Behavior of spores of Penicillium roquefortii during fed-batch bioconversion of octanoic acid into 2-heptanone

The bioconversion of octanoic acid into 2-heptanone by spores of Penicillium roquefortii is performed using a fed-batch technique with pH control by addition of the liquid substrate itself. The early stage of this process takes place with a high bioconversion rate and high yield. These values then decrease as a result of germination and growth the biocatalyst. An optimization strategy for the process would thus be to improve the characteristics of this first period, i.e., increase its duration and the reaction rate. An increase in duration is evidenced in two cases: (I) under oxygen limitation: and (ii) when the spore content in the medium is less than 10(7) spores/mL. These conditions give insufficient overall bioconversion rates: better optimization should be achieved without oxygen limitation and with high spore content. Characterization of the first period by material and bioenergetic balances suggests that an increase in the ethanol content of the medium, which acts as an energy source and a permeabilizer, and the use of specific inhibitor of the Krebs cycle, may be a way to further improve the biocatalyst performance and stability. (c) 1994 John Wiley & Sons, Inc.     

Rheological characterization of media containing Penicillium chrysogenum

Samples from fed-batch fermentations of Penicillium chrysogenum on complex medium are rheologically characterized. The behavior is well described by a power law model for which the parameters are estimates. Furthermore, two types of model media are characterized and compared with the real fermentation samples. Xanthan solutions are found to mimic the rheological properties of the filamentous fungi much better than carboxymethyl cellulose (CMC) solutions. (c) 1993 John Wiley & Sons, Inc.     

Fluorescence and bioluminescence analysis of sequential UV-biological degradation of p-cresol in water.

The photolysis and Penicillium tardum H-2 degradation of p-cresol in water containing humic acids was investigated by fluorescence and bioluminescence methods. Humic acids extracted from peat (the Vasuygan bog, Tomsk region of Russia) induce the phototransformation of p-cresol. The influence of humic acids on the phototransformation of p-cresol under different irradiation conditions was investigated. Comparison of the data on the KrCl* (lambda = 222 nm) and XeCl* (lambda = 308 nm) excilamps light showed that the most effective p-cresol degradation was observed with mercury lamp irradiation in the presence of humic acids.     

Influence of cultivating conditions on the alpha-galactosidase biosynthesis from a novel strain of Penicillium sp. in solid-state fermentation

AIMS: The work is intended to achieve optimum culture conditions of alpha-galactosidase production by a mutant strain Penicillium sp. in solid-state fermentation (SSF). METHODS AND RESULTS: Certain fermentation parameters involving incubation temperature, moisture content, initial pH value, inoculum and load size of medium, and incubation time were investigated separately. The optimal temperature and moisture level for alpha-galactosidase biosynthesis was found to be 30 degrees C and 50%, respectively. The range of pH 5.5-6.5 was favourable. About 40-50 g of medium in 250-ml flask and inoculum over 1.0 x 10(6) spores were suitable for enzyme production. Seventy-five hours of incubation was enough for maximum alpha-galactosidase production. Substrate as wheat bran supplemented with soyabean meal and beet pulp markedly improved the enzyme yield in trays. CONCLUSIONS: Under optimum culture conditions, the alpha-galactosidase activity from Penicillium sp. MAFIC-6 indicated 185.2 U g(-1) in tray of SSF. SIGNIFICANT AND IMPACT OF THE STUDY: The process on alpha-galactosidase production in laboratory scale may have a potentiality of scaling-up.     

The glucose oxidase of Penicillium variabile P16: gene cloning, sequencing and expression

AIMS: Isolation and characterization of the glucose oxidase (GOX)-encoding gene from a Penicillium variabile strain (P16) having a high level of GOX activity and comparison of its expression with that of another strain of P. variabile (NRRL 1048) characterized by low GOX activity. METHODS AND RESULTS: The gene, isolated by PCR consisted of 1818 bp encoding 605 amino acid residues. Gene expression was analysed by Northern blotting and compared with that of P. variabile NRRL 1048. The higher GOX activity of strain P16 appeared likely because of de novo mRNA synthesis. Southern blotting analyses of the genomic DNA showed that the hybridization pattern of the two strains differed for the size of hybridizing fragment detected by the probe and slightly for their signal intensity. CONCLUSIONS: The GOX-encoding gene of P. variabile P16 was isolated and characterized to identify the molecular bases of its high level of expression and in view of improving enzyme production by developing a process based on heterologous expression. SIGNIFICANCE AND IMPACT OF THE STUDY: GOX-encoding genes can be subjected to high difference in their expression levels. The P16 strain of P. variable producing large amount of GOX as well as its encoding gene might be exploited for industrial applications.     

Production of a novel syrup containing neofructo-oligosaccharides by the cells of Penicillium citrinum

A novel syrup containing neofructo-oligosaccharides was produced from sucrose (Brix 70) by whole cells of Penicillium citrinum. The efficiency of fructo-oligosaccharides production was more than 55% and those of the main carbohydrate components, 1-kestose (Fruf 21Fruf 21 Glc), nystose (Fruf 21Fruf 21 Fruf 21 Glc) and neokestose (Fruf 26 Glc12 Fruf), were 22, 14 and 11%, respectively.     

Fusarinines and dimerum acid, mono- and dihydroxamate siderophores from Penicillium chrysogenum, improve iron utilization by strategy I and strategy II plants

Cucumber, as a strategy I plant, and Maize as a strategy II plant, were cultivated in hydroponic culture in the presence of a ferrated siderophore mixture (1 M) from a culture of Penicillium chrysogenumisolated from soil. The siderophore mixture significantly improved the iron status of these plants as measured by chlorophyll concentration to the same degree as a 100-fold higher FeEDTA supply. Analysis of the siderophore mixture from P. chrysogenum by HPLC and electrospray mass spectrometry revealed that besides the trihydroxamates, coprogen and ferricrocin, large amounts of dimerum acid and fusarinines were present which represent precursor siderophores or breakdown products of coprogen. In order to prove the iron donor properties of dimerum acid and fusarinines for plants, purified coprogen was hydrolyzed with ammonia and the hydrolysis products consisting of dimerum acid and fusarinine were used for iron uptake by cucumber and maize. In short term experiments radioactive iron uptake and translocation rates were determined using ferrioxamine B, coprogen and hydrolysis products of coprogen. While the trihydroxamates revealed negligible or intermediate iron uptake rates by both plant species, the fungal siderophore mixture and the ammoniacal hydrolysis products of coprogen showed high iron uptake, suggesting that dimerum acid and fusarinines are very efficient iron sources for plants. Iron reduction assays using cucumber roots or ascorbic acid also showed that iron bound to hydrolysis products of coprogen was more easily reduced compared to iron bound to trihydroxamates. Ligand exchange studies with epi-hydroxymugineic acid and EDTA showed that iron was easily exchanged between coprogen hydrolysis products and phytosiderophores or EDTA. The results indicate that coprogen hydrolysis products are an excellent source for Fe nutrition of plants.     

Clinical presentation and significance of emerging opportunistic infections

In recent years the clinical face of the Acquired Immune Deficiency Syndrome has changed significantly as a consequence of use of prophylaxis against Pneumocystis carinii pneumonia and combination antiretroviral therapy. In this context several opportunistic pathogens have emerged as causes of clinically important disease. Many of these infective agents have previously been defined by specific geographical locations. Their clinical presentation frequently mimics other (non) opportunistic infections with which they may co-exist. The diagnosis is frequently delayed as the diagnostic possibility may not be in the clinician's differential diagnosis. Invasive procedures are frequently required in order to secure a diagnosis. Despite treatment, prognosis is often poor. Clinicians should be aware of these opportunistic pathogens in order that a timely diagnosis may be made and appropriate therapy given.     

The Biosynthesis of Low-Molecular-Weight Nitrogen-Containing Secondary Metabolites—Alkaloids—by the Resident Strains of Penicillium chrysogenum and Penicillium expansum Isolated on Board the Mir Space Station

The analysis of the absorption spectra of the low-molecular-weight nitrogen-containing secondary metabolites—alkaloids—of four Penicillium chrysogenum strains and six P. expansum strains isolated on board the Mir space station showed that all these strains synthesize metabolites of alkaloid origin (roquefortine, 3,12-dihydroroquefortine, meleagrin, viridicatin, viridicatol, isorugulosuvin, rugulosuvin B, N acetyltryptamine, and a yellow metabolite containing the benzoquinone chromophore).