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Enzymes of polyol metabolism were studied in basidiospore germination of Schizophyllum commune during periods of in vivo arabitol and mannitol pool depletion (growth on glucose-asparagine) and during their subsequent synthesis (growth on acetate-NH4+). Optimal conditions for assays were established and specific activities of enzymes employing d-arabitol, d-mannitol, d-ribulose, d-fructose and d-xylulose as substrates were traced. Inquiries into the products formed during these reactions showed that d-ribulose generated arabitol while d-fructose produced mannitol with d-xylulose giving rise to xylitol. The dehydrogenase reactions were further investigated using polyacrylamide disc gel electrophoresis. Here was revealed the existence of at least two separate enzymatic activities pertaining to the catabolism of arabitol and mannitol. Also noted were the electrophoretic patterns when d-sorbitol, ribitol, xylitol and ethanol were used as substrates.

International audience; The influence of different polyols (ethylene glycol, glycerol, erythritol, xylitol, and sorbitol) on the thermostability of fungal alpha-amylase at 60°C has been studied. The results obtained show a stabilizing effect in the presence of polyols. In the case of 4 m sorbitol solution, the enzyme half-life is 2000-fold longer than in pure water. These polyols have been found as competitive inhibitors for alpha-amylase andtheir stabilizing effect has been correlated to their affinity constant except for sorbitol. The influence of two polyol isomers (arabitol and mannitol) on activity and stability of alpha-amylase has also been investigated.

The hydrolyses of p-nitrophenyl α- and β-galactosides and p-nitrophenyl α- and β-glucosides by an α-galactosidase from Aspergillus fumigatis, an α-glucosidase from germinated barley, and almond β-glucosidase, which also has β-galactosidase activity, have been examined in the presence of glycerol, erythritol, d -threitol, ribitol, xylitol, d -arabitol and dl -butan-1,2,4-triol. The α-galactosidase was best inhibited by d -threitol, while the α-glucosidase was best inhibited by erythritol. Both inhibitions were competitive. The inhibitory character of these compounds may be attributed to their similarity in structure with the glycon of the substrate between C-3, C-4, C-5, and C-6. The β-glucosidase was best inhibited by erythritol, demonstrating a similarity of action between α- and β-glucosidases. However, the best inhibitor of β-galactosidase was erythritol. This observation confirmed the view that in almond emulsin, the glucosidase and galactosidase activities are found in the same enzyme.

A study was made of the effects of oxygen tension and inorganic phosphate concentration on the production of glycerol, arabitol, and ethanol by a strain of osmophilic yeast. Increasing the oxygen tension increased the yields of glycerol and arabitol and decreased the yield of ethanol, while increasing the concentration of inorganic phosphate had the opposite effect.The changes in yields of products with increasing phosphate concentration were most pronounced at a partial pressure of oxygen of 280 mm. of mercury. At lower oxygen tensions the yields of polyols were low and the yield of ethanol was high at all concentrations of phosphate, while at very high oxygen tensions the opposite effect was observed. When the ethanol yield was high, the respiratory quotient was also high. These results are discussed in relation to the oxidative phosphate-lack theory of the Pasteur effect.

Electron microscopic features and biochemical events were outlined in basidiospore germination of Schizophyllum commune . Normal ultrastructural changes included prominent vacuolization and more abundant endoplasmic reticulum. A lag phase in outgrowth included depletion of cellular reserves of trehalose, mannitol, and arabitol and subsequent increases in ribonucleic acid and protein. Depletion of polyols required exogenous carbon and nitrogen sources and was arrested by protein synthesis antagonists. Outgrowth subsequent to the lag period was accompanied by increased glycogen deposition and alkali-soluble glucan production.

The inhibition of crystalline d -xylose isomerase from Lactobacillus brevis by pentitols and carbohydrate derivatives has been examined. Of the pentitols, xylitol and l - and d -arabitol inhibited competitively, whereas ribitol was ineffective. The inhibition constants ( K i ) are: 0.0027, 0.13, or 0.146 m for xylitol, d -arabitol, and l -arabitol, respectively. d -Lyxose also inhibited competitively with a K i of 0.07 m . The kinetic data indicate that the substrate, d -xylose, and these inhibitors combine at the active site(s) through a manganous ion bridge.

Botrytis cinerea, Colletotrichum gloeosporioides, Aspergillus niger andPenicillium griseofulvum were grown in flasks as stationary cultures in the ordinary Czapek-Dox medium at 24° C in the dark for long periods of time. At convenient intervals during autolysis samples of mycelium were harvested and its polyol content determined. The loss of mycelial mannitol during autolysis reached to a little more than 60 %, more than 70 %, to nearly 80 % and 90 % forC. gloeosporioides, P. griseofulvum, A. niger andB. cinerea, respectively. Seventy per cent of the arabitol contained inP. griseofulvum and 85 % of the arabitol inC. gloeosporioides disappeared during autolysis. Mannitol remained present in appreciable amounts in these four fungi throughout the whole period of autolysis described, whereas arabitol disappeared fromB. cinerea and fromA. niger during the process.

Uptake and respiration of radioactive glucose, mannitol and arabitol were studied during basidiospore germination of the woodrotting mushroomSchizophyllum commune. Glucose uptake was rapid and immediate, depressed at 4° C and unaffected by the protein synthesis antagonist cycloheximide. In contrast, uptake of either mannitol or arabitol exhibited a lag phase while the induction of this process was sensitive to cycloheximide. Prior incubation of basidiospores in unlabelled mannitol induced uptake processes for either labelled mannitol or arabitol. Respiratory rates for either arabitol or mannitol increased markedly upon germination in glucose-asparagine minimal culture medium.

The photosynthetic assimilation of 14 CO 2 has been studied in healthy and mildew-infected barley. The parasite was separated from the host by removing the mycelium with a camel9s hair brush. The ethanol soluble metabolites of the parasite, infected host and healthy host were extracted, separated by paper chromatography and individually identified. From this work it appears that there is a rapid movement of label from host to parasite mainly in the form of sucrose which is then quickly metabolized into many compounds. The majority is converted into mannitol, and lesser amounts are converted into trehalose, arabitol, aspartic acid, and glutamic acid. In conidia the major carbon reserve is arabitol instead of mannitol, with lesser amounts of trehalose and mannitol. Photosynthetic uptake of 14 CO 2 by the complex decreases steadily after inoculation as compared with healthy leaves. However, the ethanol soluble metabolites of the infected host tissue differ only slightly from those of healthy host tissue. The major differences are a slight decrease in the amount of sucrose and increases in malic acid and serine.

Three enzymes of the l -arabinose catabolic pathway in Aerobacter aerogenes , l -arabinose isomerase, l -ribulokinase, and l -ribulose-5-phosphate 4-epimerase, are specifically induced in the presence of l -arabinose. Mutants constitutive for kinase activity are also constitutive for the isomerase and 4-epimerase activities, suggesting that these three enzymes are coordinately controlled in A. aerogenes . l -Ribulokinase activity can still be induced in the presence of l -arabinose in an isomerase-deficient strain of A. aerogenes . Since l -arabinose is not converted to l -ribulose in such a strain, it appears that l -arabinose must be the inducer of l -ribulokinase, as well as the coordinately controlled isomerase and 4-epimerase. As in the metabolism of l -arabinose, growth of A. aerogenes on l -arabitol also requires a 4-epimerase for the conversion of l -ribulose-5-phosphate to d -xylulose-5-phosphate. However, loss of ability to metabolize l -arabinose, due to a deficiency in 4-epimerase synthesis in the presence of l -arabinose, does not affect growth on l -arabitol. In addition, synthesis of the 4-epimerase associated with l -arabitol metabolism is not accompanied by l -arabinose isomerase or l -ribulokinase synthesis. These results suggest either the existence of two different l -ribulose-5-phosphate 4-epimerases in A. aerogenes , or of two different regulatory mechanisms for the control of the same epimerase.

SUMMARY: A recent report that the major soluble carbohydrates of Aspergillus clavatus include ribitol and sorbose is wrong. The pentitol is arabitol and no sorbose could be detected, demonstrating that A. clavatus is not unlike many other moulds. Previous work on the metabolism of acyclic polyols in A. clavatus is re-evaluated.

Dikaryotic cells of S. commune synthesized polyols throughout the life cycle when grown on glucose, cellobiose, or cellulose. Basidiospores contained arabitol and mannitol which were depleted during germination. The mannitol content of the young germlings rose to normal levels within a day; arabitol accumulation remained depressed for 5 to 7 days and then returned to normal levels characteristic of vegetative cells. Individual homokaryons differed in their production of intracellular polyols, which, unlike germlings, remained constant with cultural age. Homokaryon (str. 699) produced low levels of arabitol but high levels of glycerol while another homokaryon (str. 845) was the reverse. Mixtures of these homokaryons as well as the dikaryon (699×845) produced arabitol and glycerol levels intermediate between the parent homokaryons. High concentrations of glucose did not change the nature of the polyols produced. Arabitol formation could be induced prematurely in germlings or elevated in the dikaryon by growth on acetate or ethanol. Both homokaryons responded to growth on acetate with elevated arabitol production; acetate induction of arabitol formation was repressed in all types of cells if glucose were added simultaneously with acetate. Maltose, cellobiose, and trehalose also stimulated arabitol formation in young germlings, suggesting that glucose repression was the cause of decreased arabitol formation in basidiospore germlings. There was no correlation between the formation of arabitol and the derepression of isocitrate lyase or change in specific activities of alkaline and acid phosphatase in germlings grown on various carbon sources.

A readily fermentable pentose-containing hydrolysate was obtained from Brewery's spent grain by a two-step process consisting of an auto-hydrolysis (converting the hemicelluloses into oligosaccharides) followed by an enzymatic or sulfuric acid-catalyzed posthydrolysis (converting the oligosaccharides into monosaccharides). Enzymatic hydrolyses were performed with several commercial enzymes with xylanolytic and cellulolytic activities. Acid-catalyzed hydrolyses were carried out at 121°C under various sulfuric acid concentrations and reaction times, and the effects of treatments were interpreted by means of a corrected combined severity factor (CS 1), which varied in the range of 0.80–2.01. Under the tested conditions, chemicalhydrolysis allowed higher pentose yields than enzymatic hydrolysis. Optimized conditions (defined by CS 1=1.10) allowed both complete monosaccharide recovery and low content of inhibitors. Liquors subjected to posthydrolysis under optimal conditions were easily fermented by Debaryomyces hansenii CCMI 941 in semiaerobic shake-flask experiments, leading to xylitol and arabitol as major fermentation products. The bioconversion process was improved by hydrolysate concentration and supplementation of fermentation media with casamino acids.

Bacillus methanolicus is a Gram-positive, thermophilic, methanol-utilizing bacterium. As a facultative methylotroph, B. methanolicus is also known to utilize D-mannitol, D-glucose and, as recently discovered, sugar alcohol D-arabitol. While metabolic pathways for utilization of methanol, mannitol and glucose are known, catabolism of arabitol has not yet been characterized in B. methanolicus. In this work we present the elucidation of this hitherto uncharted pathway. In order to confirm our predictions regarding genes coding for arabitol utilization, we performed differential gene expression analysis of B. methanolicus MGA3 cells grown on arabitol as compared to mannitol via transcriptome sequencing (RNA-seq). We identified a gene cluster comprising eight genes that was up-regulated during growth with arabitol as a sole carbon source. The RNA-seq results were subsequently confirmed via qRT-PCR experiments. The transcriptional organization of the gene cluster identified via RNA-seq was analyzed and it was shown that the arabitol utilization genes are co-transcribed in an operon that spans from BMMGA3_RS07325 to BMMGA3_RS07365. Since gene deletion studies are currently not possible in B. methanolicus, two complementation experiments were performed in an arabitol negative Corynebacterium glutamicum strain using the four genes discovered via RNA-seq analysis as coding for a putative PTS for arabitol uptake (BMMGA3_RS07330, BMMGA3_RS07335, and BMMGA3_RS07340 renamed to atlABC) and a putative arabitol phosphate dehydrogenase (BMMGA3_RS07345 renamed to atlD). C. glutamicum is a natural D-arabitol utilizer that requires arabitol dehydrogenase MtlD for arabitol catabolism. The C. glutamicum mtlD deletion mutant was chosen for complementation experiments. Heterologous expression of atlABCD as well as the arabitol phosphate dehydrogenase gene atlD from B. methanolicus alone restored growth of the C. glutamicum ΔmtlD mutant with arabitol. Furthermore, D-arabitol phosphate dehydrogenase activities could be detected in crude extracts of B. methanolicus and these were higher in arabitol-grown cells than in methanol- or mannitol-grown cells. Thus, B. methanolicus possesses an arabitol inducible operon encoding, amongst others, a putative PTS system and an arabitol phosphate dehydrogenase for uptake and activation of arabitol as growth substrate.

The sweetclover root disk bioassay was used to test the activity of 21 sugars and related compounds as feeding stimulants for the sweetclover weevil Sitona cylindricollis Fahraeus. Of the compounds tested, sucrose was the most effective feeding stimulant. Compounds with moderate stimulant activity were fructose, glucose, galactose, mannose, myo-inositol, and maltose. Slightly active feeding stimulants included ribose, xylose, sorbose, and sedoheptulose. Arabinose, arabitol, mannitol, xylitol, cellobiose, raffinose, soluble starch, ascorbic acid, glucuronic acid, and glucosamine failed to exhibit feeding stimulant activity in these tests. Four compounds (arabinose, ascorhic acid, glucuronic acid, and mannitol) were tested for feeding deterrent activity, and all displayed such activity. Although the structural requirements for feeding stimulant or deterrent activity were not established, it was clear that small differences in chemical structure could cause large differences in feeding response.

THE acetylation of sugars has hitherto involved the use of acetic anhydride and a catalyst such as sodium acetate1, zinc chloride2, sulphuric acid3 or pyridine4. We have shown that glucose may be acetylated rapidly by means of a mixture of acetic anhydride and acetic acid if a small amount of perchloric acid is added to act as a catalyst5. No external application of heat is necessary to aid the reaction. By pouring the acetylation mixture into water, an almost quantitative yield of α-pentacetyl glucose is produced. This new procedure does not afford crystalline acetyl derivatives of galactose or mannose ; but it works well for the acetylation of maltose, difructofuranose anhydride,α-methyl-glucoside, and polyhydric alcohols such as mannitol, sorbitol, erythritol, arabitol and pentaerythritol.

Debaryomyces nepalensis, osmotolerant yeast isolated from rotten apple, is known to utilize both hexoses and pentoses and produce industrially important metabolites like ethanol, xylitol and arabitol. In the present study, the effect of different growth substrates, trace elements, nitrogen concentration and initial pH on growth and formation of ethanol and arabitol were examined. Optimum conditions for maximizing the product yields were established: glucose as carbon source, an initial pH of 6.0, 6 g/L of ammonium sulphate and addition of micronutrients. Under these best suited conditions, a concentration of 11g/L of arabitol and 19 g/L of ethanol was obtained in shake flask fermentations. The fermentation was scaled up to 2.5 L bioreactor and the influence of aeration, agitation and initial substrate concentration was also determined. Under optimal conditions (150 g/L glucose, 400 rpm and 0.5 vvm) ethanol concentration reached 52 g/L, which corresponds to a yield of 0.34 g/g and volumetric productivity of 0.28 g/L/h, whereas arabitol production reached a maximum of 14 g/L with a yield and volumetric productivity of 0.1 g/g and 0.07 g/L/h respectively.