Screening and evaluation of lactic acid bacteria with probiotic potential from local Holstein raw milk

Abstract

There are massive bacteria in the raw milk, especially the lactic acid bacteria (LABs), which have been considered probiotics in humans and animals for a long time. Novel probiotics are still urgently needed because of the rapid development of the probiotic industry. To obtain new LABs with high probiotic potential, we obtained 26 LAB isolates, named L1 ~ L26, from local Holstein raw milk collected from a farm whose milk had never been used for LAB isolation. We identified them at the species level by biochemical and 16S rDNA sequencing methods. Their antagonistic activities against four target pathogens (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa PAO1, and Salmonella enterica H9812), co-aggregative ability with these target pathogens, survivability in the simulated gastrointestinal tract conditions and phenol, auto-aggregation and hydrophobicity, hemolytic activity, and antibiotic susceptibility, were evaluated in vitro. Five Lactiplantibacillus plantarum isolates (L5, L14, L17, L19, and L20) showed more promising probiotic potential than others. Specifically, these five isolates conglutinated with and inhibited all the target pathogens, and survived in the simulated gastric juice (92.55 ~ 99.69%), intestinal juice (76.18 ~ 83.39%), and 0.4% phenol (76.95 ~ 88.91%); possessed considerable auto-aggregation (83.91 ~ 90.33% at 24 h) and hydrophobicity (79.32 ~ 92.70%); and were non-hemolytic, sensitive to kinds of common antimicrobials. Our findings demonstrated that these five isolates could be preliminarily determined as probiotic candidates because they have better probiotic potential than those previously reported. Again, this study highlighted the potential of raw milk for probiotic isolating and screening and provided the probiotic industry with five new LAB candidates.

Acetolactate Decarboxylase as an Important Regulator of Intracellular Acidification, Morphological Features, and Antagonism Properties in the Probiotic Lactobacillus reuteri

“…These results are desirable properties of potential probiotics that could enhance bacterial growth and promote the recovery of gut microbiota. [ 51 ]…”

“…These results are desirable properties of potential probiotics that could enhance bacterial growth and promote the recovery of gut microbiota. [51] Oxidative stress is a defense mechanism for the host against invading pathogens. [48] The results of this experiment indicated that the mutant strain ΔaldB and the WT strain have similar tolerance to H 2 O 2 .…”

“…The two L. reuteri strains were tested for antimicrobial susceptibility by the agar disc diffusion method. Commercially available antibiotic discs, [ 51 ] including penicillin G (2 units), ampicillin (25 µg), ceftriaxone (30 µg), vancomycin (30 µg), streptomycin (10 µg), gentamicin (10 µg), ciprofloxacin (10 µg), chloramphenicol (30 µg), erythromycin (10 µg), tetracycline (10 µg), and novobiocin (30 µg) were aseptically placed on a dried plate surface and incubated for 24 h at 37 °C. Then, the clear zones of microbial growth inhibition around each antibiotic were determined using a ruler.…”

Lacticaseibacillus huelsenbergensis sp. nov., isolated from grass silage and corn silage

“…catalase activity, cell motility) were performed using standard protocols [54]. Furthermore, a haemolysis test on blood agar plates was carried out as previously described [55][56][57].…”

Genomic and in-vitro characteristics of a novel strain Lacticaseibacillus chiayiensis AACE3 isolated from fermented blueberry

“…Thus, the application and exploitation of functional LAB strains in the food fermentation industry, livestock industry and other related industries has greatly increased over the years (De Melo Pereira et al, 2018). However, more studies have emerged that focus on the rational improvement of industrially useful LAB strains (Zhang et al, 2022). Therefore, more precise confirmation of the phenotypes of novel LAB strains will certainly be required before their adoption for better application purposes.…”