The binding of several metals by waste biomass of Streptomyces noursei was investigated. With respect to the binding capacity, the following order was observed: Ag > Cr > Pb > Cu > Zn > Cd > Co > =Ni. The sorption of metal ions increased with the increasing initial concentration of metal. The adsorption equilibrium of copper, lead and chromium sorption, and silver sorption at low concentration can be described by the Freundlich and Langmuir models. The possibilities for desorbing the metals from loaded biomass and the repeated use of biomass were investigated. The influence of various ions in water on metal sorption was tested. The metal capacity and selectivity of metal binding by biomass are important qualities for practical use.
The yeast Candida tropicalis HP 15 was able to utilize phenol up to concentrations of 2.5 g/l as a sole carbon and energy source. Phenol was metabolized via the beta-ketoadipate pathway by an inducible enzyme system. Besides phenol, resorcinol, quinol, hydroxyquinol, catechol, and to a lesser extend 4-chlorocatechol, protocatechuate, p-cresol, m-chlorophenol, and p-chlorophenol were metabolized by the yeast. A total of 30 aromatic compounds were tested as substrates.
The enzyme phenol hydroxylase (EC 1.14.13.7) was determined and characterized in crude extracts of Rhodococcus sp. P 1. This enzyme catalyzed the first step of phenol degradation. It was inducible, had a pH optimum of 7.9 and a temperature optimum at 20 degrees C and catalyzed also the hydroxylation of some other phenolic compounds.
The first two enzymes of the phenol degradation pathway were determined and characterized in crude extracts from Candida tropicalis HP 15. The phenol hydroxylase (EC 1.14.13.7) was a stable NADPH2- and FAD-dependent enzyme with a pH-optimum of 7.6 to 8.0 and a broad substrate specificity. Influence of ultrasound rapidly reduced the enzyme activity. The catechol 1,2-oxygenase (EC 1.13.1.1) had a broad pH-optimum between 7.5 and 9.6 and a limited substrate specificity. Two active protein bands indicating the presence of two isofunctional enzymes were detectable after electrophoretic separation of crude and partially purified extracts on polyacrylamide gels and specific staining for catechol 1,2-oxygenase activity.
Two bacterial isolates (i.e. strains An 117 and An 213) capable of growing with aniline, phenol as well as benzoate as the sole carbon and energy source were studied with respect to (i) their taxonomic position, (ii) the enzyme reactions which initiate catabolism of the respective aromatic compounds, and (iii) the general type of regulation of the respective enzymes.
Both isolates were established to be representatives of the actinomycete‐genus Rhodococcus. Experiments with resting cells and cell‐free extracts, respectively, revealed that in the two strains under study catabolism of each of the unsubstituted aromatic compounds occurs via the β‐ketoadipate pathway (with catechol as the central metabolite) due to the action of inducible enzymes. Although being potent inducers of the ring‐cleaving catechol 1,2‐dioxygenase in strains An 117 and An 213, all of the monochlorinated derivatives of aniline, phenol and benzoate, respectively, failed to support cell growth of the organisms. Cis, cis‐muconic acid proved to be non‐metabolizable by resting An 117 and An 213 cells, although substantial (inducible) muconate cycloisomerase activity was detectable in crude extracts prepared from the respective cell preparations. NADPH‐depending phenol hydroxylase activity could be demonstrated in crude extracts from phenol‐grown An 117 and An 213 cells. Evidence is presented that in both Rhodococcus strains under study substantial de novo synthesis of at least the initial aromatics‐oxygenating enzymes can be induced by phenol and aniline, respectively, even in the presence of either succinate (An 117) or acetate (An 213) which are known to be ortho‐pathway catabolites.
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