Glycerol Production Research Articles

Ultrafast Electron Transfer in Au–Cyanobacteria Hybrid for Solar to Chemical Production

The rise of inorganic–biohybrid organisms for solar-to-chemical production has spurred mechanistic investigations into the dynamics of the biotic–abiotic interface to drive the development of next-generation hybrid systems. The model system, cyanobacteria–gold nanoparticle hybrids, combines a light harvester with a photosynthetic bacterium to drive the reduction of CO2 to glycerol with improved efficiency and increased glycerol production by 14.6%, in comparison to cyanobacteria only. In this work, we report insights into this unique photochemical behavior and propose a charge-transfer pathway from Au nanoparticle to cyanobacteria. Transient absorption (TA) spectroscopy revealed that photoexcited electron transfer rates are on the order of a few ps to the potential electron acceptor in photosystem II. This work represents a promising platform to utilize a conventional spectroscopic methodology to extract insights from more complex biotic–abiotic hybrid systems.

Starmerella bacillaris Released in Vineyards at Different Concentrations Influences Wine Glycerol Content Depending on the Vinification Protocols.

Starmerella bacillaris is a non-Saccharomyces yeast proposed for must fermentation together with Saccharomyces cerevisiae because of its high glycerol and moderate volatile acidity production. Furthermore, it was demonstrated that the same S. bacillaris strains that possess interesting technological properties exhibited antifungal activity against Botrytis cinerea, suggesting the release of this yeast in the vineyard. To obtain a positive effect during the following winemaking process, the maintenance of suitable concentrations of S. bacillaris is essential. Therefore, to obtain information on the survival of S. bacillaris, a small-scale field trial was performed. One week before the harvest, two different concentrations of S. bacillaris (106 and 107 cells/mL) were sprayed on Pinot grigio bunches, and the strain concentration was monitored by means of qPCR during the subsequent fermentation process. In addition, the combined effect of different winemaking techniques was evaluated, i.e., the vinification of juice, juice with marc and cryomaceration treatment. Results demonstrated that, under the tested conditions, S. bacillaris released in the vineyard remained viable for one week on grape bunches and increased glycerol content during the subsequent fermentation process. Different vinification protocols influenced cell concentrations. In particular, the cryomaceration treatment, due to the use of low temperature, supported S. bacillaris growth due to its cryotolerant aptitude. The collected data open new perspectives on the control of alcoholic fermentation, involving both vineyard and cellar management.

Establishing a growth-coupled mechanism for high-yield production of β-arbutin from glycerol in Escherichia coli

Biodiesel production has increased significantly in recent years, leading to an increase in the production of crude glycerol. In this study, a novel growth-coupled erythrose 4-phosphate (E4P) formation strategy that can be used to produce high levels of β-arbutin using engineered Escherichia coli and glycerol as the carbon source was developed. In the strategy, E4P formation was coupled with cell growth, and a growth-driving force made the E4P formation efficient. By applying this strategy, efficient microbial synthesis of β-arbutin was achieved, with 7.91 g/L β-arbutin produced in shaking flask, and 28.1 g/L produced in a fed batch fermentation with a yield of 0.20 g/g glycerol and a productivity of 0.39 g/L/h. This is the highest β-arbutin production through microbial fermentation ever reported to date. This study may have significant implications in the large-scale production of β-arbutin as well as other aromatic compounds of importance.

Serum metabolomic characterization in pigs in relation to birth weight category and neonatal nutrition.

The objective of this study was to characterize developmental differences in low birth weight (LBW) and normal birth weight (NBW) piglets with or without pre-weaning nutrient restriction using serum metabolomic profile analysis. At farrowing, 112 piglets were identified as LBW (1.22 ± 0.28 kg) or NBW (1.70 ± 0.27 kg) and were randomly assigned to receive normal nutrition (NN) or restricted nutrition (RN) (6 h/day no suckling) from days 2 to 28 post farrow (n = 8 pigs/group). On day 28, piglets were weaned onto a common diet. Fasted blood samples were obtained on days 28 and 56 (n = 8 pigs/group) and were analyzed using quantitative metabolomics via a combination of direct injection mass spectrometry with a reverse-phase LC-MS/MS custom assay. Data were normalized using logarithmic transformation and auto-scaling. Partial least squares discriminant analysis (PLS-DA) was carried out to further explore the differential metabolites among the groups (metaboanalyst.ca) with an integrated enrichment and pathway topography analysis. On day 28, LBW piglets had lower levels of essential amino acids as well as reduced metabolites associated with fatty acid oxidation, glycolysis, and the tri-carboxylic acid (TCA) cycle compared to the NBW group. The overall reduction of metabolites associated with energy production and regulation suggests that LBW vs. NBW are in an energy-survival state. On day 56, LBW pigs had increased utilization of fatty acids and resultant ketone production, evident by increased carnitines, acetoacetate, β-hydroxybutyrate, and glycerol compared to NBW pigs. In addition, compared to the NBW pigs LBW pigs had a consistent decrease in serum glucose and lactate as well as reduced TCA cycle metabolites: pyruvate, succinate, citrate, and α-ketoglutaric acid similar to day 28. Low reliance on glycolysis and the TCA cycle and higher glycerol production in the LBW pigs may indicate impairments in glucose tolerance at 56 d. In summary, LBW piglets appear to have more metabolic alterations in early life, which is not resolved with adequate nutrition or refeeding and may elucidate physiological and metabolic mechanisms of poor growth and life performance compared to NBW pigs later in life.

ODP424 Postprandial Adipose Insulin Resistance in Adolescent Girls with PCOS and Obesity

Abstract Background Polycystic ovary syndrome (PCOS) is common and associated with metabolic disease, in particular glucose abnormalities and insulin resistance (IR). Fat metabolism is linked with IR, manifesting as decreased suppression of lipolysis following meals, inflammation, and ectopic fat accumulation. Our previous work demonstrated adipose IR during a hyperinsulinemic-euglycemic clamp and increased hepatic fat in adolescents with PCOS. We hypothesized that postprandial fat metabolism would be altered compared to controls with obesity. Design/Methodology Data from 133 girls aged 13-21 years with obesity (BMI >90th%ile) enrolled in 1 of 4 cross-sectional metabolic studies were included in this secondary analysis. PCOS was determined per NIH diagnostic standards. Controls had regular menses and were >1-year post-menarche. Metabolic assessments were identical across studies and included fasting labs (lipid panel, inflammatory markers, androgens, insulin sensitivity indices), 4-hour oral sugar tolerance test (OSTT, 75 grams glucose, 25 grams fructose), liver fat by MRI, and body composition by DXA. Glycerol production (Ra) D5 glycerol infusion to measure lipolysis was evaluated in a subset. Metrics of glucose, insulin, glycerol, free fatty acid (FFA), and glucagon during the OSTT were calculated including AUC, fasting, nadir, and peak. Adipo IR (fasting FAA x fasting insulin) was determined. Data between controls and girls with PCOS were compared by Student's t-tests with Welch correction. Spearman's correlations were used within groups to evaluate associations. Results Participants included 110 girls with PCOS (age 16.4±1.6 years; BMI 35.9±5.8 kg/m2) and 23 without PCOS (15.9±1.6; 34.6±6.7). Per design, markers of androgen excess including total testosterone (p<0.001), free testosterone (p<0.001), degree of hirsutism (p=0.004), and severity of acne (p<0.001) were worse in girls with PCOS. Consistent with previous work, girls with PCOS had worse markers of glycemia including higher HbA1c (p<0.001), fasting glucose (p=0.027), 2-hour glucose (p=0.008), glucose AUC (p=0.033), and insulin AUC (p=0.034). They also had higher liver (p<0.001) and visceral fat (p=0.007), total (p=0.007) and LDL cholesterol (p=0.006), and triglycerides (p=0.005). Regarding adipose IR, fasting FFA (699±175 µmol/L vs. 593±163, p=0.007), FFA nadir (68±26 vs. 51±16, p=0.003), FFA AUC (114210 vs. 92518, p = 0.018), glycerol AUC (13815 vs. 8393, p<0.0001), and Adipo IR (p=0.034) were significantly higher while fasting glycerol Ra (p=0.571) did not differ. There were no differences between groups in markers of inflammation. Within the PCOS group, higher glycerol AUC correlated with higher HbA1c (p=0.001) and highly-sensitive C-reactive protein (hsCRP) (p=0.029), while increased FFA AUC correlated with increased hsCRP (p=0.043) and AST (p=0.037), but not markers of insulin resistance or dysglycemia. Conclusions Adolescents with PCOS and obesity have increased adipose IR. Future focus and treatment of adipose IR may be a promising avenue to delay onset of metabolic syndrome complications in girls with PCOS and obesity. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Flexibility concept in design of advanced multi-energy carrier systems driven by biogas fuel for sustainable development

In this paper, a new and comprehensive multigeneration system is developed exploiting biogas fuel. The system is examined from the perspective of energy, exergy, exergoeconomic, exergoenvironment, and safety for supplying the energy demands of large buildings such as modern hospitals located near industrial places. Multi-objective optimization is applied along with a new concept of flexibility in the system considering these five indicators. The Brayton cycle and closed Brayton cycle for power generation, dual-loop organic Rankine cycle and ejector refrigeration for power and cooling production, multi-effect distillation unit for freshwater production, carbon dioxide absorption unit by microalgae for biodiesel production, water heaters for domestic heating production, and PEM electrolyzer for hydrogen production are integrated into the devised system. From the environmental point of view, using biogas fuel and absorption of carbon dioxide leads to the best environmental efficiency in the proposed system. Moreover, the safety facet is analyzed to lower the level of damage and risk in the system. Based on the results of the optimization, the net output power, air conditioning refrigeration, freezing, and heating are reckoned at 1864, 286.6, 75.89, and 398.9 kW, and the production of freshwater, hydrogen, biodiesel, and glycerol is predicted to be 2.111, 0.00038, 0.0088, and 0.00091 kg/s, respectively. Also, the system performance ratio, unit cost of product, exergy efficiency, environmental effect of product, and overall system risk are equal to 1.828, 40.58 $/GJ, 31.11%, 6232 mPts/GJ, and 1656 $/year.

Hepatic glycerol shunt and glycerol-3-phosphate phosphatase control liver metabolism and glucodetoxification under hyperglycemia

ObjectiveGlycerol-3-phosphate (Gro3P) phosphatase (G3PP) hydrolyzes Gro3P to glycerol that exits the cell, thereby operating a “glycerol shunt”, a metabolic pathway that we identified recently in mammalian cells. We have investigated the role of G3PP and the glycerol shunt in the regulation of glucose metabolism and lipogenesis in mouse liver. MethodsWe generated hepatocyte-specific G3PP-KO mice (LKO), by injecting AAV8-TBG-iCre to male G3PPfl/fl mice. Controls received AAV8-TBG-eGFP. Both groups were fed chow diet for 10 weeks. Hyperglycemia (16–20 mM) was induced by glucose infusion for 55 h. Hepatocytes were isolated from normoglycemic mice for ex vivo studies and targeted metabolomics were measured in mice liver after glucose infusion. ResultsLKO mice showed no change in body weight, food intake, fed and fasted glycemia but had increased fed plasma triglycerides. Hepatic glucose production from glycerol was increased in fasted LKO mice. LKO mouse hepatocytes displayed reduced glycerol production, elevated triglyceride and lactate production at high glucose concentration. Hyperglycemia in LKO mice led to increased liver weight and accumulation of triglycerides, glycogen and cholesterol together with elevated levels of Gro3P, dihydroxyacetone phosphate, acetyl-CoA and some Krebs cycle intermediates in liver. Hyperglycemic LKO mouse liver showed elevated expression of proinflammatory cytokines and M1-macrophage markers accompanied by increased plasma triglycerides, LDL/VLDL, urea and uric acid and myocardial triglycerides. ConclusionsThe glycerol shunt orchestrated by G3PP acts as a glucose excess detoxification pathway in hepatocytes by preventing metabolic disturbances that contribute to enhanced liver fat, glycogen storage, inflammation and lipid build-up in the heart. We propose G3PP as a novel therapeutic target for hepatic disorders linked to nutrient excess.

Development of an industrial yeast strain for efficient production of 2,3-butanediol

As part of the transition from a fossil resources-based economy to a bio-based economy, the production of platform chemicals by microbial cell factories has gained strong interest. 2,3-butanediol (2,3-BDO) has various industrial applications, but its production by microbial fermentation poses multiple challenges. We have engineered the bacterial 2,3-BDO synthesis pathway, composed of AlsS, AlsD and BdhA, in a pdc-negative version of an industrial Saccharomyces cerevisiae yeast strain. The high concentration of glycerol caused by the excess NADH produced in the pathway from glucose to 2,3-BDO was eliminated by overexpression of NoxE and also in a novel way by combined overexpression of NDE1, encoding mitochondrial external NADH dehydrogenase, and AOX1, encoding a heterologous alternative oxidase expressed inside the mitochondria. This was combined with strong downregulation of GPD1 and deletion of GPD2, to minimize glycerol production while maintaining osmotolerance. The HGS50 strain produced a 2,3-BDO titer of 121.04 g/L from 250 g/L glucose, the highest ever reported in batch fermentation, with a productivity of 1.57 g/L.h (0.08 g/L.h per gCDW) and a yield of 0.48 g/g glucose or with 96% the closest to the maximum theoretical yield ever reported. Expression of Lactococcus lactis NoxE, encoding a water-forming NADH oxidase, combined with similar genetic modifications, as well as expression of Candida albicans STL1, also minimized glycerol production while maintaining high osmotolerance. The HGS37 strain produced 130.64 g/L 2,3-BDO from 280 g/L glucose, with productivity of 1.58 g/L.h (0.11 g/L.h per gCDW). Both strains reach combined performance criteria adequate for industrial implementation.

S3.4e Unraveling the role of DOG genes in a novel alternative pathway of glycerol biosynthesis in Candida albicans and its influence on virulence

S3.4 Free oral paper session, September 21, 2022, 4:45 PM - 6:15 PMDOG genes, encoding for 2-deoxyglucose-6-phosphate phosphatase are low molecular weight phosphatases, with an unknown biological function. In contrast to Saccharomyces cerevisiae which has two DOG homologs, C. albicans only has one DOG gene. We hypothesized that DOG1 plays an important role under osmotic or ionic stress by biosynthesizing glycerol, which is known to be vital for biofilm formation and virulence of this pathogenic yeast, via a novel alternative pathway. The known classical pathway of glycerol production begins when the glycolytic intermediate molecule dihydroxyacetone phosphate (DHAP) is converted into glycerol-3-phosphate (G-3-P) by a pair of glycerol-3-phosphate-dehydrogenases, Gpd1 and Gpd2. G-3-P is further dephosphorylated into glycerol by glycerol-3-phosphate-phosphatases, Gpp1 and Gpp2. However, an alternative pathway, where DHAP is dephosphorylated into DHA, which is subsequently converted into glycerol has been proposed, but the enzymes involved in this process have not yet been described. We recently showed that in Saccharomyces cerevisiae, the DOG enzymes are involved in the production of DHA from DHAP, thereby allowing the synthesis of glycerol in the absence of the classical pathway. Overexpression of the DOG genes restored the osmo-tolerance of the gpp1Δ gpp2Δand gpd1Δ gpd2Δ double deletion strains. Furthermore, purified DOG enzymes could also convert DHAP into DHA (Awasthy et al., submitted). Since DOG1 has a potential role in biosynthesizing glycerol via an unconventional route, we are interested to determine its contribution in influencing virulence and biofilm formation in Candida albicans. This putative pathway has been overlooked for the past two decades, leaving behind an evident knowledge gap. We have now generated multiple deletion strains, using CRISPR Cas9, for the C. albicans counterparts of the GPP, GPD, and DOG genes as well as multiple DOG1 overexpression strains in which we observed the restoration of osmotic stress tolerance phenotypically and via growth curves. We also have NMR data showing the accumulation of various metabolites of central metabolism in these strains. Additionally, we have determined the possible role of DOG1 on virulence factors like morphogenesis, adhesion, and biofilm formation in vitro as well as in vivo, the latter with our catheter-based biofilm subcutaneous mouse model system. We also linked DOG1 and its role in glycerol biosynthesis to the survival of C. albicans inside macrophages. Finally, we would be setting up a high throughput small compound screening for this phosphatase as a potential antifungal drug target.

Rewiring yeast metabolism for producing 2,3-butanediol and two downstream applications: Techno-economic analysis and life cycle assessment of methyl ethyl ketone (MEK) and agricultural biostimulant production

Rising concerns for sustainability and global climate change have driven the development of sustainable production pathways for biofuels and chemicals from lignocellulosic biomass via integrated biological and chemical processes. We constructed an engineered Saccharomyces cerevisiae capable of producing 2,3-butanediol (2,3-BDO) from glucose without accumulating ethanol and glycerol, which hinder downstream processing of 2,3-BDO, through extensive metabolic reprogramming. Specifically, we introduced heterologous 2,3-BDO biosynthetic enzymes and deleted the major isozymes of ethanol and glycerol biosynthetic enzymes. In addition, we introduced an NAD+ regenerating Pyruvate-Malate (PM) cycle and enhanced the NAD+ regenerating capability of the PM cycle to resolve the redox imbalance from the deletion of ethanol and glycerol production pathways. The resulting engineered yeast produced 109.9 g/L of 2,3-BDO with a productivity of 1.0 g/L/h and a yield of 0.36 g/g glucose in a fed-batch fermentation. We also conducted techno-economic analysis (TEA) and life cycle assessment (LCA) of the production of methyl ethyl ketone (MEK) through catalytic dehydration of 2,3-BDO. A TEA based on the experimental results indicated that the minimum product selling price (MPSP) was estimated to be $1.90/kg. Regarding cradle-to-grave LCA, 100-year global warming potential (GWP100) and fossil energy consumption (FEC) were found to be 0.37 kg CO2 eq/kg and 3.1 MJ/kg, respectively. These results demonstrated the feasibility of cost-competitive and sustainable bio-based MEK production via yeast fermentation. In addition, we explored the possibility of using the fermentation broth containing 2,3-BDO as a biostimulant inducing drought tolerance in plants. As a result, the yeast 2,3-BDO fermentation broth can induce drought tolerance in Arabidopsis thaliana without a complicated purification process.

Recent Advances on the Valorization of Glycerol into Alcohols

Glycerol, a highly functionalised polyol, can be used as a platform molecule to produce a variety of high-value chemicals. As glycerol production is projected to increase over the coming years, it’s critically important that technology and infrastructure are developed to make use of the inevitable surplus. The catalytic production of ‘green’ mono alcohols from glycerol, in the absence of H2, is an emerging area of research that, in recent years, has generated significant industrial interest. Herein, we provide an update on recent advances in this field and discuss challenges which need to be overcome if this approach is to be considered viable industrially. The economic significance of using crude glycerol as a feedstock for glycerol valorisation strategies is also addressed and suggestions for improving the impact of research conducted in this field are proposed.

Elimination of biodiesel contaminants by recombinant glucoside hydrolase produced from crude glycerol

This work presents the direct crude glycerol use by high cell-density fermentation of Escherichia coli expressing recombinant glycoside hydrolase that cleaves steryl glucosides, one of the main biodiesel contaminants. Optimized fermentation with crude glycerol reached the biomass concentration of 30 g/l with the 0.285 U/mgDCW specific activity, which is comparable with the pure glycerol production. The expression of the inclusion bodies was eliminated by the increase of the induction temperature to 40 °C. The produced enzyme was able to hydrolyze 300 ppm of steryl glucosides, the major biodiesel contaminants, and reached 100 % conversion. This model approach of waste carbon recycling (crude glycerol) for biorefinery-beneficial recombinant enzyme production is in line with the sustainable circular bioeconomy concept.

Loss of FOXA2 induces ER stress and hepatic steatosis and alters developmental gene expression in human iPSC-derived hepatocytes

FOXA2 has been known to play important roles in liver functions in rodents. However, its role in human hepatocytes is not fully understood. Recently, we generated FOXA2 mutant induced pluripotent stem cell (FOXA2−/−iPSC) lines and illustrated that loss of FOXA2 results in developmental defects in pancreatic islet cells. Here, we used FOXA2−/−iPSC lines to understand the role of FOXA2 on the development and function of human hepatocytes. Lack of FOXA2 resulted in significant alterations in the expression of key developmental and functional genes in hepatic progenitors (HP) and mature hepatocytes (MH) as well as an increase in the expression of ER stress markers. Functional assays demonstrated an increase in lipid accumulation, bile acid synthesis and glycerol production, while a decrease in glucose uptake, glycogen storage, and Albumin secretion. RNA-sequencing analysis further validated the findings by showing a significant increase in genes associated with lipid metabolism, bile acid secretion, and suggested the activation of hepatic stellate cells and hepatic fibrosis in MH lacking FOXA2. Overexpression of FOXA2 reversed the defective phenotypes and improved hepatocyte functionality in iPSC-derived hepatic cells lacking FOXA2. These results highlight a potential role of FOXA2 in regulating human hepatic development and function and provide a human hepatocyte model, which can be used to identify novel therapeutic targets for FOXA2-associated liver disorders.

Comparing the effects of isoleucine and leucine supplementation at different dosage on the growth and metabolism of Torulaspora delbrueckii Biodiva during soy whey fermentation

Soy whey is a liquid by-product generated from tofu production and it is often discarded as wastewater after it is generated. Previous studies have shown that out of the three branched-chain amino acids, isoleucine was found to have an inhibitory effect on Torulaspora delbrueckii Biodiva during soy whey fermentation. In this study, a comparison between isoleucine and leucine was carried out to ascertain how these two structural isomers could affect the growth and metabolism of T. delbrueckii Biodiva at various concentrations (40, 80 and 160 mg nitrogen/L). In general, amino acid supplementation sped up the fermentation process relative to unsupplemented samples. Even though glycerol and ethanol production were enhanced in all isoleucine supplemented samples in comparison to unsupplemented samples, isoleucine supplementation resulted in slower yeast growth at day 1 and slower sucrose hydrolysis regardless of the concentration supplemented. As for leucine supplementation, there was no impact on yeast growth, glycerol and ethanol production but sucrose hydrolysis was enhanced in comparison to the unsupplemented samples. Increasing isoleucine and leucine supplementation resulted in corresponding increase in active amyl alcohol and isoamyl alcohol production respectively, but isoleucine had a stimulating effect on increasing the production of other higher alcohols while leucine had an inhibitory effect on the production of other higher alcohols. Therefore, even though isoleucine and leucine are structural isomers with the positional difference of only one methyl group, the impact on the yeast metabolism and growth is visibly different.

The role of the glycerol transporter channel Fps1p in cellular proteostasis during enhanced proteotoxic stress.

In response to osmotic shock, the components of high-osmolarity glycerol (HOG) pathway regulate the level of intracellular glycerol in yeast and ensure cell survival. Glycerol is a compatible solute and a stabiliser of proteins. Its role in maintaining proteostasis is less explored. We show that mild stress in the form of dietary restriction leads to increased glycerol level which increases cell viability. However, dietary restriction coupled with protein aggregation decreases intracellular glycerol level and attenuates cell viability. The transcript level of FPS1, the glycerol transporter channel, remains unchanged. However, its activity is altered under enhanced proteotoxic stress. Our results provide evidence for a probable role of the Fps1p channel in the cellular proteostasis network. KEY POINTS: • Dietary restriction led to increased accumulation of glycerol in Fps1-deleted yeast cells. • This led to lower protein aggregation in these cells. • Increased production of glycerol under dietary restriction was not linked to increased level of Fps1.

D-Lactic Acid Production from Sugarcane Bagasse by Genetically Engineered Saccharomyces cerevisiae.

Lactic acid (LA) is a promising bio-based chemical that has broad applications in food, nutraceutical, and bioplastic industries. However, production of the D-form of LA (D-LA) from fermentative organisms is lacking. In this study, Saccharomyces cerevisiae harboring the D-lactate dehydrogenase (DLDH) gene from Leuconostoc mesenteroides was constructed (CEN.PK2_DLDH). To increase D-LA production, the CRISPR/Cas12a system was used for the deletion of gpd1, gpd2, and adh1 to minimize glycerol and ethanol production. Although an improved D-LA titer was observed for both CEN.PK2_DLDHΔgpd and CEN.PK2_DLDHΔgpdΔadh1, growth impairment was observed. To enhance the D-LA productivity, CEN.PK2_DLDHΔgpd was crossed with the weak acid-tolerant S. cerevisiae BCC39850. The isolated hybrid2 showed a maximum D-LA concentration of 23.41 ± 1.65 g/L, equivalent to the improvement in productivity and yield by 2.2 and 1.5 folds, respectively. The simultaneous saccharification and fermentation using alkaline pretreated sugarcane bagasse by the hybrid2 led to an improved D-LA conversion yield on both the washed solid and whole slurry (0.33 and 0.24 g/g glucan). Our findings show the exploitation of natural yeast diversity and the potential strategy of gene editing combined with conventional breeding on improving the performance of S. cerevisiae for the production of industrially potent products.

Glycerol steam reforming over hydrothermal synthetic Ni-Ca/attapulgite for green hydrogen generation

• Glycerol steam reforming over hydrothermal synthetic Ni-Ca/ATP was firstly studied. • Effect of Ca content and preparation method on Ni/ATP structure was investigated. • Hydrothermal synthesis ( hs ) enhanced the distribution of Ca and Ni species over ATP. • Ni-6Ca/ATP- hs had strong CO 2 adsorption and abundant Ni-CaO x interfaces. • Ni-6Ca/ATP- hs exhibited superior performance and sinter/coke durability for GSR. Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12%, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni- x Ca/ATP ( x = 3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation ( ci ) and hydrothermal synthesis ( hs ) method and then tested in GSR. Characterization results of XRD, N 2 adsorption–desorption, H 2 -TPR, HRTEM, XPS, and NH 3 /CO 2 -TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO 2 . This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaO x interface sites. Therefore, Ni-6Ca/ATP- hs exhibits the highest conversion (86.77%) of glycerol to gas product and H 2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP- hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

Characterization for Cleaner and Sustainable Production of Glycerol from Tallow Under Aqueous Media at High Pressure and Temperature

Characterization for Cleaner and Sustainable Production of Glycerol from Tallow Under Aqueous Media at High Pressure and Temperature

Genome-wide transcriptional regulation in Saccharomyces cerevisiae in response to carbon dioxide

Sugar metabolism by Saccharomyces cerevisiae produces ample amounts of CO2 under both aerobic and anaerobic conditions. High solubility of CO2 in fermentation media, contributing to enjoyable sensory properties of sparkling wine and beers by S. cerevisiae, might affect yeast metabolism. To elucidate the overlooked effects of CO2 on yeast metabolism, we examined glucose fermentation by S. cerevisiae under CO2 as compared to N2 and O2 limited conditions. While both CO2 and N2 conditions are considered anaerobic, less glycerol and acetate but more ethanol were produced under CO2 condition. Transcriptomic analysis revealed that significantly decreased mRNA levels of GPP1 coding for glycerol-3-phosphate phosphatase in glycerol synthesis explained the reduced glycerol production under CO2 condition. Besides, transcriptional regulations in signal transduction, carbohydrate synthesis, heme synthesis, membrane and cell wall metabolism, and respiration were detected in response to CO2. Interestingly, signal transduction was uniquely regulated under CO2 condition, where upregulated genes (STE3, MSB2, WSC3, STE12, and TEC1) in the signal sensors and transcriptional factors suggested that MAPK signaling pathway plays a critical role in CO2 sensing and CO2-induced metabolisms in yeast. Our study identifies CO2 as an external stimulus for modulating metabolic activities in yeast and a transcriptional effector for diverse applications.

Generation of intra- and interspecific Saccharomyces hybrids with improved oenological and aromatic properties.

SummaryNon‐wine yeasts could enhance the aroma and organoleptic profile of wines. However, compared to wine strains, they have specific intolerances to winemaking conditions. To solve this problem, we generated intra‐ and interspecific hybrids using a non‐GMO technique (rare‐mating) in which non‐wine strains of S. uvarum, S. kudriavzevii and S. cerevisiae species were crossed with a wine S. cerevisiae yeast. The hybrid that inherited the wine yeast mitochondrial showed better fermentation capacities, whereas hybrids carrying the non‐wine strain mitotype reduced ethanol levels and increased glycerol, 2,3‐butanediol and organic acid production. Moreover, all the hybrids produced several fruity and floral aromas compared to the wine yeast: β‐phenylethyl acetate, isobutyl acetate, γ‐octalactone, ethyl cinnamate in both varietal wines. Sc × Sk crosses produced three‐ to sixfold higher polyfunctional mercaptans, 4‐mercapto‐4‐methylpentan‐2‐one (4MMP) and 3‐mercaptohexanol (3MH). We proposed that the exceptional 3MH release observed in an S. cerevisiae × S. kudriavzevii hybrid was due to the cleavage of the non‐volatile glutathione precursor (Glt‐3MH) to detoxify the cell from the presence of methylglyoxal, a compound related to the high glycerol yield reached by this hybrid. In conclusion, hybrid generation allows us to obtain aromatically improved yeasts concerning their wine parent. In addition, they reduced ethanol and increased organic acids yields, which counteracts climate change effect on grapes.