Regulation of branched-chain amino acid biosynthesis in Streptomyces fradiae,a producer of tylosin

Synthesis of threonine dehydratase in Streptomyces fradiae was positively influenced by valine and negatively by isoleucine. However, these two amino acids had no effect on the activity of this enzyme. Synthesis of threonine dehydratase in -aminobutyrate resistant mutants of S. fradiae was pronouncedly less sensitive to the positive effect of valine and this change in regulation led to valine overproduction. Synthesis of acetohydroxy acid synthase is regulated in a similar manner to that of threonine dehydratase, however a lower level of expression was detected in -aminobutyrate resistant mutants. And again, no effect of branched-chain amino acids on acetohydroxy acid synthase activity was observed. It follows that in S. fradiae synthesis of threonine dehydratase is the main regulatory mechanism governing production and the mutual ratio of synthesized valine and isoleucine.Abbreviations -AB -aminobutyrate - AHAS acetohydroxy acid synthase - -KB -ketobutyrate - MNNG N-methyl-N-nitro-N-nitrosoguanidine - TD threonine dehydratase - Trans. B. transaminase of branched-chain amino acids - VDH valine dehydrogenase     

Production of milk-clotting enzymes by basidiomycetes

BasidiomycetesPhellinus chrysoloma, Kuehneromyces mutabilis andGanoderma applanatum produce extracellular milk-clotting enzymes. The enzymes are acid proteinases stable at 40°C and within pH 3–5.5. Only the enzyme preparation fromP. chrysoloma exhibits properties comparable with animal chymosin.     

ΔF508 frequency and associated haplotypes near the cystic fibrosis locus in the Yugoslav population

Summary Chromosomes from 19 unrelated Southern Yugoslav families in which cystic fibrosis (CF) occurs were analysed for the presence of the ΔF508 mutation, using polymerase chain reaction amplification followed by dot blot and polyacrylamide gel analysis. Of the 38 CF chromosomes, 15 (39.5%) carry the ΔF508 deletion. Restriction fragment length polymorphism haplotypes for KM19/PstI, XV2c/TaqI and J3.11/PstI marker loci were determined and are compared for a total of 34 N and 37 CF chromosomes.     

Immobilization of Escheria alcalescens cells with aspartate ammonia-lyase activity

Summary Immobilization of Escherichia alcalescens cells into genu-carrageenan gel for L-aspartic acid production was studied with respect to the optimized preparation of heterogenous biocatalyst /2.5–3.0% genu-carrageenan, 15% biomass, 50–55 °C, tannin added/.     

Nomenclatural remarks on the association names ofNardus stricta-rich communities in Central Europe

The present paper gives comments on the nomenclature of associations ofNardetalia andNardo-Caricion rigidae from Central Europe. A brief list of important homonyms and ambiguous names is added.     

Deletion ΔF508 and haplotype analysis of CFTR gene region in Slovak CF patients

Summary Analysis of a sample of 50 unrelated cystic fibrosis (CF) patients and 46 nuclear families from Slovakia (Czechoslovakia) by the polymerase chain reaction and Southern hybridization revealed that the proportion of the F508 mutation was 58% in this population, and that the frequency of the B (i.e., KM19/XV2c [1–2]) haplotype was increased in both F508 and nonF508 CF chromosomes (98% and 46%, respectively). These results support the view that the trans-European gradient of the F508 frequency is of a geographical rather than of an ethnic origin, and that in Slavonic populations, there exists an as yet unidentified but frequent CF mutation other than F508, associated with the B haplotype.     

Ligninolytic properties of different white-rot fungi

Summary Seven white-rot fungi were examined for the production of ligninase, manganese peroxidase and laccase. All these enzymes were found inTrametes gibbosa andTrametes hirsuta. Only manganese peroxidase and laccase were produced byPycnoporus cinnabarinus,Coriolopsis polyzona,Stereum hirsutum,Dichomitus squalens andGanoderma valesiacum. All fungi decolorized Poly B-411 and Indulin AT plates with low-N medium. The differences in enzyme pattern indicate that different species of fungi may employ different modes of lignin metabolism.     

abetd-Xylose metabolism in Aureobasidium pullulans: effects of aeration and vitamins

Summary The yeast-like organism Aureobasidium pullulans efficiently converted abetd-xylose to cell mass (Y _X/S=0.45 g·g^–1) with negligible production of polyols (Y _P/S=0.003 g·g^–1) under aerobic conditions. A. pullulans grown semiaerobically exhibited different fermentation capacities in seven basal (vitaminless) medium and medium containing a mixture of seven vitamins. It was found that under semiaerobic conditions a mixture of vitamins significantly enhanced production of ethanol from abetd-xylose, resulting in a 15-fold higher yield coefficient of ethanol (Y _E/S=0.22 g·g^–1) as compared to that achieved in vitaminless medium. This increase in ethanol production was accomplished at the expense of cell mass. A. pullulans produced extremely low amounts of polyols throughout all aerobic and semiaerobic experiments. A. pullulans displayed strictly NADPH-linked xylose reductase and NAD⁺-linked xylitol dehydrogenase activities.     

Transformation of a new Gram-positive methylotroph,Brevibacterium methylicum,by plasmid DNA

Summary Brevibacterium methylicum is a newly isolated Gram-positive facultatively methylotrophic bacterium that uses the NAD⁺-dependent methanol dehydrogenase for methanol oxidation and assimilates its carbon via the ribulose monophosphate cycle. Protoplasts prepared by lysozyme treatment of B. methylicum cells grown in the presence of glycine were transformed by plasmid shuttle vectors pCEM500 (16.5 kb; Sm^r/Sp^r, Km^r/Gm^r) and pEC71 (7.1 kb; Km^r/Nm^r) constructed on the basis of B. lactofermentum plasmid pAM330 and replicating in Escherichia coli and in amino-acid-producing coryneform bacteria. The resistance markers were found to be expressed in B. methylicum and autonomous plasmid DNAs of various size were isolated from the transformants. The presence of the pAM330 replicon in these plasmids was demonstrated by DNA-DNA hybridization experiments. Offprint requests to: J. Nevera