Feasibility of propionic acid production by extractive fermentation

Abstract

Production of propionic acid by fermentation is hindered by low productivity and product inhibition. Cell immobilization to increase productivity and extractive fermentation to reduce product inhibition were investigated. Propionic acid concentration in the extractive fermentation was maintained at 13 g•L-1 by concurrent extraction with a Iiquid extractant consisting of 40 % (v/v) Alamine" 304-1 (trilaurylamine) in Witcohol" 85 NF (oleyl alcohol). A final concentration of71 g-L-1 propionic acid was obtained in non extractive mode. Yields of propionic and acetic acids were doubled and higher overall productivities were obtained in the extractive fermentation. The extractant also exhibited selectivity for propionic acid over acetic acid, thus partially purifying the former. In both fermentation modes, productivity was enhanced by cell immobilization in calcium alginate beads. An economie analysis of a modified version of the fermentation based on several favorable assumptions showed that the extractive fermentation can, at best, approach economie feasibility at an annual production of 4.7 x 10 7 kg. For the assumed conditions, the production cost of the propionic acid was US$ 1.16•kg-'; this cost was reduced to US$ 0.94•kg-' when the value of the acetic acid byproduct was included.

Nutraceutical production by propionibacteria

“…Propionic acid is a commodity chemical with uses, amongst others, for grain preservation, as antifungal agent and as herbicide [18,26]. In the food industry, propionic acid and its salts are accepted as preservatives for industrial use in bread manufacture [41].…”

Two-phase partitioning bioreactors in fermentation technology

“…Efforts have also been made towards applying the products partitioning concept to propionic acid fermentation (Gu et al, 1998(Gu et al, , 1999Jin and Yang, 1998). Hollow-fiber membrane extractors were used to prevent direct contact between the organic and the aqueous phases.…”

“…Hollow-fiber membrane extractors were used to prevent direct contact between the organic and the aqueous phases. The solvents used in those studies were ditridecylamine (Jin and Yang, 1998) and trilaurylamine (Gu et al, 1999) diluted in oleyl alcohol.…”

“…The performance of this process has been demonstrated in the continuous operation for more than 1.5 months. It is evident however, that the use of the immobilized cells (Gu et al, 1999) instead of free cells could be advantageous for large-scale operation. Gu et al (1999) evaluated the process of 47 million kg annual production scale with a mixer-settler extractor in place of the hollow fiber modules.…”

“…It is evident however, that the use of the immobilized cells (Gu et al, 1999) instead of free cells could be advantageous for large-scale operation. Gu et al (1999) evaluated the process of 47 million kg annual production scale with a mixer-settler extractor in place of the hollow fiber modules. Their analysis demonstrates that even with favorable assumptions, the process reaches break-even point for the current acid values.…”