Poly(lactic acid)/thermoplastic cassava starch blends filled with duckweed biomass

Pyrogallic acid-compatibilized polylactic acid/thermoplastic starch blend produced via one-step twin-screw extrusion

In this study, a one-step extrusion method is proposed to prepare blended polylactic acid (PLA)/thermoplastic starch (TPS) using a novel plant-derived compatibilizer, pyrogallic acid (PGA), to enhance the PLA/TPS compatibility. The effects of PGA on the mechanical behavior, fractured cross-section morphology, thermal and dynamic mechanical performance, and water resistance of PLA/TPS blends were systematically studied. Results demonstrate that the addition of PGA effectively improves the compatibility between TPS and PLA, resulting in enhanced tensile strength, crystallinity, elongation at break, thermal stability, and hydrophobicity of the blends. Specifically, incorporating 1.5 phr of PGA into the blend system yields the highest values for tensile strength (23.38 MPa) and elongation at break (16.96 %), which are 24.7 % and 233.2 %, respectively, higher than those observed for pure PLA/TPS blends. Furthermore, other properties exhibit obvious improvements upon incorporation of PGA into the blends. This approach provides a promising strategy for enhancing the performance of PLA/TPS blends and expanding their applications in food packaging, agricultural film, etc.

Recent advances in extruded polylactic acid-based composites for food packaging: A review

This review article provides a comprehensive overview of recent progress in polylactic acid (PLA) extrusion, emphasizing its applications in food packaging. PLA has witnessed a significant rise in demand, particularly within the food packaging sector. A notable increase in research publications has been observed in recent years, exploring the extrusion of PLA and PLA-based composite films. In comparison to conventional techniques such as solvent casting, extrusion offers advantages in scalability and environmental sustainability, especially for industrial-scale production. The benefits of this method include faster drying times, enhanced flexibility, consistent film thickness, and less structural defects. Extensive research has focused on the effect of various PLA blends on film properties, including flexibility, elongation, and barrier properties against water vapour and gases. Furthermore, the incorporation of compounds such as antioxidants, antimicrobials, and natural pigments has enabled the development of active and intelligent PLA-based packaging. This article summarizes the types of additives employed to enhance the physicochemical properties of extruded PLA and film performance. Additionally, this article explores the diverse applications of extruded PLA in active and intelligent packaging for various food products.

Starch-based biodegradable composites: Effects of in-situ re-extrusion on structure and performance

In this study, starch-based biodegradable composites (SDC) were prepared by extruding using thermoplastic starch (TPS, 65%wt), polylactic acid (PLA, 30%wt) and poly (butylene adipate co-terephthalate) (PBAT, 5%wt). Structure and properties of the SDC were compared by performing 1-, 2-, 3-times extrusion. The results show that in-situ re-extrusion refines the TPS in composites and reduces the size of the phase. As the number of extrusions increases, the ester bond of composites at 868 cm-1 disappears, the crystallinity increases, and the thermal stability decreases. Among the three types of composites, the mechanical properties and hydrophobic properties of the material obtained by the 2-times are the most outstanding. Compared with SDC, the elongation at break and Young's modulus of SDC-2 are significantly increased, with an increase of 8.01 % and 1.28 % in the machine direction and an increase of 11.02 % and 1.79 % in the transverse direction respectively. Additionally, water contact angle range of SDC-2 from 98.7° to 101.7°. Therefore, SDC prepared by 2-times in-situ re-extrusion has the best film properties and is an ideal packaging material. This study presents a novel method for fabricating starch-degradable composite films by in-situ re-extrusion, providing new insights into the development of starch packaging materials.

New insights into Chlorella vulgaris applications

Environmental pollution is a big challenge that has been faced by humans in contemporary life. In this context, fossil fuel, cement production, and plastic waste pose a direct threat to the environment and biodiversity. One of the prominent solutions is the use of renewable sources, and different organisms to valorize wastes into green energy and bioplastics such as polylactic acid. Chlorella vulgaris, a microalgae, is a promising candidate to resolve these issues due to its ease of cultivation, fast growth, carbon dioxide uptake, and oxygen production during its growth on wastewater along with biofuels, and other productions. Thus, in this article, we focused on the potential of Chlorella vulgaris to be used in wastewater treatment, biohydrogen, biocement, biopolymer, food additives, and preservation, biodiesel which is seen to be the most promising for industrial scale, and related biorefineries with the most recent applications with a brief review of Chlorella and polylactic acid market size to realize the technical/nontechnical reasons behind the cost and obstacles that hinder the industrial production for the mentioned applications. We believe that our findings are important for those who are interested in scientific/financial research about microalgae.

The Effect of Ultrasound on the Extraction and Functionality of Proteins from Duckweed (Lemna minor)

The inclusion of protein in the regular human diet is important for the prevention of several chronic diseases. In the search for novel alternative protein sources, plant-based proteins are widely explored from a sustainable and ecological point of view. Duckweed (Lemna minor), also known as water lentil, is an aquatic plant with potential applications for human consumption due to its protein content and carbohydrate contents. Among all the conventional and novel protein extraction methods, the utilization of ultrasound has attracted the attention of scientists because of its effects on improving protein extraction and its functionalities. In this work, a Box-Behnken experimental design was proposed to optimize the alkaline extraction of protein from duckweed. In addition, an exploration of the effects of ultrasound on the morphological, structural, and functional properties of the extracted protein was also addressed. The optimal extraction parameters were a pH of 11.5 and an ultrasound amplitude and processing time of 60% and 20 min, respectively. These process conditions doubled the protein content extracted in comparison to the value from the initial duckweed sample. Furthermore, the application of ultrasound during the extraction of protein generated changes in the FTIR spectra, color, and structure of the duckweed protein, which resulted in improvements in its solubility, emulsifying properties, and foaming capacity.

Heavy metals/-metalloids (As) phytoremediation with Landoltia punctata and Lemna sp. (duckweeds): coupling with biorefinery prospects for sustainable phytotechnologies

Heavy metals/-metalloids can result in serious human health hazards. Phytoremediation is green bioresource technology for the remediation of heavy metals and arsenic (As). However, there exists a knowledge gap and systematic information on duckweed-based metal phytoremediation in an eco-sustainable way. Therefore, the present review offers a critical discussion on the effective use of duckweeds (genera Landoltia and Lemna)-based phytoremediation to decontaminate metallic contaminants from wastewater. Phytoextraction and rhizofiltration were the major mechanism in 'duckweed bioreactors' that can be dependent on physico-chemical factors and plant-microbe interactions. The biotechnological advances such as gene manipulations can accelerate the duckweed-based phytoremediation process. High starch and protein contents of the metal-loaded duckweed biomass facilitate their use as feedstock in biorefinery. Biorefinery prospects such as bioenergy production, value-added products, and biofertilizers can augment the circular economy approach. Coupling duckweed-based phytoremediation with biorefinery can help achieve Sustainable Development Goals (SDGs) and human well-being.

Property improvement of a thermoplastic starch/poly(butylene adipate-co-terephthalate) blown film by the addition of sodium nitrite

Recently, global awareness of the adverse environmental impacts of single-use plastics has risen due to their nonbiodegradability and likelihood of ending up in the ocean. Thermoplastic starch (TPS) is an alternative material employed for manufacturing single-use products because of its high biodegradability, nontoxicity, and low cost. However, TPS is moisture sensitive and has poor mechanical properties and processability. Blending TPS with biodegradable polyesters, including poly(butylene adipate-co-terephthalate) (PBAT), can expand its practical applications. This research aims to improve the performance of TPS/PBAT blends by adding sodium nitrite, a food additive, and considering its effect on the morphological characteristics and properties of TPS/PBAT blends. TPS/PBAT/sodium nitrite (TPS/PBAT/N) blends with a TPS:PBAT weight ratio of 40:60 and sodium nitrite concentrations of 0.5, 1, 1.5, and 2 wt% were prepared by extrusion and then blown into films. The acids generated from the sodium nitrite during extrusion led to the molecular weight reduction of starch and PBAT polymers, causing the increased melt flow ability of the TPS/PBAT/N blends. The incorporation of sodium nitrite improved the blends' homogeneity and the compatibility between the TPS and PBAT phases, resulting in the increased tensile strength, extensibility, impact strength, and oxygen barrier properties of the TPS/PBAT blend film.

Preparation of flexible poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide)/talcum/thermoplastic starch ternary composites for use as heat-resistant and single-use bioplastics

Poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide) block copolymer (PLLA-PEG-PLLA) is a highly flexible bioplastic, yet its use in practical applications is limited due to its poor heat resistance and high production cost. In this study, talcum was used as a nucleating agent to improve the heat resistance, and thermoplastic starch (TPS) was used as a low-cost filler to reduce the cost of production. PLLA-PEG-PLLA/talcum/TPS and PLLA/talcum/TPS ternary composites with 4 wt% talcum and various TPS contents were prepared by melt blending before injection molding and were then evaluated. When PEG middle-blocks were present, the PLLA-PEG-PLLA-based composites showed a higher crystallinity, more flexibility, and a higher heat resistance than the PLLA-based composites. Although the addition of TPS decreased the heat resistance of all the composites, the PLLA-PEG-PLLA/talcum/TPS composites still had high Vicat softening temperatures (VST, 113-131 °C) and demonstrated a good dimensional stability to heat by maintaining their original shapes upon heat exposure. The biodegradation test in soil suggested that the synergistic effect of the PEG middle-blocks and TPS significantly increased the biodegradability of the PLLA-PEG-PLLA/talcum/TPS composites. This improved heat resistance, lower cost, and accelerated biodegradation make PLLA-PEG-PLLA/talcum/TPS composites a promising material to be used as heat-resistant and single-use bioplastic products.

Examination of the Metallothionein Gene Family in Greater Duckweed Spirodela polyrhiza

Duckweeds are aquatic plants that proliferate rapidly in a wide range of freshwaters, and they are regarded as a potential source of sustainable biomass for various applications and the cost-effective bioremediation of heavy metal pollutants. To understand the cellular and molecular basis that underlies the high metal tolerance and accumulation capacity of duckweeds, we examined the forms and transcript profiles of the metallothionein (MT) gene family in the model duckweed Spirodela polyrhiza, whose genome has been completely sequenced. Four S. polyrhiza MT-like genes were identified and annotated as SpMT2a, SpMT2b, SpMT3, and SpMT4. All except SpMT2b showed high sequence homology including the conserved cysteine residues with the previously described MTs from flowering plants. The S. polyrhiza genome appears to lack the root-specific Type 1 MT. The transcripts of SpMT2a, SpMT2b, and SpMT3 could be detected in the vegetative whole-plant tissues. The transcript abundance of SpMT2a was upregulated several-fold in response to cadmium stress, and the heterologous expression of SpMT2a conferred copper and cadmium tolerance to the metal-sensitive ∆cup1 strain of Saccharomyces cerevisiae. Based on these results, we proposed that SpMT2a may play an important role in the metal detoxification mechanism of duckweed.

Thermoplastic starch based blends as a highly renewable filament for fused deposition modeling 3D printing

3D printing technology is considered as a highly flexible method which can achieve a various customized end products. The employment of bio-based materials can significantly decrease the environmental footprint of the end 3D printing products. This study presents the preparation of thermoplastic starch (TPS)/poly(lactic acid) (PLA)/poly(butyleneadipate-co-terephthalate) (PBAT) composite that dedicated for the FDM 3D printing technology, the ratio of TPS:PLA:PBAT was fixed at 50:40:10 wt%. In addition, the chain extender ADR4468 (CE) was added to improve the brittleness of the blends to obtain better 3D printing filament. The mechanical properties of blends were improved by the addition of CE with 113 % increase in elongation at break and the 190 % raise in impact strength. Dynamic rheological analysis showed the maximum degree of complex viscosity and melt strength when the content of CE reached 1 wt%. The successful printability of TPS-based filament was demonstrated by accurate and complex printing samples. This paper provided a method to prepare highly renewable filaments for 3D printing.