• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1518-1522
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• 2012

Leuconostoc mesenteroides is a heterofermentative Grampositive bacterium that plays key roles in fermentation of foods such as kimchi, sauerkraut, and milk, leading to the production of various organic acids and aromatic compounds. To study the microbiological and genomic characteristics of L. mesenteroides, we have developed a new chemically defined minimal medium by using the single omission technique. During the exponential cell growth, this species required glutamine, methionine, valine, and nicotinic acid as essential nutrients and 8 amino acids (arginine, cysteine, histidine, leucine, phenylalanine, proline, threonine, and tryptophan), 5 vitamins (ascorbic acid, folic acid, inosine, calcium panthothenate, and thiamine), and others (manganese, magnesium, adenine, uracil, and Tween 80) as supplemental nutrients. This medium is useful to study the metabolic characteristics of L. mesenteroides and to explain its role in food fermentation.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1653-1658
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• 2012

We have reported previously that a recombinant Escherichia coli co-expresses aminolevulinic acid (ALA) synthase, an NADP-dependent malic enzyme, and a dicarboxylate transporter-produced heme, an iron-chelated porphyrin, in a succinate-containing complex medium. To develop an industrially plausible process, a chemically defined medium was formulated based on M9 minimal medium. Heme synthesis was enhanced by adding sodium bicarbonate, which strengthened the C4 metabolism required for the precursor metabolite, although a pH change discouraged cell growth. Increasing the medium pH buffering capacity (100mM phosphate buffer) and adding sodium bicarbonate enabled the recombinant E. coli to produce heme at rates 60% greater than those in M9 minimal medium. Adding growth factors (1 mg/l thiamin, 0.01 mg/l biotin, 5 mg/l nicotinic acid, 1 mg/l pantothenic acid, and 1.4 mg/l cobalamin) also induced positive heme production effects at levels twice of heme production in M9-based medium. Porphyrin derivatives and heme were found in the chemically defined medium, and their presence was confirmed by liquid chromatography/mass spectroscopy (LC/MS). The formulated medium allowed for the production of $0.6{\mu}M$ heme, $29{\mu}M$ ALA, $0.07{\mu}M$ coproporphyrin I, $0.21{\mu}M$ coproporphyrin III, and $0.23{\mu}M$ uroporphyrin in a 3 L pH-controlled culture.

• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.90-96
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• 2004

A synthetic defined medium, fortified with amino acids, was developed for the stable production of the kringle fragments of human apolipoprotein(a) (apo(a)), rhLK68. Using a complex rich medium containing yeast extract and a high-cell-density fed-batch culture, the expression level of rhLK68 reached 17% of the total cellular protein, which corresponded to $5\;g\;l^{-1}$ of the culture. To replace the complex media with chemically defined media, several amino acids that positively affect cell growth and gene expression were chosen by a statistical method. The various combinations of the selected amino acids were tested for its fortifying effect on a minimal defined medium. When glutamine only was added, the overall expression level of rhLK68 reached 93% of the complex rich medium increasing the specific expression level by 22.4% and decreasing the cell growth by 24%. Moreover, the addition of glutamine resulted in a 2-fold increase in the concentration of rhLK68 in the culture broth, compared with the minimal defined medium. The synthetic defined media developed in this study could be generally applied to high-cell-density cultures of the recombinant Escherichia coli BL21(DE3), especially for the production of therapeutic proteins that require a strict quality control of the culture media and fermentation processes.

• KSBB Journal
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• v.6 no.1
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• pp.69-77
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• 1991

When S. fradiae was cultured in S medium, it stavted to produce neomycin in the middle of stationary phase of growth. Antibitoic production is regulated not only by glucose but also by metabolites formed from glucose. A chemically defined minimal salt broth was developen for the study of metabolites activating produition of antibiotic in a neomycin producer. When growth and production or antibiotic in minimal salt broth was examined with a full grown or a vefctativc mycelium, the medium was found not to be good for the growth, but to be good enough for the production of antibiotic with a full grown mycelium. When many carbotlydrates, organic acids, or alcohol were supplmented with instead of glucose in the medium suspcndcn with a full grown mycelium, the amount of antibiotic produced in the medium containing fumaratc was 5 times more than that in the medium with glucose. Further study indicated that the medium is not good also for the growth but good for the production of antibiotic. The antibiotic produced in this medium was identified to be neomycin. The activation of the production of neomycin by fumarate was further confirmed in a complex medium. Fuinarate is suspected to initiate and to activate the biosynthesis of neomycin at the gene level.