No abstract

A multi-faceted screening programme was designed to search for the oxidases, laccase, peroxidase and tyrosinase. Actinobacteria were selectively isolated from the paunch and colon region of the hindguts of the higher termite, Amitermes hastatus. The isolates were subjected to solid media assays (dye decolourization, melanin production and the utilization of indulin AT as sole carbon source) and liquid media assays. Eleven of the 39 strains had the ability to decolourize the dye RBBR, an indicator for the production of peroxidases in actinobacteria. Melanin production on ISP6 and ISP7 agar plates served as a good indicator for laccase and/or tyrosinase production and the ability of the strains to grow in the presence of indulin AT as a sole carbon source served as a good indicator of lignin peroxidase and/or general peroxidase production. Enzyme-producing strains were cultivated in liquid media and extracellular enzyme activities measured. Strains with the ability to produce oxidative enzymes under the conditions tested were identified to genus level by 16S rRNA gene analysis and compared to known oxidase producers. A strong relationship was observed between the environment sampled (termite guts where lignocellulose degradation occurs) and the dominant type of oxidative enzyme activity detected (laccases and peroxidases), which suggests the possibility of future targeted screening protocols linking the physical properties of the target enzymes with specific operational conditions required, such as lignocellulosic degradation in the preparation of biofuel feedstocks.

As part of an enzyme-screening programme, an actinobacterium, strain HSM#10 T , was isolated from a sample collected from the base of a translucent quartz rock in Miers Valley, eastern Antarctica. The isolate produced branching vegetative mycelium that was characteristic of filamentous actinobacteria. The chemotaxonomic characteristics of the strain suggested that HSM#10 T should be classified as a member of the genus Streptomyces. Furthermore, phylogenetic analysis based on 16S rRNA gene sequences showed that the strain was closely related to members of the genus Streptomyces, which supports the classification of this strain within the family Streptomycetaceae. Phenotypic and phylogenetic results allowed strain HSM # 10 T to be differentiated from known streptomycetes. DNA-DNA hybridization data also showed that strain HSM#10 T could be differentiated from its nearest phylogenetic neighbours Streptomyces chryseus DSM 40420 T (53.55±3.15 % DNA relatedness), Streptomyces helvaticus DSM 40431 T (38.75±2.75 %), Streptomyces flavidovirens DSM 40150 T (30.7±2.90 %) and Streptomyces albidochromogenes DSM 41800 T (33.9±0.10 %). Therefore, the name Streptomyces hypolithicus sp. nov. is proposed, with HSM # 10 T (5DSM 41950 T 5NRRL B-24669 T ) as the type strain.

Actinomycetes are a ubiquitous group of bacteria, and are hypothesised to produce tyrosinases for protection against the potential toxic effect of phenolic compounds and for the production of melanin. In this study, tyrosinase production by Streptomyces pharetrae CZA14 T (CZA14Tyr) andStreptomyces polyantibioticus SPR T (SPRTyr) was optimised. The enzymes were partially 1 purified and biochemically characterised to determine their suitability for industrial applications.SPRTyr was stable up to 40°C and at pH 4.5-10.0, while CZA14Tyr was stable up to 40°C and at pH 6.5-10.0. The enzymes showed variable stability in the presence of water-miscible organic solvents and were able to oxidize L-DOPA in the presence of these solvents. A limited inhibitory effect was observed with arbutin, EDTA, sodium chloride and sodium dodecyl sulphate, while both enzymes were strongly inhibited by the reducing agents used in this study. showing potential for application in the food industry and for the production of biomaterials.