceutical, and personal care product industries. This review provides a thorough analysis of the processes involved in GML production, along with the diverse applications of GML. And also, addresses various limitations and challenges associated with esterification of lauric acid with glycerol to produce GML through enzymatic, homogeneous, and heterogeneous catalytic pathways. Among these routes, heterogeneous catalytic routes exhibited superior catalytic activity, achieving over 90% selectivity with good stability. Furthermore, the review offers a constructive assessment of the process parameters associated with catalysts and reaction conditions that influence the GML yield and selectivity. Notably, wide pore and short pore length were found to be suitable for attaining higher selectivity in esterification of lauric acid. Techno-economic assessments suggest that the enzyme route is more environmentally sustainable. However, in practice, the heterogeneous catalytic route proves more suitable for industrial-scale production. Therefore, this review may provide crucial guidance for researchers and industries aiming to produce GML in an economic and eco- friendly manner.
Glycerol phenylbutyrate (GPB) lowers ammonia by providing an alternate pathway to urea for waste nitrogen excretion in the form of phenylacetyl glutamine, which is excreted in urine. This randomized, ...double‐blind, placebo‐controlled phase II trial enrolled 178 patients with cirrhosis, including 59 already taking rifaximin, who had experienced two or more hepatic encephalopathy (HE) events in the previous 6 months. The primary endpoint was the proportion of patients with HE events. Other endpoints included the time to first event, total number of events, HE hospitalizations, symptomatic days, and safety. GPB, at 6 mL orally twice‐daily, significantly reduced the proportion of patients who experienced an HE event (21% versus 36%; P = 0.02), time to first event (hazard ratio HR = 0.56; P < 0.05), as well as total events (35 versus 57; P = 0.04), and was associated with fewer HE hospitalizations (13 versus 25; P = 0.06). Among patients not on rifaximin at enrollment, GPB reduced the proportion of patients with an HE event (10% versus 32%; P < 0.01), time to first event (HR = 0.29; P < 0.01), and total events (7 versus 31; P < 0.01). Plasma ammonia was significantly lower in patients on GPB and correlated with HE events when measured either at baseline or during the study. A similar proportion of patients in the GPB (79%) and placebo groups (76%) experienced adverse events. Conclusion: GPB reduced HE events as well as ammonia in patients with cirrhosis and HE and its safety profile was similar to placebo. The findings implicate ammonia in the pathogenesis of HE and suggest that GPB has therapeutic potential in this population. (Clinicaltrials.gov, NCT00999167). (Hepatology 2014;59:1073‐1083)
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