Microbial analysis, antioxidant activity, and sensory properties of yoghurt with different starter cultures during storage

Investigating lactic acid bacteria genus Lactococcus lactis properties: Antioxidant activity, antibiotic resistance, and antibacterial activity against multidrug-resistant bacteria Staphylococcus aureus

Background

Lactic acid bacteria (LAB) are utilized as a starter culture in the manufacturing of fermented dairy items, as a preservative for various food products, and as a probiotic. In our country, some research has been carried out, even if LAB plays a principal role in food preservation and improves the texture and taste of fermented foods, that is why we tried to evaluate their probiotic effect. The objective of this research was to determine the antibacterial activity of Lactococcus lactis (L. lactis) against Staphylococcus aureus (S. aureus) ATCC 29213, investigate their antioxidant activity, and characterize their sensitivity against 18 antibiotics.

Methods

A total of 23 LAB (L. lactis subsp. cremoris, L. lactis subsp. Lactis diacetylactis, L. lactis subsp. lactis) were isolated from cow's raw milk. The antibacterial activity was performed using two techniques, competition for nutrients and a technique utilizing components nature, using the disk diffusion method. The sensitivity of the studied LAB to different antibiotics was tested on Man rogosa sharp (MRS) agar using commercial antibiotic disks. All strains of LAB were examined for their antioxidant activity. The antioxidant activity of L. lactis was tested by 2,2-diphenyl-1 picrylhydrazyl (DPPH).

Results

The results showed that the MRS medium was more adapted than Muller Hinton Agar (MHA) to investigate the antibacterial activity of L. lactis against S. aureus ATCC 29213. Also, L. lactis exhibited a notable degree of antibacterial activity against S. aureus ATCC 29213. L. Lactis subsp. Lactis displayed higher antibacterial activities, followed by L. lactis ssp. lactis biovar. diacetylactis, and lastly, L. lactis ssp. cremoris against S. aureus ATCC 29213. Lc 26 among all strains of L. lactis showed a high potential antibacterial activity reaching 40 ± 3 mm against S. aureus ATCC 29213. All strains of L. lactis showed a slightly moderate antioxidant activity (10.56 ± 1.28%-26.29 ± 0.05 %). The results of the antibiotic resistance test indicate that all strains of L. lactis were resistant to cefotaxime, sulfamethoxazole-trimethoprim, and streptomycin and were sensitive to Ampicillin, Amoxicillin, Penicillin G, Teicoplanin, Vancomycin, Gentamicin 500, Tetracycline, and Chloramphenicol. These test results indicate that this strain falls within the criteria of not posing any harmful effects on human health. The important antibacterial properties recorded for all L. Lactis strains were derived from the production of antibacterial active metabolites, such as protein, diacetyl, hydrogen peroxide, and lactic acid, together with the fight for nutrients.

Conclusion

This study suggests that the strains of L. lactis could be added as an antibacterial agent against S. aureus ATCC 29213 and can provide an important nutritional property for their antioxidant potential.

Physicochemical, microbial, and sensory characteristics of yogurt with Persian shallot (Allium hirtifolium Boiss) and probiotic bacteria

The aim of this study was to investigate the characteristics of yogurt prepared with the addition of Persian shallot and probiotic bacteria. The effect of Persian shallot on the viability of probiotic bacteria (Lactobacillus acidophilus and Bifidobacterium bifidum) was evaluated. Furthermore, the antimicrobial effects of shallot and probiotic bacteria on Listeria monocytogenes and Escherichia coli species were investigated. The experiments were performed on days 0, 1, 7, 14, and 21. The results showed that the survival of lactic acid bacteria increased significantly in the presence of shallots (p < .05). The addition of two different probiotic bacteria to the yogurt samples inhibited the pathogenic bacteria. While E. coli bacteria had a 3-log reduction, L. monocytogenes did not grow at all in the presence of probiotic bacteria and shallots. Based on these experiments, it was concluded that the addition of shallots not only increased the survival of probiotic bacteria but also reduced the growth of food-borne pathogenic bacteria. In addition, the addition of probiotic bacteria increased the acceptance of sensory properties of yogurt samples.

Quality specification of ice creams produced with different homofermentative lactic acid bacteria

This study investigated the changes in the physicochemical, microbiological, textural, and nutritional values of ice cream produced by various methods with the addition of different lactic acid bacteria. Adding lactic acid bacteria to the ice cream mix caused a decrease in firmness, consistency, cohesiveness, index of viscosity, pH, aw, first drop, complete melting, and overrun values (p < .05). These decreases were more pronounced in the samples to which lactic acid bacteria were added before mix maturation (p < .05). Firmness and consistency values varied between 15.11-16.26 (g) and 374.58-404.91 (g s), respectively, in the samples to which lactic acid bacteria were added before maturation. No significant effect of the addition of lactic acid bacteria to the ice cream mix on the L*, a*, and b* values of the bacteria before or after mix maturation was detected (p > .05). The L* values of the samples varied between 88.91 and 83.36, a* values between 0.76 and 1.32, and b* values between 6.57 and 8.38. An increase was detected in the amount of organic acid (excluding formic acid) in the samples produced with the addition of different lactic acid bacteria (p < .05). The number of fatty acids in the samples varied depending on the lactic acid addition and the production method; the rate of this change was generally higher in the samples with added lactic acid bacteria after mix maturation (p < .05). In particular, the amounts of short- and medium-chain fatty acids increased in the samples with lactic acid bacteria added after mix ripening, compared to the control sample.

Production of glutathione from probiotic Bacillus amyloliquefaciens KMH10 using banana peel extract

Glutathione, a tri-peptide (glutamate-cysteine-glycine) with the thiol group (-SH), is most efficient antioxidative agent in eukaryotic cells. The present study aimed to isolate an efficient probiotic bacterium having the potential to produce glutathione. The isolated strain Bacillus amyloliquefaciens KMH10 showed antioxidative activity (77.7 ± 2.56) and several other essential probiotic attributes. Banana peel, a waste of banana fruit, is chiefly composed of hemicellulose with various minerals and amino acids. A consortium of lignocellulolytic enzyme was used for the saccharifying banana peel to produce 65.71 g/L sugar to support the optimal glutathione production of 181 ± 4.56 mg/L; i.e., 1.6 folds higher than the control. So, the studied probiotic bacteria could be an effective resource for glutathione; therefore, the stain could be used as natural therapeutics for the prevention/treatment of different inflammation-related gastric ailments and as an effective producer of glutathione using valorized banana waste that has excellent industrial relevance.

Antioxidant activity of labneh made from cashew milk and its combination with cow or camel milk using different starter cultures

The aim of this study is to investigate the effects of three strains of probiotic Lactobacillus spp. i.e. L. plantarum (S1) L. casei (S2), and/or L. rhamnosus (S3) in co-cultures with Streptococcus thermophiles (St) and L. delbrueckii subsp. lactis (Ll) on the changes of total phenolic and flavonoid contents, and antioxidant activity of concentrated yogurt (labneh; L) made from individual cashew milk (EwM; 100:0 v/v) mixed with/without cow (Co) or camel (Ca) milk (75:25 v/v) during 0, 7, 14, and 21 days of storage. EwML100% S3 showed the highest total phenolic and flavonoid contents during 21 days of storage. Radical scavenging activity was improved in Ew-/Ca-ML (S2, S3, and S4) compared to control (containing St and Ll) on the 0th day. The maximum ferric reducing potential was observed in fresh Ew-/Ca-ML75% S1 (1.6 ± 0.05 mM Fe + 2 E/mL). All the starter cultures enhanced (p < 0.05) the chelating ability of EwML compared to control during the 7th and 14th day of storage. In conclusion, cashew milk labneh mixed with/without cow or camel milk containing probiotic Lactobacillus spp. can strengthen the health-promoting properties with antioxidant activity.

An exploration of alginate oligosaccharides modulating intestinal inflammatory networks via gut microbiota

Alginate oligosaccharides (AOS) can be obtained by acidolysis and enzymatic hydrolysis. The products obtained by different methods have different structures and physiological functions. AOS have received increasing interest because of their many health-promoting properties. AOS have been reported to exert protective roles for intestinal homeostasis by modulating gut microbiota, which is closely associated with intestinal inflammation, gut barrier strength, bacterial infection, tissue injury, and biological activities. However, the roles of AOS in intestinal inflammation network remain not well understood. A review of published reports may help us to establish the linkage that AOS may improve intestinal inflammation network by affecting T helper type 1 (Th1) Th2, Th9, Th17, Th22 and regulatory T (Treg) cells, and their secreted cytokines [the hub genes of protein-protein interaction networks include interleukin-1 beta (IL-1β), IL-2, IL-4, IL-6, IL-10 and tumor necrosis factor alpha (TNF-α)] via the regulation of probiotics. The potential functional roles of molecular mechanisms are explored in this study. However, the exact mechanism for the direct interaction between AOS and probiotics or pathogenic bacteria is not yet fully understood. AOS receptors may be located on the plasma membrane of gut microbiota and will be a key solution to address such an important issue. The present paper provides a better understanding of the protecting functions of AOS on intestinal inflammation and immunity.