Sahar Parchizadeh - Department of Biochemistry, Payame Noor University of Isfahan, Iran
Mohammad Fazilati - Department of Biochemistry, Payame Noor University of Isfahan, Iran
Hossein Salavati - Department of chemistry, ayame Noor University of Isfahan, Iran
Behrooz Salehi-Eskandari - Department of Biology, Payame Noor University of Isfahan, Iran.
Habibollah Nazem - Department of Biochemistry, Payame Noor University of Isfahan, Iran

Propionibacterium freudenreichii is a gram-positive bacterium that plays a key role in the production of vitamin B۱۲.The aim of this study was to investigate the effect of folic acid and methionine in the aerobic and anaerobic phases on the optimal production of vitamin B۱۲ and bacterial dry cell weight (DCW). The bacteria were inoculated into the fermentation medium containing corn. After incubation, methionine ۰/۰۵ ٪ (v / w) and four different concentrations of folic acid (۰.۲۵۰, ۷۵۰ and ۱۰۰۰ mg/l) were added to the culture media. The bacteria were then placed under anaerobic and aerobic conditions. Also, in order to study the thermal stress, bacteria were cultured at different temperatures (۵۰ ۴۰ ۴۰, ۴۰, ۳۰, ۲۵ º C) and their absorption was measured at ۶۰۰ nm. Vitamin B۱۲ production was assessed using HPLC under anaerobic and aerobic conditions. B۱۲ production increased in the presence of methionine, in comparison with the absence of methionine (۰.۰۵ mg/l) and at a concentration of ۷۵۰ mg/l of folic acid under anaerobic conditions (۶.۲ mg/l). Bacterial dry weight decreased with increasing folic acid concentration, which indicates the negative effect of folic acid on bacterial growth. It seems that the addition of folic acid in appropriate concentration (۷۵۰ mg/l), in the presence of methionine and under aerobic conditions can lead to the highest production of vitamin B۱۲ (۶.۹ mg/l). The optimum temperature for bacterial growth was ۲۵-۴۰ ° C, so that with increasing temperature to ۵۰ ° C, bacterial mass growth decreased. The production of this vitamin using chemical methods is difficult and expensiveby adding folic acid at the right concentration, the aerobic phase and methionine to the bacterial culture medium can increase B۱۲ production and achieve a way to economically and commercially produce this vitamin.

Dry cell weight (DCW(, High-performance liquid chromatography (HPLC)