The effect of chitosan nanoparticles onto Lactobacillus cells

Chitosan and its derivatives regulate lactic acid synthesis during milk fermentation

Introduction

The influence of chitosan's physicochemical characteristics on the functionality of lactic acid bacteria and the production of lactic acid remains very obscure and contradictory to date. While some studies have shown a stimulatory effect of oligochitosans on the growth of Lactobacillus spp, other studies declare a bactericidal effect of chitosan. The lack and contradiction of knowledge prompted us to study the effect of chitosan on the growth and productivity of L. bulgaricus in the presence of chitosan and its derivatives.

Methods

We used high molecular weight chitosan (350 kDa) and oligochitosans (25.4 and 45.3 kDa). The experiment was carried out with commercial strain of L. bulgaricus and the low fat skim cow milk powder reconstituted with sterile distilled water. After fermentation, dynamic viscosity, titratable acidity, pH, content of lactic acid, colony forming units, chitosan and oligochitosans radii were measured in the samples. Fermented dairy products were also examined using sodium dodecyl sulfate electrophoretic analysis, gas chromatography-mass spectrometry and light microscopy.

Results and discussion

The results of the study showed that when L. bulgaricus was cultured in the presence of 25.4 kDa oligochitosans at concentrations of 0.0025%, 0.005%, 0.0075% and 0.01%, the average rate of LA synthesis over 24 hours was 11.0 × 10-3 mol/L/h, 8.7 × 10-3 mol/L/h, 6.8 × 10-3 mol/L/h, 5.8 × 10-3 mol/L/h, respectively. The 45.3 kDa oligochitosans had a similar effect, while the average rate of lactic acid synthesis in the control sample was only 3.5 × 10-3 mol/L/h. Notably, 350 kDa chitosan did not affect the rate of lactic acid synthesis compared with the control sample. Interestingly, interaction of chitosan with L. bulgaricus led to a slowdown in the synthesis of propanol, an increase in the content of unsaturated and saturated fatty acids, and a change in the composition and content of other secondary metabolites. The quantity of L. bulgaricus in a sample with 0.01% chitosan exceeded their content in the control sample by more than 1,700 times. At the same chitosan concentration, the fermentation process was slowed down, increasing the shelf life of the fermented milk product from 5 to 17 days while maintaining a high content of L. bulgaricus (6.34 × 106 CFU/g).

Eco-friendly and safe alternatives for the valorization of shrimp farming waste

The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Antimicrobial Efficiency of Chitosan and Its Methylated Derivative against Lentilactobacillus parabuchneri Biofilms

Antimicrobial materials are considered potential alternatives to prevent the development of biofilm-associated contaminations. Concerns regarding synthetic preservatives necessitate the development of innovative and safe natural antimicrobials. In the present study, we discuss the in situ infrared attenuated total reflection spectroscopy (IR-ATR) investigations of the selective antimicrobial efficiency of chitosan in controlling the growth of Lentilactobacillus parabuchneri biofilms. The protonated charges of chitosan were additionally amplified by structural modification via methylation, yielding quaternized derivative TMC (i.e., N, N, N-trimethyl chitosan). To evaluate antimicrobial effectiveness against L. parab. biofilms, IR-ATR spectroscopy provided information on molecular mechanisms and insights into chemical changes during real-time biofilm inhibition studies. The integrated fiberoptic oxygen microsensors enabled monitoring oxygen (O₂) concentration gradients within biofilms, thereby confirming the metabolic oxygen depletion dropping from 4.5 to 0.7 mg L^-1. IR studies revealed strong electrostatic interactions between chitosan/its water-soluble derivative and bacteria, indicating that a few hours were sufficient to affect biofilm disruption. The significant decrease in the IR bands is related to the characteristic spectral information of amide I, II, III, nucleic acid, and extracellular polymeric matrix (EPS) produced by L. parabuchneri biofilms. Cell clusters of biofilms, microcolonies, and destabilization of the EPS matrix after the addition of biopolymers were visualized using optical microscopy. In addition, scanning electron microscopy (SEM) of biofilms grown on polystyrene and stainless-steel surfaces was used to examine morphological changes, indicating the disintegration of the biofilm matrix into individual cells. Quantification of the total biofilm formation correlated with the CV assay results, indicating cell death and lysis. The electrostatic interactions between chitosan and the bacterial cell wall typically occur between protonated amino groups and negatively charged phospholipids, which promote permeabilization. Biofilm growth inhibition was assessed by a viability assay for a period of 72 h and in the range of low MIC values (varying 0.01-2%). These results support the potential of chitosan and TMC for bacterial growth prevention of the foodborne contaminant L. parabuchneri in the dairy industry and for further implementation in food packaging.

Influence of Excipient Composition on Survival of Vaginal Lactobacilli in Electrospun Nanofibers

The lack of appropriate delivery systems hinders the use of probiotics in the treatment of vaginal infections. Therefore, the development of a new delivery system for the local administration of vaginal probiotics is necessary. In this study, we selected three vaginal lactobacilli, i.e., Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii, and incorporated them into nanofibers using electrospinning. Polyethylene oxide (PEO) was used as a carrier polymer to produce nanofibers. It was supplemented with alginate and sucrose selected from a group of carbohydrates for their growth-promoting effect on lactobacilli. The interaction between excipients and lactobacilli was evaluated thermally and spectroscopically. Bacterial survival in polymer solutions and in nanofibers immediately after electrospinning and after storage varied among species and was dependent on the formulation. Sucrose improved the survival in polymer solutions and preserved the viability of L. crispatus and L. jensenii immediately after electrospinning, and L. gasseri and L. jensenii during storage. Blending PEO with alginate did not improve species viability. However, the three lactobacilli in the nanofibers retained some viability after 56 days, indicating that composite multifunctional nanofibers can maintain the viability of vaginal lactobacilli and can be used as a potential solid delivery system for vaginal administration of probiotics.

Current trends in chitosan based nanopharmaceuticals for topical vaginal therapies

Large surface area, rich vascularisation, well defined mucous membrane, balanced pH and relatively low enzymatic activity makes vagina a suitable site for drugs associated with women's health issues like Urinary tract infection (UTI) and vaginal infections. Therapeutic performance of intravaginal dosage forms largely depends on the properties of polymers and drugs. Chitosan (CS) because of its unique physical, chemical, pharmaceutical and biopharmaceutical properties have received a great deal of attention as an essential component in vaginal drug delivery systems. Further the presence of free amino and hydroxyl groups on the chitosan skeleton allows easy derivatization under mild conditions to meet specific application requirements. Moreover, CS-based nanopharmaceuticals like nanoparticles, nanofiber, nanogel, nanofilm, liposomes and micelles are widely studied to improve therapeutic performance of vaginal formulations. However, susceptibility of CS to the acidic pH of vagina, poor loading of hydrophobic drugs, rapid mucosal turn over are the key issues need to be addressed for successful outcomes. In this review, we have discussed the application of CS and CS derivatives in vaginal drug delivery and also highlight the recent progress in chitosan based nanocarrier platforms in terms of their limitations and potentials.

Microbiota and nanoparticles: Description and interactions

The healthy human body is inhabited with a large number of bacteria, forming natural flora. It is even estimated that for a human body, its amount of DNA is less important that its bacterial genetic material. This flora plays major roles in the sickness and health of the human body and any change in its composition may lead to different diseases. Nanoparticles are widely used in numerous fields: cosmetics, food, industry, and as drug delivery carrier in the medical field. Being included in these various applications, nanoparticles may interact with the human body at various levels and with different mechanisms. These interactions differ depending on the nanoparticle nature, its structure, its concentration and manifest in different ways on the microbiota, leading to its destabilization, its restoring or showing no toxic effect. Nanoparticles may also be used as a vehicle to regulate the microbiota or to treat some of its diseases.

Microbiota and cancer: In vitro and in vivo models to evaluate nanomedicines

Nanomedicine implication in cancer treatment and diagnosis studies witness huge attention, especially with the promising results obtained in preclinical studies. Despite this, only few nanomedicines succeeded to pass clinical phase. The human microbiota plays obvious roles in cancer development. Nanoparticles have been successfully used to modulate human microbiota and notably tumor associated microbiota. Taking the microbiota involvement under consideration when testing nanomedicines for cancer treatment might be a way to improve the poor translation from preclinical to clinical trials. Co-culture models of bacteria and cancer cells, as well as animal cancer-microbiota models offer a better representation for the tumor microenvironment and so potentially better platforms to test nanomedicine efficacy in cancer treatment. These models would allow closer representation of human cancer and might smoothen the passage from preclinical to clinical cancer studies for nanomedicine efficacy.

Two-Layer Functional Coatings of Chitosan Particles with Embedded Catechin and Pomegranate Extracts for Potential Active Packaging

Two-layer functional coatings for polyethylene (PE) and polypropylene (PP) films were developed for the active packaging concept. Prior to coating, the polymer films were activated by O2 and NH3 plasma to increase their surface free energy and to improve the binding capacity and stability of the coatings. The first layer was prepared from a macromolecular chitosan solution, while the second (upper) layer contained chitosan particles with embedded catechin or pomegranate extract. Functionalized films were analyzed physico-chemically to elemental composition using ATR-FTIR spectroscopy and XPS. Further, oxygen permeability and wettability (Contact Angle) were examined. The antimicrobial properties were analyzed by the standard ISO 22196 method, while the antioxidative properties were determined with an ABTS assay. Functionalized films show excellent antioxidative and antimicrobial efficacy. A huge decrease in oxygen permeability was achieved in addition. Moreover, a desorption experiment was also performed, confirming that the migration profile of a compound from the surfaces was in accordance with the required overall migration limit. All these properties indicate the great potential of the developed active films/foils for end-uses in food packaging.

Insights into Adsorption Characterization of Sulfated Xylans onto Poly(ethylene terephthalate)

The main aim of this investigation was to study the interaction of sulfated xylans as antithrombotic substances with poly(ethylene terephthalate) (PET) model films as a model for blood contacting surfaces. The adsorption of sulfated xylans onto PET model films was studied as a function of pH and ionic strength using the quartz crystal microbalance with dissipation (QCM-D) technique. The application of positively charged polyethyleneimine (PEI) as an anchoring polymer was done to improve the adsorption. The hydrophilic/hydrophobic properties of functionalized PET surfaces were monitored by goniometry, whilst their elemental composition was determined by X-ray photoelectron spectroscopy. Sulfated xylans adsorbed favorably at pH 5 by physical interactions and by entropy gain driven adsorption. Higher ionic strengths of solutions improved adsorption, due to the reduction of electrostatic repulsive forces between PET surfaces and anionic xylans’ macromolecules. The intermediate PEI layer caused more extensive and stable adsorption due to Coulomb interactions. The surface modifications presented in this work provided important information regarding the adsorption/desorption phenomena between antithrombotic sulfated xylans and PET surfaces. The latter is of great interest when preparing advanced polymer composite material such as functional antithrombotic PET surfaces for blood-contacting medical devices and presents an extremely challenging research field.

Bioprocessing of shrimp wastes to obtain chitosan and its antimicrobial potential in the context of ethanolic fermentation against bacterial contamination

This study investigated the bioprocessing of shrimp wastes to obtain chitin and its deacetylated product chitosan by a fermentation process mediated by Lactobacillus plantarum. The concentrations of glucose, bacterial inoculum, and shrimp wastes in the Man, Rogosa and Sharpe medium were optimized for the fermentation process performed in shake flasks to achieve the maximum titratable acidity to obtain chitin. The experiments were scaled up in a 700-mL working volume bioreactor, and the resulting chitin was deacetylated by the autoclave method. The bioextracted chitosan was characterized (Fourier transform infrared spectroscopy [FTIR], deacetylation degree, and molecular weight) and evaluated for its antimicrobial effects by comparing it with a commercial chitosan sample in the context of the ethanolic fermentation process for fuel alcohol production. The effect of chitosan on such a fermentation process has not been determined yet. The bacterial contaminant Lactobacillus fermentum and the main agent of ethanolic fermentation Saccharomyces cerevisiae were cultured in semi-synthetic medium and co-cultured in sugarcane juice to verify the effect of chitosan on their growth. The bioextracted chitosan (molecular weight 4.0 × 10⁵ g mol^-1 and deacetylation degree 80%) was comparable to commercial chitosan, although higher concentrations of the former were required to achieve similar antimicrobial activities. Both commercial and bioextracted chitosan samples exhibited antimicrobial activity against S. cerevisiae and L. fermentum, but the concentration that caused the inhibition of yeast growth was almost tenfold higher than for the bacterium. Moreover, bioextracted chitosan showed no yeast inhibition or lethality in the range of 0.0075-0.96% while for the bacterium, growth inhibition occurred in concentrations varying from 0.24 to 0.48% and lethality of more than 99% at 0.96%. These results indicate the potential use of chitosan and especially of bioextracted chitosan in the bioethanol industry as a safer and more natural approach to combat unwanted bacterial contamination.

Physicochemical Characterization of Packaging Foils Coated by Chitosan and Polyphenols Colloidal Formulations

In this research, antimicrobial polysaccharide chitosan was used as a surface coating for packaging material. The aim of our research was to establish an additive formulation of chitosan and antioxidative plant extracts as dispersion of nanoparticles. Chitosan nanoparticles with embedded thyme, rosemary and cinnamon extracts were synthesized, and characterized for this purpose. Two representative, commercially used foils, polypropylene (PP) and polyethylene (PE), previously activated by UV/ozone to improve coating adhesion, were functionalized using chitosan-extracts nanoparticle dispersions. The foils were coated by two layers. A solution of macromolecular chitosan was applied onto foils as a first layer, followed by the deposition of various extracts embedded into chitosan nanoparticles that were attached as an upper layer. Since active packaging must assure bioactive efficiency at the interface with food, it is extremely important to understand the surface characteristics and phenomena of functionalized foils. The physico-chemical analyses of functionalized foils were thus comprised of surface elemental composition, surface charge, wettability, as well as surface morphology. It has been shown that coatings were applied successfully with an elemental composition, surface charge and morphology that should enable coating stability, homogeneity and consequently provide an active concept of the packaging surface in contact with food. Moreover, the wettability of foils was improved in order to minimize the anti-fogging behavior.

Gut microbiota fermentation of marine polysaccharides and its effects on intestinal ecology: An overview

The gut microbiota that resides in the mammalian intestine plays a critical role in host health, nutrition, metabolic and immune homeostasis. As symbiotic bacteria, these microorganisms depend mostly on non-digestible fibers and polysaccharides as energy sources. Dietary polysaccharides that reach the distal gut are fermented by gut microbiota and thus exert a fundamental impact on intestinal ecology. Marine polysaccharides contain a class of dietary fibers that are widely used in food and pharmaceutical industries (e.g., agar and carrageenan). In this regard, insights into fermentation of marine polysaccharides and its effects on intestinal ecology are of vital importance for understanding the beneficial effects of these glycans. Here, in this review, to provide an overlook of current advances and facilitate future studies in this field, we describe and summarize up-to-date findings on how marine polysaccharides are metabolized by gut microbiota and what effects these polysaccharides have on intestinal ecology.

NMR quantification of diffusional exchange in cell suspensions with relaxation rate differences between intra and extracellular compartments

Water transport across cell membranes can be measured non-invasively with diffusion NMR. We present a method to quantify the intracellular lifetime of water in cell suspensions with short transverse relaxation times, T₂, and also circumvent the confounding effect of different T₂ values in the intra- and extracellular compartments. Filter exchange spectroscopy (FEXSY) is specifically sensitive to exchange between compartments with different apparent diffusivities. Our investigation shows that FEXSY could yield significantly biased results if differences in T₂ are not accounted for. To mitigate this problem, we propose combining FEXSY with diffusion-relaxation correlation experiment, which can quantify differences in T₂ values in compartments with different diffusivities. Our analysis uses a joint constrained fitting of the two datasets and considers the effects of diffusion, relaxation and exchange in both experiments. The method is demonstrated on yeast cells with and without human aquaporins.

Chitosan-Based Coating with Antimicrobial Agents: Preparation, Property, Mechanism, and Application Effectiveness on Fruits and Vegetables

Chitosan coating is beneficial to maintaining the storage quality and prolonging the shelf life of postharvest fruits and vegetables, which is always used as the carrier film for the antimicrobial agents. This review focuses on the preparation, property, mechanism, and application effectiveness on the fruits and vegetables of chitosan-based coating with antimicrobial agents. Chitosan, derived by deacetylation of chitin, is a modified and natural biopolymer as the coating material. In this article, the safety and biocompatible and antimicrobial properties of chitosan were introduced because these attributes are very important for its application. The methods to prepare the chitosan-based coating with antimicrobial agents, such as essential oils, acid, and nanoparticles, were developed by other researchers. Meanwhile, the application of chitosan-based coating is mainly due to its antimicrobial activity and other functional properties, which were investigated, introduced, and analyzed in this review. Furthermore, the surface and mechanical properties were also investigated by researchers and concluded in this article. Finally, the effects of chitosan-based coating on the storage quality, microbial safety, and shelf life of fruits and vegetables were introduced. Their results indicated that chitosan-based coating with different antimicrobial agents would probably have wide prospect in the preservation of fruits and vegetables in the future.