Novel probiotic candidates for humans isolated from raw fruits and vegetables.

This study was aimed at determining the probiotic potential of a large number of autochthonous lactic acid bacteria isolated from fruit and vegetables. Survival under simulated gastric and intestinal conditions showed that 35% of the strains, mainly belonging to the species Lactobacillus plantarum maintained high cell densities. Selected strains did not affect the immune-mediation by Caco-2 cells. All strains stimulated all 27 immune-mediators by peripheral blood mononuclear cells (PBMC). A significant (P<0.05; P<0.01) increase of the major part of cytokines and growth factors was found. A few chemokines were stimulated. Immune-mediators with pro-inflammatory activity (IL-17, EOTAXIN and IFNγ) were significantly (P<0.01) stimulated by all strains, followed by IL-1b>IP-10>IL-6>MIP1α. Stimulation of IL-12, IL-2 and IL-7 was strain dependent. Only a few strains increased the synthesis of cytokines with anti-inflammatory activity. Six L. plantarum strains were further selected. Four were defined as the strongly adhesive strains (more than 40 bacteria adhering to one Caco-2 cell), and 2 as the adhesive strains (5-40 bacteria adhering to one Caco-2 cell). Five strains grew and acidified chemically defined medium with fructo-oligosaccharides (FOS) as the only carbon source. End-products of FOS fermentation were found. All strains inhibited enterohemorragic Escherichia coli K12 and Bacillus megaterium F6 isolated from human sources. The results of this study showed that some autochthonous lactic acid bacteria from raw fruit and vegetables have functional features to be considered as novel probiotic candidates.

Effect of lactic acid fermentation on antioxidant, texture, color and sensory properties of red and green smoothies.

Weissella cibaria, Lactobacillus plantarum, Lactobacillus sp. and Lactobacillus pentosus were variously identified from blackberries, prunes, kiwifruits, papaya and fennels by partial 16S rRNA gene sequence. Representative isolates from each plant species were screened based on the kinetics of growth on fruit juices. A protocol for processing and storage of red and green smoothies (RS and GS) was set up, which included fermentation by selected lactic acid bacteria starters and exo-polysaccharide producing strains. Starters grew and remained viable at ca. 9.0 log cfu g(-1) during 30 days of storage at 4 °C. No contaminating Enterobacteriaceae and yeast were found throughout storage. Values of soluble solids, total titratable acidity and viscosity distinguished started RS and GS compared to spontaneously (unstarted) fermented smoothies. Color difference dE∗(ab) and browning index were positively affected by lactic acid fermentation. Consumption of carbohydrates by lactic acid bacteria was limited as well as it was the lactic fermentation. Consumption of malic acid was evident throughout storage. Polyphenolic compounds and, especially, ascorbic acid were better preserved in started RS and GS compared to unstarted samples. This reflected on the free radical scavenging activity. A statistical correlation was only found between the level of ascorbic acid and free radical scavenging activity. As shown by a first-order equation, the rate of degradation of ascorbic acid through storage were found to be higher in the unstarted compared to started RS and GS. Fermentation by lactic acid bacteria clearly improved the sensory attributes of RS and GS.

Exploitation of sweet cherry (Prunus avium L.) puree added of stem infusion through fermentation by selected autochthonous lactic acid bacteria.

Strains of Lactobacillus plantarum, Pediococcus acidilactici, Pediococcus pentosaceus and Leuconostoc mesenteroides subsp. mesenteroides were identified from 8 cultivars of sweet cherry by partial 16S rRNA gene sequence and subjected to typing by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) analysis. Representative isolates from each species and each cultivar were screened based on the kinetics of growth on cherry puree added of (10%, v/v) stem infusion (CP-SI). A protocol for processing and storage of CP-SI, which included fermentation by selected autochthonous P. pentosaceus SWE5 and L. plantarum FP3 (started CP-SI) or spontaneous fermentation (unstarted CP-SI), was set up. Starters grew and remained viable at elevated cell numbers (ca. 9.0 log cfu g(-1)) during 60 days of storage at 4 °C. The number of presumptive lactic acid bacteria of the unstarted CP-SI did not exceed the value of ca. 3.0 log cfu g(-1). Consumption of carbohydrates (e.g., glucose and fructose) by starter lactic acid bacteria was limited as well as it was the lactic acid fermentation. Consumption of organic acids (e.g., malic acid) and free amino acids was evident, especially, throughout storage. Compared to CP-SI before processing, the concentrations of total phenolic compounds and anthocyanins did not vary in the started CP-SI. The concentration of anthocyanins slightly decreased in the unstarted CP-SI. The antioxidant activity, expressed as the scavenging activity toward DPPH radical, was found at highest level in the started CP-SI which approached that found in CP-SI before processing. During storage, viscosity and, especially, color indexes of started CP-SI were higher than those found in the unstarted CP-SI. Fermentation by autochthonous lactic acid bacteria seemed to also positively interfere with the sensory attributes of CP-SI.

Taxonomic structure of the yeasts and lactic acid bacteria microbiota of pineapple (Ananas comosus L. Merr.) and use of autochthonous starters for minimally processing.

Pichia guilliermondii was the only identified yeast in pineapple fruits. Lactobacillus plantarum and Lactobacillus rossiae were the main identified species of lactic acid bacteria. Typing of lactic acid bacteria differentiated isolates depending on the layers. L. plantarum 1OR12 and L. rossiae 2MR10 were selected within the lactic acid bacteria isolates based on the kinetics of growth and acidification. Five technological options, including minimal processing, were considered for pineapple: heating at 72 degrees C for 15 s (HP); spontaneous fermentation without (FP) or followed by heating (FHP), and fermentation by selected autochthonous L. plantarum 1OR12 and L. rossiae 2MR10 without (SP) or preceded by heating (HSP). After 30 days of storage at 4 degrees C, HSP and SP had a number of lactic acid bacteria 1000 to 1,000,000 times higher than the other processed pineapples. The number of yeasts was the lowest in HSP and SP. The Community Level Catabolic Profiles of processed pineapples indirectly confirmed the capacity of autochthonous starters to dominate during fermentation. HSP and SP also showed the highest antioxidant activity and firmness, the better preservation of the natural colours and were preferred for odour and overall acceptability.

Use of autochthonous starters to ferment red and yellow peppers (Capsicum annum L.) to be stored at room temperature.

Strains of Lactobacillus curvatus, Leuconostoc mesenteroides, Lactobacillus plantarum and Weissella confusa were identified from raw red and yellow peppers (RYPs) by partial 16S rRNA gene sequence and subjected to typing by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) analysis. L. plantarum PE21, L. curvatus PE4 and W. confusa PE36 were selected based on the kinetics of growth and acidification, and used as the autochthonous mixed starter for the fermentation of RYPs. A protocol which included blanching at 85 degrees C for 2 min, fermentation at 35 degrees C for 15 h in brine (1%, w/v), and heat treatment at 85 degrees C for 15 min, followed by storage at room temperature for 30 days with and without sunflower seeds oil was set up. Unstarted RYPs subjected to the same treatments were used as the control. Cell numbers of autochthonous starter in the RYPs were ca. 1000 times higher than presumptive lactic acid bacteria in unstarted RYPs. As shown by RAPD-PCR analysis, all three autochthonous strains persisted during processing and storage. Presumptive lactic acid bacteria found in started RYPs progressively decreased during storage, leading to a microbiota mainly consisting of autochthonous starters. Started RYPs showed rapid decrease of pH (<3.7), marked consumption of fermentable carbohydrates, and inhibition of total enterobacteria and yeasts. Unstarted RYPs were subjected to slight acidification (pH ca. 4.87) and considerable contamination by total enterobacteria and yeasts throughout storage. After 30 days of storage, started RYPs had significantly (P<0.05) higher firmness and colour indexes with respect to unstarted RYPs. The microbial and sensory features of started RYPs stored with sunflower seeds oil were almost similar to those of RYPs stored without suspending liquid.