Abstract
The production of propionic acid using skim serum by-products of the dairy industry was investigated, and the influence of inoculum concentration of Propionibacterium freudenreichii PS-1 and its time of inoculation for the production of propionic acid was evaluated using mixed culture of Lactobacillus helveticus and Propionibacterium freudenreichii . Initially, the adjustment of propionic bacteria to higher concentrations of propionic acid was tested and kinetic parameters were determined for growth. A central composite rotational design (CCRD) with 11 experiments was carried out, using different inoculum concentrations of P. freudenreichii , which were added to the cultures of lactic bacteria at different times. The maximum specific growth rate for P. freudenreichii decreased from 0.11 to 0.03 hour -1 and the growth time increased from 32h to 100h when concentration of propionic acid in lactate broth increased to 0.25%. The best result for propionic acid production was 3.78 g L -1 , inoculating 5.10 8 CFU mL -1 of propionic bacteria after 6 h. For lactose consumption, the best conditions were inoculum concentration above 5.10 8 CFU mL -1 and inoculation time of P. freudenreichii after 6 hours. Therefore, it was demonstrated that skimmed whey can be used as a renewable, low-cost raw material for propionic acid production by mixed culture.
Highlights
Cheese production is an important economic activity in Brazil and reached 1.105 million tons, according to estimates by the Brazilian Association of Cheese Industries (Associação Brasileira das Indústrias de Queijo [Abiq], 2015)
One possibility is its use in the propionic fermentation, wherein lactose and lactate whey can be converted to propionic acid by propionic bacteria (Kośmider, Drożdżyńska, Blaszka, Leja, & Czaczyk, 2010)
It was noted that cell growth of propionic bacteria in conditions of 0.25 % m v-1 of propionic acid showed a much greater lag phase and a maximum specific growth rate much smaller (0.00277 hour-1) than in the other cultures with lower concentrations of propionic acid, especially in cultures with lactate broth alone, which had only 14 hour of lag phase and μmax equal to 0.1137 hour-1
Summary
Cheese production is an important economic activity in Brazil and reached 1.105 million tons, according to estimates by the Brazilian Association of Cheese Industries (Associação Brasileira das Indústrias de Queijo [Abiq], 2015). The main by-product of the dairy industry, has aroused the interest of many researchers around the world because of its nutritional and functional capability (Jankowska, Chwiałkowska, Stodolny, & Oleskowicz-Popiel, 2015). Several studies have been conducted to develop new products in order to use whey, since the problem faced by the dairy industry worldwide is that only part of the whey produced is used, the rest is discarded as effluent because of the high cost and difficulty in processing it (Magalhães et al, 2011), despite its high nutritional value. The propionic bacteria are gram-positive, facultative anaerobic, non-spore forming bacteria that have long been used in the production of Swiss-type cheese and recently recognized for their probiotic properties for human consumption (Thierry et al, 2011).many studies had demonstrated that propionic acid could be efficiently produced through the fermentation with Propionibacterium species (Zhu et al, 2012, Wang & Yang, 2013)
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