Poly-Lactic Acid: Production, Applications, Nanocomposites, and Release Studies

Controlling Oligomer Chain Length via Ultrasonic Pretreatment in Lactic Acid Polycondensation for Enhanced Poly(lactic acid) ROP

Controlling oligomer chain length in lactic acid (LA) polycondensation is crucial for producing good properties of poly(lactic acid) (PLA). This study explores the use of ultrasonic pretreatment to reduce the water content of LA, aiming to optimize the polycondensation process and enhance the quality of PLA through ring-opening polymerization (ROP). The methodology involved varying ultrasonic treatment time and power during LA pretreatment, followed by polycondensation at the optimized temperature. The study results indicate that ultrasonic pretreatment effectively reduces the water content in LA, with optimal conditions found at 90 min and 75 W, yielding the lowest water content. The polycondensation process, conducted at a gradual temperature of 150 °C followed by 180 °C, resulted in the highest yield of 92.75% and a molecular weight of 25,126 g/mol for the oligomers. Ultrasonic pretreatment enhances water removal efficiency, reduces byproduct formation, and increases oligomer reactivity, resulting in higher-purity oligomers and improved chain length control. During the ROP stage, oligomers prepared through ultrasonic pretreatment produced PLA with a higher molecular weight and crystallinity.

Alternative plastic materials pose higher chemical hazard and aquatic ecotoxicity than conventional plastics

A comparative ecotoxicological profile was conducted on plastic materials with the same use made of conventional polymers versus alternative, potentially biodegradable polymers, frequently marketed as "bio" with claims of lower ecological impact. The sensitive in vivo sea-urchin embryo test (SET) was used for the ecotoxicological characterization, and non-target chemical analyses using GC-MS for the chemical profiling. Toxicological properties of identified chemicals were compiled from ECHA, and NIH databases using an in-house developed Python tool, and qualitative and semiquantitative Chemical Hazard Indices (CHI) were calculated for each material. The alternative materials exhibited on average 2- to 3-fold higher CHI values compared to conventional materials. All PE items, including recycled and oxodegradable samples, lacked any in vivo ecotoxicity, whereas all compostable items showed a certain degree of in vivo toxicity except for the PLA cups. The top six materials containing the highest concentrations of category 1 reproductive toxicity phthalates were all alternative plastics: the recycled bag, compostable knives, PHB resin, and both home-compostable trash sacs. Therefore, while degradable plastics may contribute to reduce the environmental persistence of plastic items, they do not necessarily reduce their ecotoxicological impact, and may increase their chemical hazard.

The Antimicrobial and Antioxidant Effects of Bilayer Films Based on Polylactic Acid (PLA)/Chitosan: Starch Containing Bitter Orange Essential Oil on the Fresh Rainbow Trout (Onchorhynchus mykiss) Fillet

This study investigated the antibacterial properties of polylactic acid (PLA)/chitosan: starch films incorporated with bitter orange essential oil (BOEO) for preserving rainbow trout fillets. Three BOEO concentrations (0.7%, 1.4%, and 2.1% w/w) were incorporated via casting. Increased BOEO concentration enhanced film hydrophobicity and thermal resistance, but reduced tensile strength while increasing elongation. Atomic force microscopy revealed altered surface roughness. Antibacterial testing showed optimal activity against both Gram-positive and Gram-negative bacteria at 1.2% BOEO. Films containing 1.2% BOEO were applied to rainbow trout fillets, significantly reducing spoilage bacteria (total bacterial count, psychrotrophic, lactic acid bacteria, and Enterobacteriaceae), slowing chemical spoilage (pH and TBA values), and minimizing weight loss during 16 days of refrigerated storage (4°C). These results demonstrate the potential of BOEO-incorporated PLA/chitosan: starch films for extending the shelf life of rainbow trout.

Sustainable and biodegradable polymer packaging: Perspectives, challenges, and opportunities

The escalating environmental impact of non-biodegradable plastic waste has intensified global efforts to seek sustainable alternatives, with biodegradable polymers from renewable sources emerging as a promising solution. This manuscript provides the current perspectives, challenges, and opportunities within the field of sustainable and biodegradable packaging. Despite a significant market presence of conventional non-biodegradable petrochemical-based plastics, there is a growing trend towards the adoption of bio-based polymers from renewable resources driven by environmental sustainability and regulatory measures. However, the transition to biodegradable packaging is fraught with challenges, including scalability, cost-effectiveness, technological limitations, comprehensive waste management systems, and infrastructural needs. The manuscript highlights the intrinsic technological challenges and the need for advancements in material science to enhance the performance and adoption of biodegradable packaging. This paper also supply insights into the development and implementation of biodegradable packaging, offering a comprehensive overview of its role in achieving global sustainability goals.

Mechanical finite element analysis of needle tip shape to develop insertable polymer-based microneedle without plastic deformation

Bioabsorbable polymer microneedles are highly attractive as modernized medical devices for efficient yet safe transdermal drug delivery and biofluid biopsy. In this study, the elastoplastic deformation of polymer microneedles, having a high aspect ratio (over 5-10), is investigated using poly(lactic) acid polymer approved by the United States Food and Drug Administration to be generally considered safe. Microneedle geometries are comprehensively analyzed for tip geometries comprising the tip diameter (ϕt) and tip taper length (lt) of 100 designs. Elastoplastic analysis is conducted using the finite element method to determine the typical geometries of the polymer microneedles to avoid elastoplastic deformation accompanied by fatal fracture based on the mechanical properties of the polymer materials. The design principles of microneedle geometries based on polymer material properties are important guidelines for developing polymer microneedles, overcoming their mechanical weakness, and ensuring excellent functions.

Developing high-performance and sustainable polylactic acid/recycled polyolefin blends: Tuning the degree of functional group reaction and performance optimization

In the current development of the plastics industry, the use of biodegradable and recycled plastics not only effectively reduces the volume of landfills and incineration but also significantly decreases environmental damage. However, the extensive application of biodegradable polylactic acid (PLA) is limited by its poor toughness and thermal properties. The study introduced recycled linear low-density polyethylene (R-LLDPE) and ethylene-octene copolymer (POE) to modify PLA, primarily based on their excellent toughness and thermal resistance. Furthermore, being a recycled material, R-LLDPE is economically advantageous and conforms to the ecological requirements of resource recycling. Therefore，the study introduced glycidyl methacrylate (GMA) and styrene (St) to synthesize the graft copolymer (R-LLDPE/POE)-g-(GMA-co-St) (RPGS). The RPGS serves as a modifier for PLA resin. The effects of different GMA amounts in RPGS on the properties and microstructure of PLA/RPGS blends were examined. The results illustrate that GMA was successfully grafted onto the molecular chains of R-LLDPE/POE (RP), with St acting as a "bridge" to enhance further the grafting efficiency of GMA on RP macromolecular chains. After introducing RPGS into the PLA matrix, the epoxy groups of GMA reacted with the terminal hydroxyl groups of PLA, significantly decreasing the particle size of the dispersed phase and closely integrating with the PLA matrix, hence greatly improving the compatibility between PLA and RP. With the increase of GMA amount, the optical, thermal, and hydrophobic properties of the blends were increased, while the flexibility first increased and then decreased. When the amount of GMA was 5 wt% in RPGS, the Gd and Ge of GMA reached optimal values of 2.55 % and 51 %, the blend exhibited the optimum overall properties: haze decreased to 28.3 %, light transmittance increased to 92.5 %, thermal decomposition temperature increased to 368.12 °C, and the Vicat softening temperature increased to 78.2 °C. While maintaining the tensile strength at 54.3 MPa, the notched impact strength and elongation at break increased to 10,182.4 J/m2 and 231.7 %, respectively, with the matrix exhibiting significant shear yielding. The research presents an eco-friendly and efficient method for producing high-performance PLA-based materials, effectively addressing the shortcomings of PLA in toughness and thermal resistance. The modified materials had excellent mechanical and thermal capabilities while offering financial and environmental benefits. The development of this material is anticipated to enhance the industrial utilization of biodegradable and recycled plastics, offering essential support for attaining sustainable manufacturing and a circular economy.

Evaluating the antagonist effect of naltrexone implant via opioid challenge tests with escalating doses of hydromorphone injection in former heroin dependent patients

Opioid dependence is a serious, life-threatening condition with severe social impacts. Naltrexone (NTX) can weaken the effect of opioids and effectively reduce opioid self-administration, discrimination, and opioid-induced subjective effects, and the oral dosage form has been approved for the treatment of opioid dependence. However, the effectiveness of oral naltrexone as an opioid antagonist has been limited due to poor patient adherence. A long-acting formulation in the form of naltrexone implant (NTX-IMP) with a five-month duration of action may address this issue and improve outcomes. This study (trial registration number: CTR20181954) aimed to evaluate the effect, safety, and pharmacokinetics of NTX-IMP in agonist effects via hydromorphone challenge test, and to determine optimal dosages for future research. Thirty-one former opioid-dependent individuals were randomized to the 0.9g or the 1.5g NTX-IMP group. All subjects exhibited significant antagonistic effects during hydromorphone challenge test. Calculation of slope between VAS score or pupil diameter and hydromorphone dose suggested a stronger antagonistic effect in the 1.5 g group. Pharmacokinetic data suggested that effective plasma naltrexone concentration (≥1ng/ml) was detected from the third day for over 148 days, with higher concentration and longer duration in the 1.5 g group. All subjects tolerated NTX-IMP well. The findings indicate that the NXT-IMP effectively blocks the agonistic effects of hydromorphone in a dose-dependent manner.

Active Polylactide-poly(ethylene glycol) Films Loaded with Olive Leaf Extract for Food Packaging-Antibacterial Activity, Surface, Thermal and Mechanical Evaluation

As the demand for sustainable and innovative solutions in food packaging continues to grow, this study endeavors to introduce a comprehensive exploration of novel active materials. Specifically, we focus on characterizing polylactide-poly(ethylene glycol) (PLA/PEG) films filled with olive leaf extract (OLE; Olea europaea) obtained via solvent evaporation. Examined properties include surface structure, thermal degradation and mechanical attributes, as well as antibacterial activity. The results indicated a significant impact of the incorporation of OLE into this polymeric matrix, increasing hydrophobicity, decreasing surface free energy, and enhancing surface roughness, albeit with slight reductions in mechanical properties. Notably, these modified materials exhibited significant bacteriostatic, bactericidal and anti-adhesive activity against both Staphylococcus aureus and Escherichia coli. Consequently, PLA/PEG/OLE films demonstrated considerable potential for advanced food packaging, facilitating interactions between products and their environment. This capability ensures the preservation and extension of food shelf life, safeguards against microbial contamination, and maintains the overall quality, safety, and integrity of the packaged food. These findings suggest potential pathways for developing more sustainable and effective food packaging films.

Production of L-lactic acid from methanol by engineered yeast Pichia pastoris

Lactic acid (LA) serves as a widely used platform compound and has received significant attention as a raw material for synthesis of biodegradable polylactic acid. Currently, LA is mainly produced through microbial fermentation, but its high costs undermine its competitive advantage against other materials, necessitating the development of novel production routes. Methanol bioconversion represents an emerging low-carbon circular economy, where LA could become an outstanding representative product. This study successfully established an efficient methanol-based LA synthesis route in Pichia pastoris. Through systematic metabolic engineering strategies, including screening lactate dehydrogenase, modification of cofactor preference, blocking LA consumption pathway, and mitochondrial LA synthesis compartmentalization, 4.2 g/L L-LA was produced in fed-batch fermentation by using methanol as the sole carbon source. Through multi-dimensional and spatial engineering of enzyme, a cell factory was developed for efficient synthesis of L-LA, highlights the significant potential of the low-carbon synthesis route for L-LA via methanol bioconversion.

Advances in the enhancement of mechanical and hydrophobic properties of nanocellulose-based packaging materials: A review

As environmental issues are hotly debated worldwide, finding suitable materials to replace petroleum-based materials as the next-generation packaging materials has become a research hotspot. Nanocellulose, as a biomass material widely available in nature, is favored for application in green packaging materials due to its environmentally friendly and bio-friendly characteristics. However, the unstable mechanical properties and strong hydrophilicity of nanocellulose limit its practical application in packaging materials. This paper starts with a discussion of nanocellulose-based packaging materials and focuses on methods to improve their mechanical and hydrophobic properties. The discussion on mechanical properties focuses on the contribution of carbon nanomaterials, which is then combined with hydrophobic modifications (including plant polyphenol modification, esterification, acetylation, in situ polymerization, etc.) to illustrate the impact on the performance of packaging materials in use. The relationship between the hydrophobic characteristics of packaging materials derived from nanocellulose and their comprehensive mechanical properties is meticulously elucidated. Furthermore, a theoretical framework is proposed, positing that enhancing the hydrophobicity of these materials can indirectly augment their mechanical attributes. This insight offers pivotal guidance for the advancement of next-generation, high-performance packaging materials based on nanocellulose.

Poly(Lactic Acid): Recent Stereochemical Advances and New Materials Engineering

Poly(lactic acid) (PLA) is a representative biobased and biodegradable aliphatic polyester and a front-runner among sustainable materials. As a semicrystalline thermoplastic, PLA exhibits excellent mechanical and physical properties, attracting considerable attention in commodity and medical fields. Stereochemistry is a key factor affecting PLA's properties, and to this end, the engineering of PLA's microstructure for tailored material properties has been an active area of research over the decade. This Review first covers the basic structural variety of PLA. A perspective on the current states of stereocontrolled synthesis as well as the relationships between the structures and properties of PLA stereosequences are included, with an emphasis on record regularity and properties. At last, state-of-the-art examples of high-performance PLA-based materials within an array of applications are given, including packaging, fibers, and textiles, healthcare and electronic devices. Among various stereo-regular sequences of PLA, poly(L-lactic acid) (PLLA) is the most prominent category and has myriad unique properties and applications. In this regard, cutting-edge applications of PLLA are mainly overviewed in this review. At the same time, new materials developed based on other PLA stereosequences are highlighted, which holds the potential to a wide variety of PLA-based sustainable materials.

Role of polylactic acid microplastics during anaerobic co-digestion of cow manure and Chinese cabbage waste enhanced by nanobubble

With the increasing use of plastic products globally, environmental pollution by plastic waste is becoming increasingly problematic. This study investigated the impacts of two types of polylactic acid microplastics, clear microplastics and aluminised film microplastics, on methane yield, microbial community, and volatile fatty acid accumulation during anaerobic co-digestion of cow manure and Chinese cabbage waste under different temperature conditions. The influence of the addition of air nanobubbles on microplastic degradation in the anaerobic digestion system we also examined. The results revealed that under thermophilic conditions, clear and aluminised film microplastics increased the methane yield, with the latter resulting in greater improvement. Conversely, under mesophilic conditions, the presence of microplastics reduced the methane yield, but the addition of air-nanobubble partially mitigated this effect. Microplastics also affected the microbial community, with specific species showing correlations with methane yield. Methanothermobacter, which is linked to lactic acid conversion, was positively correlated with methane yield, whereas Methanomassiliicoccus levels increased in the presence of microplastics, particularly in the inhibited state of the digester. These results suggest that, under thermophilic conditions, microplastics may increase the cumulative methane yield by facilitating the degradation of lactic acid monomers. Furthermore, the aluminised film on microplastics could serve as an electrically conductive material during anaerobic digestion, potentially increasing the methane yield.

Experimental evolution reveals an effective avenue for d-lactic acid production from glucose-xylose mixtures via enhanced Glk activity and a cAMP-independent CRP mutation

d-Lactic acid holds significant industrial importance due to its versatility and serves as a crucial component in the synthesis of environmentally friendly and biodegradable thermal-resistant poly-lactic acid. This polymer exhibits promising potential as a substitute for nonbiodegradable, petroleum-based plastics. The production of d-lactic acid from lignocellulosic biomass, a type of biorenewable and nonfood resources, can lower costs and improve product competitiveness. Glucose and xylose are the most abundant sugar monomers in lignocellulosic biomass materials. Despite Escherichia coli possessing native xylose catabolic pathways and transport, their ability to effectively utilize xylose is often hindered in the presence of glucose. Here, the E. coli strain Rec1.0, previously engineered to overcome carbon catabolite repression, was selected as the initial strain for reengineering to produce d-lactic acid. An adaptive evolution approach was employed to achieve highly efficient fermentation of glucose-xylose mixtures. The resulting strain, QJL010, could produce d-lactic acid of 87.5 g/L with a carbon yield of 0.99 mol/mol. Notably, the consumption rates of glucose and xylose reached 0.75 and 0.82 g/gDCW/h, respectively. Further analysis revealed that increased Glk activity, resulting from glk mutations (A142V and R188H), along with their upregulated expression, contributed to an elevated glucose consumption rate. Additionally, a CRP G141D mutation, cAMP-independent, stimulated the expression of the xylR, xylE, and galABC* genes, resulting in an accelerated xylose consumption rate. These findings provide valuable support for the utilization of E. coli platform strains in the production of value-added chemicals from lignocellulosic biomass.

Development of Functionalized Polylactide Thin Films Using Poly(methylhydrogenosiloxane) Sol-Gel Process with Improved Antifouling Properties

Biobased polylactide (PLA) films were modified with low reticulate polysiloxane gel acting as a scalable platform for the hydrophilization of polymeric film surface. The PLA thin film was first coated with poly(methylhydrogenosiloxane) (PMHS) by the sol-gel transition via the condensation of diethoxymethylsilane (DH) and triethoxysilane (TH) using trifluoromethanesulfonic acid as a catalyst. Then, hydrosilylation of Si-H bonds in the presence of Karstedt's catalyst allowed the covalent grafting of hydrophilic alkene-containing molecules, i.e., triethylene glycol monomethyl allyl (TEGMEA) and a new zwitterionic allylcarboxybetaine (ACB) synthesized for the first time by the quaternization of dimethyl allyl amine (DMAA) with β-propiolactone. PMHS coating on the PLA film was evidenced by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The observation by atomic force microscopy (AFM) revealed a homogeneous coating with low roughness (RMS = 0.29 nm). The hydrophilicity of functionalized PLA films was determined by water contact angle (WCA) measurements using the captive bubble method. A large increase in wettability properties was observed for both grafting with TEGMEA (WCA = 38°) and ACB (WCA = 42°) in comparison with the native PLA film (WCA = 80°). Moreover, the biocompatibility and antifouling efficiency of functionalized PLA films were evaluated by protein adsorption, bacterial adhesion, and cytotoxicity tests. The results indicate that the grafting of the two types of hydrophilic compounds does not affect the biocompatibility of PLA while significantly reducing protein adsorption and bacterial adhesion, thus showing the great potential of this surface functionalization strategy for applications in the medical field.

Bio-Based and Biodegradable Polymeric Materials for a Circular Economy

Nowadays, plastic contamination worldwide is a concerning reality that can be addressed with appropriate society education as well as looking for innovative polymeric alternatives based on the reuse of waste and recycling with a circular economy point of view, thus taking into consideration that a future world without plastic is quite impossible to conceive. In this regard, in this review, we focus on sustainable polymeric materials, biodegradable and bio-based polymers, additives, and micro/nanoparticles to be used to obtain new environmentally friendly polymeric-based materials. Although biodegradable polymers possess poorer overall properties than traditional ones, they have gained a huge interest in many industrial sectors due to their inherent biodegradability in natural environments. Therefore, several strategies have been proposed to improve their properties and extend their industrial applications. Blending strategies, as well as the development of composites and nanocomposites, have shown promising perspectives for improving their performances, emphasizing biopolymeric blend formulations and bio-based micro and nanoparticles to produce fully sustainable polymeric-based materials. The Review also summarizes recent developments in polymeric blends, composites, and nanocomposite plasticization, with a particular focus on naturally derived plasticizers and their chemical modifications to increase their compatibility with the polymeric matrices. The current state of the art of the most important bio-based and biodegradable polymers is also reviewed, mainly focusing on their synthesis and processing methods scalable to the industrial sector, such as melt and solution blending approaches like melt-extrusion, injection molding, film forming as well as solution electrospinning, among others, without neglecting their degradation processes.

Comparative assessment of the acute toxicity of commercial bio-based polymer leachates on marine plankton

Conventional plastics have become a major environmental concern due to their persistence and accumulation in marine ecosystems. The development of potential degradable polymers (PBP), such as polyhydroxyalkanoates (PHAs) and polylactic acid (PLA), has gained attention as an alternative to mitigate plastic pollution, since they have the potential to biodegrade under certain conditions, and their production is increasing as replacement of conventional polyolefins. This study aimed to assess and compare the toxicity of leachates of pre-compounding PBP (PLA and the PHA, polyhydroxybutyrate-covalerate (PHBv)) and polypropylene (PP) on five marine planktonic species. A battery of standard bioassays using bacteria, microalgae, sea urchin embryos, mussel embryos and copepod nauplii was conducted to assess the toxicity of leachates from those polymers. Additionally, the presence of chemical additives in the leachates was also verified through GC-MS and LC-HRMS analysis. Results showed that PHBv leachates exhibited higher toxicity compared to other polymers, with the microalgae Rhodomonas salina, being the most sensitive species to the tested leachates. On the other hand, PP and PLA generally displayed minimal to no toxicity in the studied species. Estimated species sensitivity distribution curves (SSD) show that PHBv leachates can be 10 times more hazardous to marine plankton than PP or PLA leachates, as demonstrated by the calculated Hazardous Concentration for 5 % of species (HC5). Qualitative chemical analysis supports the toxicological results, with 80 % of compounds being identified in PHBv leachates of which 2,4,6-trichlorophenol is worth mentioning due to the deleterious effects to aquatic biota described in literature. These findings underscore the fact that whereas environmental persistence can be targeted using PBP, the issue of chemical safety remains unsolved by some alternatives, such as PHBv. Gaining a comprehensive understanding of the toxicity profiles of PBP materials through a priori toxicological risk assessment is vital for their responsible application as alternatives to conventional plastics.

Terpenoid-Based High-Performance Polyester with Tacticity-Independent Crystallinity and Chemical Circularity

The development of chemically circular, bio-based polymers is an urgently needed solution to combat the plastic waste crisis. However, the most prominent, commercially implemented bio-based aliphatic polyester, poly(lactic acid) (PLA), is brittle, therefore largely limiting its broad applications. Herein, we introduce a class of aliphatic polyesters produced through the ring-opening polymerization (ROP) of (1R,5S)-8,8-dimethyl-3-oxabicyclo[3.2.1]octan-2-one (D-CamL) and the racemic mixture (rac-CamL), which exhibit superior materials properties relative to PLA. A metal-based or organic catalyst was used for the modulation of polymer tacticity. Notably, regardless of tacticity, poly(CamL) exhibits intrinsic crystallinity resulting in polyesters with high yield stress (24-39 MPa), high Young's modulus (1.36-2.00 GPa), tunable fracture strains (6-218%), and high melting temperatures (161-225 °C). Importantly, poly(CamL) can be chemically recycled to monomer in high yield and the virgin-quality poly(CamL) was obtained after repolymerization. Overall, poly(CamL) represents a new class of bio-derived and chemically circular high-performance polyesters.

Melt Compounding of Poly(lactic acid)-Based Composites: Blending Strategies, Process Conditions, and Mechanical Properties

Polylactic acid (PLA), derived from renewable resources, has the advantages of rigidity, thermoplasticity, biocompatibility, and biodegradability, and is widely used in many fields such as packaging, agriculture, and biomedicine. The excellent processability properties allow for melt processing treatments such as extrusion, injection molding, blow molding, and thermoforming in the preparation of PLA-based materials. However, the low toughness and poor thermal stability of PLA limit its practical applications. Compared with pure PLA, conditions such as processing technology, filler, and crystallinity affect the mechanical properties of PLA-based materials, including tensile strength, Young's modulus, and elongation at break. This review systematically summarizes various technical parameters for melt processing of PLA-based materials and further discusses the mechanical properties of PLA homopolymers, filler-reinforced PLA-based composites, PLA-based multiphase composites, and reactive composite strategies for PLA-based composites.

Challenges and opportunities in managing biodegradable plastic waste: A review

Biodegradable plastics have certain challenges in a waste management perspective. The existing literature reviews fail to provide a consolidated overview of different process steps of biodegradable plastic waste management and to discuss the support provided by the existing legislation for the same. The present review provides a holistic overview of these process steps and a comprehensive relative summary of 13 existing European Union (EU) laws related to waste management and circular economy, and national legislations plus source separation guidelines of 13 countries, to ensure the optimal use of resources in the future. Following were the major findings: (i) numerous types and low volumes of biodegradable plastics pose a challenge to developing cost-effective waste management infrastructure; (ii) biodegradable plastics are promoted as food-waste collection aids, but consumers are often confused about their proper disposal and are prone to greenwashing from manufacturers; (iii) industry-level studies demonstrating mechanical recycling on a full scale are unavailable; (iv) the existing EU legislation dealt with general topics related to biodegradable plastics; however, only the new proposal on plastic packaging waste and the EU policy framework for bioplastics clearly mentioned their disposal and (v) clear disparities were observed between disposal methods suggested by national legislation and available source separation guidelines. Thus, to appropriately manage biodegradable plastic waste, it is necessary to develop waste processing and material utilization infrastructure as well as create consumer awareness. In the end, recommendations were provided for improved biodegradable plastic waste management from the perspective of systemic challenges identified from the literature review.

Exploring the advantages and limitations of degradation for various biodegradable micro-bioplastic in aquatic environments

Biodegradable plastics are being the substitute for synthetic plastics and widely been used in order to combat plastic pollution. Yet not all biodegradable plastics are degradable especially when it does not meet its favourable conditions, and also when it comes to aquatic environments. Therefore, this review is intended to highlight the types of various biodegradable plastic synthesized and commercialised and identify the limitations and advantages of these micro-bioplastics or residual bioplastic upon degradation in various aquatic environments. This review paper highlights on biodegradable plastic, degradation of biodegradable plastic in aquatic environments, application of biodegradable plastic, polylactic acid (PLA), Polyhydroxyalkanoates (PHA), Polysaccharide derivatives, Poly (amino acid), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBA/T), limitations and advantages of biodegradable plastic degradation in aquatic environment. There is no limit on the period for literature search as this field is continuously being studied and there is no wide range of studies. Biodegradable plastic that is commercially available has its own advantages and limitations respectively upon degradation in both freshwater and marine environments. There is a growing demand for bioplastic as an alternative to synthetic plastic which causes plastic waste pollution. Thus, it is crucial to understand the biodegradation of biodegradable plastic in depth especially in aquatic environments. Moreover, there are also very few studies investigating the degradation and migration of micro-bioplastics in aquatic environments.

Synthesis of star-shaped poly(lactide)s, poly(valerolactone)s and poly(caprolactone)s via ROP catalyzed by N-donor tin(ii) cations and comparison of their wetting properties with linear analogues

In this study, we report the use of N-coordinated tin(ii) cations [L1→Sn(H2O)][OTf]2·THF (1) and [L1→SnCl][SnCl3] (2) (L1 = 1,2-(C5H4N-2-CH = N)2CH2CH2) as efficient ROP catalysts, which, in combination with benzyl alcohol, afford well-defined linear poly(ε-caprolactone) (PCL) and poly(δ-valerolactones) (PVL) via an activated monomer mechanism (AMM). Thanks to the versatility of complexes 1 and 2 as catalysts, star-shaped PCL, PVL and PLA were also prepared using three-, four-, five- and six-functional alcohols. The number of arms was determined by SEC-MALS-Visco analysis. Spin-coated thin layers of linear and selected six-armed polymers were further studied in terms of their wettability to water. Attention was focused on the influence of the composition and structure of the polymers. Finally, to increase the hydrophobic properties of the studied polymers, stannaboroxines L2(Ph)Sn[(OB-(C6H4-4-CF3))2O] and L2(Ph)Sn[(OB-(C6H4-3,5-CF3)2)2O] (L2 = C6H3-2,6-(Me2NCH2)2) were applied.

Poly(lactic acid) Degradation by Recombinant Cutinases from Aspergillus nidulans

Poly(lactic-acid) (PLA) is a biodegradable polymer widely used as a packaging material. Its monomer, lactic acid, and its derivatives have been used in the food, cosmetic, and chemical industries. The accumulation of PLA residues leads to the development of green degrading methodologies, such as enzymatic degradation. This work evaluates the potential use of three cutinolytic enzymes codified in the Aspergillus nidulans genome to achieve this goal. The results are compared with those obtained with proteinase K from Tritirachium album, which has been reported as a PLA-hydrolyzing enzyme. The results show that all three cutinases act on the polymer, but ANCUT 1 releases the highest amount of lactic acid (25.86 mM). Different reaction conditions assayed later led to double the released lactic acid. A decrease in weight (45.96%) was also observed. The enzyme showed activity both on poly L lactic acid and on poly D lactic acid. Therefore, this cutinase offers the potential to rapidly degrade these package residues, and preliminary data show that this is feasible.

Effects of Nozzle Temperature on Mechanical Properties of Polylactic Acid Specimens Fabricated by Fused Deposition Modeling

This paper investigates the effect of nozzle temperature, from 180 to 260 °C, on properties of polylactic acid (PLA) samples manufactured by fused deposition modeling (FDM) technology. The main objective of this research is to determinate an optimum nozzle temperature relative to tensile, flexural and compressive properties of printed specimens. After manufacturing, the samples exhibit an amorphous structure, without crystallization effects, independently of the fabrication temperature. In order to determine the influence of printing temperature on mechanical properties, uniaxial tensile, three-point flexural and compression strength tests were carried out. The obtained results suggest that a relative low printing temperature could reduce the material flow and decrease the density of the final prototype, with a negative effect on both the quality and the mechanical properties of the pieces. If temperature increases up to 260 °C, an excess of material can be deposited, but with no significant negative effect on mechanical parameters. There is an optimum nozzle temperature interval, depending on the considered piece and test, for which mechanical values can be optimized. Taking into account all tests, a recommended extruder temperature interval may be identified as 220-240 °C. This range encompasses all mechanical parameters, avoiding the highest temperature where an excess of material was observed. For this printing temperature interval, no significant mechanical variations were appreciated, which corresponds to a stable behavior of the manufactured specimens.

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

Material-binding peptides (MBPs) have emerged as a diverse and innovation-enabling class of peptides in applications such as plant-/human health, immobilization of catalysts, bioactive coatings, accelerated polymer degradation and analytics for micro-/nanoplastics quantification. Progress has been fuelled by recent advancements in protein engineering methodologies and advances in computational and analytical methodologies, which allow the design of, for instance, material-specific MBPs with fine-tuned binding strength for numerous demands in material science applications. A genetic or chemical conjugation of second (biological, chemical or physical property-changing) functionality to MBPs empowers the design of advanced (hybrid) materials, bioactive coatings and analytical tools. In this review, we provide a comprehensive overview comprising naturally occurring MBPs and their function in nature, binding properties of short man-made MBPs (<20 amino acids) mainly obtained from phage-display libraries, and medium-sized binding peptides (20-100 amino acids) that have been reported to bind to metals, polymers or other industrially produced materials. The goal of this review is to provide an in-depth understanding of molecular interactions between materials and material-specific binding peptides, and thereby empower the use of MBPs in material science applications. Protein engineering methodologies and selected examples to tailor MBPs toward applications in agriculture with a focus on plant health, biocatalysis, medicine and environmental monitoring serve as examples of the transformative power of MBPs for various industrial applications. An emphasis will be given to MBPs' role in detecting and quantifying microplastics in high throughput, distinguishing microplastics from other environmental particles, and thereby assisting to close an analytical gap in food safety and monitoring of environmental plastic pollution. In essence, this review aims to provide an overview among researchers from diverse disciplines in respect to material-(specific) binding of MBPs, protein engineering methodologies to tailor their properties to application demands, re-engineering for material science applications using MBPs, and thereby inspire researchers to employ MBPs in their research.

The Effects of Nucleating Agents and Processing on the Crystallization and Mechanical Properties of Polylactic Acid: A Review

Polylactic acid (PLA) is a biobased, biodegradable, non-toxic polymer widely considered for replacing traditional petroleum-based polymer materials. Being a semi-crystalline material, PLA has great potential in many fields, such as medical implants, drug delivery systems, etc. However, the slow crystallization rate of PLA limited the application and efficient fabrication of highly crystallized PLA products. This review paper investigated and summarized the influence of formulation, compounding, and processing on PLA's crystallization behaviors and mechanical performances. The paper reviewed the literature from different studies regarding the impact of these factors on critical crystallization parameters, such as the degree of crystallinity, crystallization rate, crystalline morphology, and mechanical properties, such as tensile strength, modulus, elongation, and impact resistance. Understanding the impact of the factors on crystallization and mechanical properties is critical for PLA processing technology innovations to meet the requirements of various applications of PLA.

A review on bio-based polymer polylactic acid potential on sustainable food packaging

Poly(lactic acid) (PLA) stands as a compelling alternative to conventional plastic-based packaging, signifying a notable shift toward sustainable material utilization. This comprehensive analysis illuminates the manifold applications of PLA composites within the realm of the food industry, emphasizing its pivotal role in food packaging and preservation. Noteworthy attributes of PLA composites with phenolic active compounds (phenolic acid and aldehyde, terpenes, carotenoid, and so on) include robust antimicrobial and antioxidant properties, significantly enhancing its capability to bolster adherence to stringent food safety standards. The incorporation of microbial and synthetic biopolymers, polysaccharides, oligosaccharides, oils, proteins and peptides to PLA in packaging solutions arises from its inherent non-toxicity and outstanding mechanical as well as thermal resilience. Functioning as a proficient film producer, PLA constructs an ideal preservation environment by merging optical and permeability traits. Esteemed as a pioneer in environmentally mindful packaging, PLA diminishes ecological footprints owing to its innate biodegradability. Primarily, the adoption of PLA extends the shelf life of products and encourages an eco-centric approach, marking a significant stride toward the food industry's embrace of sustainable packaging methodologies.

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Engineering a solar formic acid/pentose (SFAP) pathway in Escherichia coli for lactic acid production

Microbial CO2 fixation into lactic acid (LA) is an important approach for low-carbon biomanufacturing. Engineering microbes to utilize CO2 and sugar as co-substrates can create efficient pathways through input of moderate reducing power to drive CO2 fixation into product. However, to achieve complete conservation of organic carbon, how to engineer the CO2-fixing modules compatible with native central metabolism and merge the processes for improving bioproduction of LA is a big challenge. In this study, we designed and constructed a solar formic acid/pentose (SFAP) pathway in Escherichia coli, which enabled CO2 fixation merging into sugar catabolism to produce LA. In the SFAP pathway, adequate reducing equivalents from formate oxidation drive glucose metabolism shifting from glycolysis to the pentose phosphate pathway. The Rubisco-based CO2 fixation and sequential reduction of C3 intermediates are conducted to produce LA stoichiometrically. CO2 fixation theoretically can bring a 20% increase of LA production compared with sole glucose feedstock. This SFAP pathway in the integration of photoelectrochemical cell and an engineered Escherichia coli opens an efficient way for fixing CO2 into value-added bioproducts.

Effect of Aging on Tensile and Chemical Properties of Polylactic Acid and Polylactic Acid-Like Polymer Materials for Additive Manufacturing

Additive manufacturing, with its fast development and application of polymeric materials, led to the wide utilization of polylactic acid (PLA) materials. As a biodegradable and biocompatible aliphatic polyester, produced from renewable sources, PLA is widely used in different sectors, from industry to medicine and science. The aim of this research is to determine the differences between two forms of the PLA material, i.e., fused deposition modeling (FDM) printed filament and digital light processing (DLP) printed resin, followed by aging due to environmental and hygiene maintenance conditions for a period of two months. Specimens underwent 3D scanning, tensile testing, and Fourier transform infrared (FTIR) spectrometry to obtain insights into the material changes that occurred. Two-way Analysis of Variance (ANOVA) statistical analysis was subsequently carried out to determine the statistical significance of the determined changes. Significant impairment can be observed in the dimensional accuracies between both materials, whether they are non-aged or aged. The mechanical properties fluctuated for aged FDM specimens: 15% for ultimate tensile stress, 15% for elongation at yield, and 12% for elastic modulus. Regarding the DLP aged specimens, the UTS decreased by 61%, elongation at yield by around 61%, and elastic modulus by 62%. According to the FTIR spectral analysis, the PLA materials degraded, especially in the case of resin specimens. Aging also showed a significant influence on the elastic modulus, ultimate tensile stress, elongation at yield, elongation at break, and toughness of both materials, which was statistically shown by means of a two-way ANOVA test. The data collected in this research give a better understanding of the underlying aging mechanism of PLA materials.

Recent Progress and Challenges of Implantable Biodegradable Biosensors

Implantable biosensors have evolved to the cutting-edge technology of personalized health care and provide promise for future directions in precision medicine. This is the reason why these devices stand to revolutionize our approach to health and disease management and offer insights into our bodily functions in ways that have never been possible before. This review article tries to delve into the important developments, new materials, and multifarious applications of these biosensors, along with a frank discussion on the challenges that the devices will face in their clinical deployment. In addition, techniques that have been employed for the improvement of the sensitivity and specificity of the biosensors alike are focused on in this article, like new biomarkers and advanced computational and data communicational models. A significant challenge of miniaturized in situ implants is that they need to be removed after serving their purpose. Surgical expulsion provokes discomfort to patients, potentially leading to post-operative complications. Therefore, the biodegradability of implants is an alternative method for removal through natural biological processes. This includes biocompatible materials to develop sensors that remain in the body over longer periods with a much-reduced immune response and better device longevity. However, the biodegradability of implantable sensors is still in its infancy compared to conventional non-biodegradable ones. Sensor design, morphology, fabrication, power, electronics, and data transmission all play a pivotal role in developing medically approved implantable biodegradable biosensors. Advanced material science and nanotechnology extended the capacity of different research groups to implement novel courses of action to design implantable and biodegradable sensor components. But the actualization of such potential for the transformative nature of the health sector, in the first place, will have to surmount the challenges related to biofouling, managing power, guaranteeing data security, and meeting today's rules and regulations. Solving these problems will, therefore, not only enhance the performance and reliability of implantable biodegradable biosensors but also facilitate the translation of laboratory development into clinics, serving patients worldwide in their better disease management and personalized therapeutic interventions.

Physics-Informed Deep Learning Approach for Reintroducing Atomic Detail in Coarse-Grained Configurations of Multiple Poly(lactic acid) Stereoisomers

Multiscale modeling of complex molecular systems, such as macromolecules, encompasses methods that combine information from fine and coarse representations of molecules to capture material properties over a wide range of spatiotemporal scales. Being able to exchange information between different levels of resolution is essential for the effective transfer of this information. The inverse problem of reintroducing atomistic degrees of freedom in coarse-grained (CG) molecular configurations is particularly challenging as, from a mathematical point of view, it is an ill-posed problem; the forward mapping from the atomistic to the CG description is typically defined via a deterministic operator ("one-to-one" problem), whereas the reversed mapping from the CG to the atomistic model refers to creating one representative configuration out of many possible ones ("one-to-many" problem). Most of the backmapping methods proposed so far balance accuracy, efficiency, and general applicability. This is particularly important for macromolecular systems with different types of isomers, i.e., molecules that have the same molecular formula and sequence of bonded atoms (constitution) but differ in the three-dimensional configurations of their atoms in space. Here, we introduce a versatile deep learning approach for backmapping multicomponent CG macromolecules with chiral centers, trained to learn structural correlations between polymer configurations at the atomistic level and their corresponding CG descriptions. This method is intended to be simple and flexible while presenting a generic solution for resolution transformation. In addition, the method is aimed to respect the structural features of the molecule, such as local packing, capturing therefore the physical properties of the material. As an illustrative example, we apply the model on linear poly(lactic acid) (PLA) in melt, which is one of the most popular biodegradable polymers. The framework is tested on a number of model systems starting from homopolymer stereoisomers of PLA to copolymers with randomly placed chiral centers. The results demonstrate the efficiency and efficacy of the new approach.

Tailoring Pectin-PLA Bilayer Film for Optimal Properties as a Food Pouch Material

This study focuses on developing a biodegradable film using a novel hybrid citrus peel pectin. A bilayer approach with PLA was proposed and optimized using Response Surface Methodology (RSM) to complement pectin films' mechanical and barrier property limitations. The optimized film composition (2.90 g PLA and 1.96 g pectin) showed enhanced mechanical strength with a tensile strength (TS) of 7.04 MPa and an elongation at break (EAB) of 462.63%. In addition, it demonstrated lower water vapor (1.45 × 10-10 g/msPa), oxygen (2.79 × 10-7 g/ms) permeability, and solubility (23.53%). Compared to single-layer pectin films, the optimized bilayer film had a 25% increased thickness, significantly improved water barrier (3806 times lower) and oxygen barrier (3.68 times lower) properties, and 22.38 times higher stretchability, attributed to hydrogen bond formation, as confirmed by FTIR analysis. The bilayer film, effectively protected against UV and visible light, could be a barrier against light-induced lipid oxidation. Moreover, it demonstrated superior seal efficiency, ensuring secure sealing in practical applications. The bilayer pouch containing mustard dressing exhibited stable sealing with no leakage after immersion in hot water and ethanol, making it suitable for secure food pouch packaging.

Bacteria for Bioplastics: Progress, Applications, and Challenges

Bioplastics are one of the answers that can point society toward a sustainable future. Under this premise, the synthesis of polymers with competitive properties using low-cost starting materials is a highly desired factor in the industry. Also, tackling environmental issues such as nonbiodegradable waste generation, high carbon footprint, and consumption of nonrenewable resources are some of the current concerns worldwide. The scientific community has been placing efforts into the biosynthesis of polymers using bacteria and other microbes. These microorganisms can be convenient reactors to consume food and agricultural wastes and convert them into biopolymers with inherently attractive properties such as biodegradability, biocompatibility, and appreciable mechanical and chemical properties. Such biopolymers can be applied to several fields such as packing, cosmetics, pharmaceutical, medical, biomedical, and agricultural. Thus, intending to elucidate the science of microbes to produce polymers, this review starts with a brief introduction to bioplastics by describing their importance and the methods for their production. The second section dives into the importance of bacteria regarding the biochemical routes for the synthesis of polymers along with their advantages and disadvantages. The third section covers some of the main parameters that influence biopolymers' production. Some of the main applications of biopolymers along with a comparison between the polymers obtained from microorganisms and the petrochemical-based ones are presented. Finally, some discussion about the future aspects and main challenges in this field is provided to elucidate the main issues that should be tackled for the wide application of microorganisms for the preparation of bioplastics.

Production of poly(3-hydroxybutyrate)/poly(lactic acid) from industrial wastewater by wild-type Cupriavidus necator H16

The massive production of urban and industrial wastes has created a clear need for alternative waste management processes. One of the more promising strategies is to use waste as raw material for the production of biopolymers such as polyhydroxyalkanoates (PHAs). In this work, a lactate-enriched stream obtained by anaerobic digestion (AD) of wastewater (WW) from a candy production plant was used as a feedstock for PHA production in wild-type Cupriavidus necator H16. Unexpectedly, we observed the accumulation of poly(3-hydroxybutyrate)/poly(lactic acid) (P(3HB)/PLA), suggesting that the non-engineered strain already possesses the metabolic potential to produce these polymers of interest. The systematic study of factors, such as incubation time, nitrogen and lactate concentration, influencing the synthesis of P(3HB)/PLA allowed the production of a panel of polymers in a resting cell system with tailored lactic acid (LA) content according to the GC-MS of the biomass. Further biomass extraction suggested the presence of methanol soluble low molecular weight molecules containing LA, while 1 % LA could be detected in the purified polymer fraction. These results suggested that the cells are producing a blend of polymers. A proteomic analysis of C. necator resting cells under P(3HB)/PLA production conditions provides new insights into the latent pathways involved in this process. This study is a proof of concept demonstrating that LA can polymerize in a non-modified organism and paves the way for new metabolic engineering approaches for lactic acid polymer production in the model bacterium C. necator H16.

Ecotoxicity of polylactic acid microplastic fragments to Daphnia magna and the effect of ultraviolet weathering

Biodegradable plastics (BPs) are widely used as alternatives to non-BPs due to their inherent ability to undergo facile degradation. However, the ecotoxicological impact of biodegradable microplastics (MPs) rarely remains scientific documented especially to aquatic ecosystem and organisms compared to conventional microplastics. Therefore, this study aimed to investigate the ecotoxicity of biodegradable polylactic acid (PLA) MPs to Daphnia magna with that of conventional polyethylene (PE) MPs with and without ultraviolet (UV) treatment (4 weeks). The acute toxicity (48 h) of PLA MPs was significantly higher than that of PE MPs, potentially attributable to their elevated bioconcentration resulting from their higher density. UV treatment notably reduced the particle size of PLA MPs and induced new hydrophilic functional groups containing oxygen. Thus, the acute lethal toxicity of PLA MPs exhibited noteworthy increase, compared to before UV treatment after UV treatment, which was greater than that of UV-PE MPs. In addition, UV-PLA MPs showed markedly elevated reactive oxygen species concentration in D. magna compared to positive control. However, there was no significant increase in the level of lipid peroxidation, possibly due to successful defense by antioxidant enzymes (superoxide dismutase and catalase). These findings highlight the ecotoxicological risks of biodegradable MPs to aquatic organisms, which require comprehensive long-term studies.

Ring Opening Polymerization of Six- and Eight-Membered Racemic Cyclic Esters for Biodegradable Materials

The low percentage of recyclability of the polymeric materials obtained by olefin transition metal (TM) polymerization catalysis has increased the interest in their substitution with more eco-friendly materials with reliable physical and mechanical properties. Among the variety of known biodegradable polymers, linear aliphatic polyesters produced by ring-opening polymerization (ROP) of cyclic esters occupy a prominent position. The polymer properties are highly dependent on the macromolecule microstructure, and the control of stereoselectivity is necessary for providing materials with precise and finely tuned properties. In this review, we aim to outline the main synthetic routes, the physical properties and also the applications of three commercially available biodegradable materials: Polylactic acid (PLA), Poly(Lactic-co-Glycolic Acid) (PLGA), and Poly(3-hydroxybutyrate) (P3HB), all of three easily accessible via ROP. In this framework, understanding the origin of enantioselectivity and the factors that determine it is then crucial for the development of materials with suitable thermal and mechanical properties.

Modified Biomass-Reinforced Polylactic Acid Composites

Polylactic acid (PLA), as a renewable and biodegradable green polymer material, is hailed as one of the most promising biopolymers capable of replacing petroleum-derived polymers for industrial applications. Nevertheless, its limited toughness, thermal stability, and barrier properties have restricted its extensive application. To address these drawbacks in PLA, research efforts have primarily focused on enhancing its properties through copolymerization, blending, and plasticization. Notably, the blending of modified biomass with PLA is expected not only to effectively improve its deficiencies but also to maintain its biodegradability, creating a fully green composite with substantial developmental prospects. This review provides a comprehensive overview of modified biomass-reinforced PLA, with an emphasis on the improvements in PLA's mechanical properties, thermal stability, and barrier properties achieved through modified cellulose, lignin, and starch. At the end of the article, a brief exploration of plasma modification of biomass is presented and provides a promising outlook for the application of reinforced PLA composite materials in the future. This review provides valuable insights regarding the path towards enhancing PLA.

Synthesis and characterization of lactide from Bacillus amyloliquefaciens brewed lactic acid utilizing cheap agricultural sources

Lactic acid (LA) is a nifty molecule with an eclectic range of applications in innumerable industries and is produced through biological and chemical processes. Factually, LA is converted into lactide (LAC), which is the precursor for polylactic acid (PLA). PLA is considered one of the first-rate replacements for petroleum-based products and is believed to be environmentally sustainable. Nevertheless, it has always been challenging due to increased PLA productivity costs. Reduction in the LA and LAC production price directly echoes the production price of PLA. Therefore, low-cost LA and LAC production methods have to be found to produce PLA effectively. Hence, this study uses cheap agricultural sources derived microbial LA to make LAC through dimerization. Produced LAC was analyzed through FT-IR, NMR, TGA and XRD. FT-IR results revealed that the successful dimerization of LA to LAC, NMR analysis revealed that the aligning of methine and methyl groups in produced LAC, TGA analysis exposed that the microbial LAC has more thermal stability than the commercial LAC, XRD results showed that the produced LACs are crystalline with 32% and 42% crystallinity. To the best of our acquaintance, this manuscript is pioneering one to describe LA production through microbial fermentation and uses this monomer to produce LAC through dimerization.

Bioresource Polymer Composite for Energy Generation and Storage: Developments and Trends

The ever-growing demand of human society for clean and reliable energy sources spurred a substantial academic interest in exploring the potential of biological resources for developing energy generation and storage systems. As a result, alternative energy sources are needed in populous developing countries to compensate for energy deficits in an environmentally sustainable manner. This review aims to evaluate and summarize the recent progress in bio-based polymer composites (PCs) for energy generation and storage. The articulated review provides an overview of energy storage systems, e. g., supercapacitors and batteries, and discusses the future possibilities of various solar cells (SCs), using both past research progress and possible future developments as a basis for discussion. These studies examine systematic and sequential advances in different generations of SCs. Developing novel PCs that are efficient, stable, and cost-effective is of utmost importance. In addition, the current state of high-performance equipment for each of the technologies is evaluated in detail. We also discuss the prospects, future trends, and opportunities regarding using bioresources for energy generation and storage, as well as the development of low-cost and efficient PCs for SCs.

Recent trends in lactic acid-producing microorganisms through microbial fermentation for the synthesis of polylactic acid

Polylactic acid (PLA) is a range of unique bioplastics that are bio-based and biodegradable. PLA is currently driving market expansion for lactic acid (LA) due to its high demand as a building block in production. One of the most practical and environmentally benign techniques for synthesising PLA is through enzymatic polymerisation of microbial LA monomers. However, microbial LA fermentation does have some limitations. Firstly, it requires the use of a nutritionally rich medium. Secondly, LA production can be disrupted by bacteriophage infection or other microorganisms. Lastly, the yield can be low due to the formation of by-products through heterofermentative pathway. Considering the potential use of PLA as a replacement for conventional petrochemical-based polymers in industrial applications, researchers are focused on exploring the diversity of LA-producing microorganisms from various niches. Their goal is to study the functional properties of these microorganisms and their ability to produce industrially valuable metabolites. This review highlights the advantages and disadvantages of lactic acid-producing microorganisms used in microbial fermentation for PLA synthesis.

Identification of a plastic-degrading enzyme from Cryptococcus nemorosus and its use in self-degradable plastics

For decades, plastic waste management has been one of the major ecological challenges of our society. Despite the introduction of biodegradable alternatives such as polylactic acid (PLA), their beneficial environmental impact is limited by the requirement of specific compost facility as biodegradation of PLA in natural environment occurs at a very slow rate. In this work, a plastic-degrading enzyme was utilized to facilitate degradation process. Genomic and proteomic tools were employed to identify a new biodegradable plastic-degrading enzyme from Cryptococcus nemorosus TBRC2959. The new enzyme, Cr14CLE, functions optimally under mild conditions with temperature range of 30 to 40 °C and suffers no significant loss of enzymatic activity at pH ranging from 6 to 8. In addition to PLA, Cr14CLE is capable to degrade other types of biodegradable plastic such as polybutylene succinate (PBS) and polybutylene adipate terephthalate (PBAT) as well as composite bioplastic. Applications of Cr14CLE have been demonstrated through the preparation of enzyme-coated PLA film and laminated PLA film with enzyme layer. PLA films prepared by both approaches exhibited capability to self-degrade in water. KEY POINTS: • Novel plastic-degrading enzyme (Cr14CLE) was identified and characterized. • Cr14CLE can degrade multiple types of biodegradable plastics under mild conditions. • Applications of Cr14CLE on self-degradable plastic were demonstrated.

Properties of Stereocomplex PLA for Melt Spinning

Fibers made from biopolymers are one solution for conserving both resources and the environment. However, these fibers currently have limited strengths, which limit their use for textile applications. In this paper, a biopolymer stereocomplex poly(-lactide) (scPLA) formation on a technical scale of high-molecular-weight poly(D-lactide) (PDLA) and poly(L-lactide) (PLLA) is presented. This scPLA material is the basis for further research to develop scPLA yarns in melt spinning with technical strengths for technical application. scPLA is compared with standard and commercially available semi-crystalline PLA for the production of fibers in melt spinning (msPLA) with textile strengths. Differential scanning calorimetry (DSC) gives a degree of crystallization of 59.7% for scPLA and 47.0% for msPLA. X-ray diffraction (XRD) confirms the pure stereocomplex crystal structure for scPLA and semi-crystallinity for msPLA. scPLA and msPLA are also compared regarding their processing properties (rheology) in melt spinning. While complex viscosity of scPLA is much lower compared to msPLA, both materials show similar viscoelastic behavior. Thermal gravimetric analysis (TGA) shows the influence of the molecular weight on the thermal stability, whereas essentially the crystallinity influences the biodegradability of the PLA materials.

Potential Use of PLA-Based Films Loaded with Antioxidant Agents from Spent Coffee Grounds for Preservation of Refrigerated Foods

The aim of this work concerned the production of an active food packaging suitable for refrigerated foods. Polylactic-acid-based films were produced by optimizing the solvent casting technique and testing different loadings of extracts obtained from spent coffee grounds. Indeed, an extract obtained by high-pressure and -temperature extraction (HPTE) and a further purified extract by liquid-liquid extraction (LLE) were separately used as active agents, and the effects on packaging features and active compounds migration were analyzed. The selected active agents showed antioxidant and lipid peroxidation inhibition effects on food simulants (peroxide values of 9.2 ÷ 12.0 meqO2/kg extra virgin olive oil), demonstrating the possibility of enhancing food shelf life. In addition, significant effects on the packaging structure due to the presence of the extract were observed, since it can enhance gas barrier properties of the polymer (O2 permeability of 1.6 ÷ 1.3 × 10-9 cm2/s) and confer better processability. In general, the HPTE extract exhibited better performances than the further purified extract, which was due to the presence of a complex pool of antioxidants and the browning effect on the film but a limited loading capacity on the polymer (840 μg caffeine/g PLA), while higher loading capabilities were enabled using LLE extract.

Green biodegradable dielectric material made from PLA and electron beam irradiated luffa cylindrica fiber: devices for a sustainable future

The growing prevalence of polymer-based plastics in the environment is an imminent risk to the natural world. As an immediate consequence of this, extensive research has been launched over the course of the past few decades in an effort to reduce the damage that manmade plastics cause to the natural environment. The current study attempts to explore the biodegradability of polylactic acid (PLA), a bio-compatible plastic, by incorporating small amount of electron beam irradiated natural fibers (2 to 10%) derived from luffa cylindrica (LC) at varying irradiation doses (0.5 Gy, 1 Gy, and 2 Gy). Natural fiber surface treatment using electron beam irradiation is effective and environmentally friendly. The biodegradation of composites was studied for 90 days in sand, soil, compost, brackish water, fresh water, salt water, and bacterial and fungal conditions. Maximum decomposition was observed in the composite sample (PLA/10% wt of LC fiber at 2.0 Gy) at 15.42% and 4.73% in bacterial and soil environments. X-ray diffraction (XRD) and Raman spectroscopy validated the fiber and PLAs crystallinity and molecular interaction. The derivative thermo-gravimetric curve (DTGA) showed that electron beam irradiation removed moisture, hemicelluloses, and lignin from hydrophilic fibers. The incorporation of LC fibers into the bio-composites resulted in an increase in the glass transition temperature (Tg), melting temperature (Tm), and crystallization temperature (Tc). Additionally, after LC fiber reinforcement, the composites' dielectric properties were enhanced.

Study on the Biodegradation of Poly(Butylene Succinate)/Wheat Bran Biocomposites

This paper presents the results of a study investigating the biodegradation of poly(butylene succinate) (PBS)/wheat bran (WB) biocomposites. Injection mouldings were subjected to biodegradation in compost-filled bioreactors under controlled humidity and temperature conditions. The effects of composting time (14, 42 and 70 days) and WB mass content (10%, 30% and 50% wt.) on the structural and thermal properties of the samples were investigated. Measurements were made by infrared spectral analysis, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. Results demonstrated that both the thermal and structural properties of the samples depended greatly on the biodegradation time. Specifically, their crystallinity degree increased significantly while molecular mass sharply decreased with biodegradation time, whereas their thermal resistance only showed a slight increase. This resulted from enzymatic hydrolysis that led to the breakdown of ester bonds in polymer chains. It was also found that a higher WB content led to a higher mass loss in the biocomposite samples during biodegradation and affected their post-biodegradation properties. A higher bran content increased the degree of crystallinity of the biocomposite samples but reduced their thermal resistance and molecular mass.

Accelerating the Biodegradation of Poly(lactic acid) through the Inclusion of Plant Fibers: A Review of Recent Advances

As the global demand for plastics continues to grow, plastic waste is accumulating at an alarming rate with negative effects on the natural environment. The industrially compostable biopolymer poly(lactic acid) (PLA) is therefore being adopted for use in many applications, but the degradation of this material is slow under many end-of-life conditions. This Perspective explores the feasibility of accelerating the degradation of PLA through the formation of PLA-plant fiber composites. Topics include: (a) key properties of PLA, plant-based fibers, and biocomposites; (b) mechanisms of both hydrolytic degradation and biodegradation of PLA-fiber composites; (c) end-of-life degradation of PLA and PLA-plant fiber composites in aerobic and anaerobic conditions, relevant to compost, soil and seawater (aerobic), and landfills (anaerobic); and (d) sustainability and environmental impact of PLA and PLA-plant fiber composites, as evaluated using life cycle assessment. Additional degradation modes, including thermal and photodegradation, which are relevant during processing and use, have been omitted for clarity, as have other types of PLA biocomposites. Multiple studies have shown that the addition of some types of plant fibers to PLA (to form PLA biocomposites) accelerates both water transport in the material and hydrolysis, presenting a possible avenue for improving the end-of-life degradation of these materials. To facilitate the continued development of materials with enhanced biodegradability, we identify a need to implement testing protocols that can distinguish between different degradation mechanisms.

A Review of the Effect of Plasticizers on the Physical and Mechanical Properties of Alginate-Based Films

In recent years, there has been a growing attempt to manipulate various properties of biodegradable materials to use them as alternatives to their synthetic plastic counterparts. Alginate is a polysaccharide extracted from seaweed or soil bacteria that is considered one of the most promising materials for numerous applications. However, alginate potential for various applications is relatively limited due to brittleness, poor mechanical properties, scaling-up difficulties, and high water vapor permeability (WVP). Choosing an appropriate plasticizer can alleviate the situation by providing higher flexibility, workability, processability, and in some cases, higher hydrophobicity. This review paper discusses the main results and developments regarding the effects of various plasticizers on the properties of alginate-based films during the last decades. The plasticizers used for plasticizing alginate were classified into different categories, and their behavior under different concentrations and conditions was studied. Moreover, the drawback effects of plasticizers on the mechanical properties and WVP of the films are discussed. Finally, the role of plasticizers in the improved processing of alginate and the lack of knowledge on some aspects of plasticized alginate films is clarified, and accordingly, some recommendations for more classical studies of the plasticized alginate films in the future are offered.

Applications of poly(lactic acid) in bone tissue engineering: A review article

BACKGROUND

Bone tissue engineering is a promising approach to large-scale bone regeneration. This involves the use of an artificial extracellular matrix or scaffold and osteoblasts to promote osteogenesis and ossification at defect sites. Scaffolds are constructed using biomaterials that typically have properties similar to those of natural bone.

METHOD

In this study, which is a review of the literature, various evidences have been discussed in the field of Poly Lactic acid (PLA) polymer application and modifications made on it in order to induce osteogenesis and repair bone lesions.

RESULTS

PLA is a synthetic aliphatic polymer that has been extensively used for scaffold construction in bone tissue engineering owing to its good processability, biocompatibility, and flexibility in design. However, PLA has some drawbacks, including low osteoconductivity, low cellular adhesion, and the possibility of inflammatory reactions owing to acidic discharge in a living environment. To overcome these issues, a combination of PLA and other biomaterials has been introduced.

CONCLUSIONS

This short review discusses PLA's characteristics of PLA, its applications in bone regeneration, and its combination with other biomaterials.

Design and development of fused deposition modeling (FDM) 3D-Printed Orthotic Insole by using gyroid structure

The orthotic insole is a device that is placed between the bottom of the foot and the sole of the shoe. It bears the body weight and directly influences the biomechanics of the foot and the body. These insoles are used to minimize the stress by reducing plantar pressure between support points hence minimizing the pressure. Such customized insoles have usually been produced by either handmade or subtractive methods. Fused deposition modeling (FDM) has opened innovative ways for the manufacture of orthotic insoles. In recent studies, no specific computer-aided design (CAD) tools are available to design and manufacture the insole, which is the primary focus. This work aims to evaluate established CAD techniques for designing and fabricating insoles utilizing different manufacturing processes. The evaluation is based on a prior analysis of the possibilities for functionalizing insole materials and structures. In this study, multiple software tools are utilized for designing custom insoles, considering pressure points and a three-dimensional (3D) foot scan of an individual. The research highlights how the implementation of software enables a significant level of customization by integrating pressure mapping data into the insole design process. A novel CAD approach for designing an orthotic insole has been provided in this work. Soft poly-lactic acid (PLA) is used to fabricate an insole using FDM technology. The gyroid and solid samples were evaluated following ASTM standards. When compared to the solid construction, the gyroid structure has a high specific energy absorption capability, which is used to create the orthotic insole. The results of the experiment suggest that the selection of the structure for customized insole design is significantly affected by the infill density parameter.

PLA-based nature-inspired architecture for bone scaffolds: A finite element analysis

The implantation of bio-degradable scaffolds is considered as a promising approach to address the repair of bone defects. This article aims to develop a computational approach to study the mechanical behaviour, fluid dynamic, and degradation impact on polylactic acid scaffolds with nature-inspired design structures. Scaffold design is considered to be one of the main factors for the regulation of mechanical characteristics and fluid flow dynamics. In this article, five scaffolds with different nature-inspired architectures have been designed within a specific porosity range. Based on finite element analysis, their mechanical behaviour and computational fluid dynamic study are performed to evaluate the respective properties of different scaffolds. In addition, diffusion-governed degradation analysis of the scaffolds has been performed to compute the total time required for the scaffold to degrade within a given environment. Based on the mechanical behaviour, the Spider-web architecture scaffold was found to have the least deformation, and also the lowest value of equivalent stress and strain. The Nautilus Shell architecture scaffold had the highest value of equivalent stress and strain. The permeability of all the scaffolds was found to meet the requirement of the cancellous bone. All computational fluid dynamics (CFD) results of wall shear stress are in line with the requirement for cell differentiation. It was observed that the Spider-web architecture scaffold had undergone the slowest degradation, and the Giant Water Lily architecture scaffold experienced the fastest degradation.