New fungal biomasses for cyanide biodegradation.
ABSTRACT Cyanide, a hazardous substance, is released into the environment as a result of natural processes of various industrial activities which is a toxic pollutant according to Environmental Protection Agency. In nature, some microorganisms are responsible for the degradation of cyanide, but there is only limited information about the degradation characteristics of Basidiomycetes for cyanide. The aim of the present study is to determine cyanide degradation characteristics in some Basidiomycetes strains including Polyporus arcularius (T 438), Schizophyllum commune (T 701), Clavariadelphus truncatus (T 192), Pleurotus eryngii (M 102), Ganoderma applanatum (M 105), Trametes versicolor (D 22), Cerrena unicolor (D 30), Schizophyllum commune (D 35) and Ganoderma lucidum (D 33). The cyanide degradation activities of P. arcularius S. commune and G. lucidum were found to be more than that of the other fungi examined. The parameters including incubation time, amount of biomass, initial cyanide concentration, temperature, pH and agitation rate were optimized for the selected three potential fungal strains. The maximum cyanide degradation was obtained after 48 h of incubation at 30°C by P. arcularius (T 438). The optimum pH and agitation rate were measured as 10.5 and 150 rev/min, respectively. The amount of biomass was found as 3.0 g for the maximum cyanide biodegradation with an initial cyanide concentration of 100mg/L. In this study, agar was chosen entrapment agent for the immobilization of effective biomass. We suggested that P. arcularius (T 438) could be effective in the treatment of contaminated sites with cyanide due to capability of degrading cyanide.
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ABSTRACT: BACKGROUND: A simple procedure was employed to covalently immobilize a Klebsiella oxytoca hydrolase (SNSM-87) onto epoxy-activated supports of Eupergit C 250L via multipoint covalent attachment. The resultant biocatalyst was explored for the hydrolytic resolution of a variety of (R,S)-2-hydroxycarboxylic acid ethyl esters.RESULTS: With the hydrolytic resolution of (R,S)-ethyl mandelate in biphasic media as the model system, optimal conditions of 55 °C, pH 6 buffer and isooctane as the organic phase were selected for improving the enzyme stability (activity retained from 10% to 50% at 96 h) and enantioselectivity (VSVR−1 value enhanced from 44 to 319) in comparison to the performance of free enzyme. Moreover, the immobilized enzyme retained its activity and enantioselectivity after eight cycles of hydrolysis at 55 °C. When applying the resolution process to other (R,S)-2-hydroxycarboxylic acid ethyl esters, 2.4- to 4.0-fold enhancements of the enantioselectivity in general were obtainable.CONCLUSIONS: The enantioselectivity enhancement, good reusability and easy recovery after reaction indicate that the immobilized SNSM-87 may have the potential as an industrial biocatalyst for the preparation of optically pure 2-hydroxycarboxylic acids. Copyright © 2008 Society of Chemical IndustryJournal of Chemical Technology & Biotechnology 03/2008; 83(11):1518 - 1525. · 2.50 Impact Factor
Article: Bacterial cyanide detoxificationBiotechnology and Bioengineering 02/2004; 17(3):457 - 460. · 3.65 Impact Factor
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ABSTRACT: Pyruvate (Pyr) and a-ketoglutarate (aKg) accumulated when cells of Pseudomonas fluorescens NCIMB 11764 were cultivated on growth-limiting amounts of ammonia or cyanide and were shown to be responsible for the nonenzymatic removal of cyanide from culture fluids as previously reported (J.-L. Chen and D. A. Kunz, FEMS Microbiol. Lett. 156:61-67, 1997). The accumulation of keto acids in the medium paralleled the increase in cyanide-removing activity, with maximal activity (760 mmol of cyanide removed min 21 ml of culture fluid 21 ) being recovered after 72 h of cultivation, at which time the keto acid concentration was 23 mM. The reaction products that formed between the biologically formed keto acids and cyanide were unambiguously identified as the corresponding cyanohydrins by 13 C nuclear magnetic resonance spectroscopy. Both the Pyr and a-Kg cyanohydrins were further metabolized by cell extracts and served also as nitrogenous growth substrates. Radiotracer experiments showed that CO2 (and NH3) were formed as enzymatic conversion products, with the keto acid being regenerated as a coproduct. Evidence that the enzyme responsible for cyanohydrin conversion is cyanide oxygenase, which was shown previously to be required for cyanide utilization, is based on results showing that (i) conversion occurred only when extracts were induced for the enzyme, (ii) conversion was oxygen and reduced-pyridine nucleotide dependent, and (iii) a mutant strain defective in the enzyme was unable to grow when it was provided with the cyanohydrins as a growth substrate. Pyr and aKg were further shown to protect cells from cyanide poisoning, and excretion of the two was directly linked to utilization of cyanide as a growth substrate. The results provide the basis for a new mechanism of cyanide detoxification and assimilation in which keto acids play an essential role. Cyanide is a notorious poison. Its inhibitory effect on respi- ration has been known since the 1920s, when Warburg and Keilin first demonstrated that it combines with trivalent iron in cytochrome oxidase (38, 40, 44). Although highly toxic, it is a normal part of our environment for which mechanisms of bi- ological formation (cyanogenesis) and detoxification exist (8, 22, 42). Cyanide also arises from various industrial practices such as steel coking, electroplating, and mining, but significant accumulations in the environment probably do not occur be- cause of its highly reactive nature (13, 18, 41, 46). The inter- actions between microorganisms and cyanide, however, remain of interest, since the mechanisms of tolerance and assimilation are poorly understood. A number of reports documenting the ability of microorganisms to grow on cyanide have appeared, but the biochemical basis of these abilities has remained largely obscure. Most studies have reported its ability to serve as a nitrogen source only, since at the concentrations needed for it to serve as a carbon source, it is too toxic (15, 24). As far as is known, growth on cyanide requires that it be enzymati- cally converted to ammonia. Once formed it can then be readily incorporated into cellular macromolecules by estab- lished mechanisms (31). Two separate conversions have been described. They are hydrolytic and oxidative conversion, and they yield formic acid and carbon dioxide as reaction by-prod- ucts, respectively. The enzyme responsible for hydrolytic con- version has variously been described as cyanidase, cyanide di- hydratase, or cyanide nitrilase (CNN), and it catalyzes the reaction shown in equation 1.