Abstract
This study aimed to investigate the cysteine production capacities of microbial strains isolated from the environment (mainly soil). In total, 262 bacterial colonies were isolated from 47 soil samples collected from 7 different locations. Isolated bacterial colonies were first grown in tryptic soy broth to determine their cysteine production capacity. The amounts of cysteine produced by isolated bacteria varied from 0.3 to 2.0 g.L-1. Five out of 262 isolates produced a significant amount of cysteine. Based on 16S rRNA gene sequence analysis using the BLAST (basic local alignment search tool) database., the highest cysteine-producing strain was identified as Bacillus sp. strain CG1. Cysteine production potential was evaluated by adjusting the growth medium composition as well as incubations conditions. Sixteen different chemical compositions of growth media were evaluated. The incubation parameters adjusted to produce cysteine were temperature, pH, time, and agitation speed. The highest cysteine yield was 4.24 ± 0.47 g.L-1 under growth conditions of pH 7.5, 175 rpm, and 40 ℃ at 84 h. The recovery efficiency was found to be around 65% using an ion-exchange resin adsorbent.