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The effect of pH on the production of swainsonine and fungal morphology at different stages of fermentation of Metarhizium anisopliae was investigated. When no control was applied, the pH of the culture dropped from 6.5 to 3.8 within the first 72 hours and the concentration of swainsonine reached 43.3 mg 1(-1). When the pH was held constant either at the beginning or throughout the fermentation, the maximum recorded swainsonine level was only 8.4 mg 1(-1) corresponding with an increase in the formation of pellets. A late pH control applied after 72 hours, resulted in a swainsonine titer of 45.5 mg 1(-1).

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Aqueous two-phase systems formed from PEG and dextran have been applied to the synthesis of oligosaccharide by Jack bean alpha-mannosidase in reverse. Whilst rates of synthesis and percentage yields were similar in two-phase systems and one-phase aqueous buffer systems, a ten-fold increase in yield of product per unit of enzyme was seen. In addition, the use of aqueous two-phase systems offers potential process advantages over one-phase systems for the synthesis of oligosaccharides.

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An efficient procedure for the isolation of reduced delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) from culture supernatants of beta-lactam antibiotic-producing microorganisms is described. The method utilises covalent chromatography to isolate thiols from culture broths that have been deproteinised and undergone borohydride reduction. 2-Pyridyl disulphide activated thiopropyl Sepharose was employed batchwise to isolate the thiols present in such broths from cultures of the known ACV excreter Cephalosporium acremonium N2 and the penicillin producer Penicillium chrysogenum P2. ACV was separated from these mixtures of thiols by gel permeation chromatography. Reversed-phase HPLC analysis showed the ACV to be of a high purity unless isolated from a highly complex culture medium.

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As shown by both bioassay and high-performance liquid chromatographic (HPLC) analysis, penicillin G production by Aspergillus nidulans is subject to regulation by the pH of the growth medium. Penicillin titres were highest at alkaline pH and in strains carrying mutations in the regulatory gene pacC which mimics the effects of growth at alkaline pH. They were lowest at acid pH and in strains carrying mutations in the palA, palB, palC, palE or palF genes which mimic the effects of growth at acid pH.

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A novel high-performance liquid chromatography (HPLC) method is presented for the detection and trace level determination of the tripeptide delta-L-alpha-aminoadipyl-L-cysteinyl-D-valine (ACV). The tripeptide, an intermediate in penicillin production, is derived from fungal fermentation. The technique relies on ion-exchange separation of the tripeptide on an anion-exchange column followed by detection by reduction on a gold electrode using pulsed amperometry. The sensitivity of direct determination of ACV is increased by employing pulsed amperometric detection (PAD) over direct ultraviolet detection. Choice of the working electrode and optimisation of electrode potentials was based on cyclic voltammograms recorded for the tripeptide in the mobile phase. A linear regression equation was obtained over the range 0-100 micrograms ml-1. The detection limit in fermentation broths was found to be 0.1 micrograms ml-1 whereas in buffer the detection limit was found to be 10 ng ml-1. A good correlation coefficient was observed when ACV concentrations determined by ion chromatography-PAD were compared with measurements obtained by pre-column derivatisation with fluoromethylorthochloroformate followed by HPLC separation on a reversed-phase C18 silica column with UV detection. The procedure has been applied to the measurement of natural levels of ACV in fermentation broths of selected strains of Aspergillus nidulans and Penicillin chrysogenum.

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Precolumn derivatization procedures using 1,2,4-triazole for the detection and quantitation of sulbactam and clavulanic acid spiked into urine and blood serum at trace levels have been developed. Sulbactam and clavulanic acid produced derivatives which absorbed maximally at 325 and 315 nm, respectively. The methods allow the detection of clavulanic acid and sulbactam down to 0.05 micrograms ml-1 in serum and 0.5 micrograms ml-1 in urine. The relative standard deviation for five replicate analyses of sulbactam and clavulanic acid at a concentration of 20 micrograms ml-1 in serum and urine ranged from 2-6%. In further HPLC experiments with sulbactam in phosphate buffer solution, ampicillin was found as a contaminant (0.5% by mass) in the sulbactam sample provided. The significance of this finding is discussed.

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A novel method is described for the trace level quantitation of the tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) in complex fermentation media, using a high-performance liquid chromatographic, pre-column derivatisation technique. The procedure is based upon the reaction of the ACV monomer with 5-dimethylaminonaphthalene-1-sulphonylaziridine (dansylaziridine) and produces a highly fluorescent product. Reaction conditions between the reagent and tripeptide were investigated and optimal conditions established. Linear calibration graphs were obtained over the ranges 227-0.56 micrograms/ml and 227-5.6 ng/ml. The extracellular ACV levels produced in fermentation broths of several different fungal strains and species were determined using this technique. The method was compared using ACV standards in buffer solutions for ease of use, sensitivity and selectivity with two other pre-column derivatisation procedures, using dithionitrobenzoic acid and monobromobimane, which also exploit the reaction with the sulphydryl group of the ACV monomer.

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This paper describes a novel and sensitive pre-column derivatisation method for the detection and quantitation of beta-lactams and their biosynthetic precursors at trace levels in fermentation media. Filtered broths from fermentations of strains of Penicillium chrysogenum and Cephalosporium acremonium, after deproteination and centrifugation, were incubated with 9-fluorenylmethylchloroformate for 5 min at 20 degrees C in 0.2 M borate buffer at pH 7.7. Following two-fold pentane extraction of the reagent hydrolysis product, the aqueous layer was injected directly onto a C18 reversed-phase column, and products were detected spectrofluorimetrically with excitation and emission wavelengths of 260 and 313 nm, respectively. Detection limits of 0.01 and 0.05 micrograms ml-1 were achieved for both 6-aminopenicillanic acid (6-APA) and isopenicillin N in borate buffer and filtered fermentation broths, respectively, using a 10-microliter injection volume. A linear calibration for 6-APA in fermentation broth was obtained for a very wide concentration range (0.05-100 micrograms ml-1). Detection limits for solutions of cephalosporin C, deacetylcephalosporin C and deacetoxycephalosporin C in broth were all 0.25 micrograms ml-1. The detection limit for the beta-lactam precursor delta-(L-aminoadipyl)-L-alpha-cysteinyl-D-valine (ACV) dimer in borate buffer was 0.5 microgram ml-1. The cephalosporins and ACV dimer gave linear plots in the ranges 3-25 and 1-100 micrograms ml-1, respectively. Repeated analysis of 6-APA at a concentration of 10 micrograms ml-1 in filtered broth gave a mean peak area of 2.5.10(6) with a standard deviation of 2.6.10(5) using a 10-microliter injection volume. Ampicillin spiked into deproteinated blood serum gave a linear calibration in the concentration range 2-100 micrograms ml-1.

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Thirteen of 48 dermatophyte isolates were found by bioassay to produce beta-lactam antibiotics and seven produced other antibiotics. Estimation and detection of specific beta-lactams in culture broths by derivatization and HPLC was only possible following concentration and extraction procedures. Analysis of the concentrated broths demonstrated the production of penicillin X and penicillin G by two Trichophyton mentagrophytes strains and by one Microsporum canis strain; one further T. mentagrophytes strain produced only penicillin X. Additions of the beta-lactam side-chain precursors, phenylacetic acid and phenoxyacetic acid, to fermentation media failed to increase the antibiotic titres.

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New silica and organic polymer-based, wide-pore, affinity chromatographic phases have been developed for beta-lactamase purification. The resins have been evaluated in terms of binding capacity, ligand coverage, protein recovery and long-term stability of activated resins prior to ligand attachment. The columns have been applied to the isolation of beta-lactamase from fermentation media. Protein purity following high-performance liquid affinity chromatography was assessed by polyacrylamide gel electrophoresis.

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A mixed culture of Aspergillus nidulans (GH79) and Aspergillus flavus (CMI 91019B) produced two antibiotics, designated VI and VII, which were not elaborated when either fungus was grown alone. Chemical and spectroscopic analysis of VI, the major component, indicated that this compound was identical to hydroxyaspergillic acid. The minor component, VII, was produced in too low a yield for its identity to be established. However, partial characterization suggests that this antibiotic also belongs to the aspergillic acid group of mycotoxins.

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Isolates of Microsporum canis, Microsporum gypseum and Epidermophyton floccosum were observed to produce antibacterial activities under cross-resistance to fusidic acid. The activity from E. floccosum was shown to be due to fusidic acid, diketofusidic acid and 3-ketofusidic acid. Possible contributions of these antibiotics to microbial interaction during dermatophytosis is discussed.

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