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Browsing by Author "Ishchenko, Tatiana"

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  • Ishchenko, Tatiana (2014)
    Propionibacterium freudenreichii is commonly known as a Swiss-type cheese ripening culture, and is also frequently applied in the industrial production of vitamin B12 (cobalamin). One way to increase vitamin B12 productivity is the supplementation of medium with 5,6-dimethylbenzimidazole (DMBI), the lower ligand of cobalamin. The aim of this thesis was to investigate the effect of exogenous DMBI on vitamin B12 synthesis and protein production in type strain of P. freudenreichii ssp. freudenreichii. Results showed that DMBI supplementation improved cobalamin production 2.7- and 2.0-fold in cultures grown in anaerobic and two-step processes, respectively. Two-step incubation enabled the achievement of significantly higher levels of cobalamin both in the absence and presence of DMBI. The highest cobalamin level of 0.6 ?g/ml was achieved by the combination of DMBI supplementation with the two-step process. Proteome maps displayed 474 protein spots which is less than 20% of P. freudenreichii predicted proteome. No significant differences in protein production were found between cultures grown in the absence and presence of DMBI. Only two protein spots were more abundant in presence of DMBI and four spots showed higher abundance in absence of DMBI. None of detected proteins from these spots were found to be directly involved in cobalamin biosynthesis.