The microbial transformation of nitrogen and sulphur containing heterocycles fused to aromatic centres

The microbial degradation of isothiazolin rings was investigated. A mixed culture of bacteria able to utilise the isothiazolin ring containing compound saccharin as a source of carbon and nitrogen was isolated. A single type of bacterium able to utilise saccharin as a source of nitrogen was isolated from the community and identified as an Alcaligenes sp. A second organism able to utilise benzoate as a carbon source was isolated and identified as a Pseudomonas sp. Together the two bacteria were able to utilise saccharin as a source of carbon and nitrogen. The end products ammonia, sulphite, sulphate and catechol were detected during utilisation of saccharin by the Alcaligenes sp. When the Alcaligenes sp. and the Pseudomonas sp. grew in co-culture utilising saccharin as the carbon and nitrogen source the end products ammonia, sulphite and sulphate were detected.;To investigate the cleavage of sulphur-nitrogen bonds sulphamate was used as a nitrogen source for the growth of bacteria. A single type of bacterium was isolated and identified as a Mycobacterium sp. A protein, termed sulphamate hydrolase, was isolated which was able to hydrolyse sulphamate to yield sulphate and ammonia. The protein had a sub-unit molecular mass of 50.8 kDa and a native molecular mass of 286 kDa. Based on this information the protein was presumed to be a hexamer composed of identical sub-units. A relatively high Km value of 26 mM and a low catalytic efficiency value of 413 M-1.s-1 was found which suggests that the enzyme is not ideally suited to the hydrolysis of sulphamate.