Showing papers on "Arabitol published in 2007"

Ambient aerosol concentrations of sugars and sugar-alcohols at four different sites in Norway

Abstract: . Sugars and sugar-alcohols are demonstrated to be important constituents of the ambient aerosol water-soluble organic carbon fraction, and to be tracers for primary biological aerosol particles (PBAP). In the present study, levels of four sugars (fructose, glucose, sucrose, trehalose) and three sugar-alcohols (arabitol, inositol, mannitol) in ambient aerosols have been quantified using a novel HPLC/HRMS-TOF (High Performance Liquid Chromatography in combination with High Resolution Mass Spectrometry – Time of Flight) method to assess the contribution of PBAP to PM>sub>10 and PM2.5. Samples were collected at four sites in Norway at different times of the year in order to reflect the various contributing sources and the spatial and seasonal variation of the selected compounds. Sugars and sugar-alcohols were present at all sites investigated, underlining the ubiquity of these highly polar organic compounds. The highest concentrations were reported for sucrose, reaching a maximum concentration of 320 ng m−3 in PM10 and 55 ng m−3 in PM2.5. The mean concentration of sucrose was up to 10 times higher than fructose, glucose and the dimeric sugar trehalose. The mean concentrations of the sugar-alcohols were typically lower, or equal, to that of the monomeric sugars and trehalose. Peak concentrations of arabitol and mannitol did not exceed 30 ng m−3 in PM10, and for PM2.5 all concentrations were below 6 ng m−3. Sugars and sugar-alcohols were associated primarily with coarse aerosols except during wintertime at the suburban site in Elverum, where a shift towards sub micron aerosols was observed. It is proposed that this shift was due to the intensive use of wood burning for residential heating at this site during winter, confirmed by high concurrent concentrations of levoglucosan. Elevated concentrations of sugars in PM2.5 were observed during spring and early summer at the rural background site Birkenes. It is hypothesized that this was due to ruptured pollen.

l-Arabinose metabolism in Candida arabinofermentans PYCC 5603T and Pichia guilliermondii PYCC 3012: influence of sugar and oxygen on product formation

Abstract: l-Arabinose utilization by the yeasts Candida arabinofermentans PYCC 5603T and Pichia guilliermondii PYCC 3012 was investigated in aerobic batch cultures and compared, under similar conditions, to d-glucose and d-xylose metabolism. At high aeration levels, only biomass was formed from all the three sugars. When oxygen became limited, ethanol was produced from d-glucose, demonstrating a fermentative pathway in these yeasts. However, pentoses were essentially respired and, under oxygen limitation, the respective polyols accumulated—arabitol from l-arabinose and xylitol from d-xylose. Different l-arabinose concentrations and oxygen conditions were tested to better understand l-arabinose metabolism. P. guilliermondii PYCC 3012 excreted considerably more arabitol from l-arabinose (and also xylitol from d-xylose) than C. arabinofermentans PYCC 5603T. In contrast to the latter, P. guilliermondii PYCC 3012 did not produce any traces of ethanol in complex l-arabinose (80 g/l) medium under oxygen-limited conditions. Neither sustained growth nor active metabolism was observed under anaerobiosis. This study demonstrates, for the first time, the oxygen dependence of metabolite and product formation in l-arabinose-assimilating yeasts.

Physiological characterization of xylose metabolism in Aspergillus niger under oxygen‐limited conditions

Abstract: The physiology of Aspergillus niger was studied under different aeration conditions Five different aeration rates were investigated in batch cultivations of A niger grown on xylose Biomass, intra- and extra-cellular metabolites profiles were determined and ten different enzyme activities in the central carbon metabolism were assessed The focus was on organic acid production with a special interest in succinate production The fermentations revealed that oxygen limitation significantly changes the physiology of the micro-organism Changes in extra cellular metabolite profiles were observed, that is, there was a drastic increase in polyol production (erythritol, xylitol, glycerol, arabitol, and mannitol) and to a lesser extent in the production of reduced acids (malate and succinate) The intracellular metabolite profiles indicated changes in fluxes, since several primary metabolites, like the intermediates of the TCA cycle accumulated during oxygen limitation (on average three fold increase) Also the enzyme activities showed changes between the exponential growth phase and the oxygen limitation phase In general, the oxygen availability has a significant impact on the physiology of this fungus causing dramatic alterations in the central carbon metabolism that should be taken into account in the design of A niger as a succinate cell factory

Production of mannitol by Penicillium strains

Abstract: Eleven different strains of Penicillium were screened for production of mannitol. All strains produced both mannitol and glycerol. Some of the strains also produced arabitol and/or erythritol in lower amounts. The highest amount of mannitol (43 g dm−3) was produced by Pencillium scabrosum IBT JTER 4, and the highest combined yield of mannitol and glycerol (65 g dm−3) was obtained with Pencillium aethiopicumIBT MILA 4 when grown on 150 g dm−3 sucrose and 20 g dm−3 yeast extract. These yields are comparable to yields obtained with Aspergillus strains after a considerable optimization effort. It is thus likely that biotechnological production of mannitol may benefit from the development of suitable Penicillium strains.

Influence of inhibitory compounds and minor sugars on xylitol production by Debaryomyces hansenii.

Abstract: To obtain in-depth information on the overall metabolic behavior of the new good xylitol producer Debaryomyces hansenii UFV-170, batch bioconversions were carried out using semisynthetic media with compositions simulating those of typical acidic hemicellulose hydrolysates of sugarcane bagasse. For this purpose, we used media containing glucose (4.3–6.5 g/L), xylose (60.1–92.1 g/L), or arabinose (5.9–9.2 g/L), or binary or ternary mixtures of them in either the presence or absence of typical inhibitors of acidic hydrolysates, such as furfural (1.0–5.0 g/L), hydroxymethylfurfural (0.01–0.30 g/L), acetic acid (0.5–3.0 g/L), and vanillin (0.5–3.0 g/L). D. hansenii exhibited a good tolerance to high sugar concentrations as well as to the presence of inhibiting compounds in the fermentation media. It was able to produce xylitol only from xylose, arabitol from arabinose, and no glucitol from glucose. Arabinose metabolization was incomplete, while ethanol was mainly produced from glucose and, to a lesser less extent, from xylose and arabinose. The results suggest potential application of this strain in xyloseto-xylitol bioconversion from complex xylose media from lignocellulosic materials.

Xylitol conversion by fermentation using five yeast strains and polyelectrolyte-assisted ultrafiltration

Abstract: Batch fermentations for xylitol production were conducted using Candida boidinii (BCRC 21432), C. guilliermondii (BCRC 21549), C. tropicalis (BCRC 20520), C. utilis (BCRC 20334), and P. anomala (BCRC 21359) together with a mixture of sugars simulating lignocellulosic hydrolysates as the carbon source. C. tropicalis had the highest bioconversion yield (YP/S) of 0.79 g g−1 (g xylitol·g xylose−1) over 48 h. Additional fermentations with C. tropicalis achieved YP/S values of 0.6 and 0.39 g g−1 after 96 and 72 h using urea and soybean meal as the nitrogen sources, respectively. Ethanol and arabitol were also produced in all fermentation. Xylitol in the fermentation broth was recovered by cross-flow ultrafiltration. With prior application of 2 mg polydiallyl dimethylammonium chloride l−1 on the membrane surface, protein in the permeate was reduced from 7.1 to 1.5 mg l−1 after 2 h.

Biomass production by a thermotolerant yeast: Hansenula polymorpha.

Abstract: Biomass production at high temperature by Hansenula polymorpha as part of a lignocellulosic utilizing process was studied. Compromise growth conditions (45 degrees C and pH = 4.8) with an eventual saccharification step were established. The effects of stirring rate and initial glucose concentration on biomass yield coefficient, volumetric productivity and maximal cell density were determined. Process optimization led to a fed-batch fermentation process: high yield (0.63 g dry cell g-1 glucose), volumetric productivity (1.3 g dry cell dm-3 h-1) and cell concentration (60 g dry cell dm-3) were obtained. At these conditions, significant arabitol excretion (18 g dm-3) as a unique by-product associated with cell mass production was obtained, making more interesting a high temperature operating process.

Xylitol dehydrogenase-inactivated and arabinose reductase-inhibited mutant of Candida tropicalis, method of producing high-yield of xylitol using the same, and xylitol produced thereby

Abstract: Disclosed herein are Xylitol dehydrogenase-inactivated and arabinose reductase-inhibited mutant of Candida tropicalis, a method of producing a high yield of xylitol using the same, and xylitol produced by the method. More specifically, disclosed are a method for producing a high yield of xylitol, in which a high concentration of xylose contained in a biomass hydrolyzate is converted to xylitol using xylitol dehydrogenase-inactivated mutant of Candida tropicalis, without controlling dissolved oxygen to a low level, as well as xylitol produced according to the method. Also disclosed are a xylitol production method, in which the production of byproduct arabitol, which is produced when using a biomass as a substrate and adversely affects the yield of xylitol, is significantly reduced through the use of Candida tropicalis mutant ara-89 (KCTC 11136bp) having an inhibited activity of arabinose reductase converting arabinose to arabitol, thus increasing xylitol productivity, as well as xylitol produced by the method.