Leaching of petroleum refinery ash by acidophilic sulfur-oxidizing microbial cultures.

Sulfur-oxidising acidophilic bacteria were obtained from weathered sulfur piles produced by a petroleum refinery. When grown on commercial sulfur the yield was 10(10)cell/g S. Sulfur conversion to sulfate was about 95% after 17 days. Cultures were also grown together with ash obtained from incinerated refinery sludge, which contained high amounts of iron. Cultures grown in ash plus sulfur gave somewhat higher values for the growth parameters (Y=1.6 x10(10)cell/g S). The sulfur conversion was about 70% (after 17 days) and more than 90% of the iron present in the ash was also leached. The sulfur-reduced compound thiosulfate, determined using ion pair HPLC, was found in the presence and absence of ash although the profile was different in each case. Sulfite was only found in non-ash containing cultures, whereas tetrathionate was only formed in the presence of ash. These results are discussed with reference to the substrates used by the micro-organisms.

Use of laccase together with redox mediators to decolourize Remazol Brilliant Blue R.

A pure fungal laccase, obtained from a commercial formulation used in the textile industry, did not decolourize Remazol Brilliant Blue R (RBBR). Decolourization was only observed when a small molecular weight redox mediator was added together with the laccase. Under the conditions specified, violuric acid (5.7 mM) was the most effective mediator studied and almost complete decolourization was observed within 20 min. In contrast, 1-hydroxybenzotriazole (HOBT, 11 mM) decolourized RBBR at about a two-fold slower rate and to a lesser extent. Also, higher concentrations of HOBT were inhibitory which could be due to inactivation of laccase by the toxic HOBT radical. The commercial laccase formulation that contained phenothiazine-10-propionic acid as the mediator was least effective, giving 30% decolourization under equivalent conditions. We suggest that similar laccase plus mediator systems could be used for the detoxification of related anthraquinone textile dyes.

Decolorization of an anthraquinone-type dye using a laccase formulation.

Decolorization of the dye Remazol Brilliant Blue R (RBBR) was studied, as it is representative of an important class of recalcitrant anthraquinone-type dyes. For this purpose a commercial laccase formulation (CLF) containing laccase, a redox mediator and a non-ionic surfactant was used. Small molecular weight components were removed from the CLF by gel filtration, which made it possible to compare the effect of its laccase alone. Apart from slightly better thermostability of the CLF as compared with the laccase alone, the pH and temperature profiles were similar regardless of the presence of the small molecular weight components. The laccase alone did not decolorize RBBR. A small molecular weight redox mediator (HBT) was necessary for decolorization to occur. A comparison of the kinetics of RBBR decolorization using the CLF and its laccase alone is reported. Provided that a redox mediator is included, it is suggested that laccase may be suitable for the wastewater treatment of similar anthraquinone dyes.

Electroelution as a simple and fast protein purification method: isolation of an extracellular xylanase from Bacillus sp. CCMI 966.

An efficient and simple modified method of electroelution is described that can be used as a time-saving method for eluting multiple protein bands. Provided that the proteins are highly expressed, they can be purified rapidly and without requiring any prior knowledge of the protein characteristics. A xylanase excreted by Bacillus sp. CCMI 966 was purified directly from the polyacrylamide gel. Some of the properties of this enzyme are presented. It had an unusually apparent high molecular mass of 340kDa, as determined by native PAGE. The specific activity of the purified xylanase was 137 U/mg.

Identification and characterization of a new and distinct molecular subtype of human T-cell lymphotropic virus type 2.

Molecular studies have demonstrated the existence of at least two major subtypes of human T-cell lymphotropic virus type 2 (HTLV-2), designated HTLV-2a and HTLV-2b. To further investigate the heterogeneity of this family of viruses, we have characterized the HTLV-2 subtypes present in several urban areas in Brazil. DNAs from peripheral blood mononuclear cells of a large number of infected individuals, the majority of whom were intravenous drug abusers, were analyzed by using PCR with restriction fragment length polymorphism and nucleotide sequencing analysis. Restriction fragment length polymorphism analysis of the env region suggested that all individuals were infected with the HTLV-2a subtype, and this was confirmed by nucleotide sequence analysis. In contrast, nucleotide sequence analysis of the long terminal repeat demonstrated that although the viruses were more related to the HTLV-2a than to the HTLV-2b subtype, they clustered in a distinct phylogenetic group, suggesting that they may represent a new and distinct molecular subtype of HTLV-2. This conclusion was supported by nucleotide sequence analysis of the pX region, which demonstrated that the Tax proteins of the Brazilian viruses differed from that of prototype HTLV-2a isolates but were more similar to that of HTLV-2b in that they would be expected to have an additional 25 amino acids at the carboxy terminus. In transient expression assays, the extended Tax protein of the prototype HTLV-2a subtype. The studies suggest that the Brazilian viruses analyzed in this study, while being phylogenetically related to the prototypic HTLV-2a seen in North America, are phenotypically more related to HTLV-2b and can be justifiably classified as a new molecular subtype, which has been tentatively designated HTLV-2c.

Xylanolytic enzyme production by an Aspergillus niger isolate.

Production of xylanolytic enzymes by an Aspergillus niger CCMI 850 isolate was investigated in batch cultures. The effect of the composition of a fermentation medium that did not include chemical inducers, on beta-xylanase, beta-xylosidase, alpha-L-arabinofuranosidase, and total cellulase activity was studied. With 4% xylan as the carbon source, about 65 U/mL of beta-xylanase was obtained, whereas the total cellulase activity was undetectable, under the specified conditions. This beta-xylanase activity represents the highest reported for a wild-type strain of A. niger. The effect of pH and temperature on the activity of beta-xylanase was studied. Partial characterization of the beta-xylanase showed that with insoluble birchwood as substrate the Km and Vmax were 0.3 mM and 19 mumol/min, respectively. Aspects of using the crude beta-xylanase preparation for applications in the pulp and paper industry were discussed.

Aspergilli and lignocellulosics: enzymology and biotechnological applications.

Aspergilli are versatile ascomycetes that are able to transform at a rapid rate a wide spectrum of lignin-related aromatic compounds. While it is clear that these fungi can degrade phenolic and polysaccharide components from lignocellulosic material, the status regarding degradation of high-molecular mass lignins is controversial. This review compiles data from the literature as well as that from the authors' laboratory with the aim of clarifying this point. The main body of evidence points towards the inability of aspergilli alone to degrade lignin free of low-molecular mass contaminants. Nevertheless, the ability of this genus to efficiently degrade hemicelluloses makes it an essential participant in the complex microbial system necessary for wood decay under natural conditions. Aspergilli are known to overproduce high levels of hemicellulolytic enzymes. Out of the large array of these enzymes that act in concert to degrade lignocellulosic material, only endoxylanases of aspergilli are described in so far as these are the main activities required for enzyme-aided bleaching. The biochemical features of the endoxylanases from Aspergillus niger are briefly described as these serve to illustrate how a complex family of isozymes is necessary to deal with the structural and chemical heterogeneity of xylans. Emphasis is placed on the biotechnological applications of lignocellulosic materials transformed by aspergilli. The key application areas are biopulping and biobleaching where a reduction in the use of environmentally harmful chemicals traditionally used in the pulp and paper industry is envisaged. Waste water treatment represents another vast application area where aspergilli have been shown to be effective not only in colour removal but also in the bioconversion of potentially noxious substances into useful bioproducts.