Influence of different sugars on pullulan production and activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glucosyltransferase involved in pullulan synthesis in Aureobasidium pullulans Y68

Effects of different sugars on pullulan production, UDP-glucose level, and activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glucosyltransferase in Aureobasidium pullulans Y68 were examined. It was found that more pullulan was produced when the yeast strain was grown in the medium containing glucose than when it was cultivated in the medium supplementing other sugars. Our results demonstrate that when more pullulan was synthesized, less UDP-glucose was left in the cells of A. pullulans Y68. However, it was observed that more pullulan was synthesized, the cells had higher activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glycosyltransferase. Therefore, high pullulan yield is related to high activities of α-phosphoglucose mutase, UDPG-pyrophosphorylase and glucosyltransferase in A. pullulans Y68 grown on different sugars. A pathway of pullulan biosynthesis in A. pullulan Y68 was proposed based on the results of this study and those from other researchers. This study will be helpful to metabolism-engineer the yeast strain to further enhance pullulan yield.     

Sweet potato: A novel substrate for pullulan production by Aureobasidium pullulans

A strain Aureobasidium pullulans AP329, was used for the production of pullulan by employing hydrolysed sweet potato as cultivation media. Hydrolysis with α-amylase alone resulted in the lowest yields of pullulan. In contrast continuous hydrolysis with pullulanase and the β-amylase in sweet potato itself gave higher yields, but prolonged hydrolysis with amyloglucosidase decreased the yield. The maximum pullulan yield (29.43 g/l) was achieved at the dextrose equivalent value of 45 and pH of 5.5 for 96 h. As a substitute of sucrose, hydrolysed sweet potato was found to be hopeful and the yield of pullulan was higher than that of glucose and sucrose. The molecular weight of pullulan obtained from hydrolysed sweet potato media was much higher than that of sucrose and glucose media. Results of this work indicated that sweet potato was a promising substrate for the economical production of pullulan.     

Pullulan production by tropical isolates of <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis>

Tropical isolates of Aureobasidium pullulans previously isolated from distinct habitats in Thailand were characterized for their capacities to produce the valuable polysaccharide, pullulan. A. pullulans strain NRM2, the so-called “color variant” strain, was the best producer, yielding 25.1 g pullulan l⁻¹ after 7 days in sucrose medium with peptone as the nitrogen source. Pullulan from strain NRM2 was less pigmented than those from the other strains and was remarkably pure after a simple ethanol precipitation. The molecular weight of pullulan from all cultures dramatically decreased after 3 days growth, as analyzed by high performance size exclusion chromatography. Alpha-amylase with apparent activity against pullulan was expressed constitutively in sucrose-grown cultures and induced in starch-grown cultures. When the alpha-amylase inhibitor acarbose was added to the culture medium, pullulan of slightly higher molecular weight was obtained from late cultures, supporting the notion that alpha-amylase plays a role in the reduction of the molecular weight of pullulan during the production phase.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Production of pigment-free pullulan by swollen cell in <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> NG which cell differentiation was affected by pH and nutrition

A black yeast strain “NG” was isolated from strawberry fruit and identified as Aureobasidium pullulans. Strain NG displayed yeast-like cell (YL), swollen cell (SC), septate swollen cell (SSC), meristematic structure (MS), and chlamydospore (CH) morphologies. pH was the key factor regulating cell morphogenesis of strain NG. Differentiation of YL controlled by extracellular pH had no relationship with nutrition level. YL was maintained at pH >6.0, but was transformed into SC at pH ∼4.5. SC, a stable cell type of A. pullulans, could bud, septate, or transform into MS or CH, in response to nutrition level and low pH. SC produced swollen cell blastospores (SCB) at pH 2.1 with abundant nutrition, and could transform into MS at lower pH (1.5). SC was induced to form CH by low level nutrition and pH <3, and this transition was suppressed by adjusting pH to ∼4.5. Crude polysaccharides without pigment (melanin) were produced by SC of strain NG. Pullulan content of the polysaccharides was very high (98.37%). Fourier-transform infrared spectroscopy confirmed that chemical structures of the polysaccharides and standard pullulan were identical. Swollen cells produced 2.08 mg/ml non-pigmented polysaccharides at 96 h in YPD medium. Controlling pH of fermentation is an effective and convenient method to harvest SC for melanin-free pullulan production.     

Effects of melanin on the accumulation of exopolysaccharides by Aureobasidium pullulans grown on nitrate

Aureobasidium pullulans produced pullulan and melanin when grown in medium containing low nitrate levels. With high nitrate concentrations, however, this fungus produced a mixture of exopolysaccharides (EPS) without melanin synthesis. At 0.78 g l(-1) N as nitrate, where no melanin synthesis occurred, maximum EPS yields reached 6.92 g l(-1) and then decreased to the final yield of 2.36 g l(-1). Following melanin addition (0.1 g l(-1)), yields reached 7.02 g l(-1) at 48 h and fell to a final yield of 5.21 g l(-1). The EPS produced in high nitrate medium contained both pullulan and (1-->3)-beta-glucan, but only pullulan was produced with melanin-supplementation. With melanin addition a doubling of (1-->3)-beta-glucanase activity was observed in high nitrate medium compared to that without supplementation. On the other hand amylolytic activities disappeared in medium with melanin production or addition. Culture filtrates sustained a higher reducing capacity (RC) when melanin was present. Low RC appeared to reduce (1-->3)-beta-glucanase activity and increase amylolytic activities. Thus, higher RC appears to inhibit production/activity of amylose-degrading enzymes capable of degrading pullulan, and stimulates (1-->3)-beta-glucanase synthesis/activity, leading to a preferential accumulation of pullulan.     

Growth and macromolecular content of the dimorphic fungus Aureobasidium pullulans and the effect of hydroxyurea and other inhibitors

The growth kinetics and the macromolecular content of the yeast and ethanol-induced hyphal forms of Aureobasidium pullulans were studied. During the morphological transition from yeasts to hyphae, both the protein and RNA content decreased significantly, the mycelial form containing only 76% of the amount of protein in the yeasts, and 38% of the RNA. The DNA was the only component tested whose level increased during the transition. Among several compounds inhibiting macromolecular synthesis, only hydroxyurea showed a remarkable effect on the morphology of A. pullulans, inducing the mycelial morphology. The macromolecular composition of hydroxyurea-treated cultures changed with time in a way similar to that of the ethanol-Tween 80-ammonia medium, and to that of carbon-starved cultures, without ethanol or glucose.     

Pullulan production by color variant strains ofAureobasidium pullulans

Summary Naturally occurring color variant strains ofAureobasidium pullulans are distinguished from typical strains by their brilliant pigmentation, overproduction of secreted enzymes (xylanase), and low DNA relatedness. Color variants have not previously been examined for pullulan secretion. Among five independently isolated color variants, strains NRRL Y-12,974 and YB-4026 made the greatest amounts of pullulan from cornstarch, with conversion efficiencies of about 10%. Neither color variant nor typical strains made significant amounts of pullulan from the unconventional lactose or xylan substrates. Pullulan yields were inversely correlated with biomass production. Pullulan production thus appears to be a variable characteristic of both color variant and typically pigmented strains ofA. pullulans, regulated by specific inducers during growth limitation.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Polysaccharide production by immobilized Aureobasidium pullulans cells in batch bioreactors

Cells of the fungus Aureobasidium pullulans ATCC 201253 were entrapped within 4% agar cubes or 5% calcium alginate beads and were examined for their production of the polysaccharide pullulan in batch bioreactors. The batch bioreactors were utilized twice for 168 hours of polysaccharide production in medium containing corn syrup as a carbon source. The agar-entrapped cells produced nearly equivalent pullulan concentrations during both production cycles. The alginate-entrapped cells produced higher polysaccharide levels during the second cycle compared to the levels observed during the initial cycle. The agar-entrapped cells elaborated a polysaccharide with a higher pullulan content than did the alginate-entrapped cells during both production cycles.     

The Photochemical and Surface-Active Properties of Melanins Isolated from Some Black Fungi

The absorption spectra of melanins isolated from some black ascomycetes, as well as of synthetic melanin and natural melanin from Sepia officinalis, were recorded in the long-wavelength ultraviolet region A (320 nm < < 400 nm) and in the blue–violet region of the electromagnetic spectrum at illumination intensities varying from 0.02 to 1 mW/cm². The photochemical properties of fungal melanins were found to be dependent on both the producing strain and the conditions of its cultivation. The fungal melanins are more susceptible to photomodification and more biologically active than the synthetic melanin, indicating that these properties may be related. The data obtained suggest that the fungal melanins susceptible to photomodification possess higher biological activity than commercial melanins.     

Polysaccharide production by Aureobasidium pullulans: factors affecting polysaccharide formation

Aureobasidium pullulans NRRL 6220 synthesized polysaccharide most actively in media containing sucrose, fructose or maltose with (NH₄)₂SO₄ (0.6 g/l) or ammonium acetate giving greatest yields of the polysaccharide. With (NH₄)₂SO₄ at 1.2 g/l, production of polysaccharide was decreased considerably. Polysaccharide production was highest with an initial pH of 6.5 while biomass formation was better below an initial pH of 5.5. Optimum phosphate concentration for polysaccharide production was 0.03 m.S.M. Badr-Eldin, H.G. El-Masry and O.A. Abd El-Rahman are with the Microbial Chemistry Department, National Research Center, Dokki, Cairo, Egypt; F.H.A. Mohamad is with the Chemical Engineering and Pilot Plant Department, National Research Center, Dokki, Cairo, Egypt. O.M. El-Tayeb is with the Microbiology Department, Faculty of Pharmacy, Cairo University, Egypt.     

Purification and properties of intracellular fructosyl transferase fromAureobasidium pullulans

Intracellular frustosyl transferase was purified fromAureobasidium pullulans C-23 by ethanol fractionation, CM-Sephadex chromatography and preparative disc gel electrophoresis. It was shown to be homogeneous on disc polyacrylamide gel electrophoresis, with a molecular size of 190kDa. The pI value of the enzyme was about 3.7. The enzyme has aK _m value of 0.43 mM for sucrose and was optimally active at pH 5.0 and 60°C. The enzyme was stable from pH 2.5 to 12. It was almost completely inhibited by 5mM Hg²⁺ but was not significantly affected by other cations. The transferase was inactivated by treatment with the tryptophan-specific reagentN-bromosuccinimide and the tyrosine-specific reagent, I₂, suggesting that tryptophan and tyrosine residues are probably located at or near the active site of the enzyme.     

Specific Cd2+ uptake of encapsulated Aureobasidium pullulans biosorbents

Calcium alginate capsules containing Aureobasidium pullulans cells were prepared by an in-situ one-step method. The Cd²⁺uptakes of free biosorbent and capsule biosorbent were described well by the Freundlich isotherms. The Cd²⁺ uptake of capsule biosorbent was lower than that of free biosorbent with Cd^{2 +}at 100 mg l^–1. The total cadmium uptake of capsule biosorbent increased with the increase in encapsulated cell density and plateaued at a value of 23 g Cd²⁺/capsule with 150 g dry biosorbent l^–1 core volume of a capsule. The specific cadmium uptake of encapsulated biosorbent was 85% to that of free biosorbent at 35 g biosorbent dry weight l^–1 core volume of a capsule, decreased to 35% at 176 g biosorbent dry weight l^–1.     

Downstream processing of stevioside and its potential applications

Stevioside is a natural sweetener extracted from leaves of Stevia rebaudiana Bertoni, which is commercially produced by conventional (chemical/physical) processes. This article gives an overview of the stevioside structure, various analysis technique, new technologies required and the advances achieved in recent years. An enzymatic process is established, by which the maximum efficacy and benefit of the process can be achieved. The efficiency of the enzymatic process is quite comparable to that of other physical and chemical methods. Finally, we believe that in the future, the enzyme-based extraction will ensure more cost-effective availability of stevioside, thus assisting in the development of more food-based applications.     

Effect of the nitrogen source on the biosynthesis, composition, and structure of the exopolysaccharides ofAureobasidium pullulans (de Bary) Arnaud

The effect of the nitrogen source and the C/N ratio of the growth medium on the biosynthesis, composition, and structure of the exopolysaccharides (EPSs) ofAureobasidium pullulans (de Bary) Arnaud var.aubasidani Yurlova var. nov. andA. pullulans var.pullulans was studied.A. pullulans var.pullulans andA. pullulans var.aubasidani strains synthesized the maximum amounts of EPSs in the presence of, respectively, a reduced nitrogen source ((NH₄)₂SO₄) and an oxidized nitrogen source (NaNO₃) in the medium. The data presented confirm the validity of using the chemical composition and structure of the major cetavlon-precipitated fraction ofA. pullulans EPSs for the characterization of intraspecies taxa.     

出芽短梗霉菌株PA-2全基因组测序及分析

【背景】出芽短梗霉菌株PA-2是一株分离自青海省海东市平安区患病杨树叶片上的真菌,前期研究表明该菌株具有除草和抑菌能力,说明其在生物农药方面具有潜在的应用前景。【目的】了解菌株PA-2的基因组序列信息,挖掘其生防相关功能基因簇,为进一步研究解析该菌株生防机理及生防功能改造提供遗传背景信息。【方法】利用IlluminaHiSeq高通量测序平台对生防菌株PA-2进行全基因组测序,用生物信息学的方法对测序数据进行基因组组装、基因预测及功能注释、碳水化合物活性酶预测、次级代谢产物合成基因簇预测,利用刚果红染色等方法对水解酶活性进行衡量。【结果】菌株PA-2基因组序列全长28 932 793 bp,平均GC含量为50%,共编码10 839个基因,预测到该菌株具有4个已知的次级代谢产物合成基因簇,编码Melanin、Burnettramic Acid A、ACR-Toxin I、Abscisic Acid,该菌株能水解纤维素和果胶。【结论】有助于在基因组层面上解析菌株PA-2生防机制的内在原因,为深入了解出芽短梗霉菌次级代谢物合成途径提供参考,对菌株PA-2的下一步相关研究具有重要意义。     

Bioproducts from <Emphasis Type="Italic">Aureobasidium pullulans,</Emphasis> a biotechnologically important yeast

It has been well documented that Aureobasidium pullulans is widely distributed in different environments. Different strains of A. pullulans can produce amylase, proteinase, lipase, cellulase, xylanase, mannanase, transferases, pullulan, siderophore, and single-cell protein, and the genes encoding proteinase, lipase, cellulase, xylanase, and siderophore have been cloned and characterized. Therefore, like Aspergillus spp., it is a biotechnologically important yeast that can be used in different fields. So it is very important to sequence the whole genomic DNA of the yeast cells in order to find new more bioproducts and novel genes from this yeast.     

Microbial growth on polluted leaf and litter leachates: Effects on leachate pH and sulphate concentration

Summary Leaves and litter ofAcer pseudoplatanus L. (sycamore) were collected from woodland downwind of a coking works and from a site close to the industrial city of Sheffield and leached with water or simulated acid rain (pH 4.0). The effects of microbial growth on litter leachate, pH and sulphate concentration were determined by (a) allowing the indigenous litter flora to develop or (b) inoculating the fungusAureobasidium pullulans into sterilized leachates amended with synthetic aphid honeydew as carbon source. In both experiments microbial growth generally increased the pH and sulphate concentration of the leachates, independent of the origin of the litter or the leaching agent. The growth ofA. pullulans however, generally decreased the pH and sulphate content of sycamore leaf leachates. We conclude that the microbial mineralization of organic sulphur in deciduous litter leachate can act as a source of sulphate which could enhance cation leaching in atmospheric-pulluted soils.     

Bacillus fermentation of soybeans

Kinema fermentations of Indian and Canadian No. 1 soybeans by Bacillus sp. DK-W1 and by mixed cultures of Bacillus sp. DK-W1 and Enterococcus faecium DK-C1 were essentially identical. The viable cell count of Bacillus increased from an initial 10⁵ to 10¹⁰ c.f.u./g wet wt after 48 h incubation at 37°C. The pH of the fermentation dropped from an initial 6.9 to about 6.4 after 8 h and then rose to 8.6 after 32 h, with a coincident increase in proteolytic activity and ammonia concentration. The fermentations containing E. faecium and Bacillus exhibited a greater initial pH decline and a slightly retarded subseqent increase in pH compared with fermentations with Bacillus only. The presence of E. faecium had no detectable effects on growth of the Bacillus, proteolytic activity, ammonia production or the final pH of the fermentations.P.K. Sarkar was and P.E. Cook and J.D. Owens are with the Food Microbial Interactions Laboratory, Department of Food Science and Technology, University of Reading, Reading RG6 2AP, UK; P.K. Sarkar is now with the Microbiology Laboratory, Centre for Life Sciences, University of North Bengal, Siliguri 734430, India.