L- Tryptophan Production by Whole Cells of Escherichia coli Based on Iranian Sugar Beet Molasses

Abstract

Background: L-tryptophan (L-Trp) is a nutritionally essential amino acid that the body uses to synthesize proteins, niacin (vitamin B3) and serotonin (neurotransmitters). Human and animals depend on plants and microorganisms for its supply. Remarkable increasing demand has caused the development of a wide variety of biotechnological methods for its production which work as well for other amino acids.Objectives: The present work reports on the use of Iranian sugar beet molasses as an inexpensive source of L-serine (precursor) and PLP (cofactor) for the production of L-Trp by Escherichia coli (ATCC 11303). Carbon source and buffered condition are also optimized for L-Trp production by E. coli.Materials and Methods: E. coli (ATCC 11303) was used as the microbial source of tryptophan. Batch fermentation was performed with 8L sugar beet molasses medium. The fermentation was carried out at 37 °C with an agitation speed at 250 rpm. The pH was controlled at 7 with 10 N NaOH. The cells were recovered by centrifugation. A 1g mass of E. coli cells (wet mass) was used as the biocatalyst in the reaction medium (100 cc) containing (in grams/100cc): Molasses/glucose=3.5; Indole=0.2; L-Serine=0.35; PLP=0.005; (NH4)2SO4 =0.5 The reaction medium was incubated on rotatory shaker (180 rpm) for 8 h at 37 °C. The reaction was carried out in KH2PO4-K2HPO4 buffering system (pH = 8, 0.1 M). The detection of produced L-Trp was carried out by the use of chromatography methods (HPLC and TLC), and fluorescence analysis.Results: Consequently, the potassium phosphate buffer system was considered as the suitably buffered reaction medium. The concentration of L-Trp produced in reaction medium was 0.3 mM and 0.12 mM for glucose and molasses (a combination of sugar beet and cane molasses), respectively.Conclusions: In conclusion, our present study shows that sugar beet molasses is a source of PLP and L-Ser; and hence, suggests the general application of the approach to produce L-Trp more economically

Performance Evaluation of Free-Space Fibre Optic Detection in a Lab-on-Chip for Microorganism

“…These results support the previous research which showed a similar wavelength peak [32]. This outcome is contrary to that of Faghfuri et al who found the wavelength to peak around 620 nm [33]. A graph of the absorbance spectra of different concentrations of S. cerevisiae is shown in Figure 4 3 Journal of Sensors to the trend observed previously for E. coli cells.…”

Rapid Evaluation and Optimization of Medium Components Governing Tryptophan Production by Pediococcus acidilactici TP-6 Isolated from Malaysian Food via Statistical Approaches

“…This is in contrast with the findings of several other studies conducted by other researchers, where the tested carbon sources often possessed a stimulatory effect on the production of amino acid. For instance, molasses was used for the production of tryptophan by C. glutamicum [8]. Furthermore, molasses was reported as the most suitable carbon source for the synthesis of tryptophan by C. glutamicum [10].…”

“…Lim et al [25] had demonstrated the effect of medium containing meat extract, yeast extract and peptone for the production of amino acid by LAB. In comparison, yeast extract was used for the production of tryptophan by E. coli in a study conducted by Faghfuri et al [8]. In addition, Hagino and Nakayama [10] demonstrated that yeast extract was the best organic nitrogen source for tryptophan synthesis by C. glutamicum.…”

“…Previous optimization studies on the production of tryptophan have revolved around the conventional producer strains such as E. coli and Corynebacterium glutamicum. For instances, Faghfuri et al [8] reported that sugar beet molasses was a good source of pyridoxal phosphate (PLP) and serine for tryptophan production by E. coli. Meanwhile, Cheng et al [9] suggested that the growth and tryptophan production of E. coli was inhibited by acetic acid above 2 g/L and glucose concentration should be controlled at low level for tryptophan production.…”

Tryptophan Metabolites: A Microbial Perspective

“…The helix-turn-helix DNA-binding motifs of trp Rencoded tryptophan repressor are exposed to interact with the operator region of the trp promoter, whenever tryptophan is available in the cytoplasm in adequate concentrations. Hence, transcription cannot pass through operator-bound trp repressor, and the operon is repressed in abundant supply of tryptophan (Jayaraman 2011 ;Faghfuri et al 2013 ). The enzyme expression economy of tryptophan operon is further fi ne-tuned by a mechanism called attenuation .…”