Bacterial cellulose as a potential bioleather substitute for the footwear industry

Biofabrication with microbial cellulose: from bioadaptive designs to living materials

Nanocellulose is not only a renewable material but also brings functions that are opening new technological opportunities. Here we discuss a special subset of this material, in its fibrillated form, which is produced by aerobic microorganisms, namely, bacterial nanocellulose (BNC). BNC offers distinct advantages over plant-derived counterparts, including high purity and high degree of polymerization as well as crystallinity, strength, and water-holding capacity, among others. More remarkably, beyond classical fermentative protocols, it is possible to grow BNC on non-planar interfaces, opening new possibilities in the assembly of advanced bottom-up structures. In this review, we discuss the recent advances in the area of BNC-based biofabrication of three-dimensional (3D) designs by following solid- and soft-material templating. These methods are shown as suitable platforms to achieve bioadaptive constructs comprising highly interlocked biofilms that can be tailored with precise control over nanoscale morphological features. BNC-based biofabrication opens applications that are not possible by using traditional manufacturing routes, including direct ink writing of hydrogels. This review emphasizes the critical contributions of microbiology, colloid and surface science, as well as additive manufacturing in achieving bioadaptive designs from living matter. The future impact of BNC biofabrication is expected to take advantage of material and energy integration, residue utilization, circularity and social latitudes. Leveraging existing infrastructure, the scaleup of biofabrication routes will contribute to a new generation of advanced materials rooted in exciting synergies that combine biology, chemistry, engineering and material sciences.

Self-pigmenting textiles grown from cellulose-producing bacteria with engineered tyrosinase expression

Environmental concerns are driving interest in postpetroleum synthetic textiles produced from microbial and fungal sources. Bacterial cellulose (BC) is a promising sustainable leather alternative, on account of its material properties, low infrastructure needs and biodegradability. However, for alternative textiles like BC to be fully sustainable, alternative ways to dye textiles need to be developed alongside alternative production methods. To address this, we genetically engineer Komagataeibacter rhaeticus to create a bacterial strain that grows self-pigmenting BC. Melanin biosynthesis in the bacteria from recombinant tyrosinase expression achieves dark black coloration robust to material use. Melanated BC production can be scaled up for the construction of prototype fashion products, and we illustrate the potential of combining engineered self-pigmentation with tools from synthetic biology, through the optogenetic patterning of gene expression in cellulose-producing bacteria. With this study, we demonstrate that combining genetic engineering with current and future methods of textile biofabrication has the potential to create a new class of textiles.

Bacterial cellulose: Nature's greener tool for industries

Bacteria are considered mini chemical factories that help us in providing a wide range of products for various purposes. These days, bacterial cellulose (BC) is getting attention by researchers due to its quality, eco-friendly nature, and excellent physical-mechanical qualities. It is being used in the fabrication of nanocomposites. Its nanocomposites can be used in various industries, including medicine, food, leather, textiles, environment, electronics, and cosmetics. This area of research is emerging and still in its infancy stage, as new applications are still coming up. Most of the work on BC has been done during the last two decades and serious inputs are required in this direction in order to make the production process commercially viable and ultimately the application part. Biowastes, such as fruits and vegetables wastes, can be used as a cost-effective medium to minimize the cost for large-scale production of BC-based nanocomposites thus will valorize the biowaste material into a valuable product. Using biowaste as media will also aid in better waste management along with reduction in detrimental environmental effects. This review will help the readers to understand the potential applications of BC and its nanocomposites as well as their vital role in our daily lives.

Hands on Biofilm! Utilizing a public audience in a citizen science project to assess yield variability when culturing kombucha pellicle

The pellicle biofilm generated during the Kombucha tea fermentation process has, when dried, textile-like properties that may have real-life applications. However, pellicle yield can vary depending on inoculation and incubation conditions, which affects research investigations on the properties of the pellicle. To generate data on variability to help define optimum pellicle growth conditions, as part of a public engagement event about biofilm, a citizen science activity was hosted whereby visitors to a science festival were invited to select incubation conditions and inoculate different media with liquid or solid (pellicle). More than 220 samples were inoculated (in excess of 1200 visitors, mainly in family groups). The most popular incubation conditions were coconut water or tea medium, 30°C/room temperature and liquid inoculum. The most productive/reproducible in terms of yield and variability were tea medium, 30°C, and liquid inoculum, which reflect some of the conditions most used in the domestic setting for kombucha culture. The event provided both useful research data and generated public interest in a research area of which many will have been unaware. Interest in the results of the activity, available several weeks after the activity, was sustained using email contact and FlickR for the dissemination of images and data.

SCOBY Cellulose Modified with Apple Powder-Biomaterial with Functional Characteristics

The need for new non-animal and non-petroleum-based materials is strongly emphasized in the sustainable and green economy. Waste materials have proven a valuable resource in this regard. In fact, there have been quite a large number of goods obtained from wastes called "Vegan leather" that have gained the clothing market's attention in recent years. In practice, they are mostly composites of waste materials like cactus, pineapples, or, eventually, apples with polymers like polyurethane or polyvinyl chloride. The article presents the results of work aimed at obtaining a material based entirely on natural, biodegradable raw materials. Bacterial cellulose produced as a byproduct of the fermentation carried out by SCOBY was modified with glycerol and then altered by the entrapment of apple powder. The effect of introducing apple powder into the SCOBY culture media on the mechanical properties of the obtained bacterial cellulose was also evaluated The resulting material acquired new mechanical characteristics that are advantageous in terms of strength. Microscopic observation of the apple powder layer showed that the coverage was uniform. Different amounts of apple powder were used to cover the cellulose surface from 10 to 60%, and it was found that the variant with 40% of this powder was the most favorable in terms of mechanical strength. Also, the application of the created material as a card folder showed that it is durable in use and retains its functional characteristics for at least 1 month. The mechanical properties of modified bacterial cellulose were favorably affected by the entrapment of apple powder on its surface, and as a result, a novel material with functional characteristics was obtained.

Developing textile sustainability education in the curriculum: pedagogical approaches to material innovation in fashion

The textile industry needs to adopt environmentally sustainable approaches to address ecologically damaging practices. Whilst driven by initiatives such as Textiles 2030, it is current students who will carry this agenda forward. This project investigated pedagogical approaches to develop sustainable textiles for the fashion design curriculum. Pilot studies, using bacterial cellulose (BC) as a material for millinery, revealed members of the public were prepared to experiment with this novel material, and BC was compatible with traditional hat-making techniques. A further study challenged secondary school students, based on an experiential learning model, to grow their own BC biofilm, exploring this as a sustainable apparel fabric. Initial attitudes of reluctance developed into acceptance once engaged in the practical activity. This study illustrates that with appropriate communication and education strategies, the principles of sustainability in fashion, and the acceptability of novel materials, can be engendered in different audiences.

Reproducibility of Bacterial Cellulose Nanofibers Over Sub-Cultured Generations for the Development of Novel Textiles

The textile industry is in crisis and under pressure to minimize the environmental impact on its practices. Bacterial cellulose (BC), a naturally occurring form of cellulose, displays properties superior to those of its cotton plant counterpart, such as enhanced purity, crystallinity, tensile strength, and water retention and is thus suitable for an array of textile applications. It is synthesized from a variety of microorganisms but is produced in most abundance by Komagataeibacter xylinus. K. xylinus is available as a type strain culture and exists in the microbial consortium commonly known as Kombucha. Whilst existing literature studies have described the effectiveness of both K. xylinus isolates and Kombucha in the production of BC, this study investigated the change in microbial communities across several generations of sub-culturing and the impact of these communities on BC yield. Using Kombucha and the single isolate strain K. xylinus as inocula in Hestrin and Schramm liquid growth media, BC pellicles were propagated. The resulting pellicles and residual liquid media were used to further inoculate fresh liquid media, and this process was repeated over three generations. For each generation, the thickness of the pellicles and their appearance under SEM were recorded. 16S rRNA sequencing was conducted on both pellicles and liquid media samples to assess changes in communities. The results indicated that the genus Komagataeibacter was the most abundant species in all samples. Cultures seeded with Kombucha yielded thicker cellulose pellicles than those seeded with K. xylinus, but all the pellicles had similar nanofibrillar structures, with a mix of liquid and pellicle inocula producing the best yield of BC after three generations of sub-culturing. Therefore, Kombucha starter cultures produce BC pellicles which are more reproducible across generations than those created from pure isolates of K. xylinus and could provide a reproducible sustainable model for generating textile materials.

Production of coffee-dyed bacterial cellulose as a bio-leather and using it as a dye adsorbent

Owing to its sustainability and environmentally friendliness, bacterial cellulose (BC) has received attention as a zero-waste textile material. Since the color of original BC was mostly yellowish white, a dyeing process is necessary to suggest BC as a textile. Thus, this study aimed to suggest a natural dyeing method using coffee to produce an eco-friendly coffee-dyed bacterial cellulose (BC-COF) bio-leather and to propose a reusing method as a dye adsorbent. To determine the dyeing and mordanting conditions with the highest color strength value, parameters such as dyeing temperature, time, mordanting methods were evaluated. Fourier-transform infrared spectroscopy and X-ray diffraction analysis confirmed that BC-COF was successfully colorized with coffee without changing its chemical and crystalline structures. In addition, field-emission scanning electron microscopy and Brunauer-Emmett-Teller surface area analysis confirmed that coffee molecules were successfully incorporated into fiber structures of BC. The effects of pH, concentration, temperature, and time on the adsorption of methylene blue dye using BC-COF bio-leather were also evaluated using ultraviolet-visible spectroscopy and zeta potential measurement. The results showed that BC-COF was found to be most effective when pH 6 of methylene blue solution with a concentration of 50 mg/L was adsorbed for 30 minutes at 25°C. Moreover, BC-COF could be reused for multiple times and had better dye adsorption rate compared to the original BC. From the results, it was confirmed that BC-COF could be employed as a dye adsorbent.

Developments in bioprocess for bacterial cellulose production

Bacterial cellulose (BC) represents a novel bio-origin nonomaterial with its unique properties having diverse applications. Increased market demand and low yield are the major reason for its higher cost. Bacteria belonging to Komagataeibacter sp are the most exploited ones for BC production. Development of a cost-effective bioprocess for higher BC production is desirable. Though static fermentation modes have been majorly employed for BC production using tray fermenters, agitated mode has also been employed successfully with air-lift fermenters as well as stirred tank reactors. Bioprocess advances in recent years has led BC production to an upper level; however, challenges of aeration requirement and labor cost towards the higher end is associated with static cultivation at large scale. We have discussed the bioprocess development for BC production in recent years along with the challenges associated and the path forward.

Bacterial Biopolymer: Its Role in Pathogenesis to Effective Biomaterials

Bacteria are considered as the major cell factories, which can effectively convert nitrogen and carbon sources to a wide variety of extracellular and intracellular biopolymers like polyamides, polysaccharides, polyphosphates, polyesters, proteinaceous compounds, and extracellular DNA. Bacterial biopolymers find applications in pathogenicity, and their diverse materialistic and chemical properties make them suitable to be used in medicinal industries. When these biopolymer compounds are obtained from pathogenic bacteria, they serve as important virulence factors, but when they are produced by non-pathogenic bacteria, they act as food components or biomaterials. There have been interdisciplinary studies going on to focus on the molecular mechanism of synthesis of bacterial biopolymers and identification of new targets for antimicrobial drugs, utilizing synthetic biology for designing and production of innovative biomaterials. This review sheds light on the mechanism of synthesis of bacterial biopolymers and its necessary modifications to be used as cell based micro-factories for the production of tailor-made biomaterials for high-end applications and their role in pathogenesis.

Cellular Agriculture: Opportunities and Challenges

Cellular agriculture is the controlled and sustainable manufacture of agricultural products with cells and tissues without plant or animal involvement. Today, microorganisms cultivated in bioreactors already produce egg and milk proteins, sweeteners, and flavors for human nutrition as well as leather and fibers for shoes, bags, and textiles. Furthermore, plant cell and tissue cultures provide ingredients that stimulate the immune system and improve skin texture, with another precommercial cellular agriculture product, in vitro meat, currently receiving a great deal of attention. All these approaches could assist traditional agriculture in continuing to provide for the dietary requirements of a growing world population while freeing up important resources such as arable land. Despite early successes, challenges remain and are discussed in this review, with a focus on production processes involving plant and animal cell and tissue cultures.

Preparation and Characterization of Nonwoven Fibrous Biocomposites for Footwear Components

Chromium-tanned leathers used in the manufacture of footwear and leather goods pose an environmental problem because they contain harmful chemicals and are very difficult to recycle. A solution to this problem can be composite materials from tree leaves, fruit residues and other fibrous agricultural products, which can replace chromium-tanned leather. The present study describes the preparation of biocomposite leather-like materials from microbial cellulose and maple leave fibers as bio-fillers. The formulation was optimized by design of experiment and the prepared biocomposites characterized by tensile test, FTIR, DMA, SEM, adhesion test, volume porosity, water absorptivity, surface wettability and shape stability. From the viewpoint of future use in the footwear industry, results obtained showed that the optimized material was considerably flexible with tensile strength of 2.13 ± 0.29 MPa, elastic modulus of 76.93 ± 1.63 MPa and porosity of 1570 ± 146 mL/min. In addition, the material depicted good shape stability and surface adhesive properties. The results indicate that a suitable treatment of biomass offers a way to prepare exploitable nonwoven fibrous composites for the footwear industry without further burdening the environment.

Towards control of cellulose biosynthesis by Komagataeibacter using systems-level and strain engineering strategies: current progress and perspectives

The strains of the Komagataeibacter genus have been shown to be the most efficient bacterial nanocellulose producers. Although exploited for many decades, the studies of these species focused mainly on the optimisation of cellulose synthesis process through modification of culturing conditions in the industrially relevant settings. Molecular physiology of Komagataeibacter was poorly understood and only a few studies explored genetic engineering as a strategy for strain improvement. Only since recently the systemic information of the Komagataeibacter species has been accumulating in the form of omics datasets representing sequenced genomes, transcriptomes, proteomes and metabolomes. Genetic analyses of the mutants generated in the untargeted strain modification studies have drawn attention to other important proteins, beyond those of the core catalytic machinery of the cellulose synthase complex. Recently, modern molecular and synthetic biology tools have been developed which showed the potential for improving targeted strain engineering. Taking the advantage of the gathered knowledge should allow for better understanding of the genotype–phenotype relationship which is necessary for robust modelling of metabolism as well as selection and testing of new molecular engineering targets. In this review, we discuss the current progress in the area of Komagataeibacter systems biology and its impact on the research aimed at scaled-up cellulose synthesis as well as BNC functionalisation.

Key points • The accumulated omics datasets advanced the systemic understanding of Komagataeibacter physiology at the molecular level. • Untargeted and targeted strain modification approaches have been applied to improve nanocellulose yield and properties. • The development of modern molecular and synthetic biology tools presents a potential for enhancing targeted strain engineering. • The accumulating omic information should improve modelling of Komagataeibacter’s metabolism as well as selection and testing of new molecular engineering targets.

Improved Hydrophobicity of a Bacterial Cellulose Surface: Click Chemistry in Action

The vast application potentials of bacterial cellulose (BC)-based materials for developing leather-like materials, wound-healing materials and electronic materials have been realized very recently. Surface functionalization of these materials can help in improvement of certain properties such as water repellency, mechanical strength, and so forth. In this paper, we reported functionalization of BC surfaces using "click" polymerization for the first time. By this methodology, dense aromatic groups have been incorporated for the improvement of hydrophobicity. For comparative studies, various fluorine-based compounds have been introduced using conventional click reactions. The surface-modified BC materials have been confirmed by various spectroscopic methods. Particularly, the chemical structures of the materials were studied by solid-state ¹³C NMR spectroscopy and attenuated total reflection-infrared spectroscopy. X-ray photoelectron spectroscopy was used to study the elemental composition of the materials. Moreover, the crystallite changes of modified BC surfaces were investigated by X-ray diffraction. Further, the changes in the morphology of the material after functionalization were evaluated by scanning electron microscopy and atomic force microscopy. Finally, water contact angle measurement revealed manyfold increase in hydrophobicity after click polymerization. A video is also provided in the Supporting Information to show the application potential of this material for developing leather-like materials.

Functionalization of Bacterial Cellulose Nonwoven by Poly(fluorophenol) to Improve Its Hydrophobicity and Durability

The present study aims to improve the hydrophobicity and durability of bacterial cellulose (BC) nonwoven by functionalization with poly(fluorophenol). To this end, laccase was first entrapped onto BC and then used to polymerize the fluorophenol {4-[4-(trifluoromethyl) phenoxy] phenol} in-situ. The polymerization of fluorophenol by laccase was confirmed through 1H NMR and MALDI-TOF analyses. The effect of poly(fluorophenol) on BC nonwoven was determined by evaluation of the surface hydrophobicity and olephobicity properties such as water contact angle (WCA), oil contact angle (OCA), surface energy and water/oil absorption time. After BC functionalization with poly(fluorophenol) (20 mM), the WCA increased from 54.5 ± 1.2° to 120 ± 1.5° while the surface energy decreased (11.58 ± 1.4 mN/m). The OCA was also increased from 46.5 ± 2.5° to 87 ± 2° along to the decrease of surface energy (8.7 ± 1.5°). X-ray photoelectron spectroscopy (XPS) analysis confirmed an increase in the fluorine content in BC from 5.27 to 17.57%. The findings confirmed the polymerization of fluorophenol by laccase and its entrapment onto a BC nanofiber structure. The durability of the functionalization with poly(fluorophenol) was confirmed by evaluating the washing fastness, tensile strength after washing and dimensional stability. The results indicate that the functionalized BC nonwoven had higher tensile strength (×10 times) and better dimensional stability (30%) than the non-functionalized BC nonwoven material.

Automotive wastes

A review of the literature from 2018 related to automotive wastes is presented. Topics include solid wastes from autobodies, batteries, tires, and vehicle electronics, in addition to sustainable building materials. Treatment and control of automotive pollution is also discussed, as well as potential toxicological and health risks. PRACTITIONER POINTS: Life cycle analyses and sustainable development automotive components were a key focus of the 2018 literature. Automobiles have been identified as point sources for air and water pollution. Research into energy consumption, emissions control, and catalytic converter behavior was conducted to mitigate the impact of automobile emissions. Potential non-point source control measures were identified. These included biological and chemical degradation of pollutants, as well as adsorption of heavy metals.

Bacterial cellulose as a potential bioleather substitute for the footwear industry

Shoe patterns and a sole made of BC, baby shoe made of BC and, on the right BC material dyed in red. (prototype made by www.patent-shoes.com).