Effect of Dissolved Oxygen on Continuous Production of Methionine

Abstract

Methionine production by a mutant strain of Corynebacterium lilium was studied at different dilution rates and different dissolved oxygen concentrations, based on a statistical central composite design. The effect of dissolved oxygen levels between 2 % and 60 % and dilution rate levels between 0.04 to 0.29 on continuous production of methionine was studied. The process is described by the Leudeking‐Piret model. The experimentally obtained maxima for methionine and biomass productivities, observed at the same dilution rate of 0.17 h–1, also corresponds to the theoretical prediction based on this model. This experimental observation is further supported by the surface response prediction of a dilution rate of 0.16 h–1 for maximum methionine productivity and 0.15 h–1 for cell mass productivity. Also, beyond the critical value of 30 % dissolved oxygen, the apparent benefits of oxygen transfer become less significant.

Sequential adaptive networks: An ensemble of neural networks for feed forward control of L-methionine production

“…Consequently, the intra-cellular methionine production is strictly regulated at the genetic and enzymatic level via feedback inhibition, repression and dissipative carbon flux into branch pathways . Bioreactor studies with mutant microorganisms also revealed that methionine production is strongly dependent upon and regulated by DO, and residual substrate concentration present in reactor (Kumar et al, 2003;Sharma and Gomes, 2001). Several important characteristics were observed from those reactor studies such as prolonged lag phase, existence of a maximum in the methionine concentration profile, reutilization of methionine below a critical residual substrate concentration and maximum methionine production rate at 40% DO concentration.…”

A model for L‐methionine production describing oxygen–productivity relationship

“…Experimental data is taken from the published work of Gomes et al 10, 13 for modeling the process. A series of continuously stirred tank reactor (CSTR) experiments were carried out to determine the relationship between DO and D on methionine and cell mass productivity.…”

“…1. From the collective results of all CSTR experiments it was established that methionine productivity was highest when the DO was 40% of the saturation value and D was 0.16 h −1 13. Subsequently, batch reactor experiments were performed.…”

“…The main characteristics are extended delay period before the onset of methionine synthesis, existence of a maximum in the methionine concentration profile, a critical residual substrate concentration below which methionine is re‐utilized and a maximum specific growth rate and methionine production rate at 40% dissolved oxygen ( DO ) concentration 8–13. In this paper, the development of an unstructured model for methionine production by a mutant strain of Corynebacterium lilium (M 128) is presented.…”

Toward an era of utilizing methionine overproducing hosts for recombinant protein production inEscherichia coli

“…23,24 Similarly, dissolved oxygen and glucose concentrations in the medium affect methionine biosynthesis. 25,26 Fermentation process conditions that affect methionine biosynthesis in the cell could potentially lead to norleucine incorporation in the recombinant protein when using a methionine overproducing host for recombinant protein production. Alternatively, process conditions that lead to increased biosynthesis of methionine could potentially have an impact on product yields due to a competition for glucose, which is a carbon and energy source in the cell, between pathways that lead to methionine overproduction and product synthesis.…”