Lab Scale Production of Fermented Dairy Beverage Containing Vitamin B12 in Fed Batch System

Propionibacterium is capable of producing important industrial products such as propionic acid, vitamin B12 and bacteriocin. They have also probiotic benefits and growth factors for the intestinal useful bacteria. The goal of this research was evaluation of the influence of process variables on vitamin B12 production in fed-batch fermentation of a dairy beverage containing propionic acid by Propionibacterium freudenreichii ssp. shermanii. Fermentation was conducted in a 3-L fermentor containing base medium and molasses as the carbon source to which the feeding was added after 36 hours. Sampling was done for biomass and vitamin measurements in 24 h intervals. The content of dry biomass and vitamin B12 was measured by freeze drying method and HPLC, respectively. Statistical analysis of the results showed that all process variables had significant effect on the response of the system (P<0.05). The final concentration of vitamin B12 (30 mg/L) and productivity (7.5 mg/L.h) was obtained from Treatment 9 while the condition of this treatment was the best. In this research, inocula and their volume as well as feeding had no significant impact on the productivity of vitamin B12 fermentation (P>0.05). Type of nitrogen source and feeding strategy were the most significant factors in this research, so using corn steep liquor and lactose significantly increased vitamin B12 production. The best conditions for vitamin B12 production include: 30 °C, pH=6.5, 25 g/L molasses, 10 g/L corn steep liquor instead of yeast extract, 96 h fermentation, using Propionibacterium freudenreichii with 5% v/v, and continuous feeding of lactose by 0.04 L/h rate. The results showed that the highest level of vitamin B12 was at concentration of 30 mg/L, production yield of 14.48 mg/g, and productivity of 7.5 mg/L.day.