Transcriptional analysis of the molecular mechanism underlying the response of Lactiplantibacillus plantarum to lactic acid stress conditions

Bioconversion of Fe3O4 Nanoparticles by Probiotics

Background/Objectives: Iron deficiency anemia remains a primary global health concern, affecting millions worldwide. Despite the widespread availability of iron supplements, their efficacy is often hindered by poor bioavailability and adverse gastrointestinal effects. This study explores the potential of probiotics to enhance the bioavailability of Fe3O4 NPs through probiotic-mediated mechanisms. Methods: Lactobacillus fermentum, Lactobacillus rhamnosus, and Lactobacillus plantarum were utilized to investigate their interactions with Fe3O4 NPs, synthesized via co-precipitation and characterized using transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Results: The results indicated that probiotics adhere to the nanoparticle surface, with L. fermentum exhibiting the highest adhesion and internalization capacity, leading to a significant increase in 4-hydroxyphenylacetic acid (4-HPLA) production (11.73 ± 0.09 mg/mL at 24 h, p < 0.05). Spectroscopic analyses further revealed that probiotic metabolism facilitates the oxidation of Fe3O4 to Fe2O3. Additionally, Fe3O4 nanoparticle-treated cultures demonstrated enhanced bacterial viability and metabolic activity, highlighting a synergistic effect between probiotics and iron nanoparticles. Conclusions: These findings provide compelling evidence for probiotic-assisted iron supplementation as a promising strategy to enhance iron bioavailability while mitigating the gastrointestinal side effects of conventional iron supplements.

Lactic Acid Production by Lactiplantibacillus plantarum AC 11S-Kinetics and Modeling

Lactic acid is a versatile chemical with wide application in many industries. It can be produced by the fermentation of different sugars by various lactobacilli and investigations on lactic acid production from different substrates and by different strains are still in progress. The present study aimed to study lactic acid production from lactose by Lactiplantibacillus plantarum AC 11S and to choose a mathematical model describing in the best way the experimental data obtained. The influence of initial substrate concentration was investigated, and optimal pH and temperature were determined. An unstructured mathematical model was developed comprising equations for bacterial growth, substrate consumption, and product formation. The model was solved with different terms for specific growth rates considering substrate and/or product inhibition. The best bacterial growth and lactic acid production were achieved at pH = 6.5 and 30 °C. Production of lactic acid was mainly growth-associated, and at initial substrate concentration over 15 g/L, a considerable product inhibition was observed. The parameters of different models were determined and compared. The modified Gompertz equation gave the best fit when solving only the equation for biomass growth at different initial substrate concentrations. Solving the entire set of differential equations for bacterial growth, substrate consumption, and product formation, the best results were obtained when using a variant of the logistic equation for biomass growth. This variant included a term for product inhibition and described in the best way all experimental data. Solving the model for different biomass concentrations showed that an increase in biomass led to a shorter lag phase and the stationary phase was reached faster. The results obtained, optimum conditions and the kinetic model, are good bases for studying pH-controlled fermentation, as well as a continuous process.

Strain-specific metabolomic diversity of Lactiplantibacillus plantarum under aerobic and anaerobic conditions

The chemotaxonomic diversity of 20 Lactiplantibacillus plantarum strains was investigated using non-targeted metabolite profiling under different culture conditions. Multivariate and metabolic pathway analyses based on GC-MS and LC-MS/MS datasets showed that amino acid metabolism, especially 2-hydroxy acids, was enriched under aerobic conditions (AE), whereas fatty acid & sugar metabolism was increased under anaerobic conditions (AN). Based on the metabolite profiles, L. plantarum strains were clustered into three main groups (A, B, and C). Overall, 79 and 83 significantly discriminant metabolites were characterized as chemical markers of AE and AN growth conditions, respectively. Notably, alcohols were more abundant in group A whereas amino acids, peptides, purines, and pyrimidines were significantly higher in group C. 2-hydroxy acids and oxylipins biosynthesized through amino acid and fatty acid metabolism, respectively, were more abundant in groups A and B. Furthermore, we observed a strong correlation between the chemical diversity of L. plantarum groups and their antioxidant activity from metabolite extracts. We propose a non-targeted metabolomic workflow to comprehensively characterize the chemodiversity of L. plantarum strain under different culture conditions, which may help reveal specific biomarkers of individual strains depending on the culture conditions.