Optimization of L-Tryptophan Biosynthesis From L-Serine of Processed Iranian Beet and Cane Molasses and Indole by Induced Escherichia coli ATCC 11303 Cells

Abstract

Background:L-tryptophan is an important ingredient in medicines, especially in neuromedicines such as antidepressants. Many commercial processes employ various microorganisms with high tryptophan synthase activity to produce L-tryptophan from indole and L-serine, but these processes are very costly due to the costs of precursors, especially L-serine.Objectives:For this reason, we studied the ability to use processed Iranian cane and beet molasses as L-serine sources for L-tryptophan production, which enables us to reach a cost-effective process.Materials and Methods:Whole cells of Escherichia coli ATCC 11303 were induced for L-tryptophan synthase by addition of indole to the growth medium and bacterial cells harvested from the growth medium were used as biocatalysts in the production medium. Conditions of the production medium were optimized and Iranian cane and beet molasses were processed by solvent extraction with ethanol and n-butanol and used as L-serine sources of the production medium. Amount of L-tryptophan and theoretical yield of L-tryptophan production were determined by High Performance Liquid Chromatography and by a colorimetrical method on the basis of the remaining indole assay, respectively.Results:L-tryptophan production increased by 15 folds, when indole was used as an inducer. L-tryptophan was produced from processed Iranian beet molasses in satisfactory amounts (0.53 mM) and no exogenous pyridoxal phosphate was required as a cofactor under our experimental conditions.Conclusions:The obtained results proved that Iranian beet molasses include significant amounts of L-serine that makes them a suitable substitution for L-serine. Findings of the present study give impetus to use of Iranian beet molasses for cost-effective L-Trp production in the amino acid industry.

Probiotic potentials of the silkworm gut symbiont Enterococcus casseliflavus ECB140, a promising L-tryptophan producer living inside the host

“…This also gives the possibility of further L‐tryptophan research into improving yields and reducing production costs. The glycolysis pathway and shikimate pathway have been previously reported as the main pathways to produce precursors for L‐tryptophan synthesis from glucose or sucrose in E. coli ATCC 11303 (Sadeghiyan‐Rizi et al, 2014) and Corynebacterium glutamicum (Ikeda & Katsumata, 1999). ECB140 uses phosphoenolpyruvate (PEP) as an intermediate, which can be formed from the glycolysis pathway (Figure 6).…”

A Study on Escherichia Coli Isolated from Urogenital Tract Infections, Emphasizing their Occurrence and Antibiograms

“…Indole Test: Indole test is used to identifythe organisms capable of tryptophan production. When these tryptophan producers are incubated in a medium containing tryptophan (aminoacid), they degrade it and covert it into a compound named, indole [13]. This conversion is indicated when is addition of Kovac's or Ehrlich's reagentwas done in the medium and reaction of 4 (p)dimethylaminobenzaldehyde take place with indoleandyields a red colouredcompound.Indole test plays a significant role in the differentiation ofEnterobacteriaceae and other genera.…”