Abstract
Propionic acid is a platform chemical, antifungal agent and important chemical intermediate. Current industrial production of propionic acid is mainly through petrochemical processes because the conventional method of the propionic acid fermentation is uneconomical due to low product yield, productivity and product concentration caused by end-product inhibition. The coproduction of acetic and succinic acids in the propionic acid fermentation processes also makes downstream processing more complicated and costly. To the best of our knowledge there are several and recent reviews in the available literature on propionic acid fermentation processes and strain improvement techniques, but only a few on product recovery and purification, i.e. downstreaming. However, to realize a biorefinery, where propionic acid is a key intermediate, complex discussion of up-, and downstreaming is required. Therefore in this review a short overview of the whole bio-based propionic acid production process is presented including recent results of both upstream and downstream area. Thus the biosynthetic pathways, the significant results of native and recombinant producer strains as well as product recovery are discussed.
Highlights
Propionic acid is a valuable C-3 platform chemical.propionic acid and its derivatives are used in agriculture, food and pharmaceutical industries, e.g. propionic acid is an important chemical intermediate in the synthesis of herbicides, perfumes, cellulose fibres and pharmaceuticals
Propionic acid titres have been improved by overexpressing enzymes such as glycerol dehydrogenase, malate dehydrogenase [2] and fumarate hydratase in Propionibacterium jensenii, phosphoenolpyruvate carboxylase (PPC) in Propionibacterium freudenreichii, and propionyl-CoA:succinate CoA transferase in Propionibacterium shermanii [8]
5 Conclusions and future developments Fermentation using renewable resources is an attractive alternative route of propionic acid production, commercial production is mostly conducted by chemical synthesis from petroleum feedstocks
Summary
Propionic acid is a valuable C-3 platform chemical. propionic acid and its derivatives are used in agriculture, food and pharmaceutical industries, e.g. propionic acid is an important chemical intermediate in the synthesis of herbicides, perfumes, cellulose fibres and pharmaceuticals. Propionibacteria can be utilized for the growth and product formation of several carbon sources, e.g. glucose, lactose, lactate, xylose, arabinose, glycerol and sorbitol. Propionic acid titres have been improved by overexpressing enzymes such as glycerol dehydrogenase, malate dehydrogenase [2] and fumarate hydratase in Propionibacterium jensenii, phosphoenolpyruvate carboxylase (PPC) in Propionibacterium freudenreichii, and propionyl-CoA:succinate CoA transferase in Propionibacterium shermanii [8]. Compared to the wild type, the mutant expressing the ppc gene grew significantly faster, consumed more glycerol, and produced propionate of a larger final titre at a faster rate, i.e. productivity increased by 46% [29] To eliminate such end-product inhibition, various extractive fermentation processes have been developed to continuously remove propionic acid from the fermentation medium resulting in the product yield increasing by 24% [30]. When glycerol was added after 48 h, the highest product concentration (propionic acid: 42.7 g*L-1), the highest yield (propionic acid: 0.71 g*g-1), and highest productivity (propionic acid: 0.36 g*L-1*h-1) of this experiment were obtained [46]
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