Development of a microecologic product from Lactobacillus rhamnosus based on silica.

BACKGROUND: Probiotics are primarily made into microecologic products for use in the food and feed industries. The freeze-drying technique is widely used in their preparation to maintain their high level of bioactivity. This causes high costs in terms of the energy and time needed. In this study, we developed a method to produce a highly active microecologic product from Lactobacillus rhamnosus using heating and silica. RESULTS: A microecologic product was made successfully from L. rhamnosus using the whole bacterial culture broth, without waste, and using food-grade silica (4.5 mL g-1 ) to absorb water before drying at 37 °C for 8 h. The activity of L. rhamnosus cells was increased significantly by adding water extracts of green tea to the culture medium. The viable amount of L. rhamnosus in the obtained microecologic product was 9.80 × 1010 cfu g-1 with a survival rate of 224.67% in simulated gastric juice for 3 h and 68.2% in simulated intestinal juice for 3 h. The microecologic product treated an intestinal infection by multi-drug-resistant Staphylococcus aureus in mice very efficiently. CONCLUSION: The study developed an economic, eco-friendly, and efficient method for preparing highly active microecologic agents using heating and without waste. © 2022 Society of Chemical Industry.

The capability of Bacillus pseudomycoides from soil to remove Cu(II) in water and prevent it from entering plants.

AIMS: Copper ion is widespread in wastewater and threatens the condition and human health. Micro-organisms have unique advantages to remove heavy-metal ions from water, but are rarely reported in the removal of copper ion. This aims to develop micro-organisms that can remove copper ion in water, characterize their properties and analyse their potential application in practice. METHODS AND RESULTS: Sewage sludge was used as the source to isolate wild bacteria that can remove copper ion in water. The most efficient strain was screened out from 23 obtained isolates, identified as Bacillus pseudomycoides and coded as C6. The properties of C6 in the removal of copper ion in water were investigated in the aspects of reaction conditions, reaction groups, reaction dynamic and the application in oat planting. The reaction at pH 7 within 10 min yielded the highest removal rate of copper ion, 83%. The presence of lead ion in the reaction system could promote the removal rate of copper ion. Carboxyl groups and amidogen of C6 biomass were mainly involved in the removal of copper ion. The removal of copper ion was in accord with single-layer adsorption and Langmuir adsorption isotherm model. In application, C6 biomass reduced the copper content in the oat seedlings grown in copper ion containing water by more than seven times. CONCLUSIONS: B. pseudomycoides C6 can efficiently remove copper ion in water and inhibit it from entering plants. SIGNIFICANCE AND IMPACT OF STUDY: This is the first time to report the capability of B. pseudomycoides to remove copper ion in water, which is also more efficient than the currently reported chemical and biological methods.

Antifungal activity of silver nanoparticles synthesized by iturin against Candida albicans in vitro and in vivo.

Candida albicans (C. albicans) is a fungal pathogen that is difficult to cure clinically due to lack of effective antifungal agents with low toxicity. In this study, iturin, a cyclic peptide having wide antifungal spectrum, was used to synthesize nanosilver particles (AgNPs), and a complex of iturin-AgNPs was formed. The antifungal activity of iturin-AgNPs against C. albicans and its mechanisms were tested in vitro. Iturin-AgNPs were also loaded in chitosan (CS) composite dressing and applied to skin wound healing in mice. As results, iturin-AgNPs showed excellent antifungal activity with the minimum inhibitory concentrations (MIC) of 1.25, 2.5, and 5 µg/mL at C. albicans concentrations of 1×105, 1×106, and 1×107 CFU/mL, respectively. The MIC value still kept at 2.5 µg/mL against C. albicans (105 CFU/mL) after 15 regeneration, showing less induction of drug resistance to the pathogenic fungus. The antifungal mechanisms of iturin-AgNPs against C. albicans were identified as the increase of membrane permeability, damage of cell membrane integrity, and leakage of cellular protein and nucleic acids. No toxicity was found for iturin-AgNPs to HaCaT cells at concentrations of lower than 10 µg/mL. In wound healing application, iturin-AgNP CS composite dressing significantly accelerated the healing of C. albicans infected skin wounds at the early 10 days. In conclusion, iturin-AgNPs were developed as an efficient antifungal agent against C. albicans in vitro and in vivo and showed potential application in wound healing promotion.

Recovery of Ag+ by cyclic lipopeptide iturin A and corresponding chain peptide: reaction mechanisms, kinetics, toxicity reduction, and applications.

Iturin A, a cyclic lipopeptide produced by Bacillus subtilis, has great potential in removal of Ag+ from water, but the mechanisms and kinetic remain unclear. By comparison with the chain peptide (CP) that has the same amino acid sequence as iturin A, the mechanisms were found as iturin A reduced Ag+ to Ag0 and formed silver nanoparticles (AgNPs) via the groups of Ar-OH, CO, -NH-, O=C-O, and -C(CH).The cycle peptide fraction played an important role for the faster formation of AgNPs by iturin A than by CP. The overall Ag+ removal process by iturin A and CP could be well described by a Freundlich isotherm, with the equilibrium Ag+ removal capacity ranging from 58.41 to 61.03 mg/g within 293.15-333.15 K for iturin A. With the application of iturin A, the overall removal rate of Ag+ reached 91.8% in wastewater, the formed AgNPs could be easily recovered via charging the direct electric current, and the toxicity of Ag+ to paddy growth was greatly reduced.

Therapeutic effect of Lactobacillus rhamnosus SHA113 on intestinal infection by multi-drug-resistant Staphylococcus aureus and its underlying mechanisms.

Staphylococcus aureus, especially multi-drug-resistant (MDR) pathogenic S. aureus, poses a severe threat to food safety and human health. Probiotics offer promising potential for the control of MDR pathogens because of their safe and biofunctional properties. This study shows that Lactobacillus rhamnosus SHA113, a strain isolated from the milk of healthy women, could efficiently inhibit MDR S. aureus both in vitro and in vivo. In vitro, L. rhamnosus efficiently inhibited and even killed drug resistant and drug sensitive S. aureus strains. In vivo experiments showed that SHA113 could efficiently decrease the number of S. aureus cells, inhibit the expression of inflammatory factors TNF-α and IL-6, and restore the level of white cells and neutrophils in the blood. SHA113 could also efficiently repair damage of the intestinal barrier and other functions impaired by S. aureus infection. This was indicated by a change of intestinal villi length and structure, and an up-regulated expression of tight junction proteins ZO-1 and occludin. SHA113 also restored the structural damage of immune organs, such as the enlargement of the spleen and the increased level of inflammatory cytokines caused by S. aureus infection. More importantly, L. rhamnosus SHA113 showed more effective inhibitory and therapeutic effects on MDR S. aureus strain ZBQ006 than on drug sensitive S. aureus strain 29213. These results illustrated that L. rhamnosus SHA113 has great potential for the treatment of MDR S. aureus contamination as food control and for therapeutic treatment.

Novel Biomedical Functions of Surfactin A from Bacillus subtilis in Wound Healing Promotion and Scar Inhibition.

Surfactin produced by Bacillus subtilis is a powerful biosurfactant in food, cosmetics, and pesticide industries. However, its suitability in wound healing applications is uncertain. In this article, we determined the effects of surfactin A from B. subtilis on wound healing, angiogenesis, cell migration, inflammatory response, and scar formation. The results indicated that 80.65 ± 2.03% of surfactin A-treated wounds were closed, whereas 44.30 ± 4.26% of the vehicle-treated wound areas remained open on day 7 (P < 0.05). In mechanisms, it upregulated the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), accelerated keratinocyte migration through mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathways, and regulated the secretion of proinflammatory cytokines and macrophage phenotypic switch. More attractive, surfactin A showed a seductive capability to inhibit scar tissue formation by affecting the expression of α-smooth muscle actin (α-SMA) and transforming growth factor (TGF-ß). Overall, the study revealed a new function and potential of surfactin A as an affordable and efficient wound healing drug.

Capability of Bacillus Subtilis to remove Pb2+ via producing lipopeptides.

Lead contamination is widely found in soil and waters, which makes great threat to animal and human health. Environmentally friendly, efficient, and economical methods for the removal of Pb2+ pose significant challenges for environmental protection. Bacillus subtilis lipopeptide was firstly used to remove Pb2+ from water. In mechanisms, the lipopeptides formed complexes and chelated with Pb2+ via OH, CO, OCO, and NH. In kinetics, the Pb2+ removal process closely followed a pseudo-first-order model, and the equilibrium Pb2+ adsorption capacity ranged from 112.6 to 113.7 mg/g within a temperature range of 293.13-313.13 K. The Pb2+ removal process could be well described by a Langmuir isotherm. The maximum Pb2+ removal capability of lipopeptides was 164.4 mg/g in manually metal contaminated water and 130.4 mg/g in actual wastewater. Furthermore, the lipopeptides can not only decrease the amount of lead in oats grown, but also promote oat growth under Pb2+ stress. The results showed that lipopeptides can be used as a highly efficient adsorbent to remove Pb2+ from water, which means the great potential of lipopeptides in practical environments.

Development of a paper-based method to detect Hg2+ in waste water using iturin from Bacillus subtilis.

Colorimetric, fluorescence, and paper-based method were developed to measure the Hg2+ level in water using iturin A, a lipopeptide produced by Bacillus subtilis. Firstly, iturin was used to synthesize highly stable and uniformly sized silver nanoparticles (AgNPs). Secondly, the iturin-AgNPs were found to be highly selective and sensitive to Hg2+. The absorbance of the reaction system showed a good linear correlation with the Hg2+ concentration from 0.5 to 5 mg/L at 450 nm in the UV-Vis spectroscopy detection with the limit of detection (LOD) of 0.5 mg/L. When the reaction system was detected by fluorescence measurement, a good linear relationship was found between the fluorescence intensity and Hg2+ concentration from 0.05 to 0.5 mg/ at 415 nm with the LOD of 0.05 mg/L. Lastly, a paper-based detection method was developed. The developed method was successfully used to detect Hg2+ in contaminated polluted waters and showed acceptable results in terms of sensitivity, selectivity and stability. The paper-based method could distinguish Hg2+ at levels higher than 0.05 mg/L, thereby meeting the guidelines of the effluent quality standard for industries (0.05 mg/L). In summary, this method can be used daily by various industries to monitor the Hg2+ level in effluent water.