Postbiotics: a perspective on their quantification

Gabriel Vinderola^1,2*Andrzej Benkowski³Marion Bernardeau bernARDEAU⁴Empar Chenoll⁵Maria Carmen Collado⁶Ultan Cronin cRONIN⁷Erk Eckhardt eCKHARDT⁸Justin Green⁹Ignacio R Ipharraguerre¹⁰Rober Kemperman kemperman¹¹Christophe Lacroix¹²Junichi Minami Minami¹³Martin G Wilkinson¹⁴Mary Ellen Sanders¹⁵Seppo Salminen¹⁶

• ¹Faculty of Chemical Engineering, National University of Littoral, Santa Fe, Argentina
• ²CONICET Instituto de Lactología Industrial (INLAIN), Santa Fe, Santa Fe, Argentina
• ³Eurofins (France), Nantes, Pays de la Loire, France
• ⁴Université de Caen Normandie, Caen, Lower Normandy, France
• ⁵ADM Biopolis, Paterna, Valencia, Spain
• ⁶University of Valencia, Valencia, Valencian Community, Spain
• ⁷Becton Dickinson (United States), Franklin Lakes, New Jersey, United States
• ⁸DSM (France), Saint-Louis, France
• ⁹Cargill (Canada), Winnipeg, Manitoba, Canada
• ¹⁰University of Kiel, Kiel, Schleswig-Holstein, Germany
• ¹¹Lesaffre Human Care, Marcq-en-Barœul, France
• ¹²ETH Zürich, Zurich, Zürich, Switzerland
• ¹³Morinaga (Japan), Tokyo, Japan
• ¹⁴University of Limerick, Limerick, Ireland
• ¹⁵isapp, Centennial, California, United States
• ¹⁶Turku University Hospital, Turku, Finland

A "postbiotic" is a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. To encourage collaborative problem-solving to address the issues related to the characterization and quantification of postbiotics, a working group of academic and industry scientists involved in research or commercial production of postbiotics convened at the International Scientific Association for Probiotics and Prebiotics (ISAPP) 2024 meeting. This paper reports the outcomes of that discussion. Postbiotics are potentially compositionally complex mixtures, leading us to anticipate that full characterization and quantification of all components of a postbiotic product is not feasible. However, confirmation of the identity and quantity of the progenitor microorganism(s), quantification of some of its functional components, and a suitable description of the process of inactivation will be needed to assure the product can be sufficiently described and consistently reproduced. Measurement and quantification must be fit for purpose. Some useful methods include flow cytometry (FC), including innovations such as imaging FC, which has evolved into a mainstream technique suited to quantify inanimate cells, and quantitative polymerase chain reaction, which complements FC by enabling quantification and identity of microbes to the strain level. Other methods can be utilized depending on the complexity, type of microorganisms used (bacteria, yeasts, filamentous fungi), number of strains and cell integrity (intact vs. fragmented). Hence, no 'gold standard' methodology -analogous to colony-forming units for probiotics -is envisioned for postbiotics.