An Overview into Polyethylene Terephthalate (PET) Hydrolases and Efforts in Tailoring Enzymes for Improved Plastic Degradation.

Plastic or microplastic pollution is a global threat affecting ecosystems, with the current generation reaching as much as 400 metric tons per/year. Soil ecosystems comprising agricultural lands act as microplastics sinks, though the impact could be unexpectedly more far-reaching. This is troubling as most plastic forms, such as polyethylene terephthalate (PET), formed from polymerized terephthalic acid (TPA) and ethylene glycol (EG) monomers, are non-biodegradable environmental pollutants. The current approach to use mechanical, thermal, and chemical-based treatments to reduce PET waste remains cost-prohibitive and could potentially produce toxic secondary pollutants. Thus, better remediation methods must be developed to deal with plastic pollutants in marine and terrestrial environments. Enzymatic treatments could be a plausible avenue to overcome plastic pollutants, given the near-ambient conditions under which enzymes function without the need for chemicals. The discovery of several PET hydrolases, along with further modification of the enzymes, has considerably aided efforts to improve their ability to degrade the ester bond of PET. Hence, this review emphasizes PET-degrading microbial hydrolases and their contribution to alleviating environmental microplastics. Information on the molecular and degradation mechanisms of PET is also highlighted in this review, which might be useful in the future rational engineering of PET-hydrolyzing enzymes.

Adverse environmental effects of disposable face masks due to the excess usage.

The widespread use of disposable face masks as a preventative strategy to address transmission of the SARS-CoV-2 virus has been a key environmental concern since the pandemic began. This has led to an unprecedented new form of contamination from improperly disposed masks, which liberates significant amounts of heavy metals and toxic chemicals in addition to volatile organic compounds (VOCs). Therefore, this study monitored the liberation of heavy metals, VOCs, and microfibers from submerged disposable face masks at different pH (4, 7 and 12), to simulate distinct environmental conditions. Lead (3.238% ppb), cadmium (0.672 ppb) and chromium (0.786 ppb) were found in the analyzed leachates. By pyrolysis, 2,4-dimethylhept-1-ene and 4-methylheptane were identified as the VOCs produced by the samples. The chemically degraded morphology in the FESEM images provided further evidence that toxic heavy metals and volatile organic compounds had been leached from the submerged face masks, with greater degradation observed in samples submerged at pH 7 and higher. The results are seen to communicate the comparable danger of passively degrading disposable face masks and the release of micro- or nanofibers into the marine environment. The toxicity of certain heavy metals and chemicals released from discarded face masks warrants better, more robust manufacturing protocols and increased public awareness for responsible disposal to reduce the adverse impact on ecology and human health.

Fabrication, characterization and application of electrospun polysulfone membrane for phosphate ion removal in real samples.

Due to simplicity and flexibility, electrospinning technique can produce many types of fibers at nanoscale via different operational parameters for various applications including industrial wastewater treatment, air filtration and so on. Nonetheless, the study on the electrospinning operational parameter is very limited and many researchers are still using trial-and-error method to design their targeted fiber. In this study, a series of electrospun polysulfone (PSF; 20% w/v) nanofibrous membranes that made up from different ratios of dimethylformamide (DMF) and tetrahydrofuran (THF) mixtures in order to achieve different dielectric constant (ϵ) of solvent system. The fabricated PSF nanofibers were characterized by field emission scanning electron microscopy (FESEM), tensile strength tester and contact angle measurement. The THF-DMF binary solvent system with ϵ = 16.33 to 27.97 produced a smooth surface electrospun PSF nanofibers, while THF mono solvent system (ϵ = 7.60) and DMF mono solvent system (ϵ = 36.70) produced a rough and porous surface electrospun PSF nanofibers. This finding is contradicted with the common finding in which only a binary solvent is able to fabricate a rough or grooved surface electrospun nanofibers. In addition, the dielectric constant can be another key factor, besides boiling point and solubility of binary solvent system, that induces phase separation in the polymeric solution jet and eventually fabricate non-smooth surface electrospun nanofibers. The fabricated electrospun PSF nanofibrous membranes showed high efficiency in phosphate removal.

The impact of water quality on the Asian clam, Corbicula fluminea, distribution in Pergau Lake, Kelantan, Malaysia.

In the present study described the impact of water quality on the Asian clam, Corbicula fluminea, distribution in man - made Pergau Lake was carried out. Recently, Pergau Lake was gazette as state park and any activities related to fishery and agricultural were not allowed in the park. Subsequently, the nearby lake community was affected as many of them earn a living by carrying fisheries activity in the lake especially harvesting Asian clam. 10 sampling sites were selected in the lake to monitor water quality and Asian clam distribution. Water parameters data were also subjected to cluster analysis by using Ward's method with squared Euclidean distances as a measure of similarity and a dendrogram was successfully generated. The water quality of the lake is under good condition and suitable to carry fishery activities by referred to Malaysia National Water Quality Standards (NWQS). The dendrogram revealed that the sampling sites can be divided into 2 clusters where Location 1 alone in its own cluster. Another cluster possesses 2 sub-clusters where Location 2 and 3 shared similar sub cluster. Another sub-cluster has two groups namely Location 5, 6 and 8 in one group whereas Location 4, 7, 9 and 10 shared similar group. The findings of the present study showed most of sampled Asian clam in Pergau Lake was semi mature indicating highly exploitation of Asian clam in the Lake. Furthermore, there were no correlation was detected between the population of Asian clam and water quality of the lake. Hence, we suggest that seasonal harvesting Asian clam should be implemented in order to conserve the population of Asian clam in the lake at the mean time the community to continue earn a living through carrying fishery activities in the lake.

Electrospun Magnetic Nanocellulose-Polyethersulfone-Conjugated Aspergillus oryzae Lipase for Synthesis of Ethyl Valerate.

A novel greener MNC/PES membrane was developed through an electrospinning technique for lipase immobilization to catalyze the synthesis of ethyl valerate (EV). In this study, the covalent immobilization of Aspergillus oryzae lipase (AOL) onto an electrospun nanofibrous membrane consisting of magnetic nanocellulose (MNC) and polyethersulfone (PES) to produce EV was statistically optimized. Raman spectroscopy, Fourier-transform infrared spectroscopy: attenuated total reflection, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis (TGA), and differential thermal gravimetric (DTG) of MNC/PES-AOL demonstrated that AOL was successfully immobilized onto the fibers. The Taguchi design-assisted immobilization of AOL onto MNC/PES fibers identified that 1.10 mg/mL protein loading, 4 mL reaction volume, 250 rpm stirring rate, and 50 °C were optimal to yield 72.09% of EV in 24 h. The thermal stability of MNC/PES-AOL was improved by ≈20% over the free AOL, with reusability for up to five consecutive esterification cycles while demonstrating an exceptional half-life of 120 h. Briefly, the electrospun MNC/PES fibers that immobilized AOL showed promising applicability in yielding relatively good EV levels. This study suggests that using MNC as fillers in a PES to improve AOL activity and durability for a longer catalytic process could be a viable option.

Characterization of microplastics in the water and sediment of Baram River estuary, Borneo Island.

The Baram River is one of the largest rivers in Sarawak, where many large industries, such as plywood, sawmills, shipyards, interisland ports, and other wood-based industries are located along the river. Microplastic contamination has become a widespread and growing concern worldwide because of the small sizes of microplastics and their presence in seafood such as fish, squid, scallop, crabs, shrimp, and mussels. In this study, microplastics were found in all sampling stations. Out of the 4017 microplastics found in the water and sediment, microplastics fragment accounted for 67.8% of total microplastics, followed by fiber, film, pellet, and foam. Five microplastic polymer types were detected by ATR-FTIR, including polyethylene (PE), polyester (PET) fibers, silicon polymer, nitrile, and polystyrene (PS). The most common microplastics size range in Baram River was 0.3-1 mm, with blue as the highly abundant color.

Proximate analysis and fatty acid of Corbicula fluminea (C. fluminea) tissue in Kelantan, Malaysia.

Corbicula fluminea (C. fluminea) is one of the mollusc species commonly eaten as a popular snack in Kelantan, Malaysia. This species contributes to the local economic activity. However, the handling process of C. fluminea at different processing stages (raw, smoke and selling stages) is believed to have affected the nutritional value in their soft tissue. Hence, this study aims to provide information about the chemical content (moisture, crude fat, ash, crude protein and carbohydrate) of C. fluminea and fatty acid of smoked C. fluminea at different processing stages. Samples were collected from Pasir Mas and Tumpat, Kelantan, Malaysia. The chemical content analysis was carried out based on the Association of Official Analytical Chemists (AOAC) standard procedures. The results have indicated that moisture (80.93 ± 0.37%) and crude fat (10.82 ± 0.21%) in C. fluminea were significantly higher (p < 0.05) at the raw stage. On the other hand, the ash (2.09 ± 0.03%) and crude protein (9.45 ± 0.42%) were significantly higher (p < 0.05) at smoked stage. Meanwhile, carbohydrate (3.39 ± 0.49%) was significantly higher (p < 0.05) at the selling stage. The fatty acid percentage of smoked C. fluminea indicates that the total saturated fatty acid (SFA) content was higher than the total of both monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA). The obtained data indicates that the composition percentage of omega-6 (n-6) in PUFA is significantly greater than omega-3 (n-3). The n-6/n-3 ratio of smoked C. fluminea is 2.95-3.11 and therefore can be considered as a healthy diet. The findings of this study can improve consumers' health through sufficient nutrient consumption and also provide economic benefits by increasing sellers' income in Kelantan.

Health Risk Assessment of Heavy Metals from Smoked Corbicula fluminea Collected on Roadside Vendors at Kelantan, Malaysia.

Corbicula fluminea serves as traditional food to the local people in Kelantan, Malaysia. Concerns regarding river contamination, smoking method, and associated adverse effects on public health had been increasing. Hence, this study aims to measure the level of heavy metals (Cd, Cu, Mn, Pb, and Zn) and assess human health risk in C. fluminea consumption at Kelantan. Heavy-metal analysis was done using flame atomic absorption spectrophotometry, while human health risk was assessed using provisional tolerable weekly intake (PTWI), target hazard quotient (THQ), and hazard index (HI). The estimated weekly intake (EWI) for all metals was found within PTWI, while THQ for Cd, Cu, Mn, Pb, and Zn was 0.12, 0.06, 0.04, 0.41, and 0.03, respectively. The HI was calculated at 0.61 which is less than 1, considered as the safe consumption level. Therefore, C. fluminea consumption in this study was found safe from the health risk of noncarcinogenic effect over a lifetime.