Fermentation production ofL-Homoserine byCorynehacterium sp. and its possible use in the preparation of threonine and lysine

Abstract

A mutant Corynebacterium sp. requiring threonine and cultivated for 3 d in a medium containing 15% sucrose, 8% corn-steep and 50 micrograms biotin per litre accumulated 14.5 g L-homoserine per litre. The possibility of fermenting the homoserine obtained for threonine and lysine production was investigated.

Metabolic Fluxes in Corynebacterium glutamicum during Lysine Production with Sucrose as Carbon Source

“…Tracer experiments were carried out in 25-ml baffled shake flasks with 4 ml of minimal medium, which did not contain any threonine, methionine, leucine, or citrate. Three parallel studies with 20 mM [1- 13 C Fru ]sucrose, i.e., sucrose specifically 13 C labeled at carbon 1 of its fructose monomer, 20 mM [1- 13 C Glc ]sucrose, i.e., sucrose specifically 13 C labeled at carbon 1 of its glucose monomer, and 20 mM [ 13 C 6 Fru ]sucrose, i.e., sucrose fully 13 C labeled at all carbons of its fructose monomer, respectively, were carried out. ]sucrose, all with 99% 13 C enrichment, were purchased from Campro Scientific (Veenendaal, The Netherlands).…”

“…The outputs of the correction were mass isotopomer fractions of the carbon skeleton of the analytes (M i,corr ). The total 13 C enrichment of the carbon skeleton of a compound with n carbon atoms, termed summed fractional labeling (SFL) (6), was calculated according to equation 1:…”

“…In each of the experiments, the two monomer units of sucrose, glucose and fructose, had different 13 C enrichment. 13 C enrichment of lysine and trehalose, determined by SFL, therefore provides direct information on the extent to which each of the two monomers was utilized for their synthesis. Based on this, some important basic characteristics of the metabolism of C. glutamicum on sucrose can be investigated.…”

“…Only selected investigations have been based on other substrates such as lactate (2), acetate (1,23), or fructose (4,10). Sucrose, however, has not been studied so far, despite the fact that it is successfully used for production of lysine (11,13), valine (12), homoserine (13), or tryptophan (7) and shows high relevance for all industrial molasses-based production processes with C. glutamicum (8). Sucrose uptake in C. glutamicum occurs via a phosphotransferase system (PTS) whereby sucrose is phosphorylated at the glucose ring into sucrose-6-phosphate, followed by invertase-catalyzed hydrolysis into glucose-6-phosphate and fructose (14).…”

“…For this purpose, 13 C tracer experiments with different substrate labelings were combined with gas chromatography-mass spectrometry (GC-MS) labeling measurement of secreted metabolites, metabolite balancing, and isotopomer modeling.…”