In Vitro Characterization of Lactobacillus Strains Isolated from Fruit Processing By-Products as Potential Probiotics

Abstract

Nine wild Lactobacillus strains, namely Lactobacillus plantarum 53, Lactobacillus fermentum 56, L. fermentum 60, Lactobacillus paracasei 106, L. fermentum 250, L. fermentum 263, L. fermentum 139, L. fermentum 141, and L. fermentum 296, isolated from fruit processing by-products were evaluated in vitro for a series of safety, physiological functionality, and technological properties that could enable their use as probiotics. Considering the safety aspects, the resistance to antibiotics varied among the examined strains, and none of the strains presented hemolytic and mucinolytic activity. Regarding the physiological functionality properties, none of the strains were able to deconjugate bile salts; all of them presented low to moderate cell hydrophobicity and were able to autoaggregate, coaggregate with Listeria monocytogenes and Escherichia coli, and antagonize pathogenic bacteria. Exposure to pH 2 sharply decreased the survival of the examined strains after 1- or 2-h exposure; variable decreases were noted after 3-h exposure to pH 3. Overall, exposure to pH 5 and to bile salts (0.15, 0.3, and 1%) did not decrease the strains' survival. Examined strains presented better ability to survive from the exposure to simulated gastrointestinal conditions in laboratorial media and milk than in grape juice. Considering the technological properties, all the strains were positive for proteolytic activity and EPS and diacetyl production, and most of them had good tolerance to 1-4% NaCl. These results indicate that wild Lactobacillus strains isolated from fruit processing by-products could present performance compatible with probiotic properties and technological features that enable the development of probiotic foods with distinct characteristics.

The performance of five fruit‐derived and freeze‐dried potentially probiotic Lactobacillus strains in apple, orange, and grape juices

“…Stock cultures were stored at −20 °C in De Man, Rogosa, and Sharpe (MRS) broth (HiMedia, Mumbai, India) containing glycerol (Sigma Aldrich, St Louis, USA; 200 g L −1 ). Working cultures were maintained aerobically on MRS agar (HiMedia, Mumbai, India) at 4 °C and were transferred to new media monthly …”

“…Working cultures were maintained aerobically on MRS agar (HiMedia, Mumbai, India) at 4 ∘ C and were transferred to new media monthly. 21…”

“…Apple, orange, and grape juices and MRS broth samples containing the freeze-dried Lactobacillus cells (initial viable counts of 8-9 log CFU mL −1 ; inoculation procedures were the same as those described above) were exposed to the simulated gastrointestinal conditions as previously described. 21 First, 25 mL of fresh fruit juice or MRS broth was aliquoted into 50-mL glass flasks, in which the subsequent steps of the test were performed continuously. The simulation was performed in stages to mimic mastication, and conditions in the oesophagus-stomach, duodenum, and ileum.…”

Clusters of Lactobacillus Strains from Vegetal Origins Are Associated with Beneficial Functions: Experimental Data and Statistical Interpretations

“…Then, the obtained precipitates were recovered by centrifugation (2000× g, 15 min, 4 • C), washed with distilled water and dried at 60 • C until constant weight was reached. The dried weight was then measured to determine the amount of EPS produced by the Lactobacillus strains [29].…”

“…Therefore, screening of new Lactobacillus strains endowed with such beneficial attributes is more than timely. Related to that, there is an increasing interest in unconventional sources such as traditional foods, which are steadily reported for their richness in Lactobacillus with probiotic and bio-preservative features [ 28 , 29 , 30 ].…”