L-Phenylalanine and L-Tyrosine Catabolism by Thermophilic Geobacillus stearothermophilus

Aims: This study investigated the potential of soil thermophile Geobacillus stearothermophilus for the biotransformation of phenylalanine and tyrosine.

Study Design: G. Stearothermopilus grows well at 65ºC and has a good potential for transformation and biodegradation of many compounds including steroids, bile acids, tryptophan and other compounds. In this study G. stearothermophilus was harvested at mid-log phase at 65ºC, on tryptone yeast extract (TYE) medium. Cells were collected by centrifugation under aseptic conditions, washed with sterile water and suspended in phosphate buffer with phenylalanine or tyrosine as sole source of carbon at 65ºC. Metabolic parameters were optimized for optimal growth of the organism utilizing aromatic amino acids as an exclusive source of carbon.

Methodology: The amino acid metabolites were exhaustively extracted with methanol from freeze dried broth. The concentrated pooled extracts were analyzed by thin layer chromatography (TLC) using polar solvent systems and purification of the extracts was achieved on preparative tlc plates and GC separations. The molecular structures of purified metabolites were established through spectral data.

Results: Sixteen metabolites of phenylalainine and seventeen metabolites of tyrosine were identified in this study. Tyrosine metabolism extensively produced melanin pigments that caused hitches in the purification of tyrosine metabolites. Tyr metabolites were analyzed in cells cultured for short time.

Conclusion: Our data suggest that G. stearothermophilus has a good potential to metabolize aromatic amino acids yielding hydroxylated, deaminated, decarboxylated and many other products. Oxidative metabolism of phenylalanine and tyrosine by a thermophilic G. stearothermophilus is being reported for the first time.