Improving the drying of Propionibacterium freudenreichii starter cultures

Abstract

Propionibacterium freudenreichii is a beneficial food-grade actinobacterium, widely implemented, and thus consumed, in various food products. As the main application, P. freudenreichii is used as a cheese-ripening starter, mostly in hard type cheeses. Indeed, during manufacture of "Swiss-type" cheeses (or opened-body cheeses), the technological process favors propionibacteria growth, as well as the corresponding propionic fermentation. This leads to the characteristic flavor of these cheeses, through the release of short chain fatty acids and through lipolysis, as well as to their specific texture. To fulfil this ripening, massive amounts of propionibacteria are industrially produced, dried and stored, prior to cheese making. Furthermore, P. freudenreichii is commercialized in various probiotic food supplements aiming at preserving intestinal health and comfort, in line with its ability to produce beneficial metabolites (short chain fatty acids, vitamins), as well as immunomodulatory compounds. Other industrial applications of P. freudenreichii include the production of food-grade vitamins of the B group, of trehalose, of conjugated linoleic acid, and of biopreservatives. For these different applications, maintaining survival and activity of propionibacteria during production, drying, storage and finally implementation, is crucial. More widely, maintaining live and active probiotic bacteria represents a challenge as the market for probiotic products increases. Probiotic bacteria are, for a bulk majority, freeze-dried, but spray drying is also more and more considered. Indeed, this process is both continuous and more cost-efficient, as it utilizes less energy compared to freeze-drying; on the other hand, it exposes bacteria to higher heat and oxidative stresses. Apart from process optimization and strain selection, it is possible to enhance the resistance of bacteria by taking advantage of their adaptation capacity. Indeed, P. freudenreichii stress tolerance can be boosted by different pretreatments applied before the drying step, thus considerably increasing its final survival. In particular, adaptation to hyperosmotic conditions improves stress tolerance, while the presence of osmoprotectants may mitigate this improvement. Thermal adaptation also modulates tolerance towards these technological challenges. The composition of the growth medium, including the ratio between the carbohydrates provided and the non-protein nitrogen, plays a key role in driving the accumulation of osmoprotectants. This, in turn, determines P. freudenreichii tolerance towards different stresses, and overall towards both freeze-drying and spray-drying. As an example, the accumulation of trehalose enhances its spray-drying survival, while the accumulation of glycine betaine enhances its freeze-drying survival. Growth of propionibacteria in hyperconcentrated whey was used to trigger multiple stress tolerance acquisition, underpinned by overexpression of key stress protein, accumulation of cytoplasmic storage compounds, and leading to enhanc...

Reprocessing of side-streams towards obtaining valuable bacterial metabolites

“…They have also been isolated from rotten fruit juices or granulation lesions in cattle (Piwowarek et al 2018 ). PAB is used in the dairy industry (mainly in the production of cheese: Swiss-Emmental cheese, Dutch-Leerdammer, French-Comté, Polish-Tylżycki, Polish-Królewski), in the production of animal silage, and as probiotics in animal nutrition (they are tested for applications as probiotics for humans) (Ahmadi et al 2017 ; Piwowarek et al 2018 ; Jeantet and Jan 2021 ).…”

Metagenomic Analysis of Microbial Communities from Coal Waste

“…This group of bacteria is distributed in various environments, such as animal hosts and soil. They are known to produce active compounds such as antimicrobials (Jeantet & Jan, 2021).…”

Characteristics of Probiotic Preparations and Their Applications

“…Spray drying can be divided into four stages: atomization, gas heating, particle formation and separation [ 107 , 108 ]. During the spray drying process, the probiotic bacteria are affected by desiccation, heat, oxidation and osmotic stresses and their cell membranes are easily damaged, leading to their death [ 109 ]. Therefore, it is extremely important to choose protective material types and control process parameters, such as temperature, time and the feed rate, during the entire process [ 110 ].…”