Antioxidant activity of the postbiotics
The data that are presented in Table 2 show the DPPH scavenging activity of different postbiotics.
Table 2
Antioxidant activity of different postbiotics against DPPH (µg TE/ml media)
Postbiotics | Antioxidant activity (µg TE/ml media) |
L. acidophilus | 220.97 |
L. helveticus CNRZ 32 | 225.44 |
L. plantarum DSA 20174 | 234.38 |
L. rhamnosus GG | 229.52 |
B. bifidum | 227.58 |
Insert table (2)
For instance, the antioxidant activity of L. plantarum showed 234.38 µg TE/ml media, followed by L. rhamnosus GG (229.52 µg TE/ml), B. bifidum (227.58 µg TE/ml media), L. helveticus (225.44 µg TE/ml media) and L. acidophilus (220.97 µg TE/ml media). Our results are similar to those of [21, 22, 23] who reported that the antioxidant activity increased in juices inoculated by L. acidophilus and L. plantarum. Dilna et al., [24] confirmed the important of antioxidant activity, helpful in the food and feed industry and positively affect human health. Furthermore, Izuddin et al., [25] assessed the antioxidant features of L. plantarum-derived postbiotics.
Antimicrobial activity
The antagonistic activity of five postbiotic of probiotic strains on pathogenic bacteria and fungi was determined using a well diffusion assay.
Generally, as presented in Table 3, all postbiotics derived from tested probiotic strains showed zones of inhibition against most indicator strains, but with different diameters. The diameter of inhibition zones in the case of B. cereus were 14, 13.5, 6, and 6 mm for L. acidophilus, L. helveticus, L. plantarum, and rhamnosus GG postbiotics, respectively. Retarding of Staphylococcus aureus growth was obtained at 7, 8.5, 6.5, and 6.5 due to L. acidophilus, L. helveticus, L. plantarum, and L. rhamnosus GG, respectively. Just L. acidophilus and L. helveticus hindered listeria monocytogenes, while L. plantarum, L. rhamnosus GG, and B. bifidum did not show any zones of inhibition. Gram-negative bacteria were affected by all five LAB strains, but with smaller zones of inhibition when compared with Gram-positive strains. The greatest zones of inhibition were obtained for Salmonella enterica (8.5 mm) and Pseudomonas aeruginosa (9 mm) because of L. acidophilus. There was no significance among all lactic acid bacteria strains in the case of gram-negative bacteria. The obtained antifungal activity of the tested Lactic acid bacterial strains showed stronger potential than bacteria. However, just L. acidophilus (7mm), L. helveticus (6 mm) and L. plantarum (9 mm) prevented Aspergillus flavus from proper radial growth. Candida albicans was greatly inhibited at 27, 25, 24.5, 13.5, and 15.5 mm, respectively, due to the treatment with L. acidophilus and B. bifidum. Probiotic bacteria produce antimicrobial compounds such as organic acids and bacteriocins [26]. Contrary to our results, Noori et al., [13] found that L. acidophilus and L. plantarum were unable to eliminate the pathogenic bacteria; however, L. casei and L. rhamnosus postbiotics exhibited excellent antimicrobial activity. Magnusson et al., [27] reported that the antimicrobial activity L. plantarum depends on bacteriocins, organic acids and other inhibitory substances. Russo et al., [28] and Dinev et al., [29] confirmed the previous research and added that L. plantarum has inhibitory activity against Gram-negative pathogens and many moulds and yeasts, including pathogenic and mycotoxigenic strains. Al-Gamal et al., [18] found that both L. helveticus and L. plantarum have the strongest antagonism against some pathogens.
Table 3
Antimicrobial activity of the postbiotics
Pathogenic and spoilage strains | Inhibition zone diameter (mm) |
L. acidophilus | L. helveticus | L. plantarum | L. rhamnosus GG | B.bifidum |
B. cereus | 14.0 | 13.5 | 6.0 | 6.0 | ND |
S. aureus | 7.0 | 8.5 | 6.5 | 6.5 | ND |
L. monocytogenes | 11.5 | 9.5 | ND | ND | ND |
E. coli | 7.0 | 7.0 | 6.5 | 6.0 | 7.0 |
Sal. enterica | 8.5 | 8.0 | 6.0 | 7.5 | 6.0 |
Ps. aeruginosa | 9.0 | 8.0 | 6.0 | 6.5 | 6.5 |
Asp. flavus | 7.0 | 6.0 | 9.0 | ND | ND |
C. albicans | 27.0 | 25.0 | 24.5 | 13.5 | 15.5 |
Insert table (3)
The amount of vitamin B in postbiotics
The vitamin content of the different postbiotic strains are shown in Table 3 and Fig. 1.
Table 4
Vitamins B content (µg/ml) of postbiotics.
Postbiotics | Vitamins B content (µg/ml) |
B1 | B2 | B6 | B9 | B12 |
L. acidophilus | 20.49 | 1.90 | 191.13 | 28.45 | ND |
L. rhamnosus GG | 27.61 | 1.99 | 154.60 | 16.32 | ND |
L. helveticus | 22.07 | 2.24 | 266.09 | 25.11 | ND |
L. plantarum | 17.61 | 1.97 | 237.22 | 22.5 | ND |
B. bifidum | 23.91 | 1.29 | 259.13 | 13.69 | ND |
ND = not detectable |
Insert table (4)
The vitamin concentrations of the different postbiotic strains are shown in Table 4 and Fig. 1. All strains produced different levels of vitamin B1, B2, B6, B9 and B12. From five strains, L. rhamnosus GG showed the highest B1 level 27.61 µg/ml. The highest conc. of B2, B6, B9 were produced by L. helveticus (2.24 µg/ml), L. helveticus (266.09 µg/ml), and L. acidophilus (28.45 µg/ml), respectively. B-group vitamins have the ability to dissolve in water and play an important role in the metabolism of carbohydrates, proteins and lipids [30]. In this regard, it was previously described that LAB produce a variety of amounts of B-group vitamins Del Valle et al., [31] and LeBlanc et al., [32] found that L. rhamnosus GG was a good folate and riboflavin producer and B. longum and B. bifidum were low but significant producers of intracellular thiamine. Hill et al., [33] reported that vitamin B12 (Cobalamin) produced by a few bacteria, such as some kind of Lactobacillus and Propionibacterium. Probiotic bacteria, mostly belonging to the genera Lactobacillus and Bifidobacterium, confer a number of health benefits, including vitamin production [34, 35, 36]. Some LABs are able to synthesize B vitamins such as riboflavin [37]. Currently, the strains of Lactobacillus with the greatest relevance for the manufacturing of functional foods [38]. Lactobacillus plantarum CRL 725 was able to significantly increase the initial concentration of riboflavin in soymilk [31]. Strains of Bifidobacteria were able to produce elevated concentrations of thiamin in soymilk and fermented milks [39, 40].
Insert figure (1)
The amount of organic acid and SCFAs in postbiotics
Organic acids, including SCFA (acetic acid, propionic acid and butyric acid), produced in postbiotics by the probiotic strains is presented in Table 5 and Fig. 2.
Table 5
Organic acids content (µg/ml) of postbiotics.
Organic acids | L. acidophilus | L. helveticus | L. plantarum | L. rhamnosus | B. bifidum |
Formic acid | 2.392.3 2.39 | 213.04 | ND | 12.15 | 83.20 |
Lactic acid | 13927.58 | 10901.39 | 3711.84 | 1022.16 | 2901.72 |
Citric acid | 134.57 | 204.33 | 390.09 | 745.13 | 481.61 |
Acetic acid | 5898.18 | 5663.19 | 8111.85 | 11355.13 | 9239.13 |
Succinic acid | 3016.19 | 2920.55 | 185.55 | 525.85 | 195.46 |
Propionic acid | 105.89 | 740.61 | 706.66 | 1520.23 | 554.09 |
Butyric Acid | ND | ND | ND | ND | ND |
ND = not detectable |
Insert table (5)
Lactic acid was produced by L. acidophilus (13927.58 µg/ml), followed by L. helveticus (10901.39 µg/ml). The highest levels of formic acid, citric acid and acetic acid were recorded by L. helveticus (213.04 µg/ml), L. rhamnosus (745.13 µg/ml), and L. rhamnosus (11355.13 µg/ml). The highest concentrations of propionic acid and succinic acid were produced by L. rhamnosus (1520.23 µg/ml) and L. acidophilus (3016.19 µg/ml), respectively. It was observed that all the strains used did not produce butyric acid. Jankowsket et al., [41] found that the production of acetic acid was lower than that of lactic acid in the postbiotic of different strains of L. plantarum. LeBlanc et al., [33] found that LGG was able to produce and release propionate in a significant amount but was not able to produce either butyrate or acetate. On the other hand, Zalan et al., [42] mentioned that lactic acid is well known for its antimicrobial activity against pathogenic bacteria. Besides, Van Thu et al., [43] reported the production of acetic acid and lactic acid by the combination of postbiotics produced by various L. plantarum strains.
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