Arabitol Research Articles

Screening of environmental yeasts for the fermentative production of arabitol from lactose and glycerol

Screening of environmental yeasts for the fermentative production of arabitol from lactose and glycerol

FIRST REPORT OF PECTOBACTERIUM CAROTOVORUM subsp. CAROTOVORUM CAUSING STEM ROT ON GREENHOUSE TOMATOES IN SYRIA

During winter 2010 and 2011, stem rot symptoms were seen on greenhouse-grown tomato (Lycopersicom esculentum) plants in Tartous governorate (Syria). Affected plants showed darkening and water soaking of the stem and vascular browning, followed by wilting and death. These symptoms were similar to those re- ported from Tunisia by Hibar et al. (2007). Bacteria isolated on King’s medium B (KB) from rotting stems, formed round, slightly convex, white- to cream-coloured colonies. Twelve isolates were Gram-negative, not fluorescent on KB, facultative anaerobic in Hugh and Leifson medium, negative for levan production, oxi- dase, arginine dihydrolase, acid from malonate and utilization of keto-methyl glucoside and catalase-positive and induced hyper- sensitive reaction on tobacco and soft rot of potato slices. Acid was produced from trehalose, sucrose, arabinose, rafinose, but not form arabitol, sorbitol and maltose. These tests indicated the presence of P. carotovorum subsp. carotovorum (Pcc), whose iden- tity was confirmed by PCR, using the Pcc-specific primer pair Y1: 5’-TTACCGGACGCCGAGCTGTGGCGT-3’ and Y2: 5’- CAGGAAGATGTCGTT ATCGCGAGT-3’ (Helias et al., 1998). Pathogenicity tests consisted in needle puncture inoculation of tomato seedling stems with bacteria suspension in distilled water (108 CFU/ml) whereas controls were injected with sterile distilled water. All plants were covered with polyethylene bags for 24 h and placed in a climatic chamber at 25°C, 80% RH and a 12 h phothoperiod. After three to seven days, all inoculated plants, but not controls, showed darkening and water-soaking of the stem and vascular browning. Some plants died within three days. To our knowledge this is the first record of the occurrence of soft rot, caused by Pcc on greenhouse tomatoes in Syria.

The level of arabinitol in autistic children after probiotic therapy

ObjectiveThe level of D-arabinitol (DA) and the ratio of D-/L-arabinitol (DA/LA) in the urine of children with autism were investigated. The changes in DA/LA after probiotic treatment in urine samples of children with autism were studied. MethodsDA and LA and the DA/LA ratio were identified by capillary gas chromatography/mass spectrometry in urine before and after the probiotic therapy. ResultsThe level of DA is significantly higher (P < 0.05) in the urine of autistic children before (A) and after probiotic supplementation (A1) (160.04 ± 22.88 μmol/mmol creatinine and 89.53 ± 37.41 μmol/mmol creatinine, respectively). Nonetheless, the probiotic supplementation let to a significant decrease in DA and DA/LA and to a significant improvement in ability of concentration and carrying out orders. ConclusionThe use of probiotics seems to be helpful in reducing the level of DA and the ratio of DA/LA in the urine of children with autism.

Fungal arabinan and l-arabinose metabolism

l-Arabinose is the second most abundant pentose beside d-xylose and is found in the plant polysaccharides, hemicellulose and pectin. The need to find renewable carbon and energy sources has accelerated research to investigate the potential of l-arabinose for the development and production of biofuels and other bioproducts. Fungi produce a number of extracellular arabinanases, including α-l-arabinofuranosidases and endo-arabinanases, to specifically release l-arabinose from the plant polymers. Following uptake of l-arabinose, its intracellular catabolism follows a four-step alternating reduction and oxidation path, which is concluded by a phosphorylation, resulting in d-xylulose 5-phosphate, an intermediate of the pentose phosphate pathway. The genes and encoding enzymes l-arabinose reductase, l-arabinitol dehydrogenase, l-xylulose reductase, xylitol dehydrogenase, and xylulokinase of this pathway were mainly characterized in the two biotechnological important fungi Aspergillus niger and Trichoderma reesei. Analysis of the components of the l-arabinose pathway revealed a number of specific adaptations in the enzymatic and regulatory machinery towards the utilization of l-arabinose. Further genetic and biochemical analysis provided evidence that l-arabinose and the interconnected d-xylose pathway are also involved in the oxidoreductive degradation of the hexose d-galactose.

Hydroxylated Linear Polyurethanes Derived from Sugar Alditols

AbstractA set of linear [m,n]‐type polyurethanes was synthesized by reaction of HDI or MDI with conveniently protected sugar alditols L‐threitol (LTh), L‐arabinitol (LAr) and xylitol (Xy). $\overline M _{\rm n}$ of the resulting polyurethanes ranged between 10 000 and 60 000 with polydispersities around 2. They were thermally stable, showing no decomposition up to temperatures near 300 °C. They all were amorphous polymers with Tg highly dependent on the constitution of the diisocyanate, but scarcely dependent on the structure of the alditol. Hydrogenation of the LThBn‐HDI polyurethane yielded partially debenzylated products with Tg values ranging between 20 and 30 °C. Fully benzylated polyurethanes showed high resistance to hydrolytic degradation, whereas polyurethane with free hydroxyl side groups degraded significantly in saline buffer at pH = 10 and 37 °C.magnified image

Robust glycogen shunt activity in astrocytes: Effects of glutamatergic and adrenergic agents

The significance and functional roles of glycogen shunt activity in the brain are largely unknown. It represents the fraction of metabolized glucose that passes through glycogen molecules prior to entering the glycolytic pathway. The present study was aimed at elucidating this pathway in cultured astrocytes from mouse exposed to agents such as a high [K +], d-aspartate and norepinephrine (NE) known to affect energy metabolism in response to neurotransmission. Glycogen shunt activity was assessed employing [1,6- 13C]glucose, and the glycogen phosphorylase inhibitor 1,4-dideoxy-1,4-imino- d-arabinitol (DAB) to block glycogen degradation. The label intensity in lactate, reflecting glycolytic activity, was determined by mass spectrometry. In the presence of NE a substantial glycogen shunt activity was observed, accounting for almost 40% of overall glucose metabolism. Moreover, when no metabolic stimulant was applied, a compensatory increase in glycolytic activity was seen when the shunt was inhibited by DAB. Actually the labeling in lactate exceeded that obtained when glycolysis and glycogen shunt both were operational, i.e. supercompensation. A similar phenomenon was seen when astrocytes were exposed to d-aspartate. In addition to glycolysis, tricarboxylic acid (TCA) cycle activity was monitored, analyzing labeling by mass spectrometry in glutamate which equilibrates with α-ketoglutarate. Both an elevated [K +] and d-aspartate induced an increased TCA cycle activity, which was altered when glycogen degradation was inhibited. Thus, the present study provides evidence that manipulation of glycogen metabolism affects both glycolysis and TCA cycle metabolism. Altogether, the results reveal a highly complex interaction between glycogenolysis and glycolysis, with the glycogen shunt playing a significant role in astrocytic energy metabolism.

D-arabinitol--a marker for invasive candidiasis.

The five-carbon sugar alcohol D-arabinitol (DA) is a metabolite of most pathogenic Candida species, in vitro as well as in vivo, and can be determined by gas chromatography or enzymatic analysis. Endogenous DA and L-arabinitol (LA) are present in human body fluids, and serum DA and LA increase in renal dysfunction. In prospective clinical studies, elevated DA/LA or DA/creatine ratios in serum or urine have been found in immunocompromised, usually neutropenic, patients with invasive candidiasis. In addition, positive DA results have been obtained several days to weeks before positive blood cultures, and the normalization of DA levels has been correlated with therapeutic response in both humans and animals. However, to date, only a few prospective studies have been conducted in which adequate analytical methods were used. Thus, further investigation of various patient groups is needed to establish the applicability of the 'arabinitol method' in the diagnostic battery for invasive Candida infections.

Diagnosis and therapeutic monitoring of invasive candidiasis by rapid enzymatic detection of serum d-arabinitol

Using a rapid automated enzymatic assay, we prospectively investigated serum D-arabinitol (DA), a biochemical marker of invasive candidiasis, in a large population of high-risk patients to determine its potential diagnostic, therapeutic, and prognostic significance in invasive candidiasis. A total of 3,223 serum samples were collected from 274 patients with cancer. Serum DA concentrations were determined in coded serum samples analyzed by rapid enzymatic assay. Creatinine also was analyzed in the same system to determine a serum DA and creatinine ratio (DA/Cr). The sensitivity, specificity, correlation with therapeutic response, and prognostic significance were analyzed for all patient study groups. A DA/Cr of > or = 4.0 mumol/L per mg/dL was detected in 31 (74%) of all 42 cases of fungemia and 25 (83%) of the 30 cases of the subset of persistent fungemia. Elevated DA/Cr was detected in 4 (40%) of 10 patients with tissue-proven, deeply invasive candidiasis and negative blood cultures (eg, hepatosplenic candidiasis or localized abscess) and 7 (44%) of 16 cases of deep mucosal candidiasis (eg, esophageal candidiasis). Elevated serial DA/Cr levels also were detected in persistently febrile and granulocytopenic patients requiring empirical amphotericin B. Among 26 assessable cases of fungemia, abnormally elevated DA/Cr values were detected in 14 (54%) before, 10 (38%) after, and 2 (8%) simultaneously with the first microbiologic report of fungemia. The trends of serial DA/Cr values correlated with therapeutic response in 29 (85%) of 34 patients with assessable cases of fungemia, decreasing in 8 (89%) of 9 patients with clearance of fungemia and increasing in 21 (84%) of 25 patients with persistence of fungemia. Among the 34 assessable patients with fungemia, mortality was directly related to the trend of serial DA/Cr determinations over time: 71% among fungemic patients who had persistently elevated or increasing DA/Cr, and 18% among the fungemic patients who had resolving DA/Cr or never had elevated DA/Cr (P < 0.01). Rapid enzymatic detection of DA in serially collected serum samples from high-risk cancer patients permitted detection of invasive candidiasis, early recognition of fungemia, and therapeutic monitoring in DA-positive cases. Serially collected serum DA determinations complement blood cultures for improving detection and monitoring therapeutic response in patients at risk for invasive candidiasis.

Serum D-arabinitol measured by automated quantitative enzymatic assay for detection and therapeutic monitoring of experimental disseminated candidiasis: correlation with tissue concentrations of Candida albicans.

In order to further understand serum D-arabinitol (DA) as a marker for the diagnosis of disseminated candidiasis and for monitoring response to antifungal therapy, we studied the serum levels of this Candida carbohydrate metabolite by rapid automated enzymatic assay in rabbits with experimental disseminated candidiasis. The enzymatic reaction steps were performed on a standard automated clinical chemistry analyser. As a correction for renal impairment, data were expressed as serum D-arabinitol/creatinine ratio (DA/Cr). Serum creatinine concentrations were determined from the same sample with the same instrument, thereby allowing rapid determination of the DA/Cr within one laboratory. The DA/Cr was determined in 321 samples from 132 rabbits. The mean serum DA/Cr in 31 normal non-infected rabbits was 1.51 +/- 0.2 microM mg-1 dl-1. Among 84 rabbits with disseminated candidiasis and pre-terminal samples, there was a direct correlation between DA/Cr and tissue concentration of Candida albicans (r = 0.80; P < 0.001). A threshold of elevated DA/Cr (> or = 3.0 microM mg-1 dl-1) was evident in rabbits with a tissue concentration of C. albicans > or = 3 x 10(4) colony forming units (CFU) g-1. Elevated DA/Cr was detected in 48 (89%) of 54 rabbits at a C. albicans tissue concentration of > or = 3 x 10(4) CFU g-1 vs. one (3%) of 30 rabbits with < 3 x 10(4) CFU g-1 (P < 0.0001). Among all 101 rabbits with disseminated candidiasis, an elevated DA/Cr was detected at any point during infection in 60 (92%) of 65 rabbits having a C. albicans tissue concentration > or = 3 x 10(4) CFU g-1 vs. 13 (36%) of 36 rabbits with < 3 x 10(4) CFU g-1 (P < 0.0001). The relationship between the tissue response to antifungal therapy and change in DA/Cr was then further analysed. Ten (91%) of 11 rabbits with a tissue-proven response to antifungal therapy (defined as > or = 10(2)-fold reduction of CFU g-1 in comparison to untreated controls) had a > 50% reduction in elevated DA/Cr levels. By comparison, 10 (83%) of 12 treated rabbits with no response to therapy had persistently elevated DA/Cr levels (P < 0.001). These findings provide an experimental basis for understanding the patterns of expression of serum DA in disseminated candidiasis and further indicate that serial DA/Cr measurements may be useful for diagnosis and therapeutic monitoring of disseminated candidiasis.

Identification, Purification, and Characterization of a D-Arabinitol-Specific Dehydrogenase from Candida tropicalis

A novel D-arabinitol (DA) dehydrogenase was identified and purified more than 300-fold from Candida tropicalis. The enzyme is specific for DA and catalyzes the NAD +-dependent oxidation at carbon 4 to yield D-ribulose. Purification was accomplished by a combination of protamine sulfate and ammonium sulfate precipitation and dye ligand chromatography on a reactive yellow 86 column. The apparent K m of the enzyme for DA ( [NAD +] = 2.2 mM) is 39.8 mM. The apparent K m for NAD + ( [DA] = 384 mM) is 0.12 mM. The pH-optimum for the enzymatic oxidation of DA is approximately 10. Cofactor stereospecificity studies demonstrate that the enzyme catalyzes transfer of the 4(S) hydrogen of NADH with D-ribulose as substrate. The polyol substrate specificity of the present DA dehydrogenase makes the enzyme potentially useful for the development of a simple and specific method for the measurement of DA, a metabolite of pathogenic Candida spp. which has been described as a marker for disseminated candidiasis.