Recent advancements in development and application of microbial cellulose in food and non-food systems

Abstract

Microbial cellulose is a fermented form of very pure cellulose with a fibrous structure. The media rich in glucose or other carbon sources are fermented by bacteria to produce microbial cellulose. The bacteria use the carbon to produce cellulose, which grows as a dense, gel-like mat on the surface of the medium. The product was then collected, cleaned, and reused in various ways. The properties of microbial cellulose, such as water holding capacity, gas permeability, and ability to form a flexible, transparent film make it intriguing for food applications. Non-digestible microbial cellulose has been shown to improve digestive health and may have further advantages. It is also very absorbent, making it a great option for use in wound dressings. The review discusses the generation of microbial cellulose and several potential applications of microbial cellulose in fields including pharmacy, biology, materials research, and the food industry.

Introduction

Cellulose, a complex, fibrous, and water-insoluble polysaccharide, is essential for maintaining the stability of the structure of plant cell walls. Cellulose is a fiber component of plant cell walls found in fruits, vegetables, and other plant-based meals and is one of the most abundant biomaterials (Kimbonguila et al., 2019). Although some microorganisms can also manufacture it, plants typically synthesize it. Like starch, cellulose is a homopolymer of glucose found chiefly in tree bark and plant leaves. Many living things, like the bacterium Acetobacter xylinum and forest trees, may manufacture cellulose. Numerous research on the cellulose product's structure and cellulose manufacture have employed the bacterium A. xylinum as a model system. Cellulose is tasteless, odorless, hydrophilic with a contact angle of 20 to 30 degrees, chiral, biodegradable, insoluble in water, and most organic solvents. It can be chemically broken down into its glucose components by treating it with concentrated mineral acids at high temperatures (Rusdi et al., 2022).

Microbial cellulose (MC) is an organic material with the chemical formula (C₆H₁₀O₅)_n created by specific bacterial species, such as A. xylinum (Corzo Salinas et al., 2021). Bacterial or MC differs from plant cellulose (PC) in that it is more robust, has more moldability, and can better hold onto water. It is distinguished by its high degree of purity (it does not contain hemicellulose, lignin, waxes, or pectin). In addition to medicinal uses, this material is employed in a wide range of commercial applications, such as textile, cosmetic, and culinary goods. The most prevalent cellulose polymer has a long, linear chain-like structure of (1,4) linked -D glucopyranosyl units formed into microfibrils with outstanding strength and stiffness. Nanocellulose refers to cellulosic materials with well-defined structural dimensions at the nanoscale. They could be bacterial nanocellulose, cellulose nanofibers, or cellulose nanocrystals (CNC or NCC) (Sharma et al., 2019). Nanocellulose has no harmful impacts on human health or the environment and is non-toxic, biodegradable, and biocompatible. They find many uses in thermo-reversible and tenable hydrogels, paper making, coating additives, food packaging, flexible screens, optically transparent films, lightweight materials for ballistic protection, and automobile windows due to their low thermal expansion coefficient, high aspect ratio, better tensile strength, and good mechanical and optical properties (cellulose). The most prevalent biopolymer on the earth's surface is cellulose (Ullah et al., 2016). The Hestrin and Sharma (HS) medium, which contains glucose, peptone, yeast extract, disodium phosphate, citric acid, and pH 6, is frequently employed in synthesizing MC. It is a medium with outstanding MC production. Still, the high-cost constraints of its industrial application, so it is crucial to explore ways to generate MC at a reduced production cost (Kumar et al., 2019). Each technique producing MC has a unique macroscopic morphology, microstructure, and MC characteristics. MC production can occur in bioreactors or a static, agitated environment (Wang et al., 2018). According to theories about the purpose of cellulose is synthesis by microbes, MC is either produced as a self-defense mechanism to shield bacteria from the harmful effects of UV light or to assist bacteria in floating at the air–liquid interface in order to obtain an adequate amount of oxygen (Azeredo et al., 2019). To adhere to the cells and protect them from severely unfavorable conditions like ultraviolet radiation, hydrostatic solid pressure, or any other environmental difficulties. It also assists in continuously exposing the aerobic atmosphere, which is necessary for fermentation (Laavanya et al., 2021).

Conductive MC by polyaniline was used as a bio-anode in microbial fuel cells. MC is a promising biomaterial because of its exceptional and distinctive characteristics, including high cellulose purity, mechanical strength, high crystallinity, and biodegradability. Due to its features, MC has potential uses in electronics, cosmetics, medicine, food, and related products (Andriani et al., 2020). Based on this, the objective of the review is to analyze the synthesis of MC, its chemical properties and reactions, and its prospective uses for both food and non-food products.

Mechanism of cellulose production

Cellulose is a linear extracellular polysaccharide. Bacteria, fungi, and algae are just a few of the microbes that can manufacture MC through a variety of synthetic processes. While fructose and galactose have also been converted to cellulose through other metabolic routes, glucose is the primary precursor (Pandit & Kumar, 2021). MC looks like a semi-transparent gel-like material made of microfibrils woven in a web-like pattern. Although glucose serves as the primary precursor for the creation of MC, a variety of other monomer sugars, such as fructose and galactose, can also be used in the process. In the bacterial body, monosaccharides undergo a sequence of enzyme activities that form cellulose chains. These chains emerge from the bacterial cell wall through pores, join via hydrogen bonding, form microfibre ribbons, and ultimately take the form of a net-shaped sheet structure (Pandit & Kumar, 2021). Processively polymerizing UDP-activated glucose, it is produced by membrane-embedded glycosyltransferases. Polymer production is connected to membrane translocation through a channel that the cellulose synthase creates. Prokaryotic synthases link the periplasm and the outer membrane by collaborating with different subunits, whereas eukaryotic cellulose synthases work in macromolecular complexes of multiple distinct enzyme isoforms. The inner membrane-associated MC synthase (Bcs)A and BcsB subunits in bacteria catalyze the production and translocation of cellulose. MC is thought to play a role in developing sessile bacterial populations, just like alginate and poly-1,6 N-acetylglucosamine (Kondo et al., 2022). The various cultures used for the production of MC and types of cellulose product are presented in Table 1.

Table 1.

Various cultures used for the production of Microbial cellulose and types of cellulose product

Sr. No	Microbial strain	Type (bacteria/yeast or mold)	Microbial characters	Type of cellulose
1	Acetobacter	Bacteria	Rod shape	Extracellular pellicle, ribbons
2	Agrobacterium	Bacteria	Rod shape	Short Fibrils
3	Gluconacetobacter	Bacteria	Rod shape	Not defined (ND)
4	Rhizobium	Bacteria	Rod shape	Short Fibrils
5	Achromobacter	Bacteria	Curved or hooked at one pole	Ribbons
6	Alcaligenes	Bacteria	Rod shape	Fibrils
7	Aerobacter	Bacteria	Rod shape	Fibrils
8	Azotobacter	Bacteria	The oval or spherical shape	ND
9	Salmonella	Bacteria	Rod shape	ND
10	Escherichia	Bacteria	Rod shape	ND
11	Sarcina	Bacteria	Cocci	Amorphous
12	Pseudomonas	Bacteria	Rod shape	Non-distinct

Plant cells are primarily composed of cellulose, which also serves as their structural support. Cellulose is a polysaccharide composed of several glucose molecules that are chemically bonded together in a repeating pattern. The glucose units in cellulose are linked together through beta-1,4-glycosidic linkages. This indicates that the glucose molecules are connected in a specific orientation, where the first carbon (C1) of one glucose molecule is bonded to the fourth carbon (C4) of the subsequent glucose molecule, with an oxygen bridge connecting them. Considering cellulose, the terms "alpha" and "beta" pertain to the precise arrangement of the hydroxyl (-OH) group connected to the first carbon (C1) of the glucose molecule. In the alpha (α) configuration, the hydroxyl (-OH) group connected to the first carbon (C1) of the glucose molecule positioned below the plane of the ring formed by the glucose structure. In the β form, the hydroxyl (-OH) group connected to the first carbon (C1) of the glucose molecule positioned above the plane of the ring formed by the glucose structure. Understanding the structural features and functions of cellulose requires recognising the significance of differentiating between its alpha and beta forms. This distinction is particularly important in comprehending its mechanical strength and its interactions within plant cell walls. Cellulose consists of a linear β-(1,4)-linked D-glucopyranosyl units with DP ranging from 500 to 14,000. This results in the formation of long, linear chains where each glucose unit is flipped 180 degrees with respect to the next unit, leading to a more elongated structure. The configuration facilitates strong hydrogen bonding between adjacent chains, hence enhancing the strength and rigidity of cellulose fibres in plants. Cellulose, found in the cell walls of plants, forms microfibrils consisting of linear chains of glucose molecules. The microfibrils possess distinct regions that contribute to the overall structure. Within regions of crystallinity, the cellulose chains exhibit a high degree of organisation and alignment, running parallel to one another. This arrangement facilitates maximum hydrogen bonding among the chains, resulting in strong and rigid structures. Crystalline areas exhibit greater resistance to degradation and provide a substantial contribution to the strength of cellulose fibres. Para-crystalline regions exhibit a certain level of organisation; however, they lack the perfect arrangement found in crystalline zones. Amorphous regions in the cellulose structure are characterised by a lack of well-defined alignment and organisation. The cellulose chains in the amorphous regions exhibit a higher degree of random orientation, leading to a reduced number of hydrogen bonds formed between the cellulose molecules. The susceptibility to degradation is higher in these locations, and they exhibit less rigidity in comparison to the crystalline sections. The presence of these zones, namely crystalline, para-crystalline, and amorphous, collectively influences the overall characteristics of cellulose. The presence of crystalline sections in cellulose imparts strength and stiffness, whereas the less structured regions enhance flexibility and facilitate interactions with other molecules, such as water absorption or chemical alterations. (Navarro et al., 2019). The enzyme cellulose synthase is the main enzyme that produces cellulose by binding several glucose molecules together. Systematically, it is known as UDP-glucose:(1 → 4)-β-D-glucan 4-β-D-glucosyltransferase, a membrane protein catalyzes the direct polymerization of glucose from the substrate UDP-glucose into a cellulose product. Numerous bacteria, Dictyostelium discoideum, and higher plants all have cellulose synthase genes that have been discovered. The four genes, cesA, cesB, cesC, and cesD, each code for a particular protein, make up the BCS operons, which control how much cellulose is produced by bacteria. These proteins control how glucan chains are transported over the exterior cell barrier as well as how they are synthesized intracellularly. Bacterial cells and cell-free enzyme systems can manufacture MC in aerobic and anaerobic conditions (Kamal et al., 2022). Conserved residues in cellulose synthases from various organisms have been found by analyzing the predicted protein sequences.

MC production requires a culture medium rich in glucose and other nutrients, which results in high production costs and restricts the possible uses of MC. Hestrin and Schramm (HS) medium is the commonly used culture medium for MC synthesis, which contains glucose and other nutrients (Salari et al., 2019). In low-oxygen environments, genetically modified strains have also boosted MC production, making it possible to use static culture for cellulose manufacture. It has been suggested that (Kondo et al., 2022) adding organic acids, sugars, and ethanol to the growth medium will increase MC production. The general cultivation method resulted in the production of the MC pellicles (Ariff et al., 2023; Tsouko et al., 2023).

The Komagataeibacter genus (former) is home to the majority of MC producers. Due to its ability to metabolize a variety of carbon/nitrogen sources, Gluconacetobacter is a popular choice for MC synthesis (Azeredo et al., 2019). A few factors influencing MC yield and characteristics are the bacterial strain utilized, the composition of the culture media, and the operating conditions used during the cultivation process. The spectrum of potential applications is influenced by the physical characteristics and material morphology of the resultant material, which are determined by the culture medium's composition (Azeredo et al., 2019). The conventional cellulose utilization is shown in Fig. 1 (Tomme et al., 1995). There are four enzymatically catalyzed steps in the synthesis of MC (a) The conversion of glucose to glucose-6-phosphate, (b) glucose-6-phosphate is isomerized to glucose-1-phosphate, (c) Uridine diphosphate glucose (UDP–glucose) is produced from glucose-1-phosphate, (d) finally, glucan chains are synthesized from UDP–glucose (Naomi et al., 2020). The pathway for the synthesis of MC is presented in Fig. 2.

Fig. 1.

Utilization of cellulose by conventional pathway for energy

Fig. 2.

Pathway for synthesis of Microbial cellulose

Chemical properties and reactions of cellulose

Each cellulose link has three hydroxyl groups, which display the polyatomic alcohol features. As a result, all chemical reactions involving alcohols, such as the production of alkaline cellulose and the esters and ethers of organic and inorganic acids, exhibit this property. Anhydro glucose units with dominant hydroxyl groups comprise most of the cellulose's chemical structure, which is now well understood. Each anhydrous glucose unit is connected to the next by 1–4 glycosidic bonds; because of unique chemical configurations, cellulose is an entirely linear homopolysaccharide with a significant capacity for intra- and intermolecular hydrogen bonding. Rewetting reduces the chemical and physical characteristics of fibers (cellulose) (Yu et al., 2018). Because of changes in the fundamental structure during swelling and decreased fiber bonding potential, the absorption and strength properties of rewetted fibers consistently decline (Sulaeva et al., 2020). The properties, production, and applications of MC are presented in Table 2.

Table 2.

Properties of microbial cellulose in comparison with plant cellulose

Physicochemical properties	Plant cellulose	Microbial cellulose
Colour	White	White
The smell	Odourless	Odourless
Taste	No taste	No taste
Aggregate state (at 20 °C and an atmospheric pressure of 1 ATM.)	Solid	Solid/Gel in the presence of water
Hydrophilicity	Hydrophilic	Hydrophilic
Density (at 20 °C and an atmospheric pressure of 1 ATM.) (g/cm3)	1,52–1,54	ND
Thermal degradation temperature	315 °C	190 °C
The molar mass of monomer link cellulose C6H10O5, g/mol	162,1406	ND
Melting point, °C	260–270	145–160 °C

In plants, cellulose is a structural carbohydrate. Cellulose fibers are embedded in a polysaccharide matrix to support plant cell walls. Cellulose fibers are dispersed in a lignin matrix, where the cellulose works as reinforcing bars, supporting plant stems and wood (Helmenstine, 2019). Cellulose is the most significant structural element of plant cell walls. Plant cell walls include the carbohydrate cellulose. 40% to 50% of a dry plant is made of cellulose. The most ubiquitous macromolecule and organic compound on the earth, cellulose helps plants stay rigid and upright. The main component of many industrial products, cellulose, is made up of glucose units. As it affects the shape of the plant and enables the plant to grow erect, cellulose gives plant cells their rigidity. Additionally, it connects cells to form tissues. Additionally, it plays a part in cell division, proliferation, and signaling. Plants' stems, branches, and leaves are made of cellulose, which gives them strength. Fungi and algae also have cellulose in their cell walls, but bacteria hardly ever do. The genera of bacteria, including Agrobacterium, Saccharomyces, and Rhizobium, exhibit the intriguing ability to convert sugars into cellulose.

Similar in chemical composition to cellulose generated from plants, MC is produced by Acetobacter xylinum, which also makes cellulose II (thermodynamically stable polymer). Acetobacter xylinum converts several carbon molecules into cellulose, the end product of carbon metabolism, with an efficiency of about 50% (Lupașcu et al., 2022). MC has superior qualities as compared to PC. MC, for instance, is highly pure because it is free of lignin, hemicellulose, and other contaminants. As a result, its purifying procedure is easy. Additionally, it has outstanding biocompatibility, with little inflammatory reaction and little chance of rejection (Pang et al., 2020). In terms of structure, MC is made up of ribbon-like cellulose nanofibers. It is distinguished by its high purity, high degree of polymerization, and high crystallinity. Plant cell walls contain complex organic polymers such as lignin, hemicellulose, and pectin. These complex organic polymers surround cellulose fibers and provide flexibility to the cell wall. In order to separate the cellulose fibers during the purification process, lignin, hemicellulose, and pectin are often removed by various treatments. Unlike PC, MC is free of these substances. Bacterial cells, leftover nutrients, and metabolic byproducts are present in the raw pellicle extracted after microbial fermentation. These components may be removed from the MC network to provide a highly pure product. Compared to PC, MC typically has a higher level of polymerization (Zhong, 2020). There are crystalline and non-crystalline areas in the structure of MC, just like in PC The high crystallinity of MC, which consists primarily of crystalline areas with brief periods of disorder, is likely responsible for the material's remarkable mechanical strength and flexibility. MC has superior and varied physical, mechanical, and biological characteristics compared to PC. It is around 100 times thinner than PC fibres and has superior qualities that make it useful in food, cosmetics, biomedicine, and drug delivery. MC's involvement in food, cosmetics, and medication delivery systems as a functional additive, formulation stabilizer, platform for biocatalysts, and component (Zhang et al., 2021).

Microfibrils 100 times smaller than those seen in PC make up the cellulose that the bacteria create. It is also utilized as a PC alternative to avoid wasting resources. To create carboxymethyl cellulose (CMC), for instance, fungal tea cellulose has been used. Structural comparison of MC with PC reveals that MC is finer and more unbranched, which positively impacts several attributes, including greater surface area, higher water absorption, and better mechanical strength in wet conditions (Laavanya et al., 2021). High purity and molecular similarity to PC (i.e., C₆ H₁₀ O₅) n) are two characteristics of the ribbon-like MC structure. Both its crystallinity and water-holding capacity are high (over 100 times its dry weight). However, the actual crystallinity values of MC and PC can change depending on the analytical technique, such as by X-ray diffraction (XRD) peak height, peak deconvolution, amorphous subtraction, or C4 peak separation using NMR (Kamal et al., 2022). The MC (MC) was present as thick, 25 mm-thick white gelatinous pellicles on the surface of a liquid media. The microbe that produced this MC membrane (MCM) was initially known as Bacterium xylinum, afterward known as Acetobacter xylinum (A. xylinum), and is now known as Gluconacetobacter xylinus (G. xylinus) (Marghaki et al., 2020).

In addition to replacing lipids, MC has been shown to have several other health advantages due to its role as a dietary fiber. MC has been found to have much more hypolipidemic and hypocholesterolaemia effects in hamsters than in PC (Andriani et al., 2020). According to 13 C nuclear magnetic resonance (NMR) data, MC displayed an amorphous peak at C-4 and C-6, and its crystallinity index was 75.4. MC had a 19-fold greater capacity to absorb water than PC. A pellicle formed upon inoculation on a standing culture primarily consists of MC. In addition to providing the bacteria access to the oxygen-rich air-media interface, MC also serves as a UV light protection device.

Compared to cellulose derived from plants, MC, a pure exocellular polymer made by microbes, exhibits numerous superior qualities, such as a high capacity to store water, a large surface area, rheological properties, and biocompatibility. MC has been shown to be a promising low-calorie bulking ingredient for the development of novel and fiber-rich functional foods in a variety of forms, such as powder gelatinous or shred foams, which facilitates its application in the food industry. MC also has the ability to suspend, thicken, hold water, stabilize, bulk up, and add fluidity (Lin et al., 2020). Due to its soft texture and delicate fibers, MC's qualities make it excellent for formulation stabilizer, thickening, scouring, and exfoliating without harming the skin (Gregory et al., 2021).

Food application of MC

Conventional application

MC, acknowledged as a dietary fiber, has received the stamp of approval from the US Food and Drug Administration (FDA) as a food ingredient deemed "Generally Regarded As Safe" (GRAS). It could be used as a classic dessert, a low-cholesterol diet, vegetarian meat, a beverage ingredient, or food packaging. The primary uses for MC are raw materials for food items and desserts. MC is created by static fermentation and has a jelly-like pellicle (Zhong, 2020).

The ancient Chinese were the first to notice the biosynthesis of MC while making kombucha tea, a fermented liquid produced by a symbiotic colony of yeast and bacteria with acetic acid embedded within a cellulose mat that forms at the liquid's surface. A byproduct of the fermentation of Kombucha tea is SCOBY (Symbiotic Culture of Bacteria and Yeast), a biofilm of cellulose that contains a symbiotic culture of bacteria and yeast (Leonarski et al., 2021). Numerous studies on the kombucha SCOBY are being conducted to explore all the potential uses for this cellulose as a viable raw material in industries like food technology, the creation of biomaterials, the fashion and textile industries, and environmental biotechnology. The main purpose of MC, a static fermented product with a jelly-like pellicle, is as a raw material for dessert and cuisine ingredients. MC, a hydrocolloid-containing product of agitated fermentation, is used in beverages as a thickener and suspending agent (Zhong, 2020). Compared to PC, MC has a greater capacity for storing water and exchanging cations, and it also significantly lowers serum lipids and cholesterol. Thus, MC can be used to create fat-free products, low in cholesterol products with another advantage of reduced calorie intake. Kombucha, the popular name for fermented beverages made by a group of microorganisms using the Camellia sinensis or other caffeine-rich plants as a starting point, is a method of growing bacteria-containing cellulose. Due to its deliciousness and positive effects on human health, this beverage is enjoyed all over the world (da Silva et al., 2021).

Due to its indigestibility by humans, MC's allure as a food ingredient makes it a popular choice for dietetic cuisine. It enhances the mouthfeel and promotes intestinal transit (like other dietary fibers). MC is a multipurpose ingredient since it improves food texture while also making them lower in calories and cholesterol, and hence healthier (Marghaki et al., 2020). MC has long been used as the primary ingredient in the Philippines' nata-de-coco dessert, a chewy, juicy, and luscious treat made primarily from MC grown from coconut water that has been fortified with a variety of carbohydrates and amino acids, cubed, and then covered in sugar syrup (H. M. C. Azeredo et al., 2019). Similar products, such as nata-de-pina (made with pineapple juice), may be created using modifications to the technique, with the culture medium source controlling the flavors. Nata products can be added as texture-rich cubes to liquids, yoghurts, and jellies in addition to being eaten on their own (Karuni et al., 2021). MC can load different nutrients and even substances with medicinal properties due to its very porous microstructure; MC is a suitable material for laxative effects and a low-cholesterol diet due to its excellent water retention and ion exchange capabilities respectively (Zhong, 2020). The conventional food application of MC is shown in Fig. 3.

Fig. 3.

Conventional food application

Novel application

MC can be applied in a variety of processes, including thickening, gelling, and water binding. It has been shown to maintain beverage viscosity following heat treatment, increase the gel strength of tofu, and stop cocoa from precipitating in chocolate beverages (Lin et al. 2020). MC has been used in a variety of food applications, including ice creams, confectionary goods, imitation meat for vegetarians, and as an emulsion stabilizer or carrier for the immobilization of probiotics and enzymes (Fig. 3) (Lappa et al., 2019). MC enhances the value of pasty meals by reducing their stickiness and serving as a filler for the reinforcement of delicate food hydrogels as well as a heat-stable suspending agent. Tofu is a product of coagulating and pressing soy milk, and MC (0.2–0.3%) considerably improves the texture and stiffness of the tofu's gel. Kamaboko, processed Japanese seafood, now has better stiffness and brittleness, virtually eradicating springiness (Apriyana et al., 2020).

In meatballs, MC has been utilized to replace fat. On the one hand, using 20% MC (replacing the product's added fat) had major significant impacts, like cooking losses and softening, which hurt consumer acceptability of the product. Due to its improved network structure, the MC-added surimi product's fat substitution increased the gel's strength and water-holding capacity. However, adding 10% MC (which reduced the meatballs' extra fat content by half) led to sensory outcomes and shelf stability that were comparable to the control (regular meatballs) (Oliveira et al., 2021). There are several types of bacteria and yeast on the cellulose zoogleal mat. A variety of acetic acid bacteria are present, including Bacterium gluconicum, Acetobacter xylium, Acetobacter xylinoides, Acetobacter pasteurianus, and Acetobacter aceti. The microflora also consist of several yeast strains that mainly includes Zygosaccharomyces rouxii, Zygosaccharomyces bailii, Brettanomyces bruxellensis, Kloeckera apiculata, Saccharomyces cerevisiae, and Schizosaccharomyces pombe strains (Laavanya et al., 2021). MC combined with Monascus extract from a naturally occurring red-colored mould can be used to cook vegetarian meat. In addition to the numerous benefits of MC dietary fibers, vegetarian meat has a cholesterol-lowering impact (Azeredo, 2018). MC is a naturally occurring substance produced by microbial fermentation that is extremely biocompatible.

Non-food application

Gluconacetobacter xylinus, a surface-dwelling, oxygen-dependent bacteria, produces a biofilm at the air–water interface called MC. A highly connected MC nanoporous network that can be directly applied to the biomedical industry because the native pellicle's structure is similar to collagen’s is the result of such biofilm formation. MC has been effectively implanted and has not resulted in the production of fibrotic tissue. This characteristic makes the naturally occurring MC structure a prime choice for synthetic skin products, bandages, surface-patterned implants, and blood vessels (Rühs et al., 2018).

MC exhibits new physicochemical characteristics, such as high crystallinity, a network structure made of nanofibers, purity, and degree of polymerization. Better tensile strength, better biocompatibility, resistance to chemical and heat shock, lack of toxicity, selective porosity, and renewable properties are a few advantages of MC, which have been used in a variety of biomedical applications, including the development of artificial blood vessels, skin, cornea, cartilage, and bone. MC is a medical product in skin wound healing and dressing; MC is a suitable biomaterial for wound dressings due to its low cytotoxicity, swelling ratio, physicochemical qualities, and mechanical properties (Swingler et al., 2021), an important advantage of the MC dressing includes its transparency, which allows for continuous clinical observation of the healing progress, immediate pain relief, good and close adhesion to the wound bed, a good barrier against infection, ease of wound inspection, faster healing, improved exudates retention, or reduced time of treatment, as well as reduced costs (Ahmed et al., 2020). The use of fragmented MC for paper production is promising, and Mitsubishi Paper Mills Co. has created test pieces of flexure-durable papers and high filler-content papers that are perfect for banknote papers and bible papers. Fancy papers contain only a small amount of MC (Fillat et al., 2018). MC serves as a food packer to ensure the products' safety and lengthen their shelf lives. Active MC-based packaging methods use antimicrobial chemicals, ethylene, oxygen scavengers, and moisture and taint removers (Xu et al., 2021). It has been demonstrated that MC is biocompatible with biological tissues. Additionally, its porous structure and mechanical qualities are excellent for biomedical applications. This is because the MC's porous structure resembles the skin’s extracellular matrix (Sajjad et al., 2019).

A new form of biodegradable and highly specialized materials for environmental applications can be generated using MC, a biopolymer created during bacterial fermentation. The 3D nanofibrillar network and intriguing structure of MC make it an attractive candidate for technologies for wastewater treatment and reuse (Urbina et al., 2021). The treatment of arterial and venous ulcers, diabetic ulcers, pressure ulcers, burns, post-operative surgical wounds, skin grafts, skin graft sites, abrasions, and lacerations are all conditions that are commonly treated with MC-based wound dressings because they perform more effectively than this conventional gauze or synthetic materials (Portela et al., 2019). MC is a good option for topical and transdermal medication administration and dermal cosmetics applications (Mbituyimana et al., 2021). Similarly, MC is an ideal agent for facial masks, contact lenses, and medicine delivery to wounds with ease of wound examination due to its transparency and high permeability to fluids and gases (Liu et al., 2019).

MC monofilament's Young's modulus can reach 114 GPa. Therefore, based on its superior mechanical attributes, it has been developed into food packaging film, shielding film, and tympanic membrane perforation treatment (Gorgieva, 2020). Due to their biodegradability, low toxicity, and skin-hydrating properties, MC facial masks are highly sought-after cosmetic treatments for dry skin. On a single treatment, the MC masks considerably increased the moisture content of the skin compared to moist towels; the MC mask can be used to make the skin more moisturized (Bilgi et al., 2021). Face masks made of MC have a better ability to contain water than nonwoven cellulose or silk masks and provide a more pleasant sensation of coolness and smoothness because of their 3D nanoscale reticulated network (Zhong, 2020). Multifunctional nanocomposite materials from MC are being employed in new fields of biomedical research, including wound dressing systems, drug delivery systems, bioengineering, cardiovascular system, ophthalmology and skeletal systems, cartilage and endodontics, and tissue engineering scaffolds, Due to its innate ability to speed up the healing process, MC is frequently employed in the regenerative skin medicine and wound care industries. Because MC's fibril network has a lot of empty spaces, it can be reinforced with medications and modifiers like nanoparticles to increase its antifungal, antibacterial, tissue regeneration, and biocompatible capabilities. MC-zinc oxide and MC-titanium dioxide nanocomposites recently demonstrated outstanding antibacterial and wound healing properties. Capsule shells made of MC were created for immediate and sustained released oral and transdermal drug delivery applications (Hussain et al., 2019). In a fuel cell, MC was employed to assemble the membrane electrodes. MC was also used as a substrate for microbial cell culture and solar cell growth for possible photovoltaic uses (Vilela et al., 2020). Agricultural corn stalk pre-hydrolysis liquid containing acetic acid was used as a low-cost carbon source for the environmentally friendly production of MC (Moradi et al., 2021).

Numerous biomedical applications, including artificial skin, dental implants, drug delivery, hemostatic materials, vascular grafts, scaffolds for tissue engineering, biosensors, and diagnosis, provide considerable potential for MC (Fig. 4). All biomedical applications require that MC be of excellent purity and biocompatibility. Due to its superior moisture management, high wet tensile strength, permeability, flexibility, semi-transparent nature, and excellent biocompatibility, MC is initially used as a wound dressing. Under the trade names Nanoderm™, Bionext, Membracell, Suprasorb® X, Biofill®, Gengiflex®, and Xcell®, a variety of MC-based wound dressings are sold (Song & Kim, 2019). Using MC as a medication delivery system for anti-cancer treatment, researchers discovered that MC could enhance the regulated release of medicines. Vaccination is administered orally and is kept active in the stomach by employing MC as a drug carrier. Other MC-based medicinal products include prosthetic tympanic membranes, contact lenses, and vascular grafts (Chung et al., 2022). The bio-medical applications of MC are shown in Fig. 4.

Fig. 4.

Bio-medical applications of Microbial cellulose

Future scope

Over the past few years, the distinctive qualities of MC have received much attention. Since it is essential to reduce the cost of culture medium formulation to make the large-scale production of MC profitable, MC is made using unusual, low-cost fermentation raw ingredients. In many instances, the MC production values obtained through these alternate mediums were higher than those obtained by the conventional, significantly more expensive methods. MC does not have any inherent anti-aging, whitening, and cleansing, limiting its applications in the cosmetology area. Therefore, it is critical to functionalize MC with active ingredients to maximize its potential in the cosmetics industry (Mbituyimana et al., 2021). Consumers now have higher expectations for businesses and their products as they are more aware of environmental issues, including climate change, resource scarcity, labor exploitation, and water resource contamination. In this sense, using MC and other natural resources in industrial processes is a form of biotechnology (da Silva et al., 2021). Pharmaceutical and biotechnology firms began to be interested in the potential uses of MC as a wound treatment method. The structural arrangement of MC fibers, which provides them with mechanical qualities, the absence of contaminating polymers, and a higher crystallinity are the causes of the structural differences between MC and cellulose derived from plants that can be seen. Because of the cultural media, making MC is an expensive process. Waste from polysaccharide fermentation, industrial leftovers, steep corn liquor, and thin stillage are among the waste items that can be used to produce MC. The sustainability of MC production could be increased while pollution levels are decreased by using various waste items from industrial and agricultural processes (Ul-Islam et al., 2020). There is a significant market demand for MC goods in their dry form and a growing commercial interest in MC for the cosmetics and personal care market segments. Dry goods can really be transported and stored more efficiently than hydrated goods since they take up less space, are less likely to be contaminated, and sometimes have a longer shelf life (Martins et al., 2021).

MC refers to a refined variant of cellulose that is produced by microorganisms. It exhibits a superior nanofibrous structure when compared to cellulose derived from plants. The morphological alterations result in enhanced aesthetic attributes as well as improved mechanical, crystalline, and biological characteristics. The process of regeneration significantly alters the original properties of native cellulose and produces a range of intermediate forms with diverse structural and physicochemical characteristics. MC is synthesized by microorganisms in an ecologically sustainable way, exhibiting biodegradability and environmental friendliness. In addition, the use of MC in textile production allows for the application of dyes, resulting in an aesthetically pleasing surface that aligns with the socio-environmental considerations of the sector. An example of a successful application is the use of a MC membrane as a replacement for small-diameter blood arteries and as a tool for wound healing in cases with severe skin damage. The nonwoven ribbons composed of MC microfibrils possess a striking similarity to the natural extracellular matrix. Consequently, these ribbons have potential as a structural foundation for the fabrication of various tissue-engineered structures. MC has emerged as a significant biopolymer, attracting considerable attention across several disciplines in the past few years because to its diverse range of conventional and innovative uses. These applications include but are not limited to kombucha tea, Nata de coco, wound healing, face masks, and packaging. However, the application of the MC remains underutilized in several aspects. MC is a promising contender for several tissue-engineered and medicinal uses. Based on the review's discussion of potential uses for MC, it becomes clear that the substance has found a wide range of applications in both the food and non-food industries.

Author contributions

Conceptualization, writing–original draft, writing review and editing: SSOP; Conceptualization, writing–original draft, writing review and editing, supervision: BYK, KKD, RS; writing review and editing: AHD.

Funding

Not applicable.

Declarations

Conflict of interest

The authors have no conflicts of interest to declare.