Novel bioelectrodes based on polysaccharide modified gold surfaces and electrochemically active Lactobacillus rhamnosus GG biofilms

Unveiling the microbial diversity of biofilms on titanium surfaces in full-scale water-cooling plants using metagenomics approach

Microbial colonization on the titanium condenser material (TCM) used in the cooling system leads to biofouling and corrosion and influences the water supply. The primary investigation of the titanium condenser was infrequently studied on characterizing biofilm-forming bacterial communities. Different treatment methods like electropotential charge, ultrasonication, and copper coating of titanium condenser material may influence the microbial population over the surface of the titanium condensers. The present study aimed to catalog the primary colonizers and the effect of different treatment methods on the microbial community. CFU (1.7 × 109 CFU/mL) and ATP count (< 5000 × 10-7 relative luminescence units) showed a minimal microbial population in copper-coated surface biofilm as compared with the other treatments. Live and dead cell result also showed consistency with colony count. The biofilm sample on the copper-coated surface showed an increased dead cell count and decreased live cells. In the metagenomic approach, the microbiome coverage was 10.06 Mb in samples derived from copper-coated TCM than in other treated samples (electropotential charge-17.94 Mb; ultrasonication-20.01 Mb), including control (10.18 Mb). Firmicutes preponderate the communities in the biofilm samples, and Proteobacteria stand next in the population in all the treated condenser materials. At the genus level, Lactobacillaceae and Azospirillaceae dominated the biofilm community. The metagenome data suggested that the attached community is different from those biofilm samples based on the environment that influences the bacterial community. The outcome of the present study depicts that copper coating was effective against biofouling and corrosion resistance of titanium condenser material for designing long-term durability.

Electrochemistry at Krakowian research institutions

The electrochemistry research team activity from Poland is marked by significant increase in the last 20 years. The joining of European Community in 2004 gives an impulse for the development of Polish science. The development of electrochemistry has been stimulated by cooperation with industry and the establishment of technology transfer centers, technology parks, business incubators, etc. and the mostly by simplified international collaborations. Five research institutions from Krakow reports work in the field of electrochemistry. The achievements of all teams are briefly described.

SRB-based bioelectrochemical system: A potential multipollutant combatant for enhanced landfill waste stabilization

Due to the lower proportion of organic matter and higher toxicity of the aged landfill, most of the advanced treatment technologies are not effective from economic, environmental, and social perspectives. This study evaluates the potential of sulfate-reducing bacteria (SRB) based bioelectrochemical-system (BES) in the decontamination of landfill wastes by reducing GHGs emissions and levels of soluble pollutants. The landfill waste (solid/leachate) collected from the Pirana Landfill site was assessed for economical long-term treatment and scaling up the feasibility of the designed system. The present system demonstrated significant improvement in volumetric hydrogen production of 3.1:1 (H2:CH4) by suppressing methanogenesis with a significant reduction in heavy metals concentration and other organic components. Despite being amended with 0.1 N ammonia, the treated leachate level of NO3 (2.350 ± 1.077 mg/L) was reduced by 5.3 times, hence reducing further groundwater pollution from landfill leaching. The BES-treated solid waste was more stabilized as shown by a fivefold increase in surface area and can be potentially applied for leachate immobilization and bio-fortification of agricultural fields. The vector arrangement and magnitude with differences in magnitudes for both leachate and solid waste supported the on-site applicability of BES treatment. Concerning the affinity in various treatment systems, the dendrogram clearly showed Ca and Fe placed far from each other (3506.08), in comparison to Fe and Mg (1186.6), followed by Fe and Cu (1544.6). Voltammograms proved the efficacy of the enriched electrochemically active bacteria (EAB), to support the treatment of landfill solid waste and leachate sustainably.

Physicochemical Investigation of Biosynthesis of a Protein Coating on Glass That Promotes Mammalian Cell Growth Using Lactobacillus rhamnosus GG Bacteria

Glass surfaces, although the first to be used for culturing ex vivo adherent cells, are not the perfect substrates for this purpose. Today, plastics dominate these applications, but in light of the global trend to reduce the use of synthetic polymers, it is reasonable to consider a return to glass vessels with coatings for these purposes. The ideal surface for cell growth is one that simulates the composition and structure of the mainly protein-based intercellular matrix. The work presented here shows a new idea of preparing porous protein coatings on glass using biosynthesis. The process utilizes the colonization of the gold nanoparticle-coated glass surface with Lactobacillus rhamnosus GG bacteria, followed by permeabilization (using ethanol) of their membrane and partial thermal degradation (at 160 °C in vacuum) of the surface-bound protein components of these microorganisms. It results in a development of coating on the glass that promotes mammalian cell growth, which has been preliminary confirmed using Vero cells. Subsequent steps in the formation of coating components were documented by reflectance ultraviolet and visible spectra and infrared spectroscopy. The presence of microorganisms and mammalian cells was confirmed using scanning electron and optical microscopy and crystalline violet staining.

Growth of Lactic Acid Bacteria on Gold-Influence of Surface Roughness and Chemical Composition

The main focus of this work was to establish a correlation between surface topography and chemistry and surface colonization by lactic acid bacteria. For this reason, we chose gold substrates with different surface architectures (i.e., smooth and nanorough) that were characterized by atomic force microscopy (AFM), electron scanning microscopy (SEM), and X-ray diffractometry (XRD). Moreover, to enhance biocompatibility, we modified gold substrates with polymeric monolayers, namely cationic dextran derivatives with different molar masses. The presence of those layers was confirmed by AFM, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). In order to determine the adhesion abilities of non-modified and modified gold surfaces, we tested three lactic acid bacteria (LAB) strains (i.e., Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and Lactobacillus plantarum 299v). We have shown that surface roughness influences the surface colonization of bacteria, and the most significant impact on the growth was observed for the Lactobacillus rhamnosus GG strain. What is more, covering the gold surface with a molecular polymeric film by using the layer-by-layer (LbL) method allows additional changes in the bacterial growth, independently on the used strain. The well-being of the bacteria cells on tested surfaces was confirmed by using selective staining and fluorescence microscopy. Finally, we have determined the bacterial metabolic activity by measuring the amount of produced lactic acid regarding the growth conditions. The obtained results proved that the adhesion of bacteria to the metallic surface depends on the chemistry and topography of the surface, as well as the specific bacteria strain.

Application of advanced anodes in microbial fuel cells for power generation: A review

Microbial fuel cells (MFCs) the most extensively described bioelectrochemical systems (BES), have been made remarkable progress in the past few decades. Although the energy and environment benefits of MFCs have been recognized in bioconversion process, there are still several challenges for practical applications on large-scale, particularly for relatively low power output by high ohmic resistance and long period of start-up time. Anodes serving as an attachment carrier of microorganisms plays a vital role on bioelectricity production and extracellular electron transfer (EET) between the electroactive bacteria (EAB) and solid electrode surface in MFCs. Therefore, there has been a surge of interest in developing advanced anodes to enhance electrode electrical properties of MFCs. In this review, different properties of advanced materials for decorating anode have been comprehensively elucidated regarding to the principle of well-designed electrode, power output and electrochemical properties. In particular, the mechanism of these materials to enhance bioelectricity generation and the synergistic action between the EAB and solid electrode were clarified in detail. Furthermore, development of next generation anode materials and the potential modification methods were also prospected.

Chemical Functionalization of the Zinc Selenide Surface and Its Impact on Lactobacillus rhamnosus GG Biofilms

Bacteria grow on surfaces and form communities called biofilms. Bacterial adhesion and properties of the derived biofilms depend on, among others, the nature of the supporting substrate. Here, we report how the surface properties of the substrate affect the biofilm growth of probiotic Lactobacillus rhamnosus GG (LGG). Hydrophilic (OH), hydrophobic (CH₃), and positively charged (NH₃⁺) surfaces were obtained by the functionalization of a ZnSe crystal with alkanethiol self-assembled monolayers (SAM). The self-assembly of alkanethiols onto ZnSe was studied in situ using infrared spectroscopy in attenuated total reflection mode (ATR-FTIR). The organization of grafted SAMs was analyzed based on the results of ATR-FTIR, high-energy elastic backscattering spectrometry, and contact angle measurements. The kinetics and adhesion strength of LGG initial attachment as well as its physiological state on surfaces terminated by the different functional groups were assessed by the combination of ATR-FTIR, force measurements based on atomic force microscopy, and fluorescent staining of bacteria. The strength of interactions between LGG and the surface was strongly affected by the terminal group of the alkanethiol chain. The -NH₃⁺ groups displayed the highest affinity with LGG at the first stage of interaction. The surface properties also played an important role when LGG biofilms were further grown in a nutritive medium for 24 h under flow conditions. Notably, the analysis of the infrared spectra recorded during the biofilm cultivation revealed differences in the kinetics of growth and in the polysaccharide features of the biofilm depending on the substrate functionality. LGG biofilm was stable only on the positively charged surface upon rinsing. Findings of this work clearly show that the adhesion features and the growth of LGG biofilms are substrate-dependent.

A journey in the complex interactions between electrochemistry and bacteriology: From electroactivity to electromodulation of bacterial biofilms

Although the term bioelectrochemistry tends to be associated with animal and human tissues, bioelectric currents exist also in plants and bacteria. Especially the latter, when agglomerated in the form of biofilms, can exhibit electroactivity and susceptibility to electrical stimulation. Therefore, electrochemical methods appear to become powerful techniques to expand the conventional strategies of biofilm characterization and modification. In this review, we aim to provide the insight into the electrochemical behaviour of bacteria and present the variety of electrochemical techniques that can be used either for the non-destructive monitoring of bacterial communities or modulation of their growth. The most common applications of electrical stimulation on biofilms are presented, including the prevention of bacterial growth by charging the surface of the materials, changing the direction of bacterial movement under the influence of the electric field and increasing of the potency of antibiotics when bactericides are coupled with the electric field. Also, the industrial applications of microbial electro-technologies are described, such as bioremediation, wastewater treatment, and microbial fuel cells. Consequently, we are showing the complexity of interactions that exist between electrochemistry and bacteriology that can be used for the benefit of these two disciplines.