## 1 Introduction  
A positive consumer attitude towards a healthy and balanced diet has been growing lately all over the world. Therefore, the demand for foods that promote health and well-being, such as functional foods containing phytochemicals and probiotics has increased [1]. The latest revised and accepted definition of probiotics states that they are \"live microorganisms that, when administered in adequate amounts, confer a health benefit on the host\" [2]. Although traditional matrices used for the incorporation of bacterial species with beneficial properties are dairy matrices, in the last decade there have been numerous studies demonstrating the interest in using plant-based matrices. In plant-based matrices, the beneficial activity and efficacy of the probiotic could be enhanced by the bioactive components naturally present in the plant matrix, resulting in a final functional product in which there is a synergistic effect on the health benefit between the bioactive components and the probiotic strain [3]. The lulo (_Solanum quitoense_ Lam.) stands out among tropical fruits with a pleasant flavor and a distinctive nutritional and phytochemical composition. Although lulo fruit is mainly consumed as juice in the producing countries themselves, it has gained interest in national and international markets due to its organoleptic and functional properties [4]. It has a high potential for the development of functional foods; is rich in vitamin C, fiber, and antioxidant compounds, such as all trans-\(\beta\)-carotene, lutein and zeaxanthin, chlorogenic acids, flavonoid glycosides and bioactive amines such as \(N^{1}\),\(N^{4}\),\(N^{8}\)-tris(dihydro/)l) spermidine and \(N^{1}\),\(N^{8}\)-bis(dihydroxy/rocaffeoyl) spermidine. Some in vitro and in vivo studies reveal various mechanisms through which the lulo compounds reduce risk or reverse metabolic- and inflammation-associated diseases [5]. Additionally, some fruit juices have been demonstrated to be a good matrix to proliferate probiotic microorganisms due to its content in carbohydrates, vitamins, and bioactive compounds. Coupled to fruit consumption, the intake of certain microorganisms is capable of decreasing body fat by modifying the intestinal microbiota, stimulating the synthesis of satiety-inducing peptides, reducing the synthesis of proinflammatory cytokines and possibly modifying the lipid profile or suppressing _Helicobacter_ populations [6]. Therefore, tropical fruit juices fermented with probiotics may be an effective strategy to meet dietary health requirements. However, it is known that the survival of lactic bacteria in fruit juices tends to be more complex than in dairy beverages. This is due, mainly, to the natural acidity of fruit, the high level of polyphenols and the absence of lactose, which may interfere in the survival of certain sorts of microorganisms, as well as in their growth and in their resistance to the gastrointestinal digestion process [7]. In this sense, the application of some pretreatments and a suitable selection of strain can improve the probiotic growth, resistance, and, consequently, their release to the specific target site. _Lactobacillus reuteri_ is a heterofermentative lactic acid bacterium (LAB) found in a variety of ecological niches like fermented food and the gastro-intestinal as well as the urogenital tract of humans and other animals [8]. Its consumption as a supplement has been recognized as safe [9], and some probiotic properties have been demonstrated. It was shown to inhibit _Helicobacter pylori_ in the human stomach, thus, providing new opportunities in the treatment of chronic stomach inflammation [10]. Orally administered in combination with _Lactobacillus rhamns_ enhanced vaginal flora quality and was effective against bacterial vaginosis [11; 12]. Additionally, _Lactobacillus reuteri_ showed an improve of biomarkers of inflammation and cardiovascular risk in obese adults with metabolic syndrome [13].