A Response Surface Methodological Approach for Large-Scale Production of Antibacterials from Lactiplantibacillus plantarum with Potential Utility against Foodborne and Orthopedic Infections

A variety of bacteria, including beneficial probiotic lactobacilli, produce antibacterials to kill competing bacteria. Lactobacilli secrete antimicrobial peptides (AMPs) called bacteriocins and organic acids. In the food industry, bacteriocins, but even whole cell-free supernatants, are becoming more and more important as bio-preservatives, while, in orthopedics, bacteriocins are introducing new perspectives in biomaterials technologies for anti-infective surfaces. Studies are focusing on Lactiplantibacillus plantarum (previously known as Lactobacillus plantarum). L. plantarum exhibits great phenotypic versatility, which enhances the chances for its industrial exploitation. Importantly, more than other lactobacilli, it relies on AMPs for its antibacterial activity. In this study, Response Surface Methodology (RSM) through a Box-Behnken experimental design was used to estimate the optimal conditions for the production of antibacterials by L. plantarum. A temperature of 35 °C, pH 6.5, and an incubation time of 48 h provided the highest concentration of antibacterials. The initial pH was the main factor influencing the production of antibacterials, at 95% confidence level. Thanks to RSM, the titer of antibacterials increased more than 10-fold, this result being markedly higher than those obtained in the very few studies that have so far used similar statistical methodologies. The Box-Behnken design turned out to be a valid model to satisfactorily plan a large-scale production of antibacterials from L. plantarum.

In vivo studies could not confirm in vitro prophylactic synergism between Moringa essential oil and Lactobacillus reuteri (MT180537)

Abstract Aerobic vaginitis (AV) is a recently defined vaginal recurring infection, which is treated with antibiotics. However, excessive and prolonged use of antibiotics disrupts healthy vaginal microflora and leads to the emergence of antibiotic resistance among pathogens. This situation has directed researchers to explore alternative antimicrobials. The current study describes in vitro and in vivo antimicrobial efficacy and pharmaceutical interactions between plant essential oils (EOs) and five lactic acid bacteria (LABs), isolated from the healthy vagina, against E. faecalis, one of the major etiological agents of AV. In vitro experiments confirm good antimicrobial activity of both plant EOs and cell free supernatant (CFS) from LABs. Based on high antimicrobial efficacy, Moringa essential oil (MO) was selected to determine its nature of interaction with CFS of five LAB strains. Synergism was recorded between MO and CFS of L. reuteri (MT180537). To validate in vitro findings, prophylactic responses of individual and synergistic application of MO and L. reuteri (MT180537) were evaluated in an E. faecalis (MW051601) induced AV murine model. The prophylactic efficacy was evidenced by a reduction in intensity of clinical symptoms, E. faecalis (MW051601) count per vaginal tissue along with a reduction in AV associated changes in histological markers of infection in animals receiving Moringa essential oil and L. reuteri (MT180537) alone or in combination. However, significant synergism between Moringa essential oil and L. reuteri (MT180537) could not be observed. Our data confirms the importance of in vivo experiments in deducing pharmacological interactions.

The Weissella and Periweissella genera: up-to-date taxonomy, ecology, safety, biotechnological, and probiotic potential

Bacteria belonging to the genera Weissella and Periweissella are lactic acid bacteria, which emerged in the last decades for their probiotic and biotechnological potential. In 2015, an article reviewing the scientific literature till that date on the taxonomy, ecology, and biotechnological potential of the Weissella genus was published. Since then, the number of studies on this genus has increased enormously, several novel species have been discovered, the taxonomy of the genus underwent changes and new insights into the safety, and biotechnological and probiotic potential of weissellas and periweissellas could be gained. Here, we provide an updated overview (from 2015 until today) of the taxonomy, ecology, safety, biotechnological, and probiotic potential of these lactic acid bacteria.

Evaluation of the Safety and Ochratoxin A Degradation Capacity of Pediococcus pentosaceus as a Dietary Probiotic with Molecular Docking Approach and Pharmacokinetic Toxicity Assessment

The present study evaluated the properties and ochratoxin A (OTA) degradation capacity of the dietary probiotic Pediococcus pentosaceus BalaMMB-P3, isolated from a milk coagulant. The acidic tolerance of the isolate at pH 2–3 was checked with bile salts. No hemolytic activity was noted, which confirmed the nonpathogenicity of the strain. The isolate was tested in vitro for antibiotic susceptibility, enzymatic activity, bile salts hydrolase activity and antifungal activity against Penicillium verrucosum, Fusarium graminearum and Aspergillus ochraceus. A molecular docking-based OTA toxicity assessment was carried out for multitargeted proteins. The 16S rRNA gene-based phylogenetic assessment identified the strain as P. pentosaceus, and was authenticated in GenBank. The carboxylesterase and glutathione s-transferase enzymes showed active and strong interactions with esters and amide bonds, respectively. The compound exhibited carcinogenic and cytotoxicity effects at an LD₅₀ value of 20 mg/kg. Furthermore, the strain showed a potent ability to reduce OTA and suggested the prospects for utilization in nutritional aspects of food.

Potent γ-amino butyric acid producing psychobiotic Lactococcus lactis LP-68 from non-rhizospheric soil of Syzygium cumini (Black plum)

Gamma amino butyric acid (GABA) is a chemical messenger that plays a significant role in muscle relaxation and brain health. Certain lactic acid bacteria (LAB) produce significant levels of GABA and thus act as potential psychobiotic cultures. In the present study, LAB were isolated from non-rhizospheric soil sample of Syzygium cumini (Black plum). A total of 57 LAB were isolated on the basis of their morphological and acid producing characteristic on de Man Rogosa Sharpe (MRS) agar. Only seven isolates were found to produce GABA (0.09-1.13 gL^-1) in MRS broth and were identified as Lactococcus. However, L. lactis LP-68 produced highest amount of GABA and was selected for further optimization of culture conditions (pH, temperature and MSG) by response surface methodology (RSM). The optimization resulted in approximately four-fold increase in GABA production (4.11 gL^-1). The results indicate that the L. lactis LP-68 can be used as starter culture for production of GABA-enriched functional foods.

Weissella confusa with thermostable β-hemolytic exopolysaccharide

Consuming cooked meat contaminated with bacteria that carry thermostable hemolytic exopolysaccharide (ESP), could lead to severe diseases. Culture of a 5- h boiled sample of meat goulash on blood agar showed growth of a gram positive rod-shaped, mucoid and hemolytic bacterium. Biochemical tests and amplification of 1500 bp product of 16S rDNA and sequencing revealed bacterial identity as Weissella confusa. After 1 h boiling of bacterial suspension, they were alive and hemolytic, increased in volume and aggregated. After 8 h boiling of bacterial suspension with coverslip, live bacteria showed hemolysis, clustered and adhered to coverslip. Bacterial bacteriocin and hemolytic activities remained unchanged upon autoclaving. Purified bacterial EPS retained hemolytic activity after autoclaving. Boiling contaminated meat had no negative impact on viability of heat-stable W. confusa and its hemolytic EPS. Thermostable hemolytic EPS protected W. confusa from excessive heat. Hygienic practice in butcheries and kitchens are necessary to eliminate bacterial contaminants.

Purification and Characterization of a New Halocin HA4 from Haloferax larsenii HA4 Isolated from a Salt Lake

Halocins are antimicrobial peptides secreted by different members of haloarchaea. Halocin HA4 was purified from Haloferax larsenii HA4 using combination of ultrafiltration and chromatographic techniques. It was found to be ~ 14 kDa with unique N-terminal sequence, H₂N-AEEEIFXPDX, which did not show homology with the known sequence suggesting a new/novel compound. It was found to be heat resistant up to 100 °C, stable at pH 2.0-10.0, and retained complete activity in the presence of different organic compounds such as methanol, ethanol, acetone, isopropanol, ethyl acetate, Tween 80, acetonitrile, SDS, Triton X-100, and urea. However, complete activity was reduced after the treatment with trypsin, papain, and proteinase K suggesting proteinaceous nature of the compound. The cytocidal nature of halocin HA4 was evidenced with complete loss of viable count of indicator strain, H. larsenii HA10. The change in FTIR spectrum of halocin-treated cells suggested halocin HA4 interacts with cell membrane and nucleic acids of the target cells. Thus, we report a new halocin inhibitory to related strains and may be applied in the preservation of salted foods and leather hides in the respective industries.

Identification and characterization of a halocin-producing haloarchaeon isolated from Pachpadra salt lake

Haloarchaea are known to produce antimicrobial proteins, halocins which are generally stable at extreme conditions suggesting their potential biotechnological applications. Here, we report a halocin-producing haloarchaeon isolated from salt lake and identified as Haloferax larsenii HA4 using partial 16S rDNA sequence and biochemical properties. Whole-cell methanolysate showed ether-linked lipids, which is a characteristic feature of haloarchaea. Strain HA4 was able to grow at pH 6·0-10·0 and 15-30% NaCl. The growth response was normal but antimicrobial activity was detected only during the log-phase. Crude halocin HA4 was active in the pH range of pH 2·0-10·0 with stability up to 100°C. Cell-free supernatant (CFS) was also stable in different organic solvents and detergents tested. However, halocin activity was reduced after treatment with proteinase K suggesting the proteinaceous nature of the active compound. Concentrated CFS showed the presence of several proteins from 6·5-66 kDa but bioassay suggested ~14 kDa protein as halocin. Crude halocin preparation showed cytocidal activity against indicator strain, H. larsenii HA10 and inhibited the growth of other related strains such as H. larsenii HA3, HA8, HA9 and HA10.

Fermented Seeds ("Zgougou") from Aleppo Pine as a Novel Source of Potentially Probiotic Lactic Acid Bacteria

Microorganisms inhabiting fermented foods represent the main link between the consumption of this food and human health. Although some fermented food is a reservoir of potentially probiotic microorganisms, several foods are still unexplored. This study aimed at characterizing the probiotic potential of lactic acid bacteria isolated from zgougou, a fermented matrix consisting of a watery mixture of Aleppo pine's seeds. In vitro methods were used to characterize the safety, survival ability in typical conditions of the gastrointestinal tract, and adherence capacity to surfaces, antimicrobial, and antioxidant activities. Strains belonged to the Lactobacillus plantarum group and Enterococcus faecalis showed no DNase, hemolytic, and gelatinase activities. In addition, their susceptibility to most of the tested antibiotics, satisfied some of the safety prerequisites for their potential use as probiotics. All the strains tolerated low pH, gastrointestinal enzymes, and bile salts. They displayed a good antibacterial activity and antibiofilm formation against 10 reference bacterial pathogens, especially when used as a cell-free supernatant. Furthermore, the lactic acid bacteria (LAB) strains inhibited the growth of Aspergillus flavus and Aspergillus carbonarius. Finally, they had good antioxidant activity, although depending on the strain. Overall, the results of this work highlight that zgougou represents an important reservoir of potentially probiotic LAB. Obviously, future studies should be addressed to confirm the health benefits of the LAB strains.

Comparative Analysis of Inhibition-Based and Indicator-Independent Colorimetric Assay for Screening of Bacteriocin-Producing Lactic Acid Bacteria

Screening of bacteriocin-producing lactic acid bacteria (LAB) is an important aspect for the search of new/novel probiotic strains. Here, a vesicle-based colorimetric assay was compared with conventional inhibition-based antimicrobial assays using 54 isolates of LAB. All isolates demonstrated zone of growth inhibition ranging from 2.5 to 7.5 mm against indicator strain, Micrococcus luteus MTCC106 using point inoculation method. Cell-free supernatant of the isolates showed zone of growth inhibition varying from 14.5 to 25 mm using agar well diffusion assay. These isolates inhibited the growth of indicator strain by 89.56-98.65%. The antimicrobial activity present in cell-free supernatant of different isolates was found to be in the range of 10-160 AU ml^- 1. The treatment of polydiacetylene (PDA) vesicles with cell-free supernatant of selected isolates led to blue-red color transition, and presence of protein band on tricine SDS-PAGE confirmed the presence of membrane-acting peptides, bacteriocins. The colorimetric responses (CR%) varied between 0 and 59%, and the assay was found to be more sensitive, faster, and reliable as compared to the other conventional indicator-based methods used. Therefore, the colorimetric assay may be specifically applied for screening of bacteriocin-producing LAB.

Membrane-acting bacteriocin purified from a soil isolate Pediococcus pentosaceus LB44 shows broad host-range

Bacteriocin LB44 was purified from cell-free supernatant (CFS) of Pediococcus pentosaceus LB44 using activity-guided chromatography techniques. It was stable up to 121 °C, pH 2.0-6.0, sensitive to proteinase K, papain and trypsin, and retained complete activity in the presence of organic solvents tested. The molecular weight of bacteriocin was ∼6 kDa and initial ten amino acid residues (GECGMCXECG) suggested a new compound. The loss in viable cell count and K⁺ ion efflux of target cells of Micrococcus luteus suggested bactericidal activity. The cell membrane of bacteriocin-treated cells was found to be ruptured which was further confirmed by Fourier Transform Infrared (FTIR) analysis suggesting interaction of bacteriocin with phospholipids in cell membrane. It showed broad host-range and inhibited the growth of Lactobacillus delbrueckii NRRL B-4525, L. plantarum NRRL B-4496, L. acidophilus NRRL B-4495, Enterococcus hirae LD3, Weissella confusa LM85, Staphylococcus aureus, Salmonella typhi ATCC 13311, Serratia marcescens ATCC 27137, Pseudomonas aeruginosa ATCC 27853, Proteus vulgaris ATCC 29905, Haloferax larsenii HA1, HA3, HA8, HA9 and HA10. These properties suggested a new bacteriocin from soil isolate P. pentosaceus LB44 which may offers possible applications in food-safety and therapeutics.