Development and characterization of hybrid corn starch-microalgae films: Effect of ultrasound pre-treatment on structural, barrier and mechanical performance

Effect of ultrasound/CaCl2 co-treatment on the microstructure, gelatinization, and film-forming properties of high amylose corn starch

The effect of ultrasound/CaCl2 co-treatment on aggregation structure, thermal stability, rheological, and film properties of high amylose corn starch (HACS) was investigated. The scanning electron microscopy (SEM) images revealed the number of starch fragments and malformed starch granules increased after co-treatment. The differential scanning calorimetry (DSC) results showed the co-treated HACS got a lower gelatinization temperature (92.65 ± 0.495 °C) and enthalpy values (ΔH, 4.14 ± 0.192 J/g). The optical microscope images indicated that lesser Maltase crosses were observed in co-treated HACS. The results of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) indicated ultrasound influenced the compactness of amorphous zone and CaCl2 damaged the crystalline region of HACS granules. Additionally, the rheology properties of HACS dispersion demonstrated the apparent viscosity of co-treated dispersion increased as the ultrasound time prolonged. The mechanical strength and structural compactness of HACS films were improved after ultrasound treatment. The mechanism of ultrasound/CaCl2 co-treatment improved the gelatinization and film-forming ability of HACS was that (i) ultrasound wave loosened the HACS granules shell, promoted the treatment of CaCl2 on HACS granules, and (ii) ultrasound wave improved the uniform distribution of HACS dispersion, increased the interaction between CaCl2 and starch chains during the process of film-forming.

The effect of agar from the seaweed Gracilaria fisheri on properties of biodegradable starch foam

This work focuses on the potential of agar from the seaweed Gracilaria fisheri to modify the properties of starch foam. The effects of different ratios of glycerol and agar on the properties of starch foams were investigated. All formulations used in this study produced easy-to-handle, smooth, single-use foam trays with no visible cracks. The addition of agar slightly affected the off-white color of the foam but red and yellow color values significantly decreased with increments of agar content. As the agar content was increased, the foam became less dense. A foam produced at a glycerol:agar ratio of 3:7 exhibited the highest values of flexural stress at maximum load (3.23 MPa), modulus (194.46 MPa) and hardness (97.50), and the highest temperature at maximum weight loss (Tmax) (337 °C). Therefore, starch foam modified with agar from Gracilaria fisheri showed suitable physical, mechanical and thermal properties for food packaging, and could possibly be used in the place of expanded polystyrene (EPS) foam.

Green Synthesis of Bioplastics from Microalgae: A State-of-the-Art Review

The synthesis of conventional plastics has increased tremendously in the last decades due to rapid industrialization, population growth, and advancement in the use of modern technologies. However, overuse of these fossil fuel-based plastics has resulted in serious environmental and health hazards by causing pollution, global warming, etc. Therefore, the use of microalgae as a feedstock is a promising, green, and sustainable approach for the production of biobased plastics. Various biopolymers, such as polyhydroxybutyrate, polyurethane, polylactic acid, cellulose-based polymers, starch-based polymers, and protein-based polymers, can be produced from different strains of microalgae under varying culture conditions. Different techniques, including genetic engineering, metabolic engineering, the use of photobioreactors, response surface methodology, and artificial intelligence, are used to alter and improve microalgae stocks for the commercial synthesis of bioplastics at lower costs. In comparison to conventional plastics, these biobased plastics are biodegradable, biocompatible, recyclable, non-toxic, eco-friendly, and sustainable, with robust mechanical and thermoplastic properties. In addition, the bioplastics are suitable for a plethora of applications in the agriculture, construction, healthcare, electrical and electronics, and packaging industries. Thus, this review focuses on techniques for the production of biopolymers and bioplastics from microalgae. In addition, it discusses innovative and efficient strategies for large-scale bioplastic production while also providing insights into the life cycle assessment, end-of-life, and applications of bioplastics. Furthermore, some challenges affecting industrial scale bioplastics production and recommendations for future research are provided.

Feasibility of bioplastic production using micro- and macroalgae- A review

Plastic disposal and their degraded products in the environment are global concern due to its adverse effects and persistence in nature. To overcome plastic pollution and its impacts on environment, a sustainable bioplastic production using renewable feedstock's, such as algae, are envisioned. In this review, the production of polymer precursors such as polylactic acid, polyhydroxybutyrates, polyhydroxyalkanoates, agar, carrageenan and alginate from microalgae and macroalgae through direct conversion and fermentation routes are summarized and discussed. The direct conversion of algal biopolymers without any bioprocess (whole algal biomass used emphasizing zero waste discharge concept) favours economic feasibility. Whereas indirect method uses conversion of algal polymers to monomers after pretreatment followed by bioplastic precursor production by fermentation are emphasized. This review paper also outlines the current state of technological developments in the field of algae-based bioplastic, both in industry and in research, and highlights the creation of novel solutions for green bioplastic production employing algal polymers. Finally, the cost economics of the bioplastic production using algal biopolymers are clearly mentioned with future directions of next level bioplastic production. In this review study, the cost estimation was given at laboratory level bioplastic production using casting methods. Further development of bioplastics at pilot scale level may give clear economic feasibility of production at industry. Here, in this review, we emphasized the overview of algal biopolymers for different bioplastic product development and its economic value and also current industries involved in bioplastic production.

Potential of Coccolithophore Microalgae as Fillers in Starch-Based Films for Active and Sustainable Food Packaging

Coccolithophore microalgae, such as Emiliania huxleyi (EHUX) and Chrysotila pseudoroscoffensis (CP), are composed of calcium carbonate (CaCO₃) and contain bioactive compounds that can be explored to produce sustainable food packaging. In this study, for the first time, these microalgae were incorporated as fillers in starch-based films, envisioning the development of biodegradable and bioactive materials for food packaging applications. The films were obtained by solvent casting using different proportions of the filler (2.5, 5, 10, and 20%, w/w). For comparison, commercial CaCO₃, used as filler in the plastic industry, was also tested. The incorporation of CaCO₃ and microalgae (EHUX or CP) made the films significantly less rigid, decreasing Young's modulus up to 4.7-fold. Moreover, the incorporation of microalgae hydrophobic compounds as lipids turned the surface hydrophobic (water contact angles > 90°). Contrary to what was observed with commercial CaCO₃, the films prepared with microalgae exhibited antioxidant activity, increasing from 0.9% (control) up to 60.4% (EHUX 20%) of ABTS radical inhibition. Overall, the introduction of microalgae biomass improved hydrophobicity and antioxidant capacity of starch-based films. These findings should be considered for further research using coccolithophores to produce active and sustainable food packaging material.

Revalorization of Microalgae Biomass for Synergistic Interaction and Sustainable Applications: Bioplastic Generation

Microalgae and cyanobacteria are photosynthetic microorganisms’ sources of renewable biomass that can be used for bioplastic production. These microorganisms have high growth rates, and contrary to other feedstocks, such as land crops, they do not require arable land. In addition, they can be used as feedstock for bioplastic production while not competing with food sources (e.g., corn, wheat, and soy protein). In this study, we review the macromolecules from microalgae and cyanobacteria that can serve for the production of bioplastics, including starch and glycogen, polyhydroxyalkanoates (PHAs), cellulose, polylactic acid (PLA), and triacylglycerols (TAGs). In addition, we focus on the cultivation of microalgae and cyanobacteria for wastewater treatment. This approach would allow reducing nutrient supply for biomass production while treating wastewater. Thus, the combination of wastewater treatment and the production of biomass that can serve as feedstock for bioplastic production is discussed. The comprehensive information provided in this communication would expand the scope of interdisciplinary and translational research.

Ultrasonication effects on physicochemical properties of biopolymer-based films: A comprehensive review

Biopolymeric films manufactured from materials such as starch, cellulose, protein, chitosan, gelatin, and polyvinyl alcohol are widely applied due to their complete biodegradability. While biopolymer-based films exhibit good gas barriers and optical properties when used in packaging, poor moisture resistance and mechanical properties limit their further application. Ultrasonication is a promising, effective technology for resolving these shortcomings, with its high efficiency, environmentally friendly nature, and safety. This review briefly introduces basic ultrasonication principles and their main effects on mechanical properties, transparency, color, microstructure, water vapor permeability, and oxygen resistance. We also describe the thermal performance of biopolymeric films. While ultrasonication has many positive effects on the physicochemical properties of biopolymeric films, many factors influence their behavior during film preparation, including power density, amplitude, treatment time, frequency, and the inherent properties of the source materials. This review focuses on biopolymers as film-forming materials and comprehensively discusses the promotional effects of ultrasonication on their physicochemical properties.

Use of ultrasound for aiding lipid extraction and biodiesel production of microalgae harvested by chitosan

In this work, chitosan, a biodegradable flocculant, was investigated to determine its utility in flocculating microalgae, its effect on cell integrity, and its impact on lipid extraction and the conversion to fatty acid methyl ester (FAME). Results showed that chitosan adequately performed flocculation on Chlorella vulgaris microalgae and achieved a high harvesting efficiency of 96.35 ± 1.96% when implemented under the following conditions: chitosan dose = 120 mg/L^-1, pH = 5, mixing speed = 150 rpm for 20 min, followed by 10 min of settling time. Moreover, scanning electron microscope (SEM) combined with transmission electron microscope (TEM) demonstrated that chitosan protected the cells' structure from morphological damage. Finally, the highest lipid extraction yield and biodiesel production was obtained from the chitosan-harvested biomass when the microalgae were pretreated with ultrasound.

Ordered long polyvinyl alcohol fiber-reinforced thermoplastic starch composite having comparable mechanical properties with polyethylene and polypropylene

A novel strategy is proposed to fabricate ordered long polyvinyl alcohol fiber (PVAF)-reinforced thermoplastic starch (TPS) composites with significantly improved mechanical properties. The PVAFs were uniformly fixed on two rods first; then sandwich-like TPS/fibers/TPS composite films were prepared by hot pressing, and PVAFs (0-4.08 wt%) with the same orientation were added to the composite films. The tensile test demonstrated that the tensile strength of the PVAF/TPS composite film improved from 2.13 MPa for TPS to 20.98 MPa with 4.08 wt% PVAFs, which is higher than the tensile strength of polyethylene (PE) (11.88 MPa) and polypropylene (PP) (19.29 MPa) and ten times higher than that of TPS. The sandwich-like cross-section of the composite film was observed by scanning electron microscopy to prove the better compatibility between PVAF and TPS. The nanoindentation test revealed that the addition of fibers improved the elastic modulus and hardness of the surface of the material. The strengthening mechanism for different PVAF contents was simulated by finite element analysis and attributed to the reduced maximum von Mises stress at the interface between the fiber and the TPS matrix, avoiding the stress concentration and corresponding fracture. This study provides a new way to prepare degradable composite films with suitable mechanical properties to replace PE or PP.

A Comprehensive Review on Corn Starch-Based Nanomaterials: Properties, Simulations, and Applications

Corn (Zea mays L.) is one of the major food crops, and it is considered to be a very distinctive plant, since it is able to produce a large amount of the natural polymer of starch through its capacity to utilize large amounts of sunlight. Corn starch is used in a wide range of products and applications. In recent years, the use of nanotechnology for applications in the food industry has become more apparent; it has been used for protecting against biological and chemical deterioration, increasing bioavailability, and enhancing physical properties, among other functions. However, the high cost of nanotechnology can make it difficult for its application on a commercial scale. As a biodegradable natural polymer, corn starch is a great alternative for the production of nanomaterials. Therefore, the search for alternative materials to be used in nanotechnology has been studied. This review has discussed in detail the properties, simulations, and wide range of applications of corn starch-based nanomaterials.

Effect of the application of an edible film with turmeric (Curcuma longa L.) on the oxidative stability of meat

The aim of this study was to develop an edible alginate-based film produced with turmeric (EFT), as an active compound, and evaluate its antioxidant capacity for application in fresh pork loin, beef loin, and chicken breast. The EFT was characterized by barrier parameters, color, and mechanical, structural, and antioxidant properties. Meat samples with and without EFT were stored at 4°C and analyzed at 2-day intervals. The meat samples with EFT showed significant differences (p < .05) in color (CIE L*a*b*) and exhibited lower TBARS values compared with those without EFT. The addition of turmeric in the film, besides affecting its physicochemical and structural properties, contributed an important antioxidant effect for the meat.

A sustainable solution to plastics pollution: An eco-friendly bioplastic film production from high-salt contained Spirulina sp. residues

Plastic products have become a major contaminant in environmental ecology due to their recalcitrant biodegradation, poor management and risky disposal. Therefore, much research attention has been paid to developing the biodegradable bio-based plastics. However, many of the substitute bioplastics derived from agricultural materials may present a potential threat to food security and eco-systems. Herein, we propose a sustainable, eco-friendly and simple procedure to convert the hazardous high-salt contained microalgal residues into bioplastic film. With 35 % poly (vinyl alcohol) (PVA) assistance, the composite bioplastic films achieved 22 MPa tensile strength under alkali condition and 77 % elongation at break under acidic condition. The average maximum contact angle of 94.4° confirmed a desirable water resistance potential. The synthesis mechanism demonstrated that the inorganic salts existed in microalgal residues could act as the filler in shape of sheets under alkali condition or as the cross linker under acidic condition, significantly enhancing the practical feasibility. This work demonstrates a promising biodegradable bioplastics formed from sustainable eco-friendly waste reutilization process, providing a new insight for fundamentally reducing the plastics pollution.

Progress and perspective on algal plastics - A critical review

There is a growing interest in developing bio-based biodegradable plastics to reduce the dependence on depleting fossil fuels and provide a sustainable alternative. Bio-based plastics can usually be produced from lipids, proteins or carbohydrates, which are major components of microalgae. Despite its potential for algal plastics, little information is available on strain selection, culture optimization and bioplastics fabrication mechanism. In this review, we summarized the recent developments in understanding the utilization of seaweed polysaccharides, such as alginate and carrageenan for bio-based plastics. In addition, a conceptual biorefinery framework for algal plastics through promising components (e.g., lipids, carbohydrates and proteins) from microalgae is comprehensively presented. Moreover, the reasons for variations in bioplastics performance and underlying mechanism of various algal biocomposites have been critically discussed. We believe this review can provide valuable information to accelerate the development of innovative green technologies for improving the commercial viability of algal plastics.