Molecular Routes to Specific Identification of the Lactobacillus Casei Group at the Species, Subspecies and Strain Level

The genus Lactobacillus includes, among others, Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus, species that are collectively referred to as the Lactobacillus casei group. Many studies have shown that strains belonging to this group may decrease lactose intolerance, the effects of inflammatory bowel disease, diarrhea, constipation, food allergies and even colon cancer. Moreover, evidences exists of positive effects of these bacteria on mucosal immunity and blood cholesterol level. Because of their beneficial influence on human health, many of them are used as food additives and probiotic pharmaceuticals. It should be stressed that health-promoting properties are not attributed at the species level, but to specific strains. Therefore, procedures are necessary to allow specific identification at each phylogenetic level—genus, species and strain. In this paper we present a practical overview of molecular methods for the identification and differentiation of L. casei bacteria. The research included 30 bacterial strains belonging to three species: L.casei, L. paracasei and L. rhamnosus. Among the tested procedures were genus- and species-specific PCR, multiplex-PCR, Real-Time HRM analysis, RFLP-PCR, rep-PCR, RAPD-PCR, AFLP-PCR, and proteomic methods such as MALDI-TOF MS typing and SDS-PAGE fingerprinting. The obtained results showed that multiplex-PCR and MALDI-TOF MS turned out to be the most useful methods to identify the tested bacteria at the species level. At the strain level, the AFLP-PCR method showed the highest discriminatory power. We hope that the presented results will allow for the easy selection of an appropriate procedure, depending on the experiment conducted and the equipment capabilities of any given laboratory.

Wild Lactobacillus casei Group Strains: Potentiality to Ferment Plant Derived Juices

Plant derived beverages have recently gained consumers’ interest, particularly due to their intrinsic functional properties. They can also act as non-dairy carriers for probiotics and prebiotics, meeting the needs of lactose allergic/intolerant people and vegans. Direct fermentation of fruit and vegetables juices by probiotic lactic acid bacteria could be a tool to increase safety, shelf-life, nutrients bioavailability and to improve sensorial features of plant derived juices. This study aims to screen wild Lactobacillus casei-group strains isolated from dairy matrices for probiotic features, such as acid and bile salts resistance, and test them for the potentiality to ferment celery and orange juices. Strains’ ability to produce exopolysaccharides (EPS) in situ is also checked. These evaluations were performed for the first time in fruit and vegetables matrices by means of an impedometric analysis, recently shown to be a suitable and rapid method to measure microorganisms’ growth, acidification performances and EPS production. This study allowed the selection of three potentially probiotic L. casei-group wild strains able to ferment fruit and vegetable juices and also producing EPS. These strains with three-in-one abilities could be used to produce new functional fermented plant derived juices.

Investigation of bile tolerance and deconjugation ability of various Lactobacillus Casei group strains

Lactobacillus casei group is commonly used as probiotics. Various factors affect their viability in gastrointestinal tract. Twenty two strains of Lactobacillus casei group were assessed for bile tolerance and deconjugation attribute. All strains had shown moderate activity at 0% bile concentration. At 1% bile concentration CSCC 2607 has shown highest growth while remaining Lactobacillus strains have shown fair growth. At 1.5% bile concentration only seven Lactobacillus strains showed growth and ASCC 1521 showed highest activity. All seven strains were able to deconjugate both sodium glycocholate and sodium taurocholate at varying levels. ASCC 1520 showed lowest deconjugation activity for sodium glycocholate. All seven strains showed lower deconjugation of sodium taurocholate compared to sodium glycocholate. ASCC 290 was least capable of deconjugation of sodium taurocholate. When mixture of sodium glycocholate and sodium taurocholate having the similar molar ratio in human bile, was taken, all seven strains showed consistent cholic acid secretion. ASCC 1521 also showed highest cholic acid liberation while ASCC 1520 showed lowest deconjugation ability. This study suggests the importance to identify all the useful Lactobacillus strains which are able to tolerate and deconjugate, high bile concentration in order to study further for their therapeutic benefits.