Effects of Process Variables on Fed-Batch Production of Propionic Acid

Abstract

© 2016 Wiley Periodicals, Inc. Plackett–Burman design in 12 treatments was used to evaluate the impact of 11 process variables on microbial production of propionic acid in fed-batch fermentation. Fermentation process took place in 3 L fermentor using basal medium and sugarcane molasses as a carbon source. The amounts of produced propionic acid were measured with an HPLC system. Statistical analysis of the results showed that while temperature was the most effective factor; all process variables had significant impact on the production of propionic acid. The highest concentration of propionic acid obtained was 6.66 ± 0.32 g/L. According to coefficient factor the most suitable condition of fermentation is combination of 30C, pH = 6.5, 45 g/l sugarcane molasses, addition of 10 g/l yeast extract, 96 h fermentation, using a mixture of P. freudenreichii and L. acidophilus with inoculum volume of 5% (v/v), and intermittent feeding of milk at a rate of 0.03 l/h. Practical Applications: Prevalence of overweight and obesity has been increasing in recent decades and it has incited food producers to develop products that can enhance satiety signals. Since propionic acid has satiety properties (by simulating the secretion of intestinal peptide YY, an appetite suppressant, and delaying gastric emptying) and P. freudenreichii and L. acidophilus have healthy properties (simulating growth of Bifidobacterium, boosting the immune system, increasing the absorption of iron and calcium) as probiotic bacteria, it could be expected to achieve a dairy fermented product (by using milk as a carbon source), which may potentially provide beneficial health effects and could possibly be used for the commercial production of a functional beverage to help induce satiety. Production of propionic acid in food and beverage may lead to prolonged shelf life because of ability of acid to inhibit microbial growth. In addition to nutritional enrichment and possible satiety effect, considering the antifungal properties of propionic acid, produced dairy product in this research has a natural preservative with no necessary to use any chemical preservatives, such as sorbate.