Ecotoxicity assessment of additives in commercial biodegradable plastic products: Implications for sustainability and environmental risk.

Biodegradable plastics have gained popularity as environmentally friendly alternatives to conventional petroleum-based plastics, which face recycling and degradation challenges. Although the biodegradability of these plastics has been established, research on their ecotoxicity remains limited. Biodegradable plastics may still contain conventional additives, including toxic and non-degradable substances, to maintain their functionality during production and processing. Despite degrading the polymer matrix, these additives can persist in the environment and potentially harm ecosystems and humans. Therefore, this study aimed to assess the potential ecotoxicity of biodegradable plastics by analyzing the phthalate esters (PAEs) leaching out from biodegradable plastics through soil leachate. Sixteen commercial biodegradable plastic products were qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry to determine the types and amounts of PAE used in the products and evaluate their ecotoxicity. Among the various PAEs analyzed, non-regulated dioctyl isophthalate (DOIP) was the most frequently detected (ranging from 40 to 212 µg g-1). Although the DOIP is considered one of PAE alternatives, the detected amount of it revealed evident ecotoxicity, especially in the aquatic environment. Other additives, including antioxidants, lubricants, surfactants, slip agents, and adhesives, were also qualitatively detected in commercial products. This is the first study to quantify the amounts of PAEs leached from biodegradable plastics through water mimicking PAE leaching out from biodegradable plastics to soil leachate when landfilled and evaluate their potential ecotoxicity. Despite their potential toxicity, commercial biodegradable plastics are currently marketed and promoted as environmentally friendly materials, which could lead to indiscriminate public consumption. Therefore, in addition to improving biodegradable plastics, developing eco-friendly additives is significant. Future studies should investigate the leaching kinetics in soil leachate over time and toxicity of biodegradable plastics after landfill disposal.

Circular waste management: Superworms as a sustainable solution for biodegradable plastic degradation and resource recovery.

Bioplastics offer a promising solution to plastic pollution, however, their production frequently relies on edible biomass, and their degradation rates remain inadequate. This study investigates the potential of superworms (Zophobas atratus larvae) for polybutylene succinate (PBS) waste management, aiming to achieve both resource recovery and biodegradation. Superworms exclusively fed on PBS for a month exhibited the same survival rate as those on a standard bran diet. PBS digestion yielded a 5.13% weight gain and a 23.23% increase in protein composition in superworms. Additionally, carbon isotope analyses substantiated the conversion of PBS into superworm components. Gut microbes capable of PBS biodegradation became progressively prominent, further augmenting the degradation rate of PBS under composting conditions (ISO 14855-1). Gut-free superworms fed with PBS exhibited antioxidant activities comparable to those of blueberries, renowned for their high antioxidant activity. Based on these findings, this study introduces a sustainable circular solution encompassing recycling PBS waste to generate insect biomass, employing insect gut and frass for PBS degradation and fertilizer, and harnessing insect residue as a food source. In essence, the significance of this research extends to socio-economic and environmental spheres, impacting waste management, resource efficiency, circular economy promotion, environmental preservation, industrial advancement, and global sustainability objectives. The study's outcomes possess the potential to reshape society's approach to plastic waste, facilitating a shift toward more sustainable paradigms.

Review of polymer technologies for improving the recycling and upcycling efficiency of plastic waste.

Human society has become increasingly reliant on plastic because it allows for convenient and sanitary living. However, recycling rates are currently low, which means that the majority of plastic waste ends up in landfills or the ocean. Increasing recycling and upcycling rates is a critical strategy for addressing the issues caused by plastic pollution, but there are several technical limitations to overcome. This article reviews advancements in polymer technology that aim to improve the efficiency of recycling and upcycling plastic waste. In food packaging, natural polymers with excellent gas barrier properties and self-cleaning abilities have been introduced as environmentally friendly alternatives to existing materials and to reduce food-derived contamination. Upcycling and valorization approaches have emerged to transform plastic waste into high-value-added products. Recent advancements in the development of recyclable high-performance plastics include the design of super engineering thermoplastics and engineering chemical bonds of thermosets to make them recyclable and biodegradable. Further research is needed to develop more cost-effective and scalable technologies to address the plastic pollution problem through sustainable recycling and upcycling.

Circuit-guided population acclimation of a synthetic microbial consortium for improved biochemical production.

Microbial consortia have been considered potential platforms for bioprocessing applications. However, the complexity in process control owing to the use of multiple strains necessitates the use of an efficient population control strategy. Herein, we report circuit-guided synthetic acclimation as a strategy to improve biochemical production by a microbial consortium. We designed a consortium comprising alginate-utilizing Vibrio sp. dhg and 3-hydroxypropionic acid (3-HP)-producing Escherichia coli strains for the direct conversion of alginate to 3-HP. We introduced a genetic circuit, named "Population guider", in the E. coli strain, which degrades ampicillin only when 3-HP is produced. In the presence of ampicillin as a selection pressure, the consortium was successfully acclimated for increased 3-HP production by 4.3-fold compared to that by a simple co-culturing consortium during a 48-h fermentation. We believe this concept is a useful strategy for the development of robust consortium-based bioprocesses.

Biorenewable, transparent, and oxygen/moisture barrier nanocellulose/nanochitin-based coating on polypropylene for food packaging applications.

Aluminum-coated polypropylene films are commonly used in food packaging because aluminum is a great gas barrier. However, recycling these films is not economically feasible. In addition, their end-of-life incineration generates harmful alumina-based particulate matter. In this study, coating layers with excellent gas-barrier properties are assembled on polypropylene films through layer-by-layer (LbL) deposition of biorenewable nanocellulose and nanochitin. The coating layers significantly reduce the transmission of oxygen and water vapors, two unfavorable gases for food packaging, through polypropylene films. The oxygen transmission rate of a 60 µm-thick, 20 LbL-coated polypropylene film decreases by approximately a hundredfold, from 1118 to 13.10 cc m-2 day-1 owing to the high crystallinity of nanocellulose and nanochitin. Its water vapor transmission rate slightly reduces from 2.43 to 2.13 g m-2 day-1. Furthermore, the coated film is highly transparent, unfavorable to bacterial adhesion and thermally recyclable, thus promising for advanced food packaging applications.

Biosynthesis of Polyhydroxybutyrate with Cellulose Nanocrystals Using Cupriavidus necator.

Polyhydroxybutyrate (PHB) is a natural polyester synthesized by several microorganisms. Moreover, it has excellent biodegradability and is an eco-friendly material because it converts water and carbon dioxide as final decomposition products. However, the applications of PHB are limited because of its stiffness and brittleness. Because cellulose nanocrystals (CNCs) have excellent intrinsic mechanical properties such as high specific strength and modulus, they may compensate for the insufficient physical properties of PHB by producing their nanocomposites. In this study, natural polyesters were extracted from Cupriavidus necator fermentation with CNCs, which were well-dispersed in nitrogen-limited liquid culture media. Fourier-transform infrared spectroscopy results revealed that the additional O-H peak originating from cellulose at 3500-3200 cm-1 was observed for PHB along with the C=O and -COO bands at 1720 cm-1. This suggests that PHB-CNC nanocomposites could be readily obtained using C. necator fermented in well-dispersed CNC-supplemented culture media.

Biodegradable, Efficient, and Breathable Multi-Use Face Mask Filter.

The demand for face masks is increasing exponentially due to the coronavirus pandemic and issues associated with airborne particulate matter (PM). However, both conventional electrostatic- and nanosieve-based mask filters are single-use and are not degradable or recyclable, which creates serious waste problems. In addition, the former loses function under humid conditions, while the latter operates with a significant air-pressure drop and suffers from relatively fast pore blockage. Herein, a biodegradable, moisture-resistant, highly breathable, and high-performance fibrous mask filter is developed. Briefly, two biodegradable microfiber and nanofiber mats are integrated into a Janus membrane filter and then coated by cationically charged chitosan nanowhiskers. This filter is as efficient as the commercial N95 filter and removes 98.3% of 2.5 µm PM. The nanofiber physically sieves fine PM and the microfiber provides a low pressure differential of 59 Pa, which is comfortable for human breathing. In contrast to the dramatic performance decline of the commercial N95 filter when exposed to moisture, this filter exhibits negligible performance loss and is therefore multi-usable because the permanent dipoles of the chitosan adsorb ultrafine PM (e.g., nitrogen and sulfur oxides). Importantly, this filter completely decomposes within 4 weeks in composting soil.

Highly reinforced poly(butylene succinate) nanocomposites prepared from chitosan nanowhiskers by in-situ polymerization.

Biodegradable aliphatic polyesters need to be tough for commodity-plastic applications, such as disposable bags. Herein, we show that chitosan nanowhiskers (CsWs) prepared from naturally abundant chitin is an effective nanofiller that reinforces the strength and toughness of poly(butylene succinate) (PBS). In-situ polycondensation of an aqueous solution of processed CsWs led to a PBS nanocomposite with the highest tensile strength (77 MPa) and elongation at break (530%) reported to date for all PBS types at a minimal nanofiller content of 0.2 wt%. The observed 3.2-fold increase in toughness of the CsW/PBS composite compared to neat PBS is superior to those of composites prepared using cellulose nanocrystals, chitin nanowhiskers, and unstably dispersed CsWs in 1,4-butanediol monomer. Interestingly, CsWs efficiently overcome the disadvantages of the PBS film that easily tears. The highly polar surfaces of the CsWs strongly bind to polymer chains and promote a fibrillar and micro-void structure, thereby maximizing the chain-holding ability of the nanofiller, which resists external tensile and tear stress. This sustainable all-organic nanocomposite is a promising candidate for biodegradable disposable commodities.

Sensitive fluorescence detection of SARS-CoV-2 RNA in clinical samples via one-pot isothermal ligation and transcription.

The control of viral outbreaks requires nucleic acid diagnostic tests that are sensitive, simple and fast. Here, we report a highly sensitive and specific one-pot assay for the fluorescence-based detection of RNA from pathogens. The assay, which can be performed within 30-50 min of incubation time and can reach a limit of detection of 0.1-attomolar RNA concentration, relies on a sustained isothermal reaction cascade producing an RNA aptamer that binds to a fluorogenic dye. The RNA aptamer is transcribed by the T7 RNA polymerase from the ligation product of a promoter DNA probe and a reporter DNA probe that hybridize with the target single-stranded RNA sequence via the SplintR ligase (a Chlorella virus DNA ligase). In 40 nasopharyngeal SARS-CoV-2 samples, the assay reached positive and negative predictive values of 95 and 100%, respectively. We also show that the assay can rapidly detect a range of viral and bacterial RNAs.

High-resolution pluronic-filled microchip CE-SSCP analysis system via channel width control.

Although the resolution of CE-SSCP has been significantly improved by using a poly(ethyleneoxide)-poly(propyleneoxide)-poly(ethyleneoxide) (PEO-PPO-PEO; Pluronic(®)) triblock copolymer as a separation medium, CE-SSCP on a microchip format is not widely applicable because their resolution is limited by short channel length. Therefore, a strategy to improve the resolution in channels of limited lengths is highly required for enabling microchip-based CE-SSCP. In this study, we developed a high-resolution CE-SSCP microchip system by controlling the width of the pluronic-filled channel. We tested four different channel widths of 180, 240, 300, and 400 µm, and found that 300 µm showed the highest resolution in the separation of two pathogen specific markers. Potential applications of our method in various genetic analyses were also shown by using SNP markers for spinal muscular atrophy.

Formaldehyde and heavy metal migration from rubber and metallic packaging/utensils in Korea.

The aim of this study was to determine the non-intentionally added substances--formaldehyde and trace metals--at 4% acetic acid conditions in rubber and metallic packaging/utensils. The temperature effect on migration in rubber and metallic packaging/utensils was monitored at 60 °C and 100 °C under acidic (pH < 3) circumstances. The concentrations were: formaldehyde--23.1 µg kg⁻¹, lead--13.41 µg kg⁻¹, cadmium--0.15 µg kg⁻¹, total arsenic--2.02 µg kg⁻¹ and nickel--2.92 µg kg⁻¹ at 60 °C and formaldehyde--148.9 µg kg⁻¹, lead--17.04 µg kg⁻¹, cadmium--0.14 µg kg⁻¹, total arsenic--7.25 µg kg⁻¹ and nickel--8.7 µg kg⁻¹ at 100 °C. A significant difference was noticed in formaldehyde and total arsenic between both temperatures (p < 0.01), which was not present in other trace metals. In conclusion, formaldehyde and total arsenic were more sensitive with cooking temperature than the other metals.

Enzymatic synthesis of chiral γ-amino acids using ω-transaminase.

In this study, we successfully synthesized enantiomerically pure (R)- and (S)-γ-amino acids (>99% ee) using ω-transaminase (ω-TA) through kinetic resolution and asymmetric synthesis respectively. The present study demonstrates the high potentiality of ω-TA reaction for the production of chiral γ-amino acids.

One-pot one-step deracemization of amines using ω-transaminases.

In this study, we developed a one-pot one-step deracemization method for the production of various enantiomerically pure amines using two opposite enantioselective ω-TAs. Using this method, various aromatic amines were successfully converted to their (R)-forms (>99%) with good conversion.