An overview of biotechnological production of propionic acid: from upstream to downstream processes

The increasing demand for propionic acid (PA) production and its wide applications in several industries, especially the food industry (as a preservative and satiety inducer), have led to studies on the low-cost biosynthesis of this acid. This paper gives an overview of the biotechnological aspects of PA production and introduces Propionibacterium as the most popular organism for PA production. Moreover, all process variables influencing the production yield, different simple and complex carbon sources, the metabolic pathway of production, engineered mutants with increased productivity, and modified tolerance against high concentrations of acid have been described. Furthermore, possible methods of extraction and analysis of this organic acid, several applied bioreactors, and different culture systems and substrates are introduced. It can be concluded that maximum biomass and PA production may be achieved using metabolically engineered microorganisms and analyzing the most significant factors influencing yield. To date, the maximum reported yield for PA production is 0.973 g·g-1, obtained from Propionibacterium acidipropionici in a three-electrode amperometric culture system in medium containing 0.4 mM cobalt sepulchrate. In addition, the best promising substrate for PA bioproduction may be achieved using glycerol as a carbon source in an extractive continuous fermentation. Simultaneous production of PA and vitamin B12 is suggested, and finally, the limitations of and strategies for competitive microbial production with respect to chemical process from an economical point of view are proposed and presented. Finally, some future trends for bioproduction of PA are suggested.

STUDY ON CULTURE CONDITION OF MARINE VITAMIN B_(12)-PRODUCING BACTERIA / 中国海洋药物

The vitamin B 12 Productivity of 14 marine bacterial strains isolated from the China Sea was determined microbiologically using Escherichia coli 113 3. Tests were made on the culturing media and culture conditions for Vitamin B 12 production. The results showed that the culturing medium in which the extract from soybean cake with seawater and some nutriments were added was suitable to recognize further some marine Vitamin B 12 producing bacterial strains. The medium with appropriate cobalt chloride and some salts added may be useful for Vitamin B 12 biosynthesis. The PH value of the fermentation for the testing strains was raised with the lapse of time for fermentation. A better Vitamin B 12 production may be obtained by keeping the fermentation liquid slightly basic till about 96h. No.2627 strain in all the strains tested showed well in the productivity. The mixed cultivation of some strains (including No.2627 strain) tested often has potentiality and superiority for Vitamin B 12 production.