Preliminary Study on Cost-Effective L-Tryptophan Production From Indole and L-Serine by E. Coli Cells



Sadeghiyanrizi T¹ ; Fooladi J² ; Sadrai S³ Show Affiliations
Source: Avicenna Journal of Medical Biotechnology Published:2016

Abstract

Background: L-tryptophan is used widespread in the pharmaceutical industry. The majority of L-Trp production depends on microbial processes that produce L-tryptophanfrom 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 Ltryptophan 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 LSer 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 37°C 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. © 2016, Avicenna Journal of Medical Biotechnology. All rights reserved.