Nervous system disorders are one of the common problems that affect many people around the world every year. Regarding the beneficial effects of the probiotics on the gut and the gut-brain axis, their application along with current medications has been the subject of intense interest. Psychobiotics are a probiotic strain capable to affect the gut-brain axis. The effective role of Psychobiotics in several neurological disorders is documented. Consumption of the Psychobiotics containing nutrients has positive effects on the improvement of microbiota as well as alleviation of some symptoms of central nervous system (CNS) disorders. In the present study, the effects of probiotic strains on some CNS disorders in terms of controlling the disease symptoms were reviewed. Finding suggests that Psychobiotics can efficiently alleviate the symptoms of several CNS disorders such as autism spectrum disorders, Parkinson’s disease, multiple sclerosis, insomnia, depression, diabetic neuropathy, and anorexia nervosa. It can be concluded that functional foods containing psychotropic strains can help to improve mental health. Graphical Abstract

Background: Yeasts play diverse roles in human life. Since ancient times, these microorganisms have been used to produce food products and beverages including bread and beer. Nowadays, the biotechnological products of yeast are one of the main components of commercial products. Objective: Some species of yeast such as Saccharomyces cerevisiae and Saccharomyces boulardii are recognized as probiotic yeast with extensive applications in the food and drug industries. However, certain species like Kluyveromyces marxianus are still not recognized as probiotic microorganisms despite their widespread industrial usage. In this study, the application of K. marxianus in preparing food and the medicinal product was reviewed in terms of its beneficial or harmful effects. Methods: Pub Med, Google Scholar, Scopus, and Science Direct databases were searched by using “Probiotics”, “Yeast”, and “Kluyveromyces marxianus”. Results: The findings suggest that K. marxianus can be recognized as a probiotic yeast species. Conclusion: It can be concluded that K. marxianus may be considered as a probiotic microorganism with a variety of commercial and medical applications.

Background & objectives: Probiotic dairy products as a functional food have a positive effect on the health of consumers that have been confirmed by scientific evidence. Yoghurt is considered as one of the most popular dairy foods in Iran, which the incorporation of the probiotics into the yoghurt matrix can improve their microbiological and sensory properties and subsequently will play a vital role in promoting the health of the community. The aim of this study was to investigate the effect of yeast Kluyveromyces marxianus on the microbial and sensorial properties of probiotic yoghurt during refrigerated storage. Methods: In this in vitro study, the yeast Kluyveromyces marxianus PTCC=5189 was used to produce probiotic yoghurt and Aspergillus parasiticus PTCC=5018 (IR 63) and Penicillium chrysogenum PTCC=5074 were used as known pathogens and the main spoilage agents in yoghurt. Changes in the number of probiotic yeasts and spoilage species as well as the sensory acceptability of the samples during 28 days of storage at 4°C were evaluated and compared with the control samples. Results: The population of both species, involved in yoghurt spoilage, during refrigeration were significantly reduced by the presence of Kluyveromyces marxianus (p<0.01). After 28 days of storage, the number of Kluyveromyces marxianus was at the recommended level of the International Dairy Federation with a 7.35 log CFU/g. The sensory evaluation results demonstrated that the control yoghurt samples were more acceptable. Conclusion: Kluyveromyces marxianus has a significant effect on improving microbiological properties and can be used in the formulation and production of probiotic yoghurt with high storage capability and optimal sensory acceptability.