Top 2 Vitamins Produced by Microbial Fermentation

The following points highlight the top two vitamins produced by microbial fermentation. The vitamins are: 1. Vitamin B₁₂ 2. Vitamin B₂.

1. Vitamin B₁₂ (Cyanocobalamine; Cobalbumin):

This vitamin is recovered as a by-product of streptomycin and aureomycin antibiotic fermentations. A soluble cobalt salt is added to the fermentation reaction as a precursor to vitamin B₁₂. Relatively high amounts of this vitamin accumulate in the microbial fermentation medium at concentrations that are not toxic to Streptomyces species.

Vitamin B₁₂ (Cyanocobalamine) is also produced on large scale by direct microbial fermentation. Propionibacterium shermanii or Pseudomonas denitrificans are the bacteria which are used now-a-days for fermentation processes. P. shermanii is grown in anaerobic culture for 3 days at 30°C and in aerobic culture for 4 days; the fermentation medium (growth medium) contains glucose, corn steep liquor (a waste product of starch manufacture), ammonia and cobalt chloride.

Ammonia is used in the form of ammonia hydroxide that maintains the pH of the medium at 7. Pseudomonas denitrificans is grown for 2 days in aerobic culture medium containing sucrose, betaine, glutamic acid, cobalt chloride, 5, 6 dimethylbenzimidazol, and salts.

The vitamin resulted in the microbial fermentation are retained within the cells. The cells are, therefore, collected by high-speed centrifugation and the vitamin B₁₂ is recovered by releasing the vitamin from the cells by treating with acid, heating, cyanide, etc.

The vitamin thus released from the cell is absorbed on ion-exchange resin IRC- 50 or charcoal. It is then purified further by phenol and water. The vitamin is finally crystallized from aqueous- acetone solutions. The normal yield is 23 mg/litre when Propionibacterium is used.

2. Vitamin B₂ (Riboflavin):

Riboflavin (vitamin B₂) is recovered as a by-product of acetone butanol fermentation and is produced by various Clostridium species. But, these are Eremothecium ashbyii and Ashbya gossypii, the yeasts, that are used to commercially produce this vitamin by direct microbial fermentation. The requirement nutrient medium (growth medium) for fermentation contains glucose, corn oil, soyoil, and glycine.

When Ashbya gossypii is used, the fermentation is normally carried out for 4-6 days at 36°C in aerobic conditions, and at pH 6-7.5. The recovery of the vitamin is at the rate of 4.25 g/litre. Later on, the yeast cells are recovered and used as a feed supplement for domestic animals to supply riboflavin required by them.