Characterization of bacterial biofilms developed on the biodegradable polylactide and polycaprolactone polymers containing birch tar in an aquatic environment.

Birch tar was added to polylactide (PLA) and polycaprolactone (PCL) to create films with antimicrobial properties. After incubating the films for seven days in lake water, the diversity of bacterial communities developed on the surfaces of PCL and PLA with embedded birch tar (1 %, 5 %, and 10 %, w/w) was assessed with amplicon sequencing of the 16S rRNA gene on a MiSeq platform (Illumina). Notably, Aquabacterium and Caulobacter were more abundant at the surface of PCL compared to PLA (13.4 % vs 0.2 %, p < 0.001 and 9.5 % vs 0.2 %, p < 0.001, respectively) while Hydrogenophaga was significantly more abundant at the surface of PLA compared to PCL (6.1 % vs 1.8 %, p < 0.01). Overall, lower birch tar concentrations (1 % and 5 % on both polymers) stimulated bacterial diversity in biofilms compared to the control. The number of reeds assigned to Flavobacterium and Aquabacterium showed a rising trend with the increase of birch tar concentration on the surface of both polymers.

Application Potential of Trichoderma in the Degradation of Phenolic Acid-Modified Chitosan.

The aim of the study was to determine the potential use of fungi of the genus Trichoderma for the degradation of phenolic acid-modified chitosan in compost. At the same time, the enzymatic activity in the compost was checked after the application of a preparation containing a suspension of the fungi Trichoderma (spores concentration 105/mL). The Trichoderma strains were characterized by high lipase and aminopeptidase activity, chitinase, and ß-1,3-glucanases. T. atroviride TN1 and T. citrinoviride TN3 metabolized the modified chitosan films best. Biodegradation of modified chitosan films by native microorganisms in the compost was significantly less effective than after the application of a formulation composed of Trichoderma TN1 and TN3. Bioaugmentation with a Trichoderma preparation had a significant effect on the activity of all enzymes in the compost. The highest oxygen consumption in the presence of chitosan with tannic acid film was found after the application of the consortium of these strains (861 mg O2/kg after 21 days of incubation). Similarly, chitosan with gallic acid and chitosan with ferulic acid were found after the application of the consortium of these strains (849 mgO2/kg and 725 mg O2/kg after 21 days of incubation). The use of the Trichoderma consortium significantly increased the chitinase activity. The application of Trichoderma also offers many possibilities in sustainable agriculture. Trichoderma can not only degrade chitosan films, but also protect plants against fungal pathogens by synthesizing chitinases and ß-1,3 glucanases with antifungal properties.

The adenine-modified edible chitosan films containing choline chloride and citric acid mixture.

A series of biopolymeric chitosan-based (Ch) films were prepared with choline chloride and citric acid plasticizer (deep eutectic solvent, DES). An effect of adenine (A, vitamin B4) addition on the functional properties of these films was evaluated. Several physicochemical and mechanical properties were tested: Fourier-transformed infrared spectra proved DES's plasticizing and crosslinking effect, while scanning electron microscopy and atomic force microscopy techniques confirmed the possible phase separation after adenine addition. These changes affected the mechanical characteristics and the water vapor and oxygen permeability. The prepared materials are not water soluble because the CA acts as a crosslinker. The adenine addition on antioxidative and antimicrobial properties was also checked. It was found that Ch-DES materials with A exhibit improved antioxidative properties (55.8-66.1% of H2O2 scavenging activity) in contrast to the pristine chitosan-DES material (51.1% of H2O2 scavenging activity), while the material is still non-mutagenic (lack of growth of Salmonella typhimurium) and possesses antimicrobial features (no E. coli observed for all the tested films and inhibition zones noted for S. aureus). The mentioned properties, reduced oxygen transmission (1.6-2.1 g m-2 h-1), and mechanical characteristics within the range of typical food packaging plastics proved the potential of Ch-DES-A films in the packaging sector. Moreover, the antioxidative properties, usage of substrates being allowed as food additives, and the presence of adenine create the advantage of the Ch-DES-A materials as edible coatings, being also a source of Vitamin B4.

Effect of birch tar embedded in polylactide on its biodegradation.

The plasticized film was made of polylactide and birch tar, which was used in a concentration of 1, 5 and 10 % by weight. Tar was added to the polymer to obtain materials with antimicrobial properties. The main purpose of this work is to characterize and biodegradation of this film after the end of its use. Therefore, the following analyzes were performed: enzymatic activity of microorganisms in the presence of polylactide (PLA) film containing birch tar (BT), biodegradation process in compost, barrier changes and structural properties of the film before and after biodegradation and bioaugmentation. Biological oxygen demand BOD21, water vapor permeability (Pv), oxygen permeability (Po), scanning electron microscopy (SEM) and enzymatic activity of microorganisms were assessed. Microorganism strains Bacillus toyonensis AK2 and Bacillus albus AK3 were isolated and identified, which constituted an effective consortium increasing the susceptibility of polylactide polymer material with tar to biodegradation in compost. Analyses with the use of the above-mentioned strains had an impact on the change of physicochemical properties, e.g. the presence of biofilm on the surface of the analyzed films and the reduction of the barrier properties of the film, which translates into the recorded susceptibility to biodegradation of these materials. The analyzed films can be used in the packaging industry, and after use, subjected to intentional biodegradation processes, including bioaugmentation.

Physicochemical and Antibacterial Properties of Alginate Films Containing Tansy (Tanacetum vulgare L.) Essential Oil.

Tansy (Tanacetum vulgare) is a common plant used in folk medicine for digestive problems, fevers, and migraines; against parasites; and as an insect repellent. The active substances in essential oil are responsible for its antimicrobial and antioxidant activity. Thus, tansy essential oil (TO) was added to alginate films to fabricate materials with antioxidant and antibacterial properties for food packaging. Sodium alginate films with glycerol and TO were tested in terms of structure, mechanical, thermal, antioxidant, and antibacterial properties. The structure of the films was examined using SEM and an ATR-FTIR spectrophotometer. The addition of TO to the alginate film significantly changed the films' microstructure, making them rougher and porous. A low-intensity band at 1739 cm-1, indicative of the presence of TO, appeared in all spectra of alginate films with TO. Moreover, the studies revealed that essential oil acted as a plasticizer, slightly reducing tensile strength from about 7 MPa to 5 MPa and increasing elongation at break from 52% to 56% for the sample with 2% TO. The alginate films enriched in TO exhibited antioxidant properties (280 µmol Trolox/100 g of the sample with 2% TO) and antibacterial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.

Polycaprolactone-Based Films Incorporated with Birch Tar-Thermal, Physicochemical, Antibacterial, and Biodegradable Properties.

We present new polymer materials consisting of polycaprolactone (PCL), polyethylene glycol (PEG), and birch tar (D). PEG was introduced into the polymer matrix in order to obtain a plasticizing effect, while tar was added to obtain antibacterial properties and to change the physicochemical properties of the film. The materials were obtained by the solvent method and characterized using a variety of methods to test their performance and susceptibility to biodegradation. The obtained data indicate that the introduction of the bioactive substance (D) into PCL improved the thermal stability and significantly lowered the Young's modulus values of the tested polymers. Moreover, the addition of birch tar improved the barrier and bacteriostatic properties, resulting in a reduction in the growth of pathogenic bacteria on the surface of the film. The films are not mutagenic but are susceptible to biodegradation in various environments. Due to their properties, they have potential for application in agriculture and horticulture and for packaging food, mainly vegetables grown in the field.

Birch Tar Introduced into Polylactide and Its Influence on the Barrier, Thermal, Functional and Biological Properties of the Film Obtained by Industrial Extrusion.

The aim of the study was to evaluate possibility of producing a polylactide film with birch tar by the industrial extrusion method and whether the addition of 10% birch tar can ensure adequate biocidal properties of PLA against pathogenic microorganisms (E. coli, S. aureus, P. aeruginosa, A. tumefaciens, X. campestris, P. brassicacearum, P. corrugate and P. syringae) and fungi (A. niger, A. flavus and A. versicolor) while ensuring beneficial functional properties, such as water vapor, nitrogen, oxygen and carbon dioxide permeability, which are of considerable importance in the packaging industry. The main test methods used were ISO 22196, ISO 846, ISO 2556, ASTM F 1927 and ASTM F 2476-20. The obtained results prove the possibility of extruding polymer films with a biocidal additive, i.e., birch tar, and obtaining favorable properties that qualify the produced film for applications in the packaging industry.

Comparative Characterization and Identification of Poly-3-hydroxybutyrate Producing Bacteria with Subsequent Optimization of Polymer Yield.

In this work, the strains Bacillus megaterium RAZ 3, Azotobacter chrocococcum Az 3, Bacillus araybhattay RA 5 were used as an effective producer of poly-3-hydroxybutyrate P(3HB). The purpose of the study was to isolate and obtain an effective producer of P(3HB) isolated from regional chestnut soils of northern Kazakhstan. This study demonstrates the possibility of combining the protective system of cells to physical stress as a way to optimize the synthesis of PHA by strains. Molecular identification of strains and amplification of the phbC gene, transmission electron microscope (TEM), extracted and dried PHB were subjected to Fourier infrared transmission spectroscopy (FTIR). The melting point of the isolated P(3HB) was determined. The optimal concentration of bean broth for the synthesis of P(3HB) for the modified type of Bacillus megaterium RAZ 3 was 20 g/L, at which the dry weight of cells was 25.7 g/L-1 and P(3HB) yield of 13.83 g/L-1, while the percentage yield of P(3HB) was 53.75%. The FTIR spectra of the extracted polymer showed noticeable peaks at long wavelengths. Based on a proof of concept, this study demonstrates encouraging results.

Polylactide-Based Films Incorporated with Berberine-Physicochemical and Antibacterial Properties.

A series of new polymeric materials consisting of polylactide (PLA), polyethylene glycol (PEG) and berberine chloride (B) was evaluated. PEG was incorporated into the polymer matrix with the aim of obtaining a plasticizing effect, while berberine was added in order to obtain antibacterial properties in formed packaging materials. Materials were formed using the solvent-casting procedure. Fourier transform infrared spectroscopy and scanning electron microscopy were used so as to establish the structural changes resulting from the introduction of berberine. Thermogravimetry and differential scanning calorimetry were applied to study the thermal properties. Further, mechanical properties and differences in colour and transparency between the control sample and films containing berberine were also studied. The recorded data indicates that berberine formed a network on the surface of the PLA-based materials. Introduction of an active compound significantly improved thermal stability and greatly affected the Young's modulus values of the studied polymeric films. Moreover, it should be stressed that the addition of the studied active compound leads to an improvement of the antibacterial properties, resulting in a significant decrease in growth of E. coli and the S. aureus bacteria cultures.

Biodegradability of Novel Polylactide and Polycaprolactone Materials with Bacteriostatic Properties Due to Embedded Birch Tar in Different Environments.

The microbial biodegradation of new PLA and PCL materials containing birch tar (1-10% v/v) was investigated. Product of dry distillation of birch bark (Betula pendula Roth) was added to polymeric materials to obtain films with antimicrobial properties. The subject of the study was the course of enzymatic degradation of a biodegradable polymer with antibacterial properties. The results show that the type of the material, tar concentration, and the environment influenced the hydrolytic activity of potential biofilm degraders. In the presence of PCL films, the enzyme activities were higher (except for α-D-glucosidase) compared to PLA films. The highest concentration of birch tar (10% v/v) decreased the activity of hydrolases produced by microorganisms to the most significant extent; however, SEM analysis showed the presence of a biofilm even on plastics with the highest tar content. Based on the results of the biological oxygen demand (BOD), the new materials can be classified as biodegradable but, the biodegradation process was less efficient when compared to plastics without the addition of birch tar.

Potential of Serratia plymuthica IV-11-34 strain for biodegradation of polylactide and poly(ethylene terephthalate).

Serratia plymuthica strain IV-11-34 belongs to the plant growth promoting bacteria (PGPR). In the sequenced genome of S. plymuthica IV-11-34, we have identified the genes involved in biodegradation and metabolisms of xenobiotics. The potential of S. plymuthica IV-11-34 for the degradation of biodegradable aliphatic polyester polylactide (PLA) and resistant to biodegradation - poly(ethylene terephthalate) (PET) was assessed by biochemical oxygen consumption (BOD) and carbon dioxide methods. After seven days of growth, the bacteria strain showed more than 80% and 60% increase in respiratory activity in the presence of PLA and PET, respectively. We assume that during biodegradation, S. plymuthica IV-11-34 colonise the surface of PLA and PET, since the formation of a biofilm on the surface of polymers was shown by the LIVE/DEAD method. We have demonstrated for the relA gene, which is an alarmone synthetase, a 1.2-fold increase in expression in the presence of PLA, and a 4-fold decrease in expression in the presence of PET for the spoT gene, which is a hydrolase of alarmones. Research has shown that the bacterium has the ability to biodegrade PLA and PET, and the first stage of this process involves bacterial stringent response genes responsible for survival under extreme conditions.

Microbial degradation of polyhydroxybutyrate with embedded polyhexamethylene guanidine derivatives.

The aim of this study was to isolate biofilm-forming bacteria that are capable of degrading polyhydroxybutyrate (PHB) with polyhexamethylene guanidine (PHMG) derivatives. The three types of derivatives incorporated in PHB and their concentration affected the biodegradability of the tested films in both water and compost. The PHMG derivative granular polyethylene wax at the highest concentration significantly inhibited BOD in both environments. At the same time, in water, PHB with PHMG stearate at 1% concentration was also found to inhibit biodegradation but to a lesser extent than PHMG polyethylene wax granulate. Analyzing the values of biofilm abundance and their hydrolytic activity in water, low concentrations of PHMG derivatives (0.2 and 0.6%) slightly inhibited biofilm abundance on the surface of the tested composites. Only granular polyethylene wax PHMG (at 1% concentration) significantly reduced biofilm formation and hydrolase activity in the compost to the greatest extent. Bacteria from biofilm were isolated and identified. Based on the 16S rRNA gene sequence, the strains belong to Bacillus toyonensis HW1 and Variovorax boronicumulans HK3. Introduction of the tested isolates to the environment can enhance composites degradation. However, this requires further research.

Combined use of Bacillus strains and Miscanthus for accelerating biodegradation of poly(lactic acid) and poly(ethylene terephthalate).

BACKGROUND: The aim of this study was to verify whether the presence of Bacillus strains and of miscanthus influence biodegradation and formed of biofilm of poly(lactic acid) (PLA) and poly(ethylene terephthalate) (PET). METHODS: The experiment conducted in compost soil showed that strains Bacillus subtilis and Bacillus cereus isolated from heavy metal contaminated environment have biochemical activity and accelerate biodegradation of both plastic materials. RESULTS: For PLA film it was found that the carbonyl index dropped by over 15% in the presence of B. subtilis, while the film tensile strength decreased by 35% and the oxygen to carbon O/C ratio was higher by 3% in the presence of B. cereus, and the presence of miscanthus resulted in a loss of weight. For PET film, a decrease in the carbonyl index by 16% was observed following inoculation with B. cereus. The metabolic activity of this strain contributed to the reduction of the film's tensile strength by 17% and to the increase in the permeability to O2 and CO2. The most intense degradation of PET film was observed in the presence of bacteria and plants. B. subtilis strain combined with miscanthus plantings may be a promising method for accelerating PLA and PET degradation in compost soil.

Antibacterial Films Based on Polylactide with the Addition of Quercetin and Poly(Ethylene Glycol).

A series of new films with antibacterial properties has been obtained by means of solvent casting method. Biodegradable materials including polylactide (PLA), quercetin (Q) acting as an antibacterial compound and polyethylene glycol (PEG) acting as a plasticizer have been used in the process. The effect of quercetin as well as the amount of PEG on the structural, thermal, mechanical and antibacterial properties of the obtained materials has been determined. It was found that an addition of quercetin significantly influences thermal stability. It should be stressed that samples containing the studied flavonoid are characterized by a higher Young modulus and elongation at break than materials consisting only of PLA and PEG. Moreover, the introduction of 1% of quercetin grants antibacterial properties to the new materials. Recorded results showed that the amount of plasticizer did not influence the antibacterial properties; it does, however, cause changes in physicochemical properties of the obtained materials. These results prove that quercetin could be used as an antibacterial compound and simultaneously improve mechanical and thermal properties of polylactide-based films.

Enzymatic degradation and biofilm formation during biodegradation of polylactide and polycaprolactone polymers in various environments.

The present article presents the results of research on the susceptibility of polylactide, poly(ɛ-caprolactone) and mixtures to biodegradation in conditions imitating natural extracts of compost, activated sludge, sea and river water, determined by the biochemical oxygen consumption by microorganisms and susceptibility to enzymatic degradation with the use of enzyme solutions of fungal microbial origin. Analyzes of both types of degradation were carried out over a period of seven days and in four environments: compost, activated sludge, river and sea water, and four enzymatic solutions containing proteinase K, protease, esterase, and lipase. The amount of oxygen consumed by microorganisms in the presence of the tested films was determined, as well as the weight loss determined after the samples were incubated in enzymatic solutions. Images of the surface of individual samples, taken by fluorescence microscopy and scanning electron microscopy, confirm the formation of bacterial biofilm and the results of biochemical oxygen consumption by microorganisms, or weight loss. It was shown that the compost and activated sludge extract as well as the enzymes proteinase K from Engyodontium album (synonym Tritirachium album) and protease from Bacillus licheniformis had the greatest impact on the biodegradation of the tested materials.

The Role of Birch Tar in Changing the Physicochemical and Biocidal Properties of Polylactide-Based Films.

The objective of this study was to produce bactericidal polymer films containing birch tar (BT). The produced polymer films contain PLA, plasticiser PEG (5% wt.) and birch tar (1, 5 and 10% wt.). Compared to plasticised PLA, films with BT were characterised by reduced elongation at break and reduced water vapour permeability, which was the lowest in the case of film with 10% wt. BT content. Changes in the morphology of the produced materials were observed by performing scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis; the addition of BT caused the surface of the film to be non-uniform and to contain recesses. FTIR analysis of plasticised PLA/BT films showed that the addition of birch tar did not change the crystallinity of the obtained materials. According to ISO 22196: 2011, the PLA film with 10% wt. BT content showed the highest antibacterial effect against the plant pathogens A. tumefaciens, X. campestris, P. brassicacearum, P. corrugata, P. syringae. It was found that the introduction of birch tar to plasticised PLA leads to a material with biocidal effect and favourable physicochemical and structural properties, which classifies this material for agricultural and horticultural applications.

Influence of Tea Tree Essential Oil and Poly(ethylene glycol) on Antibacterial and Physicochemical Properties of Polylactide-Based Films.

The aim of the study was to establish the influence of poly(ethylene glycol) (PEG) on the properties of potential biodegradable packaging materials with antibacterial properties, based on polylactide (PLA) and tea tree essential oil (TTO). The obtained polymeric films consisted of PLA, a natural biocide, and tea tree essential oil (5-20 wt. %) was prepared with or without an addition of 5 wt. % PEG. The PLA-based materials have been tested, taking into account their morphology, and their thermal, mechanical and antibacterial properties against Staphylococcus aureus and Escherichia coli. It was established that the introduction of a plasticizer into the PLA-TTO systems leads to an increase in tensile strength, resistance to deformation, as well an increased thermal stability, in comparison to films modified using only TTO. The incorporation of 5 wt. % PEG in the PLA solution containing 5 wt. % TTO allowed us to obtain a material exhibiting a satisfactory antibacterial effect on both groups of representative bacteria. The presented results indicated a beneficial effect of PEG on the antibacterial and functional properties of materials with the addition of TTO.

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.

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.