Isabel Cristina Gouveia

Bacterial cellulose (BC) is a versatile biopolymer prized for its remarkable water absorption, nanoscale fiber architecture, mechanical robustness, and biocompatibility, making it suitable for diverse applications. Despite its potential, the high cost of conventional fermentation media limits BC’s scalability and wider commercial use. This study investigates an economical solution by utilizing fractions from fruit processing wastewater, refined through sequential membrane fractionation, as a supplement to commercial HS medium for BC production. BC films were thoroughly characterized using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and assessments of mechanical properties and water holding capacity (WHC). FTIR confirmed the BC structure, while TEM validated its nanofibrillar 3D network. XRD analysis revealed a slight increasing trend in crystallinity with the addition of wastewater fractions, and DSC revealed a slight increase in thermal stability for F#6. Adding these fractions notably improved the BC films’ tensile strength, Young’s modulus, and WHC. Overall, the results underscore that fruit processing wastewater fractions can serve as a cost-efficient, eco-friendly alternative to traditional fermentation media. This approach supports circular economy principles by lowering reliance on intensive wastewater treatments, promoting waste valorization, and advancing sustainable production methods for high-value biopolymers.

Bacterial cellulose (BC) is a versatile biopolymer prized for its remarkable water absorption, nanoscale fiber architecture, mechanical robustness, and biocompatibility, making it suitable for diverse applications. Despite its potential, the high cost of conventional fermentation media limits BC’s scalability and wider commercial use. This study investigates an economical solution by utilizing fractions from fruit processing wastewater, refined through sequential membrane fractionation, as a supplement to commercial HS medium for BC production. BC films were thoroughly characterized using Fourier transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and assessments of mechanical properties and water holding capacity (WHC). FTIR confirmed the BC structure, while SEM and TEM validated its nanofibrillar 3D network. XRD showed increased crystallinity with the wastewater fractions, and DSC revealed a slight increase in thermal stability for F#6. Adding these fractions notably improved the BC films' tensile strength, Young's modulus, and WHC. Overall, the results underscore that fruit processing wastewater fractions can serve as a cost-efficient, eco-friendly alternative to traditional fermentation media. This approach supports circular economy principles by lowering reliance on intensive wastewater treatments, promoting waste valorization, and advancing sustainable production methods for high-value biopolymers.

Exopolysaccharides (EPSs) are a diverse class of biopolymers synthesized by microorganisms under environmental stress conditions, such as pH, temperature, light intensity, and salinity. They offer biodegradable and environmentally friendly alternatives to synthetic polymers. Their structural versatility and functional properties make them unique in various industries, including food, pharmaceuticals, biomedicine, cosmetics, textiles, petroleum, and environmental remediation. In this way, among the well-known EPSs, homopolysaccharides like dextran, bacterial cellulose, curdlan, and levan, as well as heteropolysaccharides like xanthan gum, alginate, gellan, and kefiran, have found widespread applications in numerous fields. However, recent attention has focused on the potential role of extremophile bacteria in producing EPSs with novel and unusual protective and biological features under extreme conditions. Therefore, this review provides an overview of the functional properties and applications of the commonly employed EPSs. It emphasizes their importance in various industries and scientific endeavors while highlighting the raised interest in exploring EPSs with novel compositions, structures, and properties, including underexplored protective functionalities. Nevertheless, despite the potential benefits of EPSs, challenges persist. Hence, this review discusses these challenges, explores opportunities, and outlines future directions, focusing on their impact on developing innovative, sustainable, and functional materials.

In response to escalating concerns about environmental pollution from conventional plastic packaging, there is a growing interest in ecological and sustainable materials for food packaging. Consequently, biopolymer-based electrospun materials, particularly polysaccharides such as chitosan (CH), starch, and cellulose, have emerged as promising alternatives to synthetic ones due to their remarkable barrier properties and mechanical strength. Moreover, following the trend of employing polysaccharides as ecological and sustainable solutions for packaging materials, natural colorants have also been recognized as safer alternatives to synthetic dyes, addressing concerns about potential adverse effects on human health and the environment. These natural colorants add color to food packaging and enhance food freshness, possibly extending shelf life and promoting consumers' perception of food quality and safety. Therefore, this review summarizes recent advancements in fabricating and characterizing electrospun materials based on polysaccharides and natural colorants for sustainable food packaging. It explores various electrospinning techniques and highlights the incorporation of natural colorants, including bacterial pigments, for active and intelligent packaging applications. Moreover, it emphasizes the increasing role of the biobased industry in developing sustainable packaging materials with bioactive coloration. Lastly, the review addresses challenges, opportunities, and future research directions. Graphical Abstract

The escalating incidence of Candida spp. infections among individuals with compromised immune systems is attributed to various factors, including broad-spectrum antibiotic usage, common health issues, and inadequate undergarments, requiring novel preventive measures. While the pathogenic mechanisms of Candida spp. infections remain incompletely understood, their virulence attributes and opportunistic nature challenge host defenses. In response, this research study introduces an innovative nanobiotechnological approach employing L-cysteine to develop nontoxic anti- Candida spp. textile materials. Cotton, an ideal material for women’s underwear, was functionalized with L-cysteine through an exhaustion procedure following activation with 2,2,6,6-tetramethylpiperidinyl-1-oxy free radical. The results demonstrated increased energy dispersive X-ray peaks corresponding to sulfur atoms in the functionalized cotton fabric, confirming that L-cysteine remained attached to the cotton surface even after washing cycles. Moreover, the cotton containing L-cysteine displayed morphology and mechanical properties similar to the nonfunctionalized cotton, indicating that the incorporation of L-cysteine did not impact the cotton properties. In addition, cotton functionalized with L-cysteine exhibited a significant reduction in yeast growth – 87.04 ± 1.90% for Candida albicans and 65.28 ± 3.03% for Candida parapsilosis – highlighting its potential as a class I medical device, particularly for preventing candidiasis in women’s medical underwear.

Electrospinning, a remarkable and versatile technique has been related to medical textiles, aiming to produce nanomaterials for drug delivery and tissue regeneration applications. Furthermore, electrospun nanofibrous materials with unique properties as favorable pore size distribution, porosity, surface area, and wettability, along with effective mechanical properties, are the frontrunner solutions. Also, the features of the nanofibrous structures can be designed and optimized by controlling electrospinning parameters related to the solution properties, the setup parameters, and the environmental conditions to design nanofibrous textile materials for the desired applications. Further, to accomplish the required functionality of the drug-delivery systems, a rather broad range of drugs have been loaded into the nanofibers using different electrospinning techniques, namely the blending, side-by-side, coaxial, tri-axial, emulsion, and multi-needle electrospinning, in order to accomplish specific drug-release profiles of the designed nanofibrous textiles. Thus, this chapter describes the different electrospinning techniques that have been utilized in the production of the textile nanofibrous materials as the application of these materials in bone, nerve, periodontal, and vascular regeneration, as well as in wound dressings, personal-protective-equipment (PPE), and cancer treatment, providing an overview of the recent studies and highlighting the current challenges and future perspectives for their medical applications.

Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have been widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and it results in an attractive source of biopolymers for the development of low-cost materials as an alternative to the raw materials and conventional petroleum-based plastics. In addition, deep eutectic solvents (DESs), a new type of truly green solvents, have been shown to remove gums, lignin, and other non-cellulosic components from hemp fibers. Reusing these components dissolved into the DESs to fabricate new materials directly by electrospinning is a very attractive but still unexplored endeavor. Thus, this innovative research to venture new upcycling pathways is focused on the fabrication of composite nanofibers by electrospinning of a gel-based blend of Poly(vinyl alcohol) (PVA) and hemp agro-waste (HW) dissolved into choline chloride (ChCl):Glycerol (1:2) and ChCl:Urea (1:2) DES mixtures. The results obtained revealed that the produced nanofibers displayed uniform appearance with diameters ranging from 257.7 ± 65.6 nm to 380.8 ± 134.0 nm. In addition, the mechanical properties of the electrospun composite nanofibers produced from the gel-based blends of HW dissolved in DESs and PVA (HW-DESs_PVA) were found to be superior, resulting in an enhanced tensile strength and Young’s modulus. Furthermore, the incorporation of HW into the nanofibers was able to provide bioactive antioxidant and antibacterial properties. Overall, this study demonstrated a promising, more sustainable, and eco-friendly way to produce electrospun composite nanofibers using HW in a circular economy perspective.

Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have revealed to be widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and results in an attractive source of biopolymers for the development of low-cost materials in alternative to the raw materials and conventional petroleum-based plastics. In addition, deep eutectic solvents (DESs), a new type of truly green solvents, have been tested to remove gums, lignin, and other non-cellulosic components from hemp fibers. Reusing these components dissolved into the DESs to fabricate new materials directly by electrospinning is a very attractive but still unexplored endeavor. Thus, this innovative research to venture new upcycling pathways is focused on the fabrication of composite nanofibers by electrospinning of a gel-based blend of Poly(vinyl alcohol) (PVA) and hemp agro-waste (HW) dissolved into choline chloride (ChCl) : Glycerol (1:2) and ChCl : Urea (1:2) DES mixtures. The results obtained revealed that the produced nanofibers displayed uniform appearance with diameters ranging from 257.72 ± 65.63 nm to 380.78 ± 133.98 nm. In addition, the mechanical properties of the electro-spun composite nanofibers produced from the gel-based blends of HW dissolved in DESs and PVA (HW-DESs_PVA) were found to be superior, resulting in an enhanced tensile strength and Young’s modulus. Furthermore, the incorporation of HW into the nanofibers was able to provide bioactive antioxidant and antibacterial properties. Overall, this study demonstrated a promising, more sustainable, and eco-friendly way to produce electrospun composite nanofibers using HW in a circular economy perspective.