Volatile production by Aspergillus versicolor as a possible cause of odor in houses affected by fungi

Aspergillus versicolor, which has been isolated from several mould affected houses was shown by laboratory studies under axenic conditions to produce several specific volatile compounds on water agar. These compounds were not produced by the fungus when grown on a rich malt extract medium or on several synthetic media. The volatile compounds were analysed by GC-MS. The majority of the peaks represented aromatic compounds. A non-aromatic substance which previously has been revealed by us among prominent volatile compounds sampled from building materials from so-called mould houses was produced only on water agar. According to a comparison with the mass spectrum and retention time of pure reference compound this compound is ethylhexanol, a compound not previously reported as a mould metabolite. The presence of this compound was correlated with pungent odor in the cultures.     

Correlation between manganese-deficiency,loss of respiratory chain complex I activity and citric acid production in Aspergillus niger

The correlation between manganese deficiency, loss of mitochondrial respiratory chain NADH: ubiquinone oxidoreductase (complex I) activity and citric acid overproduction in the Aspergillus niger strain B 60 was analysed. With increasing manganese-supplementation of the production medium the loss of complex I activity and the production of citric acid was reduced. Addition of manganese during growth stopped further loss of complex I activity and further increase of citric acid production. A possible causality between complex I deficiency and citric acid overproduction is discussed.     

Construction of a fusion gene comprising the Taka-amylase A promoter and the Escherichia coli β-glucuronidase gene and analysis of its expression in Aspergillus oryzae

Summary Northern blot analysis of glucose-grown and starch-grown mycelia of Aspergillus oryzae R11340 was conducted using the cloned Taka-amylase A (TAA) gene as a probe. The amount of mRNA homologous to the TAA gene was increased when this fungus was grown with starch as a sole carbon source. In order to analyze the induction mechanism, we inserted the Escherichia coli uidA gene encoding -glucuronidase (GUS) downstream of the TAA promoter and introduced the resultant fusion gene into the A. oryzae genome. Production of a functional GUS protein was induced by starch, but not by glucose. When the effects of various sugars on expression of the fusion gene were examined, the results suggested that the expression of the fusion gene was under control of the TAA gene promoter.     

Biotransformation of germacrane-type sesquiterpenoids by Aspergillus niger

Three germacrane-type sesquiterpenoids, (+)-germacrone-4,5-epoxide, germacrone and (+)-curdione were biotransformed by Aspergillus niger to give hydroxylated guaiane-type sesquiterpenoids together with allylic alcohols and spirolactone.     

Preharvest seed infection byAspergillus flavus group fungi and subsequent aflatoxin contamination in groundnuts in relation to soil types

Preharvest seed infection byAspergillus flavus and aflatoxin contamination in selected groundnut genotypes (fourA. flavus-resistant and fourA. flavus-susceptible) were examined in different soil types at several locations in India in 1985–1990. Undamaged mature pods were sampled at harvest and seed examined forA. flavus infection and aflatoxin content in two or more trials at ICRISAT Center on light sandy soils and red sandy loam soils (Alfisols), and on Vertisols, at Anantapur on light sandy soils, and at Dharwad and Parbhani on Vertisols. Rainy season trials (1985–1989) were all rainfed. Post-rainy season trials were irrigated; late-season drought stress (90 days after sowing (DAS) until harvest at 125 DAS) was imposed in the 1987/88 and 1989/90 seasons.A. flavus infection and aflatoxin contamination levels were much lower in seed of all genotypes from Vertisols than in seed from Alfisols across locations and seasons. Vertisols also had significantly lower populations ofA. flavus than Alfisols. There were no marked differences between light sandy soils and red sandy loam soils (Alfisols) in respect of seed infection byA. flavus and aflatoxin contamination. Significant interactions between genotypes and soil types were evident, especially in theA. flavus-susceptible genotypes. Irrespective of soil types,A. flavus-resistant genotypes showed lower levels of seed infection byA. flavus and other fungi than didA. flavus-susceptible genotypes. The significance of the low preharvest aflatoxin risk in groundnuts grown on Vertisols is highlighted.ICRISAT Journal Article No. JA 1122     

Liquefaction of dulse (Palmaria palmata (L.) Kuntze) by a commercial enzyme preparation and a purified endo ,β-1,4-D-xylanase

Liquefaction of dry and freshPalmaria palmata by food grade enzyme preparations and a purified endo--1,4-D-xylanase was studied.The endo--1,4-D-xylanase (EC 3.2.1.8) was purified to homogeneity from a commercial food grade enzyme prepared fromAspergillus niger. It has a molecular weight of 22 500, a pI of 3.5, is inactive toward corn arabinoxylan,p-nitrophenyl--D-xylose, carboxymethyl cellulose but shows a weak activity toward microcrystalline cellulose. It hydrolyzes oat and dulse xylan equally well in seawater and deionized water essentially into xylose and xylobiose. It is stable between pH 5.5 to 9.0 and 0 to 30 °C and its activity is optimal at pH 4.5–5.5 and 40–60 °C. It has a K_m of 2.2 and 2.8 mg ml^-1 and V_max of 3600 and 3900 nkat mg^-1 of protein on oat and dulse xylan, respectively.Acetate buffer, deionized water and seawater alone extracted 62.6 to 64.5 % of the dry weight of dry dulse, but the use of commercial food grade enzyme preparations or the purified xylanase improved liquefaction to 81.2–87.1 %. Xylose and galactose were the only sugars present in the soluble extracts. Deionized and seawater extracted 58.8–52.7 and 39.1–42.2% of the dry weight of the fresh algae collected in fall and summer, respectively. Only galactose was found in the seawater extract, while some xylose with galactose were measured in the deionized water extract of the fresh autumn algal sample. Purified and crude xylanase improved liquefaction of fresh algae to 79.8–81.4 and 71.9–77.9% of the fresh dry weight (fall and summer, respectively) in deionized and seawater, respectively, and increased the xylose content of the soluble fractions. Polysaccharides in the soluble residues were composed of 1,3/1,4-linked xylose, 1-linked galactose (floridoside) and 1,4-linked glucose (cellulose) and contained essentially 1,4-linked xylose and 1,4-linked glucose in insoluble fractions obtained after enzymatic treatment.The use of xylanase-containing food grade enzyme preparations improves liquefaction ofPalmaria palmata, particularly from fresh alga. This study indicates that processing such as drying may modify markedly the solubility ofP. palmata cell wall polysaccharides, which would imply the existence of some organization and/or other components in the fresh cell wall that lower xylan solubility in seawater.     

The appearance of an enzyme activity catalysing the conversion of norsolorinic acid to averantin in Aspergillus parasiticus cultures

The activity of the enzyme responsible for the conversion of norsolorinic acid to averantin was studied in two strains of Aspergillus parasiticus. Cell-free extracts of the enzyme were purified from different aged mycelia and little activity was found prior to 24 hours after inoculation but this quickly reached a maximum at 48 hours and declined thereafter. Both strains of A. parasiticus, one in aflatoxin producing strain, the other a versicolorin A accumulating mutant, showed this trend. It was concluded that the enzyme responsible for this conversion was a secondary metabolic enzyme and was distinct from alcohol and mannitol dehydrogenases.     

Toxigenic Aspergillus flavus and aflatoxins in Sri Lankan medicinal plant material

The fungal flora of 6 Asian medicinal plants, Aerva lanata (Linn.) Juss. Alyssicarpus vaginalis D.C., Tribulus terrestris Linn. Adhatoda vasica Nees., Centella asciatica (L.) Urb., Cardiospermum halicacabum Linn. was determined. After surface disinfection Aspergillus spp. were most frequently observed. Aspergillus flavus, isolated from Alyssicarpus vaginalis and Aerva lanata produced aflatoxins in culture. Aflatoxin B₁ was also detected in a sample of Aerra lanata at a level of 0.5 g/g. Plant material destined for medicinal use should be stored carefully prior to its use to prevent growth of naturally occurring toxigenic mold fungi.     

Some metabolic relationships between biopterin and folate: Implications for the “methyl trap hypothesis”

Tetrahydrobiopterin and the folate coenzymes can reciprocally interact in ways that would be useful to the metabolic pathways subserved by both of these coenzymes. Thus, through one of the reactions catalyzed by methylene tetrahydrofolate reductase, 5-CH₃-H₄-folate can regenerate BH₄ from q-BH₂ and q-BH₂ can provide an escape from the methyl trap.Special issue dedicated to Dr. Louis Sokoloff     

The tertiary structure of Aspergillus saitoi minor ribonuclease (Ms) predicted from the structure of RNase T1

Ribonuclease Ms from Aspergillus saitoi is a small acidic protein (11 714 Da) containing 106 amino acids of known sequence. Unlike other enzymes belonging to the RNase T₁ family this ribonuclease is base-unspecific. Using interactive computer graphics and energy minimisation we predicted the structure of RNase Ms on the basis of sequence homology to RNase T₁ of known structure. In this report the predicted structure of this protein is presented and characterised.