Stability Studies, Biodegradation Tests, and Mechanical Properties of Sodium Alginate and Gellan Gum Beads Containing Surfactant.

The excessive presence of single-use plastics is rapidly degrading our natural environment on a global scale due to their inherent resistance to decomposition. Wet wipes used for personal or household purposes contribute significantly to the accumulation of plastic waste. One potential solution to address this problem involves developing eco-friendly materials that possess the ability to degrade naturally while retaining their washing capabilities. For this purpose, the beads from sodium alginate, gellan gum, and a mixture of these natural polymers containing surfactant were produced using the ionotropic gelation method. Stability studies of the beads by observing their appearance and diameter were performed after incubation in solutions of different pH values. The images showed that macroparticles were reduced in size in an acidic medium and swelled in solution of pH-neutral phosphate-buffered saline. Moreover, all the beads first swelled and then degraded in alkaline conditions. The beads based on gellan gum and combining both polymers were the least sensitive to pH changes. The compression tests revealed that the stiffness of all macroparticles decreased with the increasing pH of the solutions in which they were immersed. The studied beads were more rigid in an acidic solution than in alkaline conditions. The biodegradation of macroparticles was assessed using a respirometric method in soil and seawater. It is important to note that the macroparticles degraded more rapidly in soil than in seawater.

Glomus sp. and Bacillus sp. strains mitigate the adverse effects of drought on maize (Zea mays L.).

Maize (Zea mays L.) is an economically important source of food and feed. This species is highly sensitive to drought, which is the most limiting factor for the biomass yield of a crop. Thus, maize cultivation methods should be improved, especially by environment-friendly agricultural practices, such as microorganisms. Here, we provide evidence that Glomus sp. and Bacillus sp. modulate maize response to drought. Inoculation of maize seeds by these microorganisms restored the proper photosynthetic activity of the plant under drought and stabilized the osmoprotectant content of the leaf. The beneficial effect of Glomus sp. and Bacillus sp. was also related to the stabilization of cell redox status reflected by hydrogen peroxide content, antioxidant enzymes, and malondialdehyde level in leaves. As we revealed by several methods, shaping maize response to drought is mediated by both microorganism-mediated modifications of cell wall composition and structure of leaves, such as downregulating pectin, affecting their methylation degree, and increasing hemicellulose content. Overall, we provide new information about the mechanisms by which Glomus sp. and Bacillus sp. induce drought tolerance in maize, which is a promising approach for mitigating abiotic stresses.

Consortium of plant growth-promoting rhizobacteria enhances oilseed rape (Brassica napus L.) growth under normal and saline conditions.

A preparation development, which stimulates plant growth under normal and saline conditions, and protects against fungal infections, would increase crop yields and reduce damage in agriculture. This study was conducted using bacterial isolates from rape rhizosphere as a plant growth promoter and an alternative to chemical fertilizers. Three from fifty bacterial isolates: B14 (Pseudomonas sp.), B16 (Sphingobacterium sp.), and B19 (Microbacterium sp.) showed the best in vitro plant growth-promoting (PGP) characteristics. B14 strain had the best antifungal activity against phytopathogens inhibiting growth of B. cinerea, C. acutatum, and P. lingam. Moreover, B14, B16 and B19 isolates coded for several genes involved in PGP activities, aimed at improving nutrient availability, resistance to abiotic stress, and fungal pathogen suppression. Microbial consortium (B14, B16, and B19) had the best effect on rape growth, significantly increasing number of live leaves, compared to the untreated control and single inoculant treatments. Moreover, the consortium induced significant increase in shoots length and chlorophyll content in comparison to Pseudomonas sp. B14 and Microbacterium sp. B19. The consortium also induced plants tolerance to salt stress. The genomic information as well as the observed traits, and beneficial attributes towards rape, make the rhizobacterial consortium an ideal candidate for further development as biofertilizers.

The Use of Chitosan and Starch-Based Flocculants for Filter Backwash Water Treatment.

Inorganic aluminum or iron salts supported with synthetic polymers are commonly used to eradicate colloidal particles from water in coagulation and flocculation processes. Nevertheless, these agents have several disadvantages, such as large volumes of sludge produced or environmental toxicity. Recently biodegradable polymers have been suggested as eco-friendly flocculants for water treatment. This study aimed to investigate the possibilities of using starch and chitosan and their oxidized derivatives as flocculants for filter backwash water treatment. Dialdehyde starch (DST) and dialdehyde chitosan (DCT) were synthesized by periodate oxidization of natural starch from corn and low molecular weight chitosan. The obtained materials have been characterized with scanning electron microscopy (SEM), ATR-FTIR spectroscopy, and thermogravimetric analysis (TGA). Furthermore, we studied the flocculation properties of polysaccharide flocculants in a series of jar tests. The effectiveness of chitosan and starched-based flocculants was compared to synthetic polymers commonly used to treat iron ions-rich filter backwash water. The environmental aspects of these chemicals, particularly the biodegradability of post-flocculation residues, were also addressed. It was found that oxidized starch and chitosan derivatives can be used as ecological flocculating materials to treat potable water or sludge.

Innovative and environmentally safe composites based on starch modified with dialdehyde starch, caffeine, or ascorbic acid for applications in the food packaging industry.

Biodegradable films based on starch modified with ascorbic acid or caffeine and dialdehyde starch (DS) were evaluated towards their applications in the food packaging industry. The morphology of the films surface was observed with SEM and AFM. The chemical structure was examined with ATR-FTIR spectroscopy and X-ray diffraction. The mechanical, thermal and barrier properties of the films were examined. The cross-linking and hydrophobic effect of dialdehyde starch on starch-based films was proven. Vitamin C addition prompts the crystalline structure formation and improves the hydrophilicity and antioxidant activity of the starch blends. Caffeine addition results in higher starch film hydrophobicity, whereas caffeine combined with DS reduces crystalline order in starch. Both caffeine and ascorbic acid incorporation influence the film stiffness, and dialdehyde starch causes an increase in brittleness. The high susceptibility to biodegradation and good antioxidant activity confirms the potential application of examined systems in the packaging industry.

Biofilm formation during biodegradation of polylactide, poly (3,4 hydroxybutyrate) and poly(ε-caprolactone) in activated sludge.

Biodegradable materials, namely pure polylactide (PLA), poly (3,4-hydroxybutyrate) (PHB), poly(ε-caprolactone) (PCL) were investigated to assess their degradability by activated sludge. The study aimed at the isolation of biofilm-forming bacteria and the determination of their hydrolytic activity toward the PLA, PHB, and PCL with embedded PHMG derivatives. The biological oxygen demand and physical properties (tensile strength, water vapor permeability, surface structure) of materials indicated that PCL was the best biodegradable film. Aeromonas and Rhodococcus isolated from the polymers' surface during the process of decomposition showed the ability to form biofilms. The introduction of PHMG derivatives into PLA, PCL, and PHB films did not affect biofilm formation and hydrolase activity for most of the isolates. PHMG derivatives at the concentration of 1% disturbed the degradation process.

Preparation and characteristics of antibacterial chitosan films modified with N-halamine for biomedical application.

Several hydantoin derivatives and their N-halamine analogues were examined by spectroscopic methods (IR, 1H-NMR, 13C-NMR), elemental analysis (content of C, H, N), thermogravimetry (TGA), antibacterial tests and experiments of stability in aqueous solution. This research allowed the structural, thermal and antibacterial characteristics of obtained compounds. It was found, the thermal stability of hydantoins depends on their chemical structure and decreases when N-halamine moieties were introduced. In next step, synthesized biocides were added to the chitosan films. The antibacterial properties of received films were proved. It was found that after modification, the thermal stability of CS films decreases in most cases. The surface properties of obtained chitosan films before and after UV irradiation were investigated by means of contact angle measurements allowing the calculation of surface free energy. The chemical and structural changes during UV irradiation were studied by FTIR spectroscopy and SEM microscopy. The results indicated that the introduction of biocides to the CS material contribute to the photooxidation process. The degradation mechanism of obtained materials was proposed. The materials studied in this work may be used in various biomedical applications due to their confirmed biological activity.

Alkaline and Halophilic Protease Production by Bacillus luteus H11 and Its Potential Industrial Applications.

This paper presents the results of the study on the production of protease by Bacillus luteus H11 isolated from an alkaline soda lime. B. luteus H11 was identified as an alkalohalophilic bacterium, and its extracellular serine endoprotease also showed an extreme alkali- and halotolerance. It was remarkably stable in the presence of NaCl up to 5 M. The enzyme was active in a broad range of pH values and temperatures, with an optimum pH of 10.5 and a temperature of 45 °C. It had a molecular mass of about 37 kDa and showed activity against azocasein and a synthetic substrate for the subtilisin-like protease, N-succinyl-l-phenylalanine-p-nitroanilide. The halo-alkaline protease produced by B. luteus H11 seems to be significant from an industrial perspective because of its tolerance towards high salinity and alkalinity as well as its stability against some organic solvents, surfactants and oxidants. These properties make the protease suitable for applications in food, detergent and pharmaceutical industries, and also in environmental bioremediation.

Changes in bacterial and archaeal communities during the concentration of brine at the graduation towers in Ciechocinek spa (Poland).

This study evaluates the changes in bacterial and archaeal community structure during the gradual evaporation of water from the brine (extracted from subsurface Jurassic deposits) in the system of graduation towers located in Ciechocinek spa, Poland. The communities were assessed with 16S rRNA gene sequencing (MiSeq, Illumina) and microscopic methods. The microbial cell density determined by direct cell count was at the order of magnitude of 107 cells/mL. It was found that increasing salt concentration was positively correlated with both the cell counts, and species-level diversity of bacterial and archaeal communities. The archaeal community was mostly constituted by members of the phylum Euryarchaeota, class Halobacteria and was dominated by Halorubrum-related sequences. The bacterial community was more diverse, with representatives of the phyla Proteobacteria and Bacteroidetes as the most abundant. The proportion of Proteobacteria decreased with increasing salt concentration, while the proportion of Bacteroidetes increased significantly in the more concentrated samples. Representatives of the genera Idiomarina, Psychroflexus, Roseovarius, and Marinobacter appeared to be tolerant to changes of salinity. During the brine concentration, the relative abundances of Sphingobium and Sphingomonas were significantly decreased and the raised contributions of genera Fabibacter and Fodinibius were observed. The high proportion of novel (not identified at 97% similarity level) bacterial reads (up to 42%) in the 16S rRNA gene sequences indicated that potentially new bacterial taxa inhabit this unique environment.

Bacterial growth and biofilm formation in household-stored groundwater collected from public wells.

The research was aimed at assessing changes in the number of bacteria and evaluating biofilm formation in groundwater collected from public wells, both aspects directly related to the methods of household storage. In the research, water collected from Cretaceous aquifer wells in Torun (Poland) was stored in a refrigerator and at room temperature. Microbiological parameters of the water were measured immediately after the water collection, and then after 3 and 7 days of storage under specified conditions. The microbiological examination involved determining the number of heterotrophic bacteria capable of growth at 22 and 37 °C, the number of spore-forming bacteria, and the total number of bacteria on membrane filters. The storage may affect water quality to such an extent that the water, which initially met the microbiological criteria for water intended for human consumption, may pose a health risk. The repeated use of the same containers for water storage results in biofilm formation containing live and metabolically active bacterial cells.

The effect of polyhexamethylene guanidine hydrochloride (PHMG) derivatives introduced into polylactide (PLA) on the activity of bacterial enzymes.

The present study was aimed at investigating bactericidal properties of polylactide (PLA) films containing three different polyhexamethylene guanidine hydrochloride (PHMG) derivatives and effect of the derivatives on extracellular hydrolytic enzymes and intracellular dehydrogenases. All PHMG derivatives had a slightly stronger bactericidal effect on Staphylococcus aureus than on E. coli but only PHMG granular polyethylene wax (at the concentration of at least 0.6 %) has a bactericidal effect. PHMG derivatives introduced into PLA affected the activity of microbial hydrolases to a small extent. This means that the introduction of PHMG derivatives into PLA will not reduce its enzymatic biodegradation significantly. On the other hand, PHMG derivatives introduced into PLA strongly affected dehydrogenases activity in S. aureus than in E. coli.

Influence of stabilizers on the antimicrobial properties of silver nanoparticles introduced into natural water.

Physical, chemical and biochemical properties of silver nanoparticles (AgNPs) depend to a great extent on their size, shape, size distribution, and stabilizers located on their surface. This study focused on two typical stabilizers, namely citrates (cit), low molecular ions protecting nanoparticles by electrostatic repulsion, and polyvinylpyrrolidone (PVP), a hydrophilic, neutral, high molecular polymer protecting nanoparticles by steric stabilization. Natural bacterioplankton was collected from a eutrophic, downtown lake and exposed to five concentrations (0.1-5 mg/L) of AgNPs-PVP and AgNPs-cit. Responses were monitored after 1, 3, 5 and 7 days of exposure, by evaluating the survival rate of bacteria, their respiratory activity, and the general activity of extracellular esterases. A significantly better (greater) survival rate of bacterioplankton was observed in water with an addition of AgNPs-cit. The inhibition of extracellular esterases was observed only in samples containing AgNPs-PVP. The inhibitory effect increased proportionally to the concentration of AgNPs-PVP applied. Within the studied concentration range, there was no statistically significant inhibition of bacterioplankton respiratory activity by AgNPs-PVP and AgNPs-cit.

The role of open-air inhalatoria in the air quality improvement in spa towns.

OBJECTIVES: The present study was aimed at evaluating microbiological contamination of air in Ciechocinek and Inowroclaw - Polish lowland spa towns. Additionally, the impact of open-air inhalatoria on the quality of air was evaluated. MATERIAL AND METHODS: Air samples were collected seasonally in the urban areas, in the recreation areas and in the vicinity of inhalatoria in both towns using impaction. The numbers of mesophilic bacteria, staphylococci, hemolytic bacteria and actinomycetes were determined on media according to the Polish Standard PN-86/Z-04111/02. The number of moulds was determined on media according to the Polish Standard PN-86/Z-04111/03. RESULTS: While the highest numbers of microorganisms were noted at the sites located in the urban areas, the lowest numbers were noted in the vicinity of the open-air inhalatoria. In all the investigated air samples the values of bioaerosol concentrations were below the recommended TLVs (≤ 5000 CFU×m(-3) for both bacteria and fungi in outdoor environments). Location of the sampling site was invariably a decisive factor in determining the number of microorganisms in the air. CONCLUSIONS: The aerosol which is formed in the open-air inhalatoria has a positive influence on microbiological air quality. Owing to a unique microclimate and low air contamination, Ciechocinek and Inowroclaw comply with all necessary requirements set for health resorts specializing in treating upper respiratory tract infections.

Microbiological contamination of water in fountains located in the city of Torun, Poland.

OBJECTIVE: The aim of this study was determination of the level of water contamination in fountains in Torun, Poland. METHODS: The studies were conducted at monthly intervals from May - September 2009, and consisted in the determination of the number of heterotrophic bacteria capable of growing at a temperature of 22 and 37°C (PN-ISO 6222), as well as the number of coliform bacteria (PN-75/C-04615/05), E. coli (ISO 9308-1) and faecal streptococci (PN-EN ISO 7899-2). RESULTS: The 'Rafter' fountain in the Old Town Market Square, continuously supplied with municipal water, had the cleanest water. The highest number of heterotrophic bacteria capable of development at 22 and 37°C was found in the fountain located in the City Park of Bydgoskie suburb. Throughout the entire research period, water from the fountain in the Old Town Moat had the worst sanitary (health) indices. CONCLUSION: The recorded results indicate that water from the 3 out of 4 examined fountains, with inappropriate exploitation--bathing, water drinking, hands washing--may constitute a danger to human health. The fountains should be carefully monitored for the presence of microorganisms, or a ban on bathing in fountains should be more rigorously enforced, in order to prevent possible infections.