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Aims To assess the ability of various newly isolated or belonging in official collections yeast strains to convert biodiesel-derived glycerol (Gly) into added-value compounds. Methods and results Ten newly isolated yeast strains belonging to Debaryomyces sp., Naganishia uzbekistanensis, Rhodotorula sp. and Yarrowia lipolytica, isolated from fishes, metabolized Gly under nitrogen limitation. The aim of the study was to identify potential newly isolated microbial candidates that could produce single-cell oil (SCO), endopolysaccharides and polyols when these micro-organisms were grown on biodiesel-derived Gly. As controls producing SCO and endopolysaccharides were the strains Rhodotorula glutinis NRRL YB-252 and Cryptococcus curvatus NRRL Y-1511. At initial Gly (Gly0 ) ≈40 g l-1 , most strains presented remarkable dry cell weight (DCW) production, whereas Y. lipolytica and Debaryomyces sp. produced non-negligible quantities of mannitol and arabitol (Ara). Five strains were further cultivated at increasing Gly0 concentrations. Rhodotorula glutinis NRRL YB-252 produced 7·2 g l-1 of lipid (lipid in DCW value ≈38% w/w), whereas Debaryomyces sp. FMCC Y69 in batch-bioreactor experiment with Gly0 ≈80 g l-1 , produced 30-33 g l-1 of DCW and ~30 g l-1 of Ara. At shake-flasks with Gly0 ≈125 g l-1 , Ara of ~48 g l-1 (conversion yield of polyol on Gly consumed ≈0·62 g g-1 ) was achieved. Cellular lipids of all yeasts contained in variable concentrations oleic, palmitic, stearic and linoleic acids. Conclusions Newly isolated, food-derived and non-previously studied yeast isolates converted biodiesel-derived Gly into several added-value metabolites. Significance and impact of the study Alternative ways of crude Gly valorization through yeast fermentations were provided and added-value compounds were synthesized.

Lichens can be used as cost-effective biomonitors of elements from road traffic in the urban environment. However, the nature of comprehensive interactions between hazardous heavy metals from road traffic and lichen metabolites remains unclear. In this study, elemental and metabolic profiles of the lichen Dirinaria picta after exposure to road traffic for 3 months in 9 sites of Singapore city were investigated. Concentrations of 34 elements reveal strong correlations among each other and a general increase with traffic exposure level. A variety of metabolites, i.e. sugar alcohols, sugars, amino acids, low-molecular mass organic acids, secondary metabolites and nucleosides, are identified through a multi-platform approach combining liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF/MS), gas chromatography quadrupole mass spectrometry (GC-Q/MS) and 1H nuclear magnetic resonance (1H NMR). The total amount of the heavy metals Fe, Zn, Cu, Cd, Pb and Co can be significantly correlated with 21 metabolites positively and 9 metabolites negatively. These correlations reveal a heavy metal detoxification mechanism through ROS scavenging, osmoregulation and chelation with N atoms and sulfhydryl groups, as well as depletion of arabitol and inhibited synthesis of certain secondary metabolites such as quinones and steroids due to heavy metal stress. This study provides new insights into the metabolic toxicity and detoxification mechanisms in lichens under heavy metal exposure.

Sugar alcohols have been widely applied in the field of food and medicine for their unique properties. Compared to chemical production, microbial production of sugar alcohol has become attractive for its environmental and sustainable pattern. In this study, a potential yeast isolated from soil of Beijing suburbs was identified as Pichia anomala TIB-x229, and its key enzyme of d-arabitol dehydrogenase for microbial production of sugar alcohols was functionally characterized. This yeast could simultaneously produce d-arabitol, xylitol, and/or ribitol from a different ratio of sugar substrates at a high efficiency by bioconversion, and no glucose repression happened when mixed sugars of xylose and glucose were used as the substrates during the bioconversion. This yeast could also efficiently convert complicated feedstock such as xylose mother liquor to d-arabitol, xylitol, and ribitol with 55 % yields. To elucidate the conversion relationship of the sugar alcohols, especially d-arabitol and xylitol, the key d-arabitol dehydrogenase gene from P. anomala was cloned, expressed and purified for further in vitro characterization. The results showed that this d-arabitol dehydrogenase could catalyze arabitol to xylulose further, which is significant for xylitol production from glucose. Our study laid the foundation for improving the production of sugar alcohols by metabolic and fermentation engineering strategies.

The growth and accumulation of intracellular polyols at reduced water activity (aw) were studied in 40 basidiomycetous yeast strains. The growth of most strains showed greater tolerance to NaCl than sorbitol at the same aw. No strain was able to grow below 0.90aw. 13C nuclear magnetic resonance spectroscopy revealed that glycerol was the major solute accumulated intracellularly by all the yeasts when grown to 0.96aw (NaCl). Arabitol or mannitol was also accumulated in some yeasts, whereas a few only accumulated glycerol. Analysis of six yeasts in detail revealed that the intracellular glycerol concentrations of five yeasts increased significantly when grown at 0.96aw (NaCl or sorbitol) compared with growth at 0.998aw. Arabitol and mannitol concentrations also increased, but not to the same degree. Intracellular potassium concentrations decreased when grown at 0.96aw (NaCl or sorbitol) and sodium increased, but only when grown at 0.96aw (NaCl). The survival of nine strains was evaluated in soil cultures and it was found that all grew at 100% field capacity, whereas at lower field capacity, only some strains grew or survived. The growth of basidiomycetous yeasts appears to be more sensitive to reduced aw than ascomycetous yeasts.

Aims: The effect of osmotic and matric potential stress on growth and sugar alcohols (polyols: glycerol, erythritol, arabitol and mannitol) and sugars (trehalose and glucose) accumulation in toxigenic and nontoxigenic colonies of Aspergillus flavus and A. parasiticus was evaluated. Methods and Results: Growth of Aspergillus section Flavi with significant reductions at 20 and 30°C was more sensitive to changes in matric potential, between 60 and 100% in the range of −7 to −14 MPa. No significant differences were found between toxigenic and nontoxigenic strains for both species. Total polyol accumulation in unamended maize meal agar medium (−0·75 MPa water potential) was higher at 30 than 20°C. The major change in concentrations of endogenous sugars and total polyols was in matrically amended medium (with PEG 8000) at −7 and −10 MPa. Accumulation of glucose, arabitol, mannitol and erythritol content of A. flavus and A. parasiticus mycelial colonies was greater in normal unstressed maize meal agar medium (−0·75 Mpa) at 20°C. This was modified by solute and matric stress. Conclusions: The data showed relative sensitivity to osmotic and matric potential, and temperature, and the impact on growth rates, polyol and sugar accumulation in mycelia of A. flavus and A. parasiticus. Significance and Impact of the Study: The matric potential effects on growth may be of particular importance for growth and survival in environments with low-matric potential stress. The tolerance of spoilage fungi such as Aspergillus section Flavi to such modifications could increase the potential for spoilage and mycotoxin production in such substrates. This knowledge is important for understanding the relative ecological fitness of these aflatoxigenic species and in the development of prevention strategies for their control.

The ability of Candida peltata NRRL Y-6888 to ferment xylose to xylitol was evaluated under different fermentation conditions such as pH, temperature, aeration, substrate concentration and in the presence of glucose, arabinose, ethanol, methanol and organic acids. Maximum xylitol yield of 0.56 g g-1 xylose was obtained when the yeast was cultivated at pH 6.0, 28 degrees C and 200 rpm on 50 g L-1 xylose. The yeast produced ethanol (0.41 g g-1 in 40 h) from glucose (50 g L-1) and arabitol (0.55 g g-1 in 87 h) from arabinose (50 g L-1). It preferentially utilized glucosexylosearabinose from mixed substrates. Glucose (10 g L-1), ethanol (7.5 g L-1) and acetate (5 g L-1) inhibited xylitol production by 61, 84 and 68%, respectively. Arabinose (10 g L-1) had no inhibitory effect on xylitol production.

We studied effects of season and soil treatments (watering, acidification, liming and combinations of these treatments) on soluble carbohydrates of mycorrhizal roots of Norway spruce (Picea abies (L.) Karst.). Arabinose, arabitol, fructose, glucose, inositol, lactose, mannitol, pinite, quinate, raffinose, shikimate, stachyose and trehalose were identified by HPLC. Concentrations of inositol, lactose and pinite were constant throughout the year, whereas concentrations of raffinose, stachyose and trehalose were higher in winter than in summer, and concentrations of glucose, fructose and mannitol increased from February to September. Soil acidification and liming had no effect on the annual mean concentrations of fructose, glucose, lactose, pinite, raffinose and stachyose. Liming increased quinate concentrations and decreased arabitol concentrations. Annual mean concentrations of arabinose and mannitol decreased in response to soil acidification. Annual mean concentrations of inositol increased in response to irrigation. None of the soil treatments affected the mean annual concentration of trehalose.

N. T EIXIDO ´, I. VINAS, J. USALL, V. SANCHIS AND N. MAGAN. 1998.The growth responses of the biocontrol agent Candida sake to changes in water activity (aw), temperature and pH and their interactions, and accumulation of sugars (glucose, trehalose) and sugar alcohols (glycerol, erythritol, arabitol and mannitol) were determined in vitro in nutrient yeast dextrose based media. The aw temperature profile for growth was between 0·995 and 0·90 and 4‐37 °C with the non-ionic solute glycerol, and between 0·995 and 0·92 and 10‐30 °C with the ionic solute NaCl. Regardless of solute, there was a longer lag time prior to growth as aw was reduced, and at marginal temperatures for growth. Relative growth rates were compared at different aw levels and temperatures and it was found that aw, temperature, solute and two and three‐way interactions were statistically significant. By contrast, C. sake was tolerant of a wide range of pH levels (3‐7) regardless of aw, although growth rates were reduced at marginal temperatures and aw. In non-stressed basal NYDB, glucose and arabitol were the predominant endogenous reserves accumulated in the cells of C. sake. However, when nutrient status was diluted (75%) and stressed by the addition of glycerol or NaCl (0·98 and 0·96 aw), significant changes in the accumulation of sugars and sugar alcohols occurred. In glycerol-stressed media, glucose and glycerol were the major compounds accumulated, with markedly lower arabitol and little trehalose or mannitol present. With NaCl-stressed media, glycerol was the only sugar alcohol accumulated, with very low levels of the sugars and other sugar alcohols. This study has defined the ecological niche within which C. sake would be active as a biocontrol agent for the first time and suggests that endogenous reserves can be significantly modified by nutrient and aw stress; these changes may be useful for improving environmental competence of such micro-organisms in the environment.

The degradation pathway for L-arabinose, which consists of a sequence of alternating reduction and oxidation reactions prior to ultimate phosphorylation, was studied in Aspergillus nidulans wild-type as well as in an L-arabinose non-utilizing mutant. The inability of the mutant to use L-arabinose was caused by the absence of L-arabitol dehydrogenase activity. The effect of the mutation on polyol accumulation patterns was studied upon growth on various carbon sources. The presence of L-arabinose resulted in intracellular accumulation of arabitol in this mutant. Moreover, the mutant secreted arabitol under these conditions and, in contrast to the wild-type, featured enhanced expression of enzymes involved in L-arabinose catabolism as well as of extracellular glycosyl hydrolases involved in degradation of the plant cell wall polysaccharide L-arabinan.

Formation of α-L-arabinosidase can be induced in Trichoderma reesei by growing the fungus on L-arabinose or dulcitol, and by adding L-arabinose, L-arabitol, D-galactose, or dulcitol ot non-growing mycelia. The same conditions also stimulated the formation of α-D-galactosidase, but not that of various other enzymes involved in hemicellulose degradation. The optimal inducer concentration with all compounds was 4 mM for both enzymes. Using L-arabinose and D-galactose, the induction efficiency was highest at pH 6.5, whereas induction by arabitol and dulcitol was more efficient at low pH (2.5). The addition of 50 mM glucose did not repress α-L-arabinosidase or α-D-galactosidase formation. These findings suggest coregulation of two hemicellulose side-chain cleaving enzymes in T. reesei.

Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus were grown on Sabouraud Dextrose Agar (SDA) modified with KCl to give a range of water activity (aw) from 0.938 to 0.998. Growth of all three species was optimal at 0.983 aw and growth occurred over the aw range tested. Acyclic sugar alcohol (polyol) and trehalose content of conidia was determined by HPLC and found to vary with species and aw. Conidia of B. bassiana and P. farinosus were found to contain totals of 1.5% and 2.3% polyols respectively at 0.998 aw, and double these amounts at

Analysis of seventeen yeast strains by 13C-NMR spectroscopy has confirmed the significance of glycerol as the sole osmoregulatory solute under salt-stressed conditions, and has shown arabitol to be present in most of the osmotolerant species. Ribitol was detected in some species, including Debaryomyces hansenii, although ribitol accumulation did not correlate with the osmotic pressure of the medium. Relative amounts of arabitol and ribitol decreased in relation to glycerol when the external osmotic pressure was increased. Trehalose was present during exponential growth of some species.

The following fractions were obtained from the wall material of Gliocladium viride : F1 (27.5%), a glucan, containing xylose, mannose and galactose, coluble in 1 M NaOH at 20°C; F2 (6.7%), a β-glucan-chitin complex, solubilized with 1 M NaOH at 20°C from the previous residue left overnight at −20°C; F3 (8.1%), a glucan, containing mannose and galactose solubilized with 1 M NaOH at 70°C; and F4, the insoluble residue, a β-glucan-chitin complex similar to F2, amounting to 31.3% of the wall material. F1 was extracted with distilled water. The soluble material (F1S) was a galactomannoglucan (54.7%) and the inscluble (F1P) a glucan (45.3%). Periodate oxidation revealed the presence of glycerol, erythritol, threitol, ribitol, arabitol, mannose, galactose and glucose in F1S, and glycerol and glucose as the main components in F1P. The fractions obtained when F1S was purified through Sepharose CL6B, were methylated.

We found that Acetobacter xylinum KU-1 produced cellulose from D-arabitol. The maximum cellulose production was obtained when it was grown in a medium containing 2.0% D-arabitol, 1.0% tryptone, and 1.0% yeast extract (pH 5) at 30°C for 96h statically. The productivity was more than 6 times as much as that of D-glucose [productivity (mg/ml-medium): from D-arabitol, 12.4; from D-glucose, 2.0].

The composition of the polyol pools in Aspergillus nidulans mycelium during active growth on sucrose depends strongly on pH. At pH 2.5, only mannitol is present. A comparison between nitrate- and ammonium-grown cultures shows stimulation of the arabitol content with nitrate a former nitrogen source. When starved mycelium is incubated either with natural-abundance or 13C-enriched glucose, label appears rapidly in mannitol and arabitol, regardless of the nitrogen source or the pH used.

Flammulina velutipes (Curt. ex Fr.) Sing. was grown on potato-glucose solution freed of most starch. Glucose uptake and dry weight changes in the colony indicated that the large fruitbodies derived their substrates partly from glucose remaining in the medium and partly from cellular constituents stored in the mycelium and small fruitbodies. Changes in the amounts of low molecular weight carbohydrates, glycogen, and four cell wall polysaccharide fractions were followed in the mycelium and fruitbodies. Trehalose, arabitol, and smaller amounts of mannitol were the main stored low molecular weight carbohydrates. A large net loss of these compounds occurred in the mycelium and small fruitbodies after their growth ceased. The carbohydrates accumulated in the large fruitbodies, but were also partly metabolized in the colony. Reducing sugars were minor components, and included about 30 to 50% glucose and a small undetermined quantity of fructose. Glycogen was the main storage carbohydrate in the mycelium, and was also stored in the small fruitbodies. It was broken down in both structures during growth of the large fruitbodies which accumulated only small amounts. During the same period, almost 45% of the maximum amount of cell wall polysaccharides were degraded in the small fruitbodies, but not in the mycelium.By feeding (14)C-glucose in replacement medium, incorporation of radioactivity into carbohydrates was followed in the colony during fruit-body development. Total incorporation was highest in trehalose, next highest in glycogen, and the rest was found in polyols and cell wall polysaccharides except for a few per cent which remained in endogenous glucose. In the large fruitbodies, specific radioactivity in glucose was much lower than in trehalose and mannitol. The labeling patterns in the mycelium and large fruitbodies suggested that trehalose, mannitol, and possibly arabitol were translocated into the stipes and pilei.

Aldopentose reductases of a Corynebacterium species were investigated.Chromatography of cell-free extracts from this bacterium on Sephadex G–100 revealed the presence of two distinct enzyme fractions with reducing activity on aldopentoses.The elution pattern of the two enzyme fractions obtained from cells grown in a gluconate-l-arabinose medium was the same as that from cells grown in a gluconate-d-ribose medium.The first fraction (Reductase I) showed considerably high activity on d-ribose, and the second fraction (Reductase II), on both l-arabinose and d-xylose.The reduction of l-arabinose to l-arabitol and of d-ribose to ribitol was demonstrated by the coupling reaction of the reductase and phosphogluconate dehydrogenase with NADP as a cofactor.

Uredospores of Puccinia graminis (Pers.) tritici (Eriks. and Henn.) were uniformly labeled with (14)C by permitting the host (Triticum aestivum L.) to carry out photosynthesis in (14)CO(2) during the process of spore production by the obligate parasite. The use of (14)C labeled spores provided advantages in a study of the utilization of endogenous substrates at frequent intervals with small amounts of spores under conditions conducive to germination.Because of previous uncertainties about the nature of the substrates of importance to germination, a detailed study of carbohydrate and lipid components, both in the spores and in the germination medium, was made during the first 7 hours after placing the spores on aqueous media. Diethyl ether and 80% ethanol soluble metabolites each constituted approximately 20% of the total spore carbon. During the first hour nearly 60% of the 80% alcohol solubles disappeared from the spores while the total ether soluble material did not change appreciably. A significant part of the 80% ethanol soluble materials appeared in the germination medium.During germination and germ tube extension, there was rapid utilization of trehalose, arabitol and mannitol even though appreciable amounts of these materials were present as exogenous pools in the germination medium. Although the total amounts of ether soluble components did not change as drastically as the carbohydrate fraction, there was extensive utilization of palmitic, oleic, linolenic and 9,10-epoxyoctadecanoic acids.The results indicate that the germination process in spores of obligate parasites is not based solely on the utilization of lipids and some possible roles of the changes in internal and external pools of soluble carbohydrates are discussed.

An HPLC procedure for determining sorbitol in bulk sorbitol is described. An Aminex HPX-87 column (Bio-Rad) is used with water as a mobile phase and with a refractive index detector to monitor column eluate. Sorbitol is separated from pentaerythritol, erythritol, ribitol, ethylene glycol, propylene glycol, arabitol, galactitol, mannitol, iditol, and other carbohydrates. The precision of the sorbitol determination, characterized by a 95% confidence interval, corresponds to ±1.22%.

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.