preliminary study on cost-effective l-tryptophan production from indole and l-serine by e. coli cells

background: l-tryptophan is used widespread in the pharmaceutical industry. the majority of l-trp production depends on microbial processes that produce l-tryptophan from indole and l-serine. these processes are very costly due to the costs of precursors, especially l-serine. use of inexpensive substitutions as the l-serine source of l-tryptophan production enables us to reach a cost-effective process. in this paper, effect of triton x-100 on l-trp production and the ability to use iranian cane molasses as inexpensive l-serine source was investigated. methods: escherichia coli (e. coli) atcc 11303 cells were grown in 10-l fermenter containing minimal medium supplemented with beet molasses as an inexpensive carbon source and indole as tryptophan synthase inducer. whole cells of stationary phase were used as biocatalyst for l-trp production. triton x-100 addition to the production medium as indole reservoir was investigated. then, cane molasses was used as l-ser source in l-trp production medium. amount of l-tryptophan and theoretical yield of l-trp production was determined by hplc and by a colorimetrically method on the basis of remaining indole assay, respectively. results: as a result, triton x-100 increased l-trp production three times.  also, the result showed that 0.68 mm l-tryptophan was produced in the presence of cane molasses at 37oc for 8 hr. conclusion: this result showed that cane molasses of qazvin sugar factory includes significant amounts of l-ser that makes it a suitable substitution for l-ser in l-trp production. therefore, it has the potential to be used for cost-effective l-trp production in industrial scale.