en 27920887 <p>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.<br /> Methods: <em>Escherichia coli (E. coli)</em> <em>ATCC 11303</em> 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.<br /> Results: As a result, triton X-100 increased L-Trp production three times.&nbsp; Also, the result showed that 0.68 <em>mM</em> L-Tryptophan was produced in the presence of cane molasses at 37^o<em>C</em> for 8 <em>hr</em>.<br /> 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.</p> Molasses, PLP, Tryptophan synthase, Tryptophanase 188 192 https://www.ajmb.org/En/Article.aspx?id=256 https://www.ajmb.org/PDF/En/FullText/256.pdf TaherehSadeghiyan-RiziDepartment of Pharmaceutical Biotechnology, Faculty of Pharmacy, Isfahan University of Medical Sciences, Isfahan, Iran1043JamshidFooladiNational Laboratory of Industrial Microbiology, Department of Biology, Faculty of Science, Alzahra University, Tehran, Iran1044SimaSadraiDepartment of Pharmaceutics, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran1045