Bacterial cellulose–alginate composite sponge as a yeast cell carrier for ethanol production

Applications of bacterial cellulose in the food industry and its health-promoting potential

Bacterial cellulose (BC) is a naturally occurring biomaterial with a wide range of potential applications in the food industry because of its exceptional mechanical qualities, unique nanofiber structure, high purity, and outstanding biocompatibility. Beyond its physical attributes, BC has gained interest recently due to research demonstrating its potential health benefits as a functional food ingredient. This article examines the many uses of BC in the food business, with a focus on how it may enhance food texture, operate as a bioactive carrier, and have promise in the packaging sector. Further research was done on the health-promoting properties of BC in functional foods, particularly with regard to its functions as a blood glucose regulator, and gastrointestinal health. This review seeks to bring fresh ideas for the study of bioactive components in the food industry by providing a summary of the existing research and demonstrating the possible role of BC in food. It also suggests future paths for research.

Filamentous fungal pellets as versatile platforms for cell immobilization: developments to date and future perspectives

Filamentous fungi are well-known for their efficiency in producing valuable molecules of industrial significance, but applications of fungal biomass remain relatively less explored despite its abundant and diverse opportunities in biotechnology. One promising application of mycelial biomass is as a platform to immobilize different cell types such as animal, plant, and microbial cells. Filamentous fungal biomass with little to no treatment is a sustainable biomaterial which can also be food safe compared to other immobilization supports which may otherwise be synthetic or heavily processed. Because of these features, the fungal-cell combination can be tailored towards the targeted application and be applied in a variety of fields from bioremediation to biomedicine. Optimization efforts to improve cell loading on the mycelium has led to advancements both in the applied and basic sciences to understand the inter- and intra-kingdom interactions. This comprehensive review compiles for the first time the current state of the art of the immobilization of animal, yeast, microalgae, bacteria, and plant cells in filamentous fungal supports and presents outlook of applications in intensified fermentations, food and biofuel production, and wastewater treatment. Opportunities for further research and development were identified to include elucidation of the physical, chemical, and biological bases of the immobilization mechanisms and co-culture dynamics; expansion of the cell-fungus combinations investigated; exploration of previously unconsidered applications; and demonstration of scaled-up operations. It is concluded that the potential exists to leverage the unique qualities of filamentous fungus as a cellular support in the creation of novel materials and products in support of the circular bioeconomy.

Structural and Physical Properties of Alginate Pretreated by High-Pressure Homogenization

To develop a high-efficient extraction method, we investigated the use of high-pressure homogenization (HPH) as a novel pretreatment technology for the extraction of sodium alginate (SA) from Laminaria japonica. After the single-factor experiment, the results demonstrated that under the conditions of 100 MPa HPH pressure, 4 cycles, pH 6.0, and 0.5% EDTA for 3.0 h, the optimized extraction yield of HPH reached 34%. To further clarify the effect on the structural properties of HPH-extracted SA, we conducted comprehensive analysis using SEM, FTIR, MRS, NMR, XRD, TGA, and a T-AOC assay. Our findings revealed that HPH pretreatment significantly disrupted the structure of L. japonica cells and reduced their crystallinity to 76.27%. Furthermore, the antioxidant activity of HPH-extracted SA reached 0.02942 mgVceq∙mg-1. Therefore, the HPH pretreatment method is a potential strategy for the extraction of alginate.

Modified Activated Carbon: A Supporting Material for Improving Clostridium beijerinckii TISTR1461 Immobilized Fermentation

This study aimed to investigate the effect of activated carbon (AC) as an immobilization material in acetone-butanol-ethanol fermentation. The AC surface was modified with different physical (orbital shaking and refluxing) and chemical (nitric acid, sodium hydroxide and, (3-aminopropyl)triethoxysilane (APTES)) treatments to enhance the biobutanol production by Clostridium beijerinckii TISTR1461. The effect of surface modification on AC was evaluated using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, surface area analyses, and X-ray photoelectron spectroscopy, while the fermented broth was examined by high-performance liquid chromatography. The chemical functionalization significantly modified the physicochemical properties of the different treated ACs and further enhanced the butanol production. The AC treated with APTES under refluxing provided the best fermentation results at 10.93 g/L of butanol, 0.23 g/g of yield, and 0.15 g/L/h of productivity, which were 1.8-, 1.5-, and 3.0-fold higher, respectively, than that in the free-cell fermentation. The obtained dried cell biomass also revealed that the treatment improved the AC surface for cell immobilization. This study demonstrated and emphasized the importance of surface properties to cell immobilization.

Preparation and characterization of a self-crosslinking sodium alginate-bioactive glass sponge

In this research, bioactive glass particles prepared by the reactive flash nanoprecipitation method (RFNP-BG particles) are used to crosslink sodium alginate to prepare biological sponges (SA-BG sponges) by freeze-drying. An experiment for the cross-linking mechanism confirms that the continuous release of Ca²⁺ from RFNP-BG is promoted by the crosslinking reaction and in turn leads to the gelation process of SA. Bioactive glass particles not only provide Ca²⁺ for the crosslinking of sodium alginate, but also enhance the mechanical properties of the SA-BG sponges. The results show that the elastic modulus of the SA-BG sponges increases from 0.026 MPa to 0.641 MPa, and the resistance to external force deformation is greatly improved; the thermal decomposition temperature increases from 105°C to 166°C; compared with a pure SA sponge, the water resistance is significantly improved. In vitro cell experiments show that the SA-BG sponges have a certain adverse effect on cell proliferation, but it is in an acceptable range. qPCR results show that the SA-BG sponges have a certain beneficial effect on promoting osteogenic gene expression. The SA-BG sponges have great application potential in the fields of medicine, hemostasis, and wound closure.

Surface Wettability of Cellulose Sponges on Effective Oil Uptake

Designing absorbents having specific wettability toward both oil and water is the key for selective and effective oil absorption and removal. For this purpose, establishing explicit correlations between surface tension of oils and surface wettability of absorbent is crucial. In this study, we modified common low-cost cellulose sponges with various organosilanes to achieve a range of hydrophobicity/oleophilicity and then assessed their oil uptake selectivity and capability. Oil uptake was followed as mass uptake versus time and analyzed based on the spreading coefficient (S) of a liquid over a solid surface. The results showed that sponges needed to be hydrophobic, not necessarily superhydrophobic, to selectively absorb oil from an oil/water mixture. To achieve a fast uptake and a high uptake capacity, an S ≥ 0 was necessary, that is, when the sponges were completely wet by the oil. Increasing the porosity of cellulose sponge led to a slight increase in oil uptake capacity, and a greater increase resulted when bacterial cellulose sponges that consisted of smaller and more uniform voids/pores were used. S ≥ 0 could be used as a criterion for evaluating effective and rapid oil uptake for porous absorbents, especially for those containing heterogeneous pore structures, such as common cellulose sponges.

Biochemistry, Synthesis, and Applications of Bacterial Cellulose: A Review

The potential of cellulose nanocomposites in the new-generation super-performing nanomaterials is huge, primarily in medical and environment sectors, and secondarily in food, paper, and cosmetic sectors. Despite substantial illumination on the molecular aspects of cellulose synthesis, various process features, namely, cellular export of the nascent polysaccharide chain and arrangement of cellulose fibrils into a quasi-crystalline configuration, remain obscure. To unleash its full potential, current knowledge on nanocellulose dispersion and disintegration of the fibrillar network and the organic/polymer chemistry needs expansion. Bacterial cellulose biosynthesis mechanism for scaled-up production, namely, the kinetics, pathogenicity, production cost, and product quality/consistency remain poorly understood. The bottom-up bacterial cellulose synthesis approach makes it an interesting area for still wider and promising high-end applications, primarily due to the nanosynthesis mechanism involved and the purity of the cellulose. This study attempts to identify the knowledge gap and potential wider applications of bacterial cellulose and bacterial nanocellulose. This review also highlights the manufacture of bacterial cellulose through low-cost substrates, that is, mainly waste from brewing, agriculture, food, and sugar industries as well as textile, lignocellulosic biorefineries, and pulp mills.

Bacterial Cellulose and Its Applications

The sharp increase in the use of cellulose seems to be in increasing demand in wood; much more research related to sustainable or alternative materials is necessary as a lot of the arable land and natural resources use is unsustainable. In accordance, attention has focused on bacterial cellulose as a new functional material. It possesses a three-dimensional, gelatinous structure consisting of cellulose with mechanical and thermal properties. Moreover, while a plant-originated cellulose is composed of cellulose, hemi-cellulose, and lignin, bacterial cellulose attributable to the composition of a pure cellulose nanofiber mesh spun is not necessary in the elimination of other components. Moreover, due to its hydrophilic nature caused by binding water, consequently being a hydrogel as well as biocompatibility, it has only not only used in medical fields including artificial skin, cartilage, vessel, and wound dressing, but also in delivery; some products have even been commercialized. In addition, it is widely used in various technologies including food, paper, textile, electronic and electrical applications, and is being considered as a highly versatile green material with tremendous potential. However, many efforts have been conducted for the evolution of novel and sophisticated materials with environmental affinity, which accompany the empowerment and enhancement of specific properties. In this review article, we summarized only industry and research status regarding BC and contemplated its potential in the use of BC.

The Effects of Curcumin Nanoparticles Incorporated into Collagen-Alginate Scaffold on Wound Healing of Skin Tissue in Trauma Patients

Wound healing is a biological process that is mainly crucial for the rehabilitation of injured tissue. The incorporation of curcumin (Cur) into a hydrogel system is used to treat skin wounds in different diseases due to its hydrophobic character. In this study, sodium alginate and collagen, which possess hydrophilic, low toxic, and biocompatible properties, were utilized. Collagen/alginate scaffolds were synthesized, and nanocurcumin was incorporated inside them; their interaction was evaluated by FTIR spectroscopy. Morphological studies investigated structures of the samples studied by FE-SEM. The release profile of curcumin was detected, and the cytotoxic test was determined on the L929 cell line using an MTT assay. Analysis of tissue wound healing was performed by H&E staining. Nanocurcumin was spherical, its average particle size was 45 nm, and the structure of COL/ALG scaffold was visible. The cell viability of samples was recorded in cells after 24 h incubation. Results of in vivo wound healing remarkably showed CUR-COL/ALG scaffold at about 90% (p < 0.001), which is better than that of COL/ALG, 80% (p < 0.001), and the control 73.4% (p < 0.01) groups at 14 days/ The results of the samples’ FTIR indicated that nanocurcumin was well-entrapped into the scaffold, which led to improving the wound-healing process. Our results revealed the potential of nanocurcumin incorporated in COL/ALG scaffolds for the wound healing of skin tissue in trauma patients.

Bacterial cellulose as an oleaginous yeast cell carrier for soybean oil refinery effluent treatment and pyrolysis oil production

Bacterial cellulose produced from soybean oil refinery effluent is a good immobilization carrier because of the large pores in its fiber network, its high water-holding capacity, and its good biocompatibility. In this study, it was applied to immobilization of oleaginous yeasts for treating soybean oil refinery effluent. The immobilization percentage reached 50%, and the removal of chemical oxygen demand and oil content reached 92.1% and 93.1%, respectively, during dynamic immobilization using a mass percentage of bacterial cellulose of 30% and an immobilization time of 24 h, which were significantly higher than those of free oleaginous yeasts or yeasts immobilized by bacterial cellulose from rich medium. The immobilized oleaginous yeasts facilitated the recovery of the yeasts and effectively treated three batches of soybean oil refinery effluent. The immobilized oleaginous yeasts recovered after soybean oil refinery effluent treatment were pyrolyzed to produce bio-oil, which contributed to more alkanes and a higher calorific value of bio-oil in the pyrolysis products as compared to those of free oleaginous yeasts. As bacterial cellulose used as an oleaginous yeast cell carrier is produced from soybean oil refinery effluent, no waste of immobilization materials is involved and an efficient waste-into-oil bioprocess is developed.

Significant enhancement of citric acid production by Yarrowia lipolytica immobilized in bacterial cellulose-based carrier

The aim of this study was to improve the yield of citric acid (CA), an industrially valuable metabolite, obtained during Yarrowia lipolytica yeast culturing. To this end, Y. lipolytica cells were immobilized on a novel bacterial cellulose (BC) based carrier and subjected to four subsequent cycles of fed-batch culturing. During the fermentation process, yeasts metabolic stability, glucose consumption and CA production were analyzed. The results of our study have shown that BC-immobilized yeasts utilized more glucose than free cells and that the metabolic activity of BC-immobilized cells and the resultant CA production remained on a stable level throughout 4 fermentation batches, while the drop in free cells' metabolic stability and the consequent drop in CA production was observed with each subsequent batch. Also, the overall concentration of CA product was higher in immobilized vs. free yeasts (121-129 g/L vs. 99-110 g/L, respectively). The presented results indicate that the application of a BC carrier for Y. lipolytica culturing correlates not only with a higher yield of CA product but also with more stable and repeatable conditions of the biotechnological fermentation process. The results obtained in this study may find multiple biotechnological applications in which immobilization of various types of cells is required.

Bacterial cellulose in food industry: Current research and future prospects

Bacterial cellulose, a pure exocellular polysaccharide produced by microorganisms, has many excellent properties as compared with plant-derived cellulose, including high water holding capability, high surface area, rheological properties, biocompatibility. Due to its suspending, thickening, water holding, stabilizing, bulking and fluid properties, BC has been demonstrated as a promising low calorie bulking ingredient for the development of novel rich functional foods of different forms such as powder gelatinous or shred foams, which facilitate its application in food industry. In this review, the recent reports on the biosynthesis, structure and general application of bacterial cellulose in food industry have been summarized and discussed. The main application of bacterial cellulose in current food industry includes raw food materials, additive ingredients, packing materials, delivery system, enzyme and cell immobilizers. In addition, we also propose the potential challenges and explore the solution of expanding the application of BC in various fields.

Bacterial Cellulose-Alginate Composite Beads as Yarrowia lipolytica Cell Carriers for Lactone Production

The demand for natural lactone gamma-decalactone (GDL) has increased in the fields of food and cosmetic products. However, low productivity during bioprocessing limits its industrial production. In this study, a novel composite porous cell carrier, bacterial cellulose-alginate (BC-ALG), was used for long-term biotransformation and production of GDL. The effects of this carrier on biotransformation and related mechanisms were investigated. BC-ALG carriers showed improved mechanical strength over ALG carriers, with their internal embedded cell pattern changed to an interconnected porous structure. In five repeated-batch biotransformation experiments, the maximum concentration of GDL obtained in culture with BC-ALG carriers was 8.37 g/L, approximately 3.7 times higher than that from the medium with an ALG carrier alone. The result indicated that multiple hydrogen bonding interactions at the interface between BC and ALG contributed to the compatibility and stability of BC-ALG carriers. On the basis of the above results, the BC-ALG composite carrier can be considered ideal for immobilisation of cells for the production of GDL on an industrial scale, and has the potential to be utilised in other biological processes.

Exploitation of olive oil mill wastewaters and molasses for ethanol production using immobilized cells of Saccharomyces cerevisiae

An alcoholic fermentation process is described, involving molasses, the main by-product of the sugar industry, blended with crude olive oil mill wastewaters (OOMWs) and immobilized Saccharomyces cerevisiae cells on delignified cellulosic material (DCM). For comparison, fermentations with free cells were also carried out. Initially, the optimum blending mixture for molasses dilution was sought after, while at a second step repeated batch fermentations at a temperature range 5-30 °C were performed to monitor the operational stability of the system. A 1/1 ratio of OOMWs/tap water blending mixture and cell immobilization resulted in higher fermentation parameters. Ethanol concentration and daily productivity values recorded at temperatures ≥ 20 °C (up to 67.8 g L^-1 and 67.6 g L^-1 d^-1, respectively) could be adopted by the industrial sector, although the decline in fermentation efficiency observed, probably due to the toxicity effects of OOMWs. Finally, the potential of OOMWs treatment for ethanol production is highlighted and assessed.

Cellulosic Nanomaterials in Food and Nutraceutical Applications: A Review

Cellulosic nanomaterials (CNMs) are organic, green nanomaterials that are obtained from renewable sources and possess exceptional mechanical strength and biocompatibility. The associated unique physical and chemical properties have made these nanomaterials an intriguing prospect for various applications including the food and nutraceutical industry. From the immobilization of various bioactive agents and enzymes, emulsion stabilization, direct food additives, to the development of intelligent packaging systems or pathogen or pH detectors, the potential food related applications for CNMs are endless. Over the past decade, there have been several reviews published covering different aspects of cellulosic nanomaterials, such as processing-structure-property relationship, physical and chemical properties, rheology, extraction, nanocomposites, etc. In this critical review, we have discussed and provided a summary of the recent developments in the utilization of cellulosic nanomaterials in applications related to food and nutraceuticals.

Yeasts in sustainable bioethanol production: A review

Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production.

Effective ethanol production from whey powder through immobilized E. coli expressing Vitreoscilla hemoglobin

Ethanol production from whey powder was investigated by using free as well as alginate immobilized E. coli and E. coli expressing Vitreoscilla hemoglobin (VHb) in both shake flask and fermenter cultures. Media with varying levels of whey (lactose contents of 3%, 5%, 8% or 15%) and yeast extract (0.3% or 0.5%) were evaluated with fermentation times of 48-96 h. Immobilization and VHb expression resulted in higher ethanol production with all media; the increases ranged from 2% to 89% for immobilization and from 2% to 182% for VHb expression. It was determined that growth medium containing 8% lactose with 0.5% yeast extract yielded the highest ethanol production for free or immobilized strains, with or without VHb expression, in both shake flask and fermenter cultures. Immobilization with alginate was found to be a promising process for ethanol production by VHb-expressing ethanologenic E. coli.

Advances in biomedical and pharmaceutical applications of functional bacterial cellulose-based nanocomposites

Bacterial cellulose (BC) synthesized by certain species of bacteria, is a fascinating biopolymer with unique physical and mechanical properties. BC's applications range from traditional dessert, gelling, stabilizing and thickening agent in the food industry to advanced high-tech applications, such as immobilization of enzymes, bacteria and fungi, tissue engineering, heart valve prosthesis, artificial blood vessels, bone, cartilage, cornea and skin, and dental root treatment. Various BC-composites have been designed and investigated in order to enhance its biological applicability. This review focuses on the application of BC-based composites for microbial control, wound dressing, cardiovascular, ophthalmic, skeletal, and endodontics systems. Moreover, applications in controlled drug delivery, biosensors/bioanalysis, immobilization of enzymes and cells, stem cell therapy and skin tissue repair are also highlighted. This review will provide new insights for academia and industry to further assess the BC-based composites in terms of practical applications and future commercialization for biomedical and pharmaceutical purposes.

Alginate/bacterial cellulose nanocomposite beads prepared using Gluconacetobacter xylinus and their application in lipase immobilization

Alginate/bacterial cellulose nanocomposite beads, with well-controlled size and regular spherical shapes, were prepared in a simple manner by entrapping Gluconacetobacter xylinus in barium alginate hydrogel beads, followed by cultivation of the entrapped cells in culture media with a low sodium ion concentration. The entire surface of the alginate hydrogel beads containing the cells was covered with cellulose fibers (∼30nm) after 36h of cultivation. The cellulose crystallinity index of the alginate/bacterial cellulose beads was 0.7, which was slightly lower than that of bacterial cellulose prepared by cultivating dispersed cells. The water vapor sorption capacity of the alginate/bacterial cellulose beads increased significantly from 0.07 to 38.00 (g/g dry bead) as cultivation time increased. These results clearly indicate that alginate/bacterial cellulose beads have a much higher surface area, crystallinity, and water-holding capacity than alginate beads. The immobilization of lipase on the surface of the nanocomposite beads was also investigated as a potential application of this system. The activity and specific activity of lipase immobilized on alginate/bacterial cellulose beads were 2.6- and 3.8-fold higher, respectively, than that of lipase immobilized on cellulose beads. The alginate/bacterial cellulose nanocomposite beads prepared in this study have several potential applications in the biocatalytic, biomedical, and pharmaceutical fields because of their biocompatibility, biodegradability, high crystallinity, and large surface area.

Recent trends in bioethanol production from food processing byproducts

The widespread use of corn starch and sugarcane as sources of sugar for the production of ethanol via fermentation may negatively impact the use of farmland for production of food. Thus, alternative sources of fermentable sugars, particularly from lignocellulosic sources, have been extensively investigated. Another source of fermentable sugars with substantial potential for ethanol production is the waste from the food growing and processing industry. Reviewed here is the use of waste from potato processing, molasses from processing of sugar beets into sugar, whey from cheese production, byproducts of rice and coffee bean processing, and other food processing wastes as sugar sources for fermentation to ethanol. Specific topics discussed include the organisms used for fermentation, strategies, such as co-culturing and cell immobilization, used to improve the fermentation process, and the use of genetic engineering to improve the performance of ethanol producing fermenters.

Drug release kinetics from carboxymethylcellulose-bacterial cellulose composite films

Composite films of sodium carboxymethyl cellulose and bacterial cellulose (NaCMC-BC) cross-linked with citric acid (CA) were prepared by solution casting method. Ibuprofen sodium salt (IbuNa) has been used to study the mechanism of drug release from composite films. Surface morphology was investigated by scanning electron microscopy (SEM) and proved that the BC content influences the aspect of the films. Fourier transformed infrared spectroscopy (FTIR) revealed specific peaks in IR spectra of composite films which sustain that NaCMC was cross-linked with CA. Starting from swelling observations, the release kinetic of IbuNa was described using a model which neglects the volume expansion due to polymer swelling and which considers non-linear diffusion coefficients for drug and solvent. The IbuNa release is also influenced by BC content, the drug release rate was decreasing with the increase of BC content.

Current Trends in Bioethanol Production by Saccharomyces cerevisiae: Substrate, Inhibitor Reduction, Growth Variables, Coculture, and Immobilization

Bioethanol is one of the most commonly used biofuels in transportation sector to reduce greenhouse gases. S. cerevisiae is the most employed yeast for ethanol production at industrial level though ethanol is produced by an array of other yeasts, bacteria, and fungi. This paper reviews the current and nonmolecular trends in ethanol production using S. cerevisiae. Ethanol has been produced from wide range of substrates such as molasses, starch based substrate, sweet sorghum cane extract, lignocellulose, and other wastes. The inhibitors in lignocellulosic hydrolysates can be reduced by repeated sequential fermentation, treatment with reducing agents and activated charcoal, overliming, anion exchanger, evaporation, enzymatic treatment with peroxidase and laccase, in situ detoxification by fermenting microbes, and different extraction methods. Coculturing S. cerevisiae with other yeasts or microbes is targeted to optimize ethanol production, shorten fermentation time, and reduce process cost. Immobilization of yeast cells has been considered as potential alternative for enhancing ethanol productivity, because immobilizing yeasts reduce risk of contamination, make the separation of cell mass from the bulk liquid easy, retain stability of cell activities, minimize production costs, enable biocatalyst recycling, reduce fermentation time, and protect the cells from inhibitors. The effects of growth variables of the yeast and supplementation of external nitrogen sources on ethanol optimization are also reviewed.