Lactobacillus Plantarum Cells Research Articles

Antibacterial Activity of Live Cells of Lactobacillus Plantarum L40 as A Probiotic Against Pathogens Associated with Diabetic Foot Infections

The present study was designed to select a suitable isolate of Lactobacillus sp. in order to use it as a probiotic formula for treating diabetic foot ulcer disease in diabetic mellitus patients. In order to determine the inhibitory action, 240 isolates of Lactobacillus from different sources, were taken and exposed for screening tests to evaluate the (antagonism-activities) toward 4 multi-drug resistant foot ulcer pathogens which were chosen from 120 pathogenic isolates: Staphylococcus aureus, Klebsiella pneumonia, Proteus mirabilis, and P. aeruginosa. Twenty Lactobacillus isolates were selected from primary screening according to the capacity to restrain its expansion of four markers, that were exposed toward second screenings to detect their ability to produce a high amount of bacteriocin. Based on the results, the isolate Lactobacillus L40 was selected as the highest bacteriocin producing isolate which was further characterized as Lactobacillus plantarum Next, several tests were performed to study the properties of L. plantarum L40, in particular its biosafety and its suitability to be a successful probiotic. Results showed that L. plantarum was resistant to cephalosporin groups such as ceftriaxone and cefepime whereas, it was sensitive to amikacin and chloramphenicol. In addition, results revealed that this bacterium was strongly adherent and a good biofilm producer; had high auto-aggregation capability and a high ability to adhere with S. Staphylococcus aureus, Klebsiella pneumonia, Proteus mirabilis and P. aeruginosa. A gel formula containing live cells of L. plantarum L40 was prepared and based on the results, cells were successfully survived in this formula over 18 days. Therefore, it was selected to be utilized as a vector to store and transport viable cells of L. plantarum L40. This gel formula showed antibacterial activity by inhibiting Staphylococcus aureus, Klebsiella pneumonia, Proteus mirabilis, and P. aeruginosa growth. The results showed the possibility of using viable cells of bacteriocin-producing Lactobacillus plantarum as an effective probiotic to deal with some skin pathogens, and hence treat skin diseases such as diabetic foot ulcer disease.

Construction of a Temperature-Sensitive Shuttle Vector between Lactic Acid Bacteria and Escherichia coli and Its Application to a Tn10-Based Random Mutagenesis Tool in Lactic Acid Bacteria.

In the present study, we have obtained a temperature-sensitive replication mutant in the Escherichia (E.) coli-lactic acid bacterium (LAB) shuttle vector pLES003-b carrying erythromycin-resistance gene by error-prone PCR technique. Among 858 clones obtained in the construction of the random mutation libraries of pLES003-b in the ori and repA regions, three clones could grow normally at 28 °C but not at 42 °C. One of the clones was designated as pLES003-b TS1. The sequencing analysis of pLES003-b TS1 revealed that the plasmid has four substitution mutations (376G > A, 435A > T, 914C > A, and 1996T > A) and one insertional mutation (1806_1807insA). Among those mutations, substitution mutation 914C > A, which leads to a CGC-to-AGC codon change at position 44 of the RepA protein (arginine-to-serine substitution mutation: R44S in RepA), was predicted to be a cause of temperature sensitivity. Therefore, the C-to-A substitution was introduced into the repA gene in pLES003-b using a site-directed mutagenesis method, and the resultant plasmid was electroporated into a Lactobacillus (L.) plantarum cell. The resultant transformant cannot grow at 42 °C in the presence of erythromycin, which is used as a selective marker, indicating that the R44S point mutation in the RepA protein may be crucial for temperature sensitivity. Furthermore, we have developed a new plasmid as an efficient genetic engineering tool for random insertional mutagenesis in LABs using a combination of transposon Tn10 and the temperature-sensitive replication system in pLES003-b. The resultant plasmid vector, which was designated pLES-Tn10-TS1, would be useful for genetic analysis of the functional molecule in lactic acid bacterial strains.

Preparation of alginate-whey protein isolate and alginate-pectin-whey protein isolate composites for protection and delivery of Lactobacillus plantarum

Probiotics are sensitive to external conditions, resulting in low survival rates after being ingested or during food production, transportation and storage. In order to improve the survival rate of Lactobacillus plantarum (LP) during gastrointestinal digestion, storage, and freeze-drying, alginate-whey protein isolate (ALG-WPI) and alginate-pectin-whey protein isolate (ALG-PEC-WPI) composites were employed to encapsulate LP. The encapsulation efficiency of ALG-WPI-LP and ALG-PEC-WPI-LP beads both reached more than 99 %. Scanning electron microscopy (SEM) indicated that dense and rough aggregates were formed on the surface of both composites, and attached LP cells could be observed inside the beads. The ALG-WPI and ALG-PEC-WPI composites can protect the viability of LP in simulated gastric fluid (SGF) and release the probiotics in simulated intestinal fluid (SIF). The storage stability of LP at 4 °C was improved by about 15 % in comparison with bare LP and the survival rates of LP in ALG-WPI-LP and ALG-PEC-WPI-LP powders after freeze-drying were increased by 65.37 % and 72.06 %, respectively. The formation mechanism of ALG-WPI and ALG-PEC-WPI composites was further explored by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The ALG-WPI and ALG-PEC-WPI composites have great potential to protect and deliver probiotics in food systems.

The Bacillary Postbiotics, Including 2-Undecanone, Suppress the Virulence of Pathogenic Microorganisms

Secreted molecules from probiotic Bacilli have often been considered potential pharmaceuticals to fight infections caused by bacterial or yeast pathogens. In the present study, we investigated the antagonistic potential of secreted probiotic filtrates (hereafter, postbiotics) derived from Lactobacillus plantarum cells against pathogenic microorganisms, such as Escherichia coli, Staphylococcus aureus, and Candida albicans. We found that the postbiotics mitigate the biofilms of the tested pathogens with no notable effect on their planktonic growth. In addition, the postbiotics suppressed some virulence traits, for instance, the dendrite swarming motility of E. coli and yeast-to-hyphal switch in C. albicans. Further assays with an active constituent produced by the L. plantarum cells–2-undecanone revealed two significant findings: (i) 2-undecanone inhibits C. albicans biofilms and hyphae in vitro and in a Caenorhabditis elegans model, and (ii) it interacts specifically with Gln 58 amino acid residue of hyphal wall protein-1 (Hwp-1) in molecular docking analysis. The results suggest the targeted mode of antagonistic action of 2-undecanone against C. albicans biofilm. In total, the findings of the study depict an appealing strategy to use postbiotics, including specific ketone molecules, produced by L. plantarum for developing novel antibiofilm and anti-hyphal pharmaceuticals.

Investigation of the Role and Effectiveness of Chitosan Coating on Probiotic Microcapsules.

Microencapsulation and coating are preferred methods to increase the viability of the probiotic strains. The effect of microencapsulation technologies and materials used as microcapsule cores on viability is being investigated during development. In the present study, chitosan-coated and Eudragit L100-55-coated alginate microspheres were produced to encapsulate Lactobacillus plantarum probiotic bacteria. After the heat loading and simulated gastrointestinal juice dissolution study, the differences in viability were compared based on the CFU/mL values of the samples. The kinetics of the bacterial release and the ratio of the released live/dead cells of Lactobacillus plantarum were examined by flow cytometry. In all cases, we found that the CFU value for the chitosan-coated samples was virtually zero. The ratio of live/dead cells in the 120 min samples was significantly reduced to less than 20% for chitosan, while it was nearly 90% in the uncoated and Eudragit L100-55-coated samples. In the case of chitosan, based on some published MIC values and the amount of chitosan coating determined in the present study, we concluded the reason for our results. It was the first time to determine the amount of the released chitosan coat of the dried microcapsule, which reached the MIC value during the dissolution studies.

Sucrose, maltodextrin and inulin efficacy as cryoprotectant, preservative and prebiotic – towards a freeze dried Lactobacillus plantarum topical probiotic

Probiotic formulations must contain the right strain(s) in sufficient numbers when administered to confer the desired health benefit. However, significant cell death can occur during freeze-drying and over storage. This study assesses various saccharides for their ability to protect Lactobacillus plantarum cells over freeze-drying and storage, as well as their potential to act as prebiotics. The cryoprotective potential of 10% (m/v) of skimmed milk, inulin, maltodextrin, and sucrose were investigated during freeze-drying. Storage was assessed over 12 weeks at 4 °C and room temperature. Improved cell survival over freeze drying was observed with all the saccharides. However, only maltodextrin and sucrose retained cell viability over storage at 4 °C. Overall, skimmed milk demonstrated the highest survival up to 91%. Despite good cryoprotectant performance, inulin provided the least protection over storage, with <1% cell survival. Prebiotic potential was determined through growth experiments with 2% (m/v) of the saccharides in glucose-free MRS. All saccharides supported cell growth, with sucrose performing best and inulin worst.

General characteristics of the influence of surfactants on the bacteriolytic activity of lysozyme based on the example of enzymatic lysis of Lactobacillus plantarum cells in the presence of Tween 21 and SDS

The general characteristics of the effect of surfactants on the activity of lysozyme were demonstrated. The kinetics of bacterial cell lysis is consistent with the Michaelis-Menten equation and the presence of surfactants does not shift the pH-optimum of activity. Surfactants do not change the Km value but instead, affect the Vmax value. The experimental dependencies are well described by theoretical equations, which assume three surfactant binding sites on the lysozyme molecule. The dependencies of the activity of lysozyme on the surfactant concentration are either a step type (i.e., a higher plateau becomes a lower plateau), or a dependency with a maximum and continuation of the curve in the form of a plateau but with an increase in the surfactant concentration. It can be assumed that there is a mechanism for the regulation of lysozyme activity by an unknown natural factor that has a suitable hydrophobic radical capable of binding to the surface of lysozyme.

Comparison of Cytokine Expression in Human PBMCs Stimulated with Normal and Heat-Shocked Lactobacillus plantarum Cell Lysate.

Regulation of immune responses is among the beneficial effects of probiotic bacteria on human health. In this study, we aim to investigate the effect of normal and heat-shocked Lactobacillus plantarum PTCC 1058 cell lysate on cytokine expression by human PBMCs. The mid-exponential phase L. plantarum (108 CFU/mL) were used to prepare cell lysate. Isolated PBMCs were stimulated with 100 µg/mL of each normal and heat-shocked L. plantarum cell lysate for 72 h. Non-stimulated PBMCs were also evaluated as negative control. The mRNA expression of IL-6, IL-10, IFN-ɣ, TNF-α, and TGF-β genes was determined by quantitative RT-PCR amplification of total RNA extracted from PBMCs. Both types of cell lysate were able to increase pro-inflammatory cytokines and decrease anti-inflammatory cytokines. However, this effect was significantly stronger in heat-shocked cell lysate-treated PBMCs. Moreover, comparison of IFN-ɣ/IL-10, IFN-ɣ/TGF-β, IL-6/IL-10, IL-6/TGF-β, and TNF-α/IL-10 ratios in both conditions demonstrated that in the heat-shocked group, all of the above ratios were significantly higher than normal lysate treatment (p˂0.001), suggesting that heat-shocked probiotics are a potent inducer of the immune system in comparison to intact probiotics. Regarding these results, it may be possible to develop a new postbiotic product for the stimulation of immune responses of cancer patients or individuals who suffer from an immune defect.

Effect of starter culture fermentation of milk on the production, sensory attributes and storage of Wara (a Nigerian unripened soft cheese)

This study investigated the effect of Lactobacillus plantarum and Lactobacillus acidophilus isolated from wara, a Nigerian unripened soft cheese, on the production of starter-mediated type with improved quality and longer shelf-life. Fresh cow milk was pasteurized and inoculated with standardized cells of Lactobacillus plantarum and o Lactobacillus acidophilus (singly and in combination) and incubated at 30 C for 24 h to ferment. The fermented (acidified) milk was then used to produce wara using juice extract of Calotropis procera as rennet. Viable cell counts and physicochemical properties were estimated in the fermenting milk, while organoleptic attributes of traditional and starter-mediated wara were determined following standard procedures. The wara samples were stored at 30±2 °C for 6 days during which samples were obtained daily for physicochemical and microbiological analysis. Overall, physicochemical analysis of the fermenting milk samples showed a gradual drop in pH, increase in total titratable acidity and diacetyl level with accompanied increase in viable count. Organoleptically, there was no significant difference (p&gt; 0.05) between the traditional and some of the starter-mediated wara. During storage, the starter mediated wara had the lowest bacteria count and extended shelf-life.&#x0D; Keywords: Wara, Starter culture, Shelf life, Sensory attributes, Fermentation.

Analyses of the Effect of Peptidoglycan on Photocatalytic Bactericidal Activity Using Different Growth Phases Cells of Gram-Positive Bacterium and Spheroplast Cells of Gram-Negative Bacterium

We conducted photocatalytic experiments focusing on the peptidoglycan layer to elucidate the details of the mechanism of photocatalytic sterilization. The previous study of our laboratory suggested that the presence of the peptidoglycan layer increases the bactericidal effect. To further verify it, the following experiments were performed: experiments on cells with different peptidoglycan layer thickness used Lactobacillus plantarum cells with different growth phases, experiments on cells with the thin peptidoglycan layer used Escherichia coli cells and spheroplast cells from which the peptidoglycan layer was removed from E. coli cells. The bactericidal effects increased as the growth progresses of L. plantarum. It was confirmed by TEM that the thickness of the peptidoglycan layer increased with cell growth. The survival rates of E. coli intact cells were significantly lower than those of spheroplast cells. These results strongly suggest that the peptidoglycan layer enhances the photocatalytic bactericidal effect. As a result of allowing the photocatalytic reaction to act on peptidoglycan, the amount of hydroxyl radical was smaller, and the amount of hydrogen peroxide was higher than in the absence of peptidoglycan. It is suggested that peptidoglycan may convert produced hydroxyl radical to hydrogen peroxide.

Analytical combinations to evaluate the macromolecular composition of extracellular substances (ECS) from Lactobacillus plantarum cell culture media.

Sugar-enriched media are used to produce extracellular substances (ECS) by Lactobacillus plantarum WCSF1, with a focus on growing stages and carbon source substrates. Combination of size exclusion chromatography and ATR-FTIR spectroscopy provides physicochemical patterns of bulk ECS produced along culture growing time. Secreted biopolymers present polydisperse and high molecular weight distributions, with significant amounts of carbohydrates and proteins. Results, supported by a multivariate statistical analysis, enable to differentiate the macromolecular content of bacterial ECS along the growing stages regardless of the growing media, highlighting a higher production of proteinaceous materials compared to polysaccharides. At the end of the exponential phase, common exoproteins were present in all the tested sugar-enriched media such as transglycosylases between 20 and 35kDa, a muropeptidase at 36.9kDa and a cell wall hydrolase. Additionally, L. plantarum WCFS1 secretes ECS with a greater diversity of proteins, when growing in the sucrose-enriched media. Graphical abstract.

Effect of hydrogen peroxide on the dehydrogenase and quinone-reductase activity of irradiated Lactobacillus plantarum cells

The resistance of lactobacilli to oxidative stress is of great importance for their applicability as probiotics. This study aimed to evaluate the response of Lactobacillus plantarum strain ATCC® 14917™, grown in either de Man, Rogosa, and Sharpe agar (MRS medium) or tryptic soy broth (TSB medium), to 1–2 mM H2O2 after the exposure to different doses of ionising radiation. Two bacterial extracellular enzyme groups, dehydrogenases (DHAs) and quinone reductases (QRs), served as the criteria of viability and antioxidant activity, respectively. The irradiated L. plantarum culture grown in TSB showed increased QR activity at irradiation doses of 2–50 Gy, with the maximum activity at 10 Gy, compared to non-irradiated cells. The QR activity of the MRS-grown culture was increased significantly (p < 0.05) in the presence of H2O2 for the cells subjected to irradiation, compared to the control. The cultivation of L. plantarum in TSB resulted in considerable morphological changes in the 24 h culture. Our results indicate that the cultivation of L. plantarum in TSB activated the antioxidative potential of these bacteria. The most important aspect of this phenomenon is the extracellular enzyme activity that may directly influence the host organism by providing antioxidant activity.

In Ukrainian

The results are presented of a study on spectral characteristics, electron microscopy data and antibacterial properties of Lactobacillus plantarum cell matrices filled with biologically synthesized in the presence of surfactants (S) silver nanoparticles (bioAgNP). The dependences of spectral characteristic of cell suspension of lactic acid bacteria L.plantarum with synthesized bioAgNP on S concentration were analyzed, namely: cationic two quaternary ammonium salt (CS) aethonium and anionic sodium decyl phosphate (AS). To control the process of bioAgNP production in microorganism cells, the method of spectroscopy in ultraviolet and visible regions was used. The antibacterial properties of modified L. plantarum cells dependent on synthesis condition and their composition were testified by disco diffusion method. The results are presented of electron-microscopy investigation of treated with concentrated sulfuric acid bionanocomposite material. It is shown that addition at the synthesis of an ionogenic S to the precursor solution affects structural and size descriptions of biogenic silver formed in L. plantarum cells. Since a concentration more then the critical concentration of micelle formation, aethonium presence resulted in forming of two NPs fractions, namely: stabilized in a cell wall subcolloidal particles having absorption band at 380 nm and also aggregated particles having spectral shoulder at 440 nm. S addition promoted the red shift of absorption spectra dependent on CS concentration and medium pH, however not dependent on AS concentration. It is shown that antibacterial properties of modified with S nanobiocomposite materials mainly depend on the NPs content in lactic acid matrices and on their size. Joint application of bionanocomposite and aethonium preparation close to the critical micelle concentration allowed to rise their activity in relation to Gram(+)bacteria and, at the same time, to bring down on an order (from 1.0 to 0.1 %) the ordinary therapeutic dose of aethonium.

Effect of fermentation time on the quality of modified gadung flour from gadung tuber (Dioscorea hispida Dennst.)

Gadung (Dioscorea hispida Dennst.) is one of the tubers in Indonesia that has the potential as a food source. However, due to the low nutritional value and high content of cyanide acid, these tubers cannot be consumed directly. Therefore, proper processing techniques are needed to improve the nutritional value of gadung tubers. The aim of this study was to investigate the effects of fermentation time on the quality of modified gadung flour in a reasonably short time. Soaking and submerged fermentation processes were applied. It was found that modified gadung flour can be used as a wheat flour substitution under the following conditions: water to gadung mass ratio of 50 for 120 min (soaking process) and initial bacteria cell number of 1.21 x 1011 cells of Lactobacillus plantarum at the temperature of 32 °C for 36 h (fermentation process). The result showed that protein, cyanide acid, starch, amylose, and amylopectin contents were 7.63%, 6.66 ppm, 75.27%, 38.18%, and 61.82%, respectively, while physicochemical properties, such as swelling power, water solubility, and flour whiteness degree were 6.75 g/g, 0.56%, and 71.43%, respectively.

Ion-selective electrode integrated in small-scale bioreactor for continuous intracellular pH determination in Lactobacillus plantarum.

The aim of the present study was to develop an ion-selective electrode method for the continuous determination of the intracellular pH in Lactobacillus plantarum using a small-scale bioreactor. This method employed a salicylate-selective electrode basing on the distribution of salicylic acid across the cytoplasmic membrane. This developed electrode responded to salicylate concentrations above 20μmol/L with a Nernstian sensitivity. The energized and concentrated cells were added into a thermostated small-scale bioreactor that contained the salicylate anions dissolved in a 100mmol/L potassium phosphate buffer at different pH values. The changes in salicylate concentration that occurred in the medium containing bacterial suspension were measured as a voltage change. The cells of Lactobacillus plantarum showed maintenance of pH homeostasis at the studied pH ranging from 4.0 to 7.0, and they kept a neutral intracellular pH up to 5.8. The simplicity of the measuring preparation and the relatively low cellular concentration, as well as the advantages of the small-scale bioreactor, lead us to believe that the described method can facilitate the study of the physicochemical factors on the intracellular pH of lactic acid bacteria using a single pH probe in one method.

Secretion and functional expression of Mycobacterium bovis antigens MPB70 and MPB83 in lactic acid bacteria

The aim of this study was to determine the reliability of lactic acid bacteria (LAB) as heterologous hosts for the expression of MPB70 and MPB83, two Mycobacterium bovis antigens that possess diagnostics and immunogenic properties, respectively. We therefore generated recombinant cells of Lactococcus lactis and Lactobacillus plantarum that carried hybrid genes encoding MPB70 and MPB83 fused to signal peptides that are specifically recognized by LAB. Only L. lactis was able to secrete MPB70 using the L. lactis signal peptide Usp45, and to produce MPB83 as an immunogenic membrane protein following its expression with the signal peptide of the L. plantarum lipoprotein prsA. Inactivated cells of MPB83-expressing L. lactis cultures enhanced NF-κB activation in macrophages. Our results show that L. lactis is a reliable host for the secretion and functional expression of antigens that are naturally produced by M. bovis, the causative agent of bovine tuberculosis (bTB). This represents the first step on a long process to establishing whether recombinant LAB could serve as a food-grade platform for potential diagnostic tools and/or vaccine interventions for use against bTB, a chronic disease that primarily affects cattle but also humans and a wide range of domestic and wild animals.

Use of gelatin and gum arabic for microencapsulation of probiotic cells from Lactobacillus plantarum by a dual process combining double emulsification followed by complex coacervation.

The objectives of this study were i) to microencapsulate probiotic cells of Lactobacillus plantarum through a dual process consisting of emulsification followed by complex coacervation using gelatin and gum arabic, ii) to characterize the lyophilized microcapsules, iii) to evaluate their behavior in simulated in vitro gastrointestinal conditions and iv) to evaluate the survival of microencapsulated probiotic cells during 45 days of storage at 8 °C, 25 °C and -18 °C. The optimized conditions for complex coacervation consisted of a 50:50 biopolymer ratio and pH = 4.0. Emulsification was followed by complex coacervation using gelatin and gum arabic. The microcapsules presented dispersibility of 0.183 ± 0.17 g·mL-1, moisture content of 4.5%, water activity of 0.34 ± 0.03 and hygroscopicity of 9.20 ± 0.43 g of absorbed water per 100 g. Their size ranged from 66.07 ± 3.04 μm to 105.66 ± 3.24 μm. Viability of the encapsulated L. plantarum cells was 8.6 log CFU·g-1 and the encapsulation efficiency was 97.78%. After in vitro simulation of gastrointestinal conditions, viability of the encapsulated cells was 80.4% whereas it was only 25.0% for the free cells at 37 °C. Probiotic cell viability was maintained during storage at 8 °C and - 18 °C for 45 days.

One-pot conjugated linoleic acid production from castor oil by Rhizopus oryzae lipase and resting cells of Lactobacillus plantarum.

Conjugated linoleic acid (CLA) has attracted as novel type of fatty acids having unusual health-promoting properties such as anticarcinogenic and antiobesitic effects. The present work employed castor oil as substrate for one-pot production of CLA using washed cells of Lactobacillus plantarum (L. plantarum) and lipases as catalysts. Among the screened lipases, the lipase Rhizopus oryzae (ROL) greatly assisted resting cells to produce CLA. Mass spectral analysis of the product showed that two major isomers of CLA were produced in the reaction mixture i.e. cis-9, trans-11 56.55% and trans-10, cis-12 43.45%. Optimum factors for CLA synthesis were found as substrate concentration (8mg/mL), pH (6.5), washed cell concentration (12% w/v), and incubation time of 20h. Hence, the combination of ROL with L. plantarum offers one pot production of CLA selectively using castor oil as a cost-effective substrate.

The regulatory effects of L. plantarum peptidoglycan microspheres on innate and humoral immunity in mouse

Objective: To study the effects of Lactobacillus Plantarum cell wall peptidoglycan (LPG) microspheres on mouse intestinal flora changes, peptidoglycan recognitions protein (PGRP) and cytokines expression levels.Method: Plate counting was used for enumeration of the intestinal flora. Real-time PCR was used for quantification PGRP in different tissues. Cytokines content were determined by ELISA kits.Result: The mouse administered orally with LPG microspheres showed significantly higher number of Lactobacillus and Bifidobacterium in caecum contents (p < 0.01). The amount of PGRP expression in different organs was highest in LPG microspheres-treated group. IL-4, 12, IFN-γ, TNF-α contents in serum from LPG microspheres-treated mouse were significantly higher than those in normal saline-treated group (p < 0.01).Conclusions: This study shows that the LPG microspheres can regulate intestinal flora imbalance and improve systemic immunity, improve both Th1 and Th2 immune response, which provide some basis for the use of LPG as potential adjuvants.

High hydrostatic pressure inactivation of Lactobacillus plantarum cells in (O/W)-emulsions is independent from cell surface hydrophobicity and lipid phase parameters

ABSTRACTInactivation efficiency of high hydrostatic pressure (HHP) processing of food is strongly affected by food matrix composition. We investigated effects of fat on HHP inactivation of spoilage-associated Lactobacillus (L.) plantarum strains using defined oil-in-water (O/W)-emulsion model systems. Since fat-mediated effects on HHP inactivation could be dependent on interactions between lipid phase and microbial cells, three major factors possibly influencing such interactions were considered, that is, cell surface hydrophobicity, presence and type of surfactants, and oil droplet size. Pressure tolerance varied noticeably among L. plantarum strains and was independent of cell surface hydrophobicity. We showed that HHP inactivation of all strains tended to be more effective in presence of fat. The observation in both, surfactant-stabilized and surfactant-free (O/W)-emulsion, indicates that cell surface hydrophobicity is no intrinsic pressure resistance factor. In contrast to the presence of fat per se, surfactant type and oil droplet size did not affect inactivation efficiency.