Search

Innovative approaches for recycling and upcycling of textile waste are required to sustainably treat the tremendous, discarded amounts. Due to their high specificity and mild reaction conditions, enzymes offer an environmentally friendly alternative for separation of blended materials. Glucose was recovered from cellulose (viscose) and polyamide blends and utilized as carbon source for biosynthesis of two biodegradable polymers. Polyhydroxybutyrate (PHB) was produced by Cupriavidus necator reaching an intracellular accumulation of 60 % (w/w) and 5.2 g/L of PHB from 20 g/L of glucose-rich hydrolysate. Bacterial cellulose (BC) was produced by Komagataeibacter sucrofermentans exhibiting equal properties to BC produced in standard media as confirmed by FTIR spectroscopy, SEM, and XRD. The recovered polyamide fibers were thermo-mechanically reprocessed and characterized by tensile testing showing comparable properties to virgin material. Thus, a combined bioconversion and mechanical reprocessing approach for textile waste is demonstrated allowing for recycling and valorization of each fraction of blended materials.

Annually, about 760 million tons of rice are produced worldwide. This results in agricultural residues such as rice straw. For 1 kg of rice grain, about 1.5 kg of rice straw is produced.Therefore, some management strategies have been studied to extract value-added compounds from this abundant residue and convert it into commodities. In this context, cellulose is one of the compounds studied that can be used for various applications, such as the development of materials and food packaging. Recently, cellulose-based aerogels have become the focus of research as a substitute for absorbent materials. However, using cellulose to absorb aqueous solutions is challenging because the material usually loses its integrity due to its hydrophilic nature. Therefore, stabilization methods should be proposed to maintain the integrity of the material under high humidity conditions to solve this problem., The aim of this work was to produce water stable cellulose-based aerogels from rice straw. Two strategies were investigated: first, TEMPO mediated oxidation followed by high pressure homogenization (HPH) and second, regeneration of cellulose by solubilization with ionic liquids.Briefly, rice straw cellulose was suspended in water by sonicating it at high intensity. Then, the suspension was oxidized and passed through HPH 2, 4 and 8 cycles at 600 bar. On the other hand, BMIM-Cl ionic liquid (IL) was used to dissolve the cellulose at 90 ºC. Then, the suspensions were poured off and freeze-dried. Both methods allowed the preparation of cellulose aerogels with improved water resistance. In addition, this work proposes a novel method to study the internal structure of the porous aerogel using confocal laser scanning microscopy (CLSM).The images acquired by CLSM showed differences in the size and distribution of microfibers in the aerogels at the different HPH cycles tested. In addition, the materials obtained by the regeneration method had different porosity/density than those produced by HPH. Therefore, HPH and regeneration by IL are valuable tools in the fabrication of materials with stable aerogel structure from rice straw. These advances mark a starting point for the development of cellulose- based aerogels without the need for compatibilization with other polymers.

Current knowledge on the properties of different types of cellulose nanofibers (CNFs) is fragmented. Properties variation is very extensive, depending on raw materials, effectiveness of the treatments to extract the cellulose fraction from the lignocellulosic biomass, pretreatments to facilitate cellulose fibrillation and final mechanical process to separate the microfibrils. Literature offers multiple parameters to characterize the CNFs prepared by different routes. However, there is a lack of an extensive guide to compare the CNFs. In this study, we perform a critical comparison of rheological, compositional, and morphological features of CNFs, produced from the most representative types of woody plants, hardwood and softwood, using different types and intensities of pretreatments, including enzymatic, chemical and mechanical ones, and varying the severity of mechanical treatment focusing on the relationship between macroscopic and microscopic parameters. This structured information will be exceedingly useful to select the most appropriate CNF for a certain application based on the most relevant parameters in each case.

Bacterial biopolymers such as bacterial cellulose (BC), alginate or polyhydroxyalkanotes (PHAs) have aroused the interest of researchers in many fields, for instance biomedicine and packaging, due to their being biodegradable, biocompatible and renewable. Their properties can easily be tuned by means of microbial biotechnology strategies combined with materials science. This provides them with highly diverse properties, conferring them non-native features. Herein we highlight the enormous structural diversity of these macromolecules, how are they produced, as well as their wide range of potential applications in our daily lives. The emergence of new technologies, such as synthetic biology, enables the creation of next-generation-advanced materials presenting smart functional properties, for example the ability to sense and respond to stimuli as well as the capacity for self-repair. All this has given rise to the recent emergence of biohybrid materials, in which a synthetic component is brought to life with living organisms. Two different subfields have recently garnered particular attention: hybrid living materials (HLMs), such as encapsulation or bioprinting, and engineered living materials (ELMs), in which the material is created bottom-up with the use of microbial biotechnology tools. Early studies showed the strong potential of alginate and PHAs as HLMs, whilst BC constituted the most currently promising material for the creation of ELMs.

Synergistic methodological strategies based on the fields of microbial biotechnology and materials science open up an enormous range of possibilities for the sustainable production of advanced materials with predictable properties. This study shows how naturally produced polyhydroxyalkanoate (PHA) particles are introduced into bacterial cellulose (BC) driven by their bacterial producers. Thanks to an extensive knowledge of the internal structure of BC, it was possible to control the colonization process, i.e. loading and localization of PHA. A subsequent acid treatment favored the PHA-BC bonding at the position reached by the bacteria. These biodegradable films showed improved mechanical and barrier properties even with respect to reference plastic films 8 times thicker, reaching a Young's modulus 4.25 times higher and an oxygen permeability 3 times lower than those of polyethylene terephthalate (PET) films. Owing to the versatility of the method, a wide variety of materials can be developed for very diverse fields of application.