Citation: A˘ gagündüz, D.; Yılmaz, B.; Koçak, T.; Altınta¸ s Ba¸ sar, H.B.; Rocha, J.M.; Özo ˘ gul, F. Novel Candidate Microorganisms for Fermentation Technology: From Potential Benefits to Safety Issues. Foods 2022, 11, 3074. https://doi.org/ 10.3390/foods11193074 Academic Editor: Luciana De Vero Received: 31 August 2022 Accepted: 29 September 2022 Published: 4 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). foods Review Novel Candidate Microorganisms for Fermentation Technology: From Potential Benefits to Safety Issues Duygu A ˘ gagündüz 1 , Birsen Yılmaz 2 , Tevfik Koçak 1 , Hilal Betül Altınta¸ s Ba¸ sar 1 , João Miguel Rocha 3,4, * and Fatih Özo ˘ gul 5 1 Department of Nutrition and Dietetics, Gazi University, Emek, Ankara 06490, Turkey 2 Department of Nutrition and Dietetics, Cukurova University, Sarıcam, Adana 01380, Turkey 3 Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, 4050-345 Porto, Portugal 4 Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, 4050-345 Porto, Portugal 5 Department of Seafood Processing Technology, Faculty of Fisheries, Cukurova University, Balcali, Adana 01330, Turkey * Correspondence: jmfrocha@fe.up.pt Abstract: Fermentation is one of the oldest known production processes and the most technologically valuable in terms of the food industry. In recent years, increasing nutrition and health awareness has also changed what is expected from fermentation technology, and the production of healthier foods has started to come a little more forward rather than increasing the shelf life and organoleptic properties of foods. Therefore, in addition to traditional microorganisms, a new generation of (novel) microorganisms has been discovered and research has shifted to this point. Novel microorganisms are known as either newly isolated genera and species from natural sources or bacterial strains derived from existing bacteria. Although novel microorganisms are mostly studied for their use in novel food production in terms of gut-microbiota modulation, recent innovative food research highlights their fermentative effects and usability, especially in food modifications. Herein, Clostridium butyricum, Bacteroides xylanisolvens, Akkermansia muciniphila, Mycobacterium setense manresensis, and Fructophilic lactic acid bacteria (FLAB) can play key roles in future candidate microorganisms for fermentation technology in foods. However, there is also some confusion about the safety issues related to the use of these novel microorganisms. This review paper focuses on certain novel candidate microorganisms for fermentation technology with a deep view of their functions, benefits, and safety issues. Keywords: novel microorganisms; fermentation; function; safety; health 1. Introduction One of the ancient methods of food processing, fermentation is responsible for a significant portion of the food consumed by humans [1]. The oldest fermented foods for which archaeological evidence is accessible are cereal products, bread, and beer [2,3]. Around 14,000 years ago, fermented products accompanied and probably aided the shift from hunter-gatherer groups to sessile farming communities. Since then, these foods have been a constant in human diets and especially recently, their popularity has been increasing as the demand for consuming functional foods has substantially expanded [4,5]. However, it is still possible to find different definitions of fermentation and fermented food. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consen- sus has defined fermented foods as “foods made through desired microbial growth and enzymatic conversion of food components” [5]. The definition of fermented foods not only covers foods that contain live microorganisms at the time of consumption but also includes fermented foods such as heat-treated or pasteurized fermented foods and bread, which might not contain live microorganisms during consumption [5]. Foods 2022, 11, 3074. https://doi.org/10.3390/foods11193074 https://www.mdpi.com/journal/foods