Metabolomics of tryptophan by a thermophile Bacillus stearothermophilus

Objective of the work was to study metabolism of tryptophan by thermophilic Bacillus stearothermophilus. Optimum temperature and pH growth parameters were studied at 65 o C. Tryptophan metabolism was studied in shake cultures for 72 hrs. The total extract was purified on a C18‐sep‐pak and resolved on an OV‐101 column using GC/MS. All purified metabolites and their TMSC derivatives were identified by GC complimented with mass spectrometry and LC/MS. The major tryptophan metabolites, identified through MS fragmentation were as follows: 5‐hydroxytryptophan, indole‐3‐carboxylic acid, 5‐hydroxyindole acetic acid, indole acetic acid (IAA), nicotenic acid, o ‐aminohippuric acid, 3‐indole carboxylate, 3‐indole acetamide, 3‐indole lactic acid, 3‐indole pyruvic acid, kynurenine, 3‐hydroxy kynurenine, N‐formyl kynurenine, N‐acetyl kynurenine, quinolinic acid, serotonin, melatonin (serotonin and melatonin were seen as trace amount in biotransformation done at pH 5), N‐acetyl serotonin, and 2‐amino‐3‐oxoprop‐1‐enyl‐fumaric acid (Fig 1). Incubation at pH 7 buffer yielded IAA, serotonin, N‐acetyl serotonin and melatonin at slightly higher yields as biotransformation products. B. stearothermophilus catalyses metabolism of tryptophan through KP pathway. This work was supported by a research grant #SL03/09 offered by RA, Kuwait University, Kuwait, for which the authors are thankful.