Upcycling of cellulosic textile waste with bacterial cellulose via Ioncell® technology.

Currently the textile industry relies strongly on synthetic fibres and cotton, which contribute to many environmental problems. Man-made cellulosic fibres (MMCF) can offer sustainable alternatives. Herein, the development of Lyocell-type MMCF using bacterial cellulose (BC) as alternative raw material in the Ioncell® spinning process was investigated. BC, known for its high degree of polymerization (DP), crystallinity and strength was successfully dissolved in the ionic liquid (IL) 1,5-diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] to produce solutions with excellent spinnability. BC staple fibres displayed good mechanical properties and crystallinity (CI) and were spun into a yarn which was knitted into garments, demonstrating the potential of BC as suitable cellulose source for textile production. BC is also a valuable additive when recycling waste cellulose textiles (viscose fibres). The high DP and Cl of BC enhanced the spinnability in a viscose/BC blend, consequently improving the mechanical performance of the resulting fibres, as compared to neat viscose fibres.

Enhanced bacterial cellulose production in Komagataeibacter sucrofermentans: impact of different PQQ-dependent dehydrogenase knockouts and ethanol supplementation.

BACKGROUND: Bacterial cellulose (BC) is a biocompatible material with unique mechanical properties, thus holding a significant industrial potential. Despite many acetic acid bacteria (AAB) being BC overproducers, cost-effective production remains a challenge. The role of pyrroloquinoline quinone (PQQ)-dependent membrane dehydrogenases (mDH) is crucial in the metabolism of AAB since it links substrate incomplete oxidation in the periplasm to energy generation. Specifically, glucose oxidation to gluconic acid substantially lowers environmental pH and hinders BC production. Conversely, ethanol supplementation is known to enhance BC yields in Komagataeibacter spp. by promoting efficient glucose utilization. RESULTS: K. sucrofermentans ATCC 700178 was engineered, knocking out the four PQQ-mDHs, to assess their impact on BC production. The strain KS003, lacking PQQ-dependent glucose dehydrogenase (PQQ-GDH), did not produce gluconic acid and exhibited a 5.77-fold increase in BC production with glucose as the sole carbon source, and a 2.26-fold increase under optimal ethanol supplementation conditions. In contrast, the strain KS004, deficient in the PQQ-dependent alcohol dehydrogenase (PQQ-ADH), showed no significant change in BC yield in the single carbon source experiment but showed a restrained benefit from ethanol supplementation. CONCLUSIONS: The results underscore the critical influence of PQQ-GDH and PQQ-ADH and clarify the effect of ethanol supplementation on BC production in K. sucrofermentans ATCC 700178. This study provides a foundation for further metabolic pathway optimization, emphasizing the importance of diauxic ethanol metabolism for high BC production.

Regenerated bacterial cellulose fibres.

The global shortage of cotton for textile production, forces the exploitation of forests´ lignocellulosic biomass to produce man-made cellulosic fibres (MMCF). This has a considerable environmental impact, pressing the textile industry to search for new sustainable materials and to the development of sustainable recycling processes. Bacterial cellulose (BC), an exopolysaccharide produced by fermentation, could represent such an alternative. In particular, we tested the possibility of improving the mechanical properties of cellulose filaments with a low degree of polymerization (DP) by combining them with high DP from BC, so far exploited to little extent in the textile field. In this work, BC with different degrees of polymerization (DPcuaxam) (BCneat: 927; BCdep:634 and BCblend: 814) were dissolved in N-methylmorpholine-N-oxide (NMMO) and their spinnability was studied. The rheological behaviour of the dopes was assessed and all were found to be spinnable, at suitable concentrations (BCneat:9.0 %; BCdep:12.2 %; BCblend:10.5 %). A continuous spinning was obtained and the resulting filaments offered similar mechanical performance to those of Lyocell. Further, the blending of BC pulps with different DPs (BCblend, obtained by combining BCneat and BCdep) allowed the production of fibres with higher stiffness (breaking tenacity 56.4 CN.tex-1) and lower elongation (8.29 %), as compared to samples with more homogeneous size distribution (neat BC and depolymerized BC).

Impact of bacterial cellulose on the physical properties and printing quality of fine papers.

Bacterial nanocellulose (BNC), due to its inherent nanometric scale and strength properties, can be considered as a good candidate to be used in papermaking. This work explored the possibility of using it in the production of fine paper as a wet-end component and for the paper coating. Filler-containing handsheet production was performed with and without the presence of common additives typically used in the furnish of office papers. It was found that, under optimized conditions, BNC mechanically treated by high-pressure homogenization could improve all the evaluated paper properties (mechanical, optical and structural) without impairing the filler retention. However, paper strength was improved only to a small extent (increase in the tensile index of 8 % for a filler content of ca. 27.5 %). On the other hand, when used at the paper surface, remarkable improvements in the gamut area of >25 % in comparison to the base paper and of >40 % in comparison to starch-only coated papers were achieved for a formulation having 50 % BNC and 50 % of carboxymethylcellulose. Overall, the present results highlight the possibility of using BNC as a paper component, particularly when applied at the paper substrate as a coating agent aiming at improving printing quality.

Análise da situação de saúde dos idosos usuários de uma política municipal de atividades físicas / Analysis of health status of older adults users of a municipal physical activity program / Análisis de la situación de salud de los adultos ancianos de una política municipal de actividad física

Introdução: Políticas públicas intersetoriais em saúde são intervenções populacionais (e de cunho ecológico) muito utilizadas para a redução da carga global de doença e otimização de recursos tanto financeiros quanto humanos. Objetivo: O objetivo deste estudo foi analisar a situação de saúde de usuários idosos de uma política municipal de atividades físicas. Métodos: Trata-se de um estudo transversal com amostragem baseada em centros comunitários (N dispositivos comunitários=11), que disponibilizam práticas de movimentos corporais e outros, subsidiados pela Secretaria Municipal de Desenvolvimento Social e Esporte (SMDSE), Prefeitura Municipal de Porto Alegre (RS). A amostragem de usuários foi ponderada para o total de usuários atendidos por centro, adotando seleção aleatória simples. A coleta de dados ocorreu entre abril de 2018 e fevereiro de 2019, em que a equipe de coleta se deslocou ao território adscrito dos usuários para a condução de inquérito de saúde autoaplicado e a avaliação funcional; de forma contrária, os usuários compareceram a um centro de coleta para a série laboratorial (sem jejum). Resultados: Foram incluídos e analisados 351 usuários (média±desvio padrão, 70±6 anos). Para fatores de risco cardiovasculares, a prevalência de hipercolesterolemia foi de 54,2% e de 49,3% para hipertensão arterial sistêmica ­ as mais elevadas. O transtorno de sono foi prevalente em 55,3% da amostra. Entre as doenças autorrelatadas, os participantes listaram as cardiovasculares (14,3%), câncer prévio (14,6%), diabetes (13,2%), artrite reumatoide/ reumatismo (29,6%) e depressão (sem discriminador de depressão maior/ menor) (18,6%). A capacidade funcional, estimada pelo teste de caminhada em 6 minutos e a força de preensão manual, preditores de mortalidade cardiovascular e agravos, tiveram valores médios encontrados de 498,05±78,96 m e 27,08±8,14 kg, respectivamente. Conclusão: Os achados do presente estudo permitem contrastar prevalências estimadas em idosos participantes de um programa público de atividades físicas com outras estimativas em grupos de comparação, possibilitando a análise de situação de saúde com base em diferentes comportamentos e fatores de risco. Por fim, o trabalho viabilizou a monitorização de intervenções públicas para idosos em nível comunitário, sendo um ponto de base para acompanhamento futuro.

Introduction: Intersectoral public policies on health are population (and ecological) interventions widely used to reduce the global burden of disease and optimize both financial and human resources. Objective: The objective of this study was to analyze the health status of older adults users of a municipal policy on physical activities. Methods: This is a cross-sectional study with a sample based on community centers (N community centers=11), which provide body movement practices and others, funded by the Municipal Department of Social Development and Sports (SMDSE), City Hall of Porto Alegre (state of Rio Grande do Sul ­ RS, Brazil). The users' sample was weighted by the number of users of each center, by simple random sampling. Data collection took place between April 2018 and February 2019, in which the collection team went to the users' assigned territory to conduct a self-administered health survey and functional assessment; conversely, the users attended a collection center for laboratory tests (without fasting). Results: A total of 351 users (mean±SD, 70±6 years old) were included. For cardiovascular risk factors, the prevalence of hypercholesterolemia was 54.2% and 49.3% for systemic arterial hypertension ­ the highest levels. Sleep disorder was prevalent in 55.3% of the sample. Among the self-reported diseases, participants listed cardiovascular (14.3%), previous cancer (14.6%), diabetes (13.2%), rheumatoid arthritis/rheumatism (29.6%), and depression (without major/minor depression discrimination) (18.6%). Functional capacity, estimated by the six-minute walk test, and handgrip strength, predictors of cardiovascular mortality and injuries, had mean values of 498.05±78.96 m and 27.08±8.14 kg, respectively. Conclusions: The findings of this study allow contrasting prevalence rates estimated in older adults participants of a public physical activity program with other estimates in comparison groups, enabling the analysis of health status based on different behaviors and risk factors. All in all, our study enabled to monitor public interventions for older adults at the community level, serving as a baseline for future monitoring.

Introducción: Las políticas de salud pública intersectoriales tienen el potencial de destacar la reducción de la carga global de enfermedad y la optimización de los recursos financieros y humanos. Objetivo: El objetivo de este estudio fue analizar la situación de salud de los usuarios, ancianos, de una política municipal de actividades físicas. Métodos: Se trata de un estudio transversal con muestreo a partir de centros comunitarios (N dispositivos comunitarios=11), que brindan prácticas de movimiento corporal y otras, subsidiadas por la Secretaria Municipal de Desenvolvimento Social e Esporte (SMDSE), Prefeitura Municipal de Porto Alegre (RS). El muestreo de usuarios fue ponderado por el total de usuarios atendidos por centro, adoptando selección aleatoria simple. La recolección de datos ocurrió entre abril/2018 y febrero/2019, cuando el equipo de recolección viajó al territorio asignado de los usuarios para realizar una encuesta de salud auto aplicada y evaluación funcional; por el contrario, los usuarios acudían a un centro de recogida de series de laboratorio (sin ayuno). Resultados: Se incluyeron y analizaron 351 usuarios (media±DP, 70±6 años). Para los factores de riesgo cardiovascular, la prevalencia de hipercolesterolemia fue de 54,2% y de hipertensión arterial sistémica de 49,3%, la más alta. El trastorno del sueño fue prevalente en el 55,3% de la muestra. Entre las enfermedades auto informadas, los participantes enumeraron enfermedades cardiovasculares (14,3%), cáncer previo (14,6%), diabetes (13,2%), artritis reumatoide/reumatismo (29,6%) y depresión (sin discriminación de depresión mayor/menor) (18,6%). La capacidad funcional, estimada por la prueba de la marcha de 6 minutos, y la fuerza de prensión manual, predictores de mortalidad y lesiones cardiovasculares, tuvieron valores medios de 498,05±78,96 m y 27,08±8,14 kg, respectivamente. Conclusiones: Los hallazgos de este estudio permiten contrastar las prevalencias estimadas en participantes ancianos de un programa público de actividades físicas con otras estimaciones en grupos de comparación, lo que permite el análisis de la situación de salud basado en diferentes comportamientos y factores de riesgo. Por último, el trabajo ha facilitado la monitorización de intervenciones públicas para personas mayores a nivel comunitario, sirviendo como punto de partida para un seguimiento futuro.

Development of a layered bacterial nanocellulose-PHBV composite for food packaging.

BACKGROUND: Most of the current materials used in food packaging are synthetic and non-degradable, raising environmental issues derived from the accumulation of plastics in landfills/waterways. The food industry increasingly needs eco-friendly sustainable materials that meet food-packaging requirements. Bacterial nanocellulose (BNC), a biopolymer obtained by fermentation, offers very good mechanical properties and the ability to carry and deliver active substances. However, its water-vapor permeability is too high for food-packaging applications. In this work, a layered biodegradable composite based on BNC and polyhydroxyalkanoate (PHBV) was produced, attempting to improve its overall barrier properties. Polyhydroxyalkanoate is a biopolymer with high degree of hydrophobicity and biodegradability, and is also obtained by fermentation. Wet BNC membranes produced by static culture were plasticized by impregnation of solutions of either glycerol (BNCgly ) or polyethylene glycol (MW 600) (BNCPEG ). The plasticized BNC was then coated with PHBV solution dissolved in formic acid, and oven dried at 148 °C. RESULTS: Overall, PHBV coating on plasticized BNC reduced water vapor permeability significantly (from 0.990 to 0.032 g.µm.m-2 .day-1 .Pa-1 ) under 50% relative humidity. It increased the hydrophobicity (contact angle from 10-40° to 80-90°) but decreased the stiffness (from 3.1 GPa to 1.3 Gpa) of the composite. CONCLUSIONS: Overall, the mechanical and barrier properties of the layered composite obtained were considered suitable for food-packaging applications. The plasticizing (with glycerol or polyethylene glycol) of BNC significantly improved the mechanical performance and the PHBV coating reduced the water affinity (vapor and liquid state) on BNC. © 2022 Society of Chemical Industry.

Tracking Bacterial Nanocellulose in Animal Tissues by Fluorescence Microscopy.

The potential of nanomaterials in food technology is nowadays well-established. However, their commercial use requires a careful risk assessment, in particular concerning the fate of nanomaterials in the human body. Bacterial nanocellulose (BNC), a nanofibrillar polysaccharide, has been used as a food product for many years in Asia. However, given its nano-character, several toxicological studies must be performed, according to the European Food Safety Agency's guidance. Those should especially answer the question of whether nanoparticulate cellulose is absorbed in the gastrointestinal tract. This raises the need to develop a screening technique capable of detecting isolated nanosized particles in biological tissues. Herein, the potential of a cellulose-binding module fused to a green fluorescent protein (GFP-CBM) to detect single bacterial cellulose nanocrystals (BCNC) obtained by acid hydrolysis was assessed. Adsorption studies were performed to characterize the interaction of GFP-CBM with BNC and BCNC. Correlative electron light microscopy was used to demonstrate that isolated BCNC may be detected by fluorescence microscopy. The uptake of BCNC by macrophages was also assessed. Finally, an exploratory 21-day repeated-dose study was performed, wherein Wistar rats were fed daily with BNC. The presence of BNC or BCNC throughout the GIT was observed only in the intestinal lumen, suggesting that cellulose particles were not absorbed. While a more comprehensive toxicological study is necessary, these results strengthen the idea that BNC can be considered a safe food additive.

Trends on the Cellulose-Based Textiles: Raw Materials and Technologies.

There is an emerging environmental awareness and social concern regarding the environmental impact of the textile industry, highlighting the growing need for developing green and sustainable approaches throughout this industry's supply chain. Upstream, due to population growth and the rise in consumption of textile fibers, new sustainable raw materials and processes must be found. Cellulose presents unique structural features, being the most important and available renewable resource for textiles. The physical and chemical modification reactions yielding fibers are of high commercial importance today. Recently developed technologies allow the production of filaments with the strongest tensile performance without dissolution or any other harmful and complex chemical processes. Fibers without solvents are thus on the verge of commercialization. In this review, the technologies for the production of cellulose-based textiles, their surface modification and the recent trends on sustainable cellulose sources, such as bacterial nanocellulose, are discussed. The life cycle assessment of several cellulose fiber production methods is also discussed.

Health profile of elderly users of a town public program of physical activity: a cross-sectional study / Perfil da situação de saúde dos idosos participantes de um programa municipal de atividades físicas: um estudo transversal

The assessment of health profile in users attending such public programs may optimize tailoring of interventions oriented to reduce the risk or incidence of lifestyle-driven diseases, resulting in a potential impact on public health. Therefore, this cross-sectional study aimed to characterize the health profile of the elderly participants in the physical activity public program in southern Brazil. Therefore, we included 11 community exercise centers managed by the city of Porto Alegre (Brazil). We used simple random sampling, with sample size weight by the number of participants in each individual center. Several health domains were measured by self-reported questionnaires (e.g., cardiovascular risk factors and quality of life), office blood pressure measurements, blood assessments (i.e., lipid profile and HbA1c) and functional tests (i.e., 6-minute walk test and handgrip strength) between April/2018 to February/2019. The results are mostly reported using descriptive statistics. We observed that high self-reported prevalences regarded to cardiovascular risk factors, more specifically for sleep disorder (55%), hypercholesterolemia (54%) and hypertension (49%). Among self-reported diseases, the participants listed cardiovascular diseases (14%), previous cancer (15%), diabetes (13%), arthritis (30%), and depression (19%). The results observed in the 6-minute walk test (mean±sd 498±78.95 m) and handgrip test (mean±sd 27±8.13 kg) showed the expected levels for active elderly. Overall, the prevalences presented herein allow to contrast the estimated prevalences of older adults using a public program of physical activity to other populational estimates or single studies, fostering the future monitoring of assessments and interventions in sensible conditions (e.g., hypertension, sleep disorder) for this population. 

O conhecimento do perfil de saúde dos usuários de programas públicos para promoção em saúde pode otimizar a elaboração e aperfeiçoamento de intervenções para controle doenças ou de eventos associados ao estilo de vida, com potencial impacto para a saúde pública. O objetivo deste estudo foi caracterizar o perfil da situação de saúde dos usuários idosos do programa público de atividade física, em 11 centros comunitários da cidade de Porto Alegre (RS, Brasil). Entre abril/2018 e fevereiro/2019, foram medidos domínios de saúde por questionários autoaplicados, avaliações sanguíneas e testes funcionais. O tamanho amostral foi ponderado pela quantidade de alunos atendidos por centro, com amostragem por aleatorização simples. As análises basearam-se em estatística descritiva. No total, 351 idosos (69±6 anos) foram incluídos. Houve elevadas prevalências de fatores de risco, sendo transtorno do sono (55%), hipercolesterolemia (54%), e hipertensão arterial (49%) as mais altas. Entre as doenças autorrelatadas, os participantes listaram condições cardiovasculares (14%), câncer prévio (15%), diabetes (13%), artrite reumatóide (30%) e depressão (19%). A capacidade de caminhada em 6 minutos e força de preensão manual estiveram em níveis de pessoas ativas. Este estudo possibilita contrastar as condições prevalentes dos idosos usuários de um programa público de atividade física com estimativas populacionais, servindo como levantamento inicial para futuro monitoramento de avaliações e/ou intervenções específicas às condições sensíveis nesta população.

Nanocellulose Bio-Based Composites for Food Packaging.

The food industry is increasingly demanding advanced and eco-friendly sustainable packaging materials with improved physical, mechanical and barrier properties. The currently used materials are synthetic and non-degradable, therefore raising environmental concerns. Consequently, research efforts have been made in recent years towards the development of bio-based sustainable packaging materials. In this review, the potential of nanocelluloses as nanofillers or as coatings for the development of bio-based nanocomposites is discussed, namely: (i) the physico-chemical interaction of nanocellulose with the adjacent polymeric phase, (ii) the effect of nanocellulose modification/functionalization on the final properties of the composites, (iii) the production methods for such composites, and (iv) the effect of nanocellulose on the overall migration, toxicity, and the potential risk to human health. Lastly, the technology readiness level of nanocellulose and nanocellulose based composites for the market of food packaging is discussed.

Effect of bacterial nanocellulose binding on the bactericidal activity of bovine lactoferrin.

Bovine lactoferrin (bLF) has been extensively described as a wide spectrum antimicrobial protein. bLF bactericidal activity has been mainly attributed to two different mechanisms: environmental iron depletion and cell membrane destabilization. Due to its antimicrobial properties, bLF has been included in the formulation nutraceutical food products and edible active packages. This work comprises the experimental evidence of the requirement of bLF unrestricted mobility ("free bLF") to effectively perform its bactericidal action. To assess the unrestricted and restricted bLF activity, a nontoxic matrix of bacterial nanocellulose (BNC) was used as carrier, and as an anchoring scaffold, respectively. Therefore, BNC was functionalized with bLF through two different methodologies: (i) bLF was embedded within the three-dimensional structure of BNC and; (ii) bLF was covalently bounded to the nanofibrils of BNC. bLF efficiency was tested against two bacteria isolated from clinical specimens, Escherichia coli and Staphylococcus aureus. bLF concentration after covalent binding to BNC was two-fold higher in comparison to the embedding method. Nevertheless, only the embedded bLF exhibited a significant bactericidal activity, due to bLF ability to permeate the BNC matrix and execute its bactericidal action.

Study and valorisation of wastewaters generated in the production of bacterial nanocellulose.

Two culture media were tested for the production of bacterial nanocellulose (BNC) under static culture fermentation, one containing molasses (Mol-HS), the other molasses and corn steep liquor (Mol-CSL), as a source of carbon and nitrogen, respectively. These are low-cost nutrients widely available, which provide very good BNC productivities. However, the use of these substrates generates wastewaters with high organic loads. Anaerobic digestion is one of the most promising treatments for industrial wastewaters with high organic loads since, beyond removal of the organic matter, it generates energy, in form of biogas. The wastewaters from BNC fermentation were thus evaluated for their biochemical methane potential through anaerobic digestion. For this, two wastewaters streams were collected: (i) the culture medium obtained after fermentation (WaF) and (ii) the WaF combined with BNC washing wastewaters (WaW). These two effluents-WaF and WaW-were characterized regarding their chemical oxygen demand, total nitrogen, total and volatile solids, to assess their suitability for anaerobic digestion. The biochemical methane potential of WaF and WaW from Mol-CSL wastewaters was (387 ± 14 L kg-1 VS) and (354 ± 4 L kg-1 VS), corresponding to a methanization percentage of (86.9 ± 3.1) % and (79.5 ± 0.9) %, respectively. After treatment, the chemical oxygen demand of WaF and WaW was reduced by (89.2 ± 0.4) and (88.7 ± 1.5), respectively. An exploratory test using an Upflow Anaerobic Sludge Blanket reactor for WaW treatment was also performed. The reactor was operated with a organic loading rate of [(6.5 ± 0.1) g L-1 d-1] and hydraulic retention time of 3.33 days, allowing a chemical oxygen demand removal of 58% of WaW. Results here obtained demonstrate, for the first time, the high potential of AD for the valorisation of the BNC fermentation wastewaters.

Bacterial Cellulose and Emulsified AESO Biocomposites as an Ecological Alternative to Leather.

This research investigated the development of bio-based composites comprising bacterial cellulose (BC), as obtained by static culture, and acrylated epoxidized soybean oil (AESO) as an alternative to leather. AESO was first emulsified; polyethylene glycol (PEG), polydimethylsiloxane (PDMS) and perfluorocarbon-based polymers were also added to the AESO emulsion, with the mixtures being diffused into the BC 3D nanofibrillar matrix by an exhaustion process. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy analysis demonstrated that the tested polymers penetrated well and uniformly into the bulk of the BC matrix. The obtained composites were hydrophobic and thermally stable up to 200 °C. Regarding their mechanical properties, the addition of different polymers lead to a decrease in the tensile strength and an increase in the elongation at break, overall presenting satisfactory performance as a potential alternative to leather.

Optimization of bacterial nanocellulose fermentation using recycled paper sludge and development of novel composites.

In this work, recycled paper sludge (RPS), composed of non-recyclable fibres, was used as a carbon source for bacterial nanocellulose (BNC) production. The biomass was enzymatically hydrolysed with Cellic CTec 2 to produce a sugar syrup with 45.40 g/L glucose, 1.69 g/L cellobiose and 2.89 g/L xylose. This hydrolysate was used for the optimization of BNC fermentation by static culture, using Komagataeibacter xylinus ATCC 700178, through response surface methodology (RSM). After analysis and validation of the model, a maximum BNC yield (5.69 g/L, dry basis) was obtained using 1.50% m/v RPS hydrolysate, 1.0% v/v ethanol and 1.45% m/v yeast extract/peptone (YE/P). Further, the BNC obtained was used to produce composites. A mixture of an amino-PolyDiMethylSiloxane-based softener, polyethyleneglycol (PEG) 400 and acrylated epoxidized soybean oil (AESO), was incorporated into the BNC membranes through an exhaustion process. The results show that BNC composites with distinct performances can be easily designed by simply varying the polymers percentage contents. This strategy represents a simple approach towards the production of BNC and BNC-based composites.

Development of novel bacterial cellulose composites for the textile and shoe industry.

This research aimed at producing malleable, breathable and water impermeable bacterial cellulose-based nanocomposites, by impregnating bacterial cellulose (BC) membranes with two commercial hydrophobic polymers used in textile finishing, Persoftal MS (polydimethylsiloxane) and Baygard EFN (perfluorocarbon), by an exhaustion process. These hydrophobic products penetrated the BC membranes and adsorbed tightly onto the surface of the nanofibres, across the entire depth of the material, as demonstrated by Scanning Electron Microscopy and Fourier Transform Infrared spectroscopy studies. The water static contact angles, drop absorption over time and vapour permeability values showed that the composites were impermeable to liquid water but permeable to water vapour. The mechanical properties of the BC-nanocomposites were improved after incorporation of the hydrophobic products, in some of the formulations tested, overall presenting a satisfactory performance. Thus, through a simple and cost-effective process, hydrophobized, robust, malleable and breathable nanocomposites based on BC were obtained, featuring promising properties for application in the textile and shoe industries.

Molecular aspects of bacterial nanocellulose biosynthesis.

Bacterial nanocellulose (BNC) produced by aerobic bacteria is a biopolymer with sophisticated technical properties. Although the potential for economically relevant applications is huge, the cost of BNC still limits its application to a few biomedical devices and the edible product Nata de Coco, made available by traditional fermentation methods in Asian countries. Thus, a wider economic relevance of BNC is still dependent on breakthrough developments on the production technology. On the other hand, the development of modified strains able to overproduce BNC with new properties - e.g. porosity, density of fibres crosslinking, mechanical properties, etc. - will certainly allow to overcome investment and cost production issues and enlarge the scope of BNC applications. This review discusses current knowledge about the molecular basis of BNC biosynthesis, its regulations and, finally, presents a perspective on the genetic modification of BNC producers made possible by the new tools available for genetic engineering.

Response surface statistical optimization of bacterial nanocellulose fermentation in static culture using a low-cost medium.

This work aimed at the optimization of bacterial nanocellulose (BNC) production by static culture, using Komagataeibacter xylinus BPR 2001 (K. xylinus). Response surface methodology - central composite design was used to evaluate the effect of inexpensive and widely available nutrient sources, namely molasses, ethanol, corn steep liquor (CSL) and ammonium sulphate, on BNC production yield. The optimized parameters for maximum BNC production were % (m/v): molasses 5.38, CSL 1.91, ammonium sulphate 0.63, disodium phosphate 0.270, citric acid 0.115 and ethanol 1.38% (v/v). The experimental and predicted maximum BNC production yields were 7.5 ± 0.54 g/L and 6.64 ± 0.079 g/L, respectively and the experimental and predicted maximum BNC productivity were 0.829 ± 0.046 g/L/day and 0.734 ± 0.079 g/L/day, after 9 days of static culture fermentation, at 30 °C. The effect of surface area and culture medium depth on production yield and productivity were also studied. BNC dry mass production increased linearly with surface area, medium depth and fermentation time. So long as nutrients were still available in the culture media, BNC mass productivity was constant. The results show that a high BNC production yield can be obtained by static culture of K. xylinus BPR 2001 using a low-cost medium. These are promising conditions for the static industrial scale BNC production, since as compared to agitated bioreactors, higher productivities may be reached, while avoiding high capital and operating costs.

Bacterial NanoCellulose: what future?

Acetic acid bacteria (AAB) have been used in various fermentation processes. Of several ABB, the bacterial nanocellulose (BNC) producers, notably Komagataeibacter xylinus, appears as an interesting species, in large part because of their ability in the secretion of cellulose as nano/microfibrils. In fact, BNC is characterized by a native nanofibrillar structure, which may outperform the currently used celluloses in the food industry as a promising novel hydrocolloid additive. During the last couple of years, a number of companies worldwide have introduced some BNC-based products to the market. The main aim of this editorial is to underline the BNC potentials.

A Review on the toxicology and dietetic role of bacterial cellulose.

Bacterial cellulose (BC) is a biopolymer synthesized by certain acetic acid bacteria strains. The safety of BC regarding its potential use in food applications is here reviewed. The acute, sub-acute and subchronic oral toxicity assays showed that consumption of BC had no adverse effects in rats. Several studies demonstrated that BC is not genotoxic, did not induce chromosomal aberrations in CHO cells under both non-activating and metabolic activating conditions, is inactive in the in vitro Rat Primary Hepatocyte Unscheduled DNA Synthesis Assay, had no reproductive toxicity in mice and exerted no embryotoxicity and teratogenicity effects in rats. Several studies on the BC in biomedical applications further reinforces its safety: a primary eye and dermal irritation studies in the rabbit showed that BC was non-irritating. The inflammatory reaction to subcutaneously implanted BC has been evaluated in animal models and for different periods of time, demonstrating that BC is biocompatible and does not trigger a harsh inflammatory reaction. Altogether, and considering its longstanding history of human consumption in Asian countries, as well as its utilization in biomedical devices, it may be concluded that BC is safe for applications in food technology.

Laccase immobilization on bacterial nanocellulose membranes: Antimicrobial, kinetic and stability properties.

This work studied the physical immobilization of a commercial laccase on bacterial nanocellulose (BNC) aiming to identify the laccase antibacterial properties suitable for wound dressings. Physico-chemical analysis demonstrates that the BNC structure is manly formed by pure crystalline Iα cellulose. The pH optimum and activation energy of free laccase depends on the substrate employed corresponding to pH 6, 7, 3 and 57, 22, 48kJmol(-1) for 2,6-dimethylphenol (DMP), catechol and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), respectively. The Michaelis-Menten constant (Km) value for the immobilized laccase (0.77mM) was found to be almost double of that of the free enzyme (0.42mM). However, the specific activities of immobilized and free laccase are similar suggesting that the cage-like structure of BNC allows entrapped laccase to maintain some flexibility and favour substrate accessibility. The results clearly show the antimicrobial effect of laccase in Gram-positive (92%) and Gram-negative (26%) bacteria and cytotoxicity acceptable for wound dressing applications.