Identification and methionine analog tolerance of environmental bacterial isolates selected on methionine analog containing medium

Abstract

Methionine is the first limiting amino acid in poultry feed. Currently, methionine supplement is synthesized from an expensive chemical process requiring hazardous chemicals. Therefore, the objectives of this study were isolation of methionine producing bacteria from environmental samples and quantification of methionine production in these isolated bacteria. MCGC medium was selected as the isolation medium for methionine-producing bacteria by using Corynebacterium glutamicum ATCC13032 and Escherichia coli ATCC23798 as the positive and negative controls, respectively. Thirty-nine bacterial strains were obtained from environmental samples. Only strains A121, A122, A151 and A181 were able to tolerate up to 0.1% (w/v) of ethionine or norleucine. These isolated strains were identified by sequencing small subunit rRNA genes. The results revealed that bacterial strains A121, A122, A151and A181 were Klebsiella species, Acinetobacter baumannii, A. baumannii and Pseudomonas aeruginosa, respectively. When methionine production in strains A121 and A181 was quantitated, strains A121 and A181 generated methionine up to 31.1 and 124.6 μg/ml, respectively.