Influence of bioreactor design on exopolysaccharide production byAureobasidium pullulans

Summary Exopolysaccharide yields byAureobasidium pullulans were affected by the bioreactor configuration in batch culture. However the yields obtained in the stirred-tank and airlift vessels were also dependent on the nitrogen source used, and independent of cell morphology.     

Co-metabolism of paint byAureobasidium pullulans BH-1-ATCC 34621

Although the ability ofAureobasidium pullulans BH-I-ATCC 34621 to cause paint deterioration during its growth on wood has been reported, the mechanism by which paint degradation occurred was unclear. Evidence now indicates that co-metabolism of acrylic, resins in the paint is the cause of paint deterioration byA. pullulans.     

Production and biochemical characterization of polygalacturonases produced byAureobasidium pullulans from forest soil

The production of individual form of extracellular polygalacturonase byAureobasidium pullulans from forest soil was found to depend on the pH of cultivation medium as well as on the nitrogen source in the precultivation or cultivation medium. Polygalacturonases were purified and characterized. The pH optima of polygalacturonases produced in the first phases of cultivation (24 or 48 h) and after 10 days as well as their molecular masses, isoelectric points, action pattern and ability to cleave polymeric and oligomeric substrates were different. Generally, polygalacturonases with random action pattern (EC 3.2.1.15) were produced only in the first phases of cultivation in acidic medium. The function of these enzymes for A.pullulans in the colonization of plant material rather than in the destruction of plant was hypothesized in physiological conditions. Exopolygalacturonases (EC 3.2.1.67) with terminal action pattern were produced in later phases of growth. Oligogalacturonate hydrolase as well as strongly basic polygalacturonase with unusual action pattern on substrates were found.     

Influence of dissolved oxygen concentration and shear rate on the production of pullulan byAureobasidium pullulans

Summary Experiments were carried out withA. pullulans (ATCC 9348) at constant dissolved oxygen concentration (DO=100 and 50% related to air saturation at 1 bar) and at constant stirrer speeds (n=500 and 150 [min^–1]). The highest pullulan yield was achieved at decreased constant DO in connection with decreased shear rate. Biomass production was not affected.     

Treatment of phenolic wastes in an aerated submerged fixed-film (ASFF) bioreactor

The biological removal of phenol was studied in a multi-stage fixed-film reactor at phenol concentrations in the range of 190–900 mg l⁻¹, hydraulic loadings of 0.02–0.22 m³ m⁻² day⁻¹ and temperatures of 20–35°C. Phenol removals up to 99.9% were obtained at 20°C but the efficiency decreased as the loading rate or phenol concentration was increased. The reactor coped with organic overloads better than with hydraulic overloads. Removal efficiencies increased as temperature was increased. Reactor performance was stable under extreme loadings and the reactor was capable of handling a ten-fold increase in loading with less than 20% loss in phenol removal efficiency. A large amount of attached biomass was retained in the reactor and was mostly present in the first stage where the majority of organic removal occurred.     

Biological treatment of phenolic wastes: Comparison between free and immobilized cell systems

Summary Phenol degradation by free and immobilized cells ofFusarium flocciferum was studied in a chemostat at steady-state conditions. For the free cell system the dilution rates varied from 0.02 to 0.13h^–1, with a total phenol removal up to 0.08h^–1. Wash-out seemed to set in at 0.11h^–1. The immobilized cells showed virtually complete phenol utilization at 1g/l, over a period of four months. At D=0.2h^–1 and above 1g/l phenol, the complete phenol removal is not achieved: a progressive increase in the outlet concentration was observed attaining a value of 284mg/l at 1.5g/l.     

Comparative study of the pullulans synthesized by Pollularia (Aureobasidium) pullulans strains of different ploidies

Pullularia pullulans strains of different ploidy synthesize pullulans similar in their characteristics to those described in literature. These are glucans whose glucose residues are linked with alpha(1 leads to 4) and alpha(1 leads to 6) bonds in the proportion of 2.2:1. The pullulans differ from one another in their water solubility, molecular mass and in the ability to be cleaved by alpha-amylase and dextranase. The minor structural modifications of pullulan molecules in the polyploid strains as compared to the pullulan synthesized by the parent haploid culture are caused, apparently, by mutations induced with mitotic poisons.     

Plasticizers Increase Adhesion of the Deteriogenic Fungus Aureobasidium pullulans to Polyvinyl Chloride

Initial adhesion of fungi to plasticized polyvinyl chloride (pPVC) may determine subsequent colonization and biodeterioration processes. The deteriogenic fungus Aureobasidium pullulans was used to investigate the physicochemical nature of adhesion to both unplasticized PVC (uPVC) and pPVC containing the plasticizers dioctyl phthalate (DOP) and dioctyl adipate (DOA). A quantitative adhesion assay using image analysis identified fundamental differences in the mechanism of adhesion of A. pullulans blastospores to these substrata. Adhesion to pPVC was greater than that to uPVC by a maximum of 280% after a 4-h incubation with 10⁸ blastospores ml⁻¹. That plasticizers enhance adhesion to PVC was confirmed by incorporating a dispersion of both DOA and DOP into the blastospore suspension. Adhesion to uPVC was increased by up to 308% in the presence of the dispersed plasticizers. Hydrophobic interactions were found to dominate adhesion to uPVC because (i) a strong positive correlation was observed between substratum hydrophobicity (measured by using a dynamic contact angle analyzer) and adhesion to a range of unplasticized polymers including uPVC, and (ii) neither the pH nor the electrolyte concentration of the suspension buffer, both of which influence electrostatic interactions, affected adhesion to uPVC. In contrast, adhesion to pPVC is principally controlled by electrostatic interactions. Enhanced adhesion to pPVC occurred despite a relative reduction of 13° in the water contact angle of pPVC compared to that of uPVC. Furthermore, adhesion to pPVC was strongly dependent on both the pH and electrolyte concentration of the suspension medium, reaching maximum levels at pH 8 and with an electrolyte concentration of 10 mM NaCl. Plasticization with DOP and DOA therefore increases adhesion of A. pullulans blastospores to pPVC through an interaction mediated by electrostatic forces.     

Enumeration of Acidithiobacillus ferrooxidans adhered to agglomerated ores in bioleaching processes

In bioleaching processes, bacteria adhered to agglomerated ores are frequently determined in the washing solution after treating the mineral with different techniques like sonification or chemical treatment with SDS, Tween 20, Tritón X-100, or only basal medium to release the adhered cells. In this work we compare the efficiency of these techniques, not only by determination of the number of released cells, but also by establishing their viability. The results indicate that, in spite of the high number of bacteria that can be released from an agglomerated ore, when detergent solutions are used, bacteria are heavily damaged and lose their ferrous-iron oxidation activity. On the other hand, when hand stirring with basal medium is used to release bacteria, a method that does not produce damage to the cells, only a percentage of the total population of active ferrous-iron-oxidizing adhered bacteria is released; therefore, the enumeration or determination of bacteria in the washing solution would be inaccurate. We thus propose that agglomerated ores be monitored directly for the presence of active bacteria, by determination of the ferrous-iron oxidation ability of the attached bacteria.     

Transformation of 7,8-dihydrocodeinone to 7,8-dihydroisocodeine by Aureobasidium pullulans

Aureobasidium pullulans reduced stereospecifically 7,8-dihydrocodeinone to 7,8-dihydroisocodeine. Activity of the culture was inhibited by some substances present in the malt extract.     

Cadmium accumulation by a Citrobacter sp. immobilized on gel and solid supports: Applicability to the treatment of liquid wastes containing heavy metal cations

Polyacrylamide gel-immobilized cells of a Citrobacter sp. removed cadmium from flows supplemented with glycerol 2-phosphate, the metal uptake mechanism being mediated by the activity of a cell-bound phosphatase that precipitates liberated inorganic phosphate with heavy metals at the cell surface. The constraints of elevated flow rate and temperature were investigated and the results discussed in terms of the kinetics of immobilized enzymes. Loss in activity with respect to cadmium accumulation but not inorganic phosphate liberation was observed at acid pH and was attributed to the pH-dependent solubility of cadmium photsphate. Similarly high concentrations of chloride ions, and traces of cyanide inhibited cadmium uptake and this was attributed to the ability of these anions to complex heavy metals, especially the ability of CN(-) to form complex anions with Cd(2+). The data are discussed in terms of the known chemistry of chloride and cyanide-cadmium complexes and the relevance of these factors in the treatment of metal-containing liquid wastes is discussed. The cells immobilized in polyacrylamide provided a convenient small-scale laboratory model system. It was found that the Citrobacter sp. could be immobilized on glass supports with no chemical treatment or modification necessary. Such cells were also effective in metal accumulation and a prototype system more applicable to the treatment of metal-containing streams on a larger scale is described.     

环境pH诱导出芽短梗霉细胞多形化

出芽短梗霉具有酵母状细胞、膨大细胞、菌丝、厚垣孢子、念珠状菌丝和分生组织状结构。在最适pH条件下,出芽短梗霉生长繁殖以酵母状细胞（CBS100225等4菌株）或膨大细胞（CBS249.65等4菌株）为主。pH 2.2或pH 7.0诱导全部8株出芽短梗霉形成分生组织状结构。酵母状细胞转变成膨大细胞受低pH值诱导的占75%,还受高pH诱导的占50%。膨大细胞是多形性细胞转变的中心环节,可以转变成菌丝、厚垣孢子或分生组织状结构。     

Plasticizers increase adhesion of the deteriogenic fungus Aureobasidium pullulans to polyvinyl chloride.

Initial adhesion of fungi to plasticized polyvinyl chloride (pPVC) may determine subsequent colonization and biodeterioration processes. The deteriogenic fungus Aureobasidium pullulans was used to investigate the physicochemical nature of adhesion to both unplasticized PVC (uPVC) and pPVC containing the plasticizers dioctyl phthalate (DOP) and dioctyl adipate (DOA). A quantitative adhesion assay using image analysis identified fundamental differences in the mechanism of adhesion of A. pullulans blastospores to these substrata. Adhesion to pPVC was greater than that to uPVC by a maximum of 280% after a 4-h incubation with 10(8) blastospores ml(-1). That plasticizers enhance adhesion to PVC was confirmed by incorporating a dispersion of both DOA and DOP into the blastospore suspension. Adhesion to uPVC was increased by up to 308% in the presence of the dispersed plasticizers. Hydrophobic interactions were found to dominate adhesion to uPVC because (i) a strong positive correlation was observed between substratum hydrophobicity (measured by using a dynamic contact angle analyzer) and adhesion to a range of unplasticized polymers including uPVC, and (ii) neither the pH nor the electrolyte concentration of the suspension buffer, both of which influence electrostatic interactions, affected adhesion to uPVC. In contrast, adhesion to pPVC is principally controlled by electrostatic interactions. Enhanced adhesion to pPVC occurred despite a relative reduction of 13 degrees in the water contact angle of pPVC compared to that of uPVC. Furthermore, adhesion to pPVC was strongly dependent on both the pH and electrolyte concentration of the suspension medium, reaching maximum levels at pH 8 and with an electrolyte concentration of 10 mM NaCl. Plasticization with DOP and DOA therefore increases adhesion of A. pullulans blastospores to pPVC through an interaction mediated by electrostatic forces.     

Effect of sugars on the morphogenesis ofAureobasidium pullulans

The dominance of individual elements of the vegetative fructification of five selected strains of the polymorphic organismAureobasidium pullulans (de Baby)Arnaud was studied in media with basic assimilable sugars,d-glucose,d-galactose,d-xylose, maltose, sucrose, lactose and a mixture ofl -arabinose andd-mannitol. Pronounced differences between cultures grown in the presence of monosaccharides and those cultivated in the presence of disaccharides were detected.     

Lipid composition of yeastlike cells of the fungusPullularia pullulans

AlthoughPullularia pullulans is a polymorphic fungus, cultures have been obtained consisting exclusively of yeastlike cells. These cells can be considered as “medium lipid content” yeasts (5.7%). Thirty percent of the total lipids are phosphoglycerides, the most abundant of which are phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. The bulk of the nonpolar lipids is made up of unsaponifiable matter, sterols, and hydrocarbons. Eighteen fatty acid species have been detected, but the C₁₆ and C₁₈ species are by far the most abundant. The major unsaturated species is oleic acid. Linolenic acid is found in significant amounts only in triglycerides and esterified sterols. Fatty acid moieties associated with phosphatidylcholine and phosphatidylethanolamine are more unsaturated than those associated with phosphatidylserine or cardiolipin. Considerable proportions of the phosphoglycerides exist in the form of plasmalogen, which is unusual in yeasts.     

Aureobasidium pullulans metabolism of prostaglandins of the A-type.

Aureobasidium pullulans, originally introduced as an inadvertent contaminant in solutions used for evaluating the stability of prostaglandins, proved to lead to the rapid disappearance of the cyclopentenone unit of PGA2 (as monitored by circular dichroic spectroscopy). The cyclopentenone unit is converted, in various metabolites, to a 9-keto, 9 alpha or 9 beta-hydroxy group lacking the ring unsaturation. The major EtoAc-soluble 9-hydroxy metabolite (Compound-I) was shown to be 9 alpha, 15 alpha-dihydroxy-2, 3, 4, 5-tetranor-13-trans-prostenoic acid. Similar tetranor 9-hydroxy metabolites with one additional degree of unsaturation, and with a 9 beta-hydroxy group, also occur but these have not been fully characterized. Only two of the wide range of 9-keto metabolites are fully characterized by mass spectral (MS) data: 9, 15-oxo-2, 3, 4, 5-tetranorprostanoic acid and 9, 15-oxo-2, 3, 4, 5-tetranor-13-trans-prostenoic acid. The water soluble metabolites have not been characterized further. The fully characterized metabolites together with MS data from mixtures of minor metabolites indicate that A. pullulans can perform the following transformation: beta-oxidation, dehydrogenation at C-15, reduction of the enone carbon-carbon double bonds (both delta 10,11 and delta 13,14), reduction of the 9-ketone, and possibly migration of the cyclopentyl double bond (delta 10, 11 leads to delta 11, 12). A. pullulans metabolizes 15-epimeric PGA2 equally readily with the production of similar products. PGA1 affords less 9-keto metabolites with compound I constituting 33% of the product by HPLC analysis. A. pullulans displays some enantioselectivity, PGA2 and 15-epi-PGA2 are each metabolized more rapidly than their enantiomers. Other prostaglandins appear to be less readily metabolized.