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Pure Glycerol (pure + glycerol)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Production of PHB from Crude Glycerol

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2007
G. Mothes
Abstract Crude glycerol , a by-product of the large scale production of diesel oil from rape , is examined for its possible use as a cheap feedstock for the biotechnological synthesis of poly(3-hydroxybutyrate) (PHB). The glycerol samples of various manufacturers differ in their contamination with salts (NaCl or K2SO4), methanol or fatty acids. At high cell density fermentation these pollutants could possibly accumulate to inhibiting concentrations. The bacteria used were Paracoccus denitrificans and Cupriavidus necator JMP 134, which accumulate PHB from pure glycerol to a content of 70 % of cell dry mass. When using crude glycerol containing 5.5 % NaCl, a reduced PHB content of 48 % was observed at a bacterial dry mass of 50 g/L. Furthermore the PHB yield coefficient was reduced, obviously due to osmoregulation. The effect of glycerol contaminated with K2SO4 was less pronounced. The molecular weight of PHB produced with P. denitrificans or C. necator from crude glycerol varies between 620000 and 750000 g/mol which allows the processing by common techniques of the polymer industry. [source]

Tribochemistry of tetrahedral hydrogen-free amorphous carbon coatings in the presence of OH-containing lubricants

LUBRICATION SCIENCE, Issue 2 2008
C. Matta
Abstract Diamond-like carbon (DLC) films are gaining attention for its use in a wide range of tribological applications because of their low friction coefficient and high wear resistance. Recently, ultra-low friction or superlubricity as low as 0.006 has been observed between hydrogen-free DLC films lubricated with oil containing a glycerol mono-oleate (GMO) additive. Consequently, there are many efforts to understand their detailed tribological behaviour. In this study, first, a characterisation of a pristine hydrogen-free tetrahedral amorphous DLC coating (denoted as ta-C) is presented. The technique used for ta-C characterisation is the energy-filtered transmission electron microscopy studied on a focus ion beam cross section of the coating. Then, to simulate the action of GMO, which is used as an additive in engine oils, and to understand its mechanism of action in boundary lubrication conditions, simple and shorter molecules such as pure glycerol and hydrogen peroxide are used in friction tests. These two molecules and GMO have the same alcohol chemical function. Friction tests in the presence of pure glycerol and hydrogen peroxide are presented. Moreover, to understand the properties of these two molecules, the overtone of GMO and their reaction mechanism in boundary lubrication, liquid phase lubrication was simulated by gas phase lubrication. Results show that very low friction coefficients are obtained with no apparent wear. Finally, the mechanisms of ultra-low friction are investigated by the wetting method and the X-ray photoelectron spectroscopy (XPS) technique. These two techniques are used to identify the physical (wetting method) and chemical (XPS) changes occurring at the ta-C surface after friction. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Enhanced hydrogen and 1,3-propanediol production from glycerol by fermentation using mixed cultures

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009
Priscilla A. Selembo
Abstract The conversion of glycerol into high value products, such as hydrogen gas and 1,3-propanediol (PD), was examined using anaerobic fermentation with heat-treated mixed cultures. Glycerol fermentation produced 0.28,mol-H2/mol-glycerol (72,mL-H2/g-COD) and 0.69,mol-PD/mol-glycerol. Glucose fermentation using the same mixed cultures produced more hydrogen gas (1.06,mol-H2/mol-glucose) but no PD. Changing the source of inoculum affected gas production likely due to prior acclimation of bacteria to this type of substrate. Fermentation of the glycerol produced from biodiesel fuel production (70% glycerol content) produced 0.31,mol-H2/mol-glycerol (43,mL H2/g-COD) and 0.59,mol-PD/mol-glycerol. These are the highest yields yet reported for both hydrogen and 1,3-propanediol production from pure glycerol and the glycerol byproduct from biodiesel fuel production by fermentation using mixed cultures. These results demonstrate that production of biodiesel can be combined with production of hydrogen and 1,3-propanediol for maximum utilization of resources and minimization of waste. Biotechnol. Bioeng. 2009; 104: 1098,1106. © 2009 Wiley Periodicals, Inc. [source]

Metabolism in 1,3-propanediol fed-batch fermentation by a D -lactate deficient mutant of Klebsiella pneumoniae

BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009
Yun-Zhen Xu
Abstract Klebsiella pneumoniae HR526, a new isolated 1,3-propanediol (1,3-PD) producer, exhibited great productivity. However, the accumulation of lactate in the late-exponential phase remained an obstacle of 1,3-PD industrial scale production. Hereby, mutants lacking D -lactate pathway were constructed by knocking out the ldhA gene encoding fermentative D -lactate dehydrogenase (LDH) of HR526. The mutant K. pneumoniae LDH526 with the lowest LDH activity was studied in aerobic fed-batch fermentation. In experiments using pure glycerol as feedstock, the 1,3-PD concentrations, conversion, and productivity increased from 95.39,g,L,1, 0.48 and 1.98,g,L,1,h,1 to 102. 06,g,L,1, 0.52,mol,mol,1 and 2.13,g,L,1,h,1, respectively. The diol (1,3-PD and 2,3-butanediol) conversion increased from 0.55,mol,mol,1 to a maximum of 0.65,mol,mol,1. Lactate would not accumulate until 1,3-PD exceeded 84,g,L,1, and the final lactate concentration decreased dramatically from more than 40,g,L,1 to <3,g,L,1. Enzymic measurements showed LDH activity decreased by 89,98% during fed-batch fermentation, and other related enzyme activities were not affected. NADH/NAD+ enhanced more than 50% in the late-exponential phase as the D -lactate pathway was cut off, which might be the main reason for the change of final metabolites concentrations. The ability to utilize crude glycerol from biodiesel process and great genetic stability demonstrated that K. pnemoniae LDH526 was valuable for 1,3-PD industrial production. Biotechnol. Bioeng. 2009; 104: 965,972. © 2009 Wiley Periodicals, Inc. [source]