# Exploring the Probiotic Potential of Dairy Industrial-Relevant Lactobacillus
Probiotics have been defined as \"live microorganisms, that when administered in adequate amounts, confer a health benefit on the host\" [6]. Health-promoting properties have also been ascribed to probiotic dead cells, and their secreted metabolites collectively referred to as postbiotics [7]. In recent years, numerous scientific advances have been achieved in this field, thus increasing the range of both possible benefits given by probiotics (e.g., balancing of the human gut microbiota, improvement of the immune system, reduction of symptoms of lactose intolerance, enhancement of the nutritional value of the matrix) and their potential targets in the population (e.g., elderly, children, subjects exposed to specific nutritional deficiencies, chronic disease patients) [8; 9; 10]. This progress contributes to justifying an annual turnover value estimate of about US $46.5 billion in the last years [11]. In food and beverage fermentations, the long-lasting exploitation of LAB also relies on their capacity to produce several metabolites (e.g., organic acids, hydrogen peroxide, bacteriocins) that have antimicrobial activity against undesired foodborne microbes, such as pathogens and spoilers [12; 13]. In the last years, the potential in biocontrol of lactobacilli has been increasingly exploited to design protective cultures that can avoid pathogen contaminations and reduce spoilers development, decreasing the use of chemical preservatives in several food chains, particularly in the field of minimally processed foods [14; 15]. Indeed, the possible risks associated with ingestion of chemical preservatives represent a relevant issue in consideration of the recent data on exposure to food additive mixtures [16]. The antimicrobial properties of lactobacilli underlie their use both for bio preservation purposes and as probiotics. Indeed, the release of molecules with anti-pathogenic effects provides the basis for the biological control of undesired microbial species in food matrices and, at the same time, contributes to preventing host gut infections, which is one of the most relevant health benefits driven by probiotics [9]. Besides the antimicrobial activity, other properties are desirable for a probiotic, such as the aptitude to survive the hostile environment of the human gastrointestinal tract (GIT), the capacity to colonise the intestinal mucosa, reinforce gut barrier function, stimulate host cells' immune-response, and to synthesise bioactive molecules. The studies focused on selecting new lactobacilli, candidate strains for the design of probiotic and protective cultures, usually follow a bottom-up approach, with new isolation, genetic characterisation, phenotyping screening and analysis of _in vitro_ probiotic features [17; 18]. In some cases, the selection was oriented to screen isolates of food origin, looking for both strains with probiotic attitude and strains with biocontrol potential, both for exploitation in the food industry [5; 19]. After screening probiotic features, it is necessary to evaluate the ability of the strains to produce biomass efficiently and to survive the stressful conditions that characterise the conservation processes (e.g., freezing, lyophilisation) [20; 21]. This is often a bottleneck in the productive scale-up at the industrial level. This work aims to reverse this approach, proposing, for the first time, the characterisation of i) the antimicrobial potential and ii) the _in vitro_ probiotic properties of lactobacilli of dairy origin that are already employed in the dairy sector. The advantage is to select strains that are ready for the market and for which it is possible to claim more beneficial properties (i.e., technological and functional) at the same time. Dairy products are generally considered as 'classic' sources of probiotic bacteria [11].