Characterization of Lanthanum Nitrate Modified CaMgZn Mixed Oxide Catalysts for Synthesis of Biodiesel

CaMgZn mixed oxide (CMZ) catalysts were modified by addition of lanthanum nitrate, and the use of modified catalysts (CMZL) for biodiesel synthesis were investigated. The conditions of biodiesel production with modified catalysts were optimized. Using optimized conditions, including lanthanum nitrate addition of 3wt.%, catalyst amount of 5wt.%, reaction temperature of 50°C, methanol to oil molar ratio of 15:1 and reaction time of 1h, the glycerol yield of 86.80% catalyzed by CMZL could be attained, which was higher compared with the CMZ catalyzed process of 82.94%. Brunauer–Emmett–Teller (BET), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were used to compare the modified CMZL catalyst with the CMZ bare catalyst. The results indicated that the lanthanum modified catalysts (CMZL) have excellent surface property. The modified catalysts could be suitable for commercial application.

Optimization of Constituents of (Ni, MO, Cu)/Kieselguhr Catalyst by Response Surface Methodology for Glycerol Production by Hydrogenolysis of Sucrose

Sucrose hydrogenolysis is industrially important forthe production of polyols. To provide high glycerol yieldunder milder reaction conditions, a nickel catalyst promotedby Molybdenum and copper supported on kieselguhr wassynthesized and optimized using Response SurfaceMethodology. A 3X5 experimental design has been adopted tostudy the effect of these constituents. A linear second-ordermodel has been developed to optimize and to study theinteraction effects on glycerol yield in the catalytichydrogenolysis of sucrose. Increase in nickel loading in thecatalyst increased its activity. Increase in Molybdenum alsoincreased the catalyst activity but changed the reactionmechanism as well. Increase in copper caused the directhydrogenolysis of sucrose instead of its first splitting intomonosaccahrides and their subsequent hydrogenolysis.Maximum glycerol yield of 27.79% was identified at anoptimum nickel, Molybdenum and copper concentration of29.80%, 10.0%, and 1.07%, respectively. The optimizedcatalyst has been characterized by the electron microscopy, Xraydiffraction, and magnetic measurement techniques.

Decreased Xylitol Formation during Xylose Fermentation in Saccharomyces cerevisiae Due to Overexpression of Water-Forming NADH Oxidase

ABSTRACTThe recombinant xylose-fermentingSaccharomyces cerevisiaestrain harboring xylose reductase (XR) and xylitol dehydrogenase (XDH) fromScheffersomyces stipitisrequires NADPH and NAD+, creates cofactor imbalance, and causes xylitol accumulation during growth ond-xylose. To solve this problem,noxE, encoding a water-forming NADH oxidase fromLactococcus lactisdriven by thePGK1promoter, was introduced into the xylose-utilizing yeast strain KAM-3X. A cofactor microcycle was set up between the utilization of NAD+by XDH and the formation of NAD+by water-forming NADH oxidase. Overexpression ofnoxEsignificantly decreased xylitol formation and increased final ethanol production during xylose fermentation. Under xylose fermentation conditions with an initiald-xylose concentration of 50 g/liter, the xylitol yields for of KAM-3X(pPGK1-noxE) and control strain KAM-3X were 0.058 g/g xylose and 0.191 g/g, respectively, which showed a 69.63% decrease owing tonoxEoverexpression; the ethanol yields were 0.294 g/g for KAM-3X(pPGK1-noxE) and 0.211 g/g for the control strain KAM-3X, which indicated a 39.33% increase due tonoxEoverexpression. At the same time, the glycerol yield also was reduced by 53.85% on account of the decrease in the NADH pool caused by overexpression ofnoxE.

Novel Conjugates of 1,3-Diacylglycerol and Lipoic Acid: Synthesis, DPPH Assay, and RP-LC-MS-APCI Analysis

1,3-Diacylglycerol is known to reduce body weight and fat deposits in humans.α-Lipoic acid is a potent antioxidant and effective against many pathological conditions, including obesity and related metabolic syndromes. The present work is based on the hypothesis that the hybrid molecules of 1,3-diacylglycerol and lipoic acid possess synergistic and/or additive effects compared with the parent compounds against obesity, overweight, and related metabolic syndromes. Laboratory scale synthesis of 1,3-dioleoyl-2-lipoyl-sn-glycerol (yield 80%) and 1,3-dioleoyl-2-dihydrolipoyl-sn-glycerol (yield 70%) was performed for the first time and supported by NMR and MS data. Free radical scavenging capacity of the conjugates was assayed using DPPH test. A remarkably highin vitrofree radical scavenging capacity was demonstrated for the 1,3-dioleoyl-2-dihydrolipoyl-sn-glycerol (EC50value 0.21). RP-HPLC-MS-APCI analysis showed satisfactory separation between the conjugates (R~1). Protonated molecular ion of the conjugates atm/z809 andm/zat 811, respectively, and their characteristic fragment ions were abundant.

Engineering of Promoter Replacement Cassettes for Fine-Tuning of Gene Expression in Saccharomyces cerevisiae

ABSTRACT The strong overexpression or complete deletion of a gene gives only limited information about its control over a certain phenotype or pathway. Gene function studies based on these methods are therefore incomplete. To effect facile manipulation of gene expression across a full continuum of possible expression levels, we recently created a library of mutant promoters. Here, we provide the detailed characterization of our yeast promoter collection comprising 11 mutants of the strong constitutive Saccharomyces cerevisiae TEF1 promoter. The activities of the mutant promoters range between about 8% and 120% of the activity of the unmutated TEF1 promoter. The differences in reporter gene expression in the 11 mutants were independent of the carbon source used, and real-time PCR confirmed that these differences were due to varying levels of transcription (i.e., caused by varying promoter strengths). In addition to a CEN/ARS plasmid-based promoter collection, we also created promoter replacement cassettes. They enable genomic integration of our mutant promoter collection upstream of any given yeast gene, allowing detailed genotype-phenotype characterizations. To illustrate the utility of the method, the GPD1 promoter of S. cerevisiae was replaced by five TEF1 promoter mutants of different strengths, which allowed analysis of the impact of glycerol 3-phosphate dehydrogenase activity on the glycerol yield.

Glycerol production by yeasts under osmotic and sulfite stress

The yeasts Saccharomyces cerevisiae,Candida boidinii,Pichia angusta, and Pichia anomala were tested for glycerol production both under osmotic stress and by addition of a sulfite-steering agent. The osmotic pressure was increased by employing glucose concentrations from 50 to 200 g/L and by supplementing with NaCl (40 g/L). Of all the yeasts, S. cerevisiae exhibited the highest level of osmotolerance. The increased osmotic pressure affected glycerol formation the most in C. boidinii. In both Pichia species, glycerol formation was not sufficiently induced when exposed to sugar and salt stress. The addition of 40 g/L Na2SO3 to the medium containing 100 g/L glucose shifted the metabolism of all yeasts towards glycerol formation. Saccharomyces cerevisiae achieved 68.6%, while C. boidinii reached 25.5% of the theoretical glycerol yield, respectively. The highest glycerol yield, 82.3% of the theoretical, was produced by S. cerevisiae under microaerophilic conditions.Key words: glycerol, osmotolerant yeast, sulfite-tolerant yeast, Saccharomyces cerevisiae,Candida boidinii.

Glycerol Yield from Dogfish Liver Oil

Variations from 8.15 to 0.96 per cent in the glycerol yield from twelve dogfish (Squalus suckleyi) liver oils are reported and shown to be inversely related to their 7.6 to 34.3 per cent yield of unsaponifiable matter, or, better, to their 6 to 31 per cent yield of glyceryl ethers. The glycerol determinations are confirmed by an independent method involving a comparison of the hydroxyl group and replaceable hydrogen contents of the hydrolyzed oils.