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Bacterial nanocellulose: a multipurpose natural and renewable polymer

Cellulose is the earth’s dominant biopolymer, most abundant, inexpensive and readily available carbohydrate polymer traditionally extracted from plants or their wastes, and is of tremendous economic importance globally. It is a hard task to obtain cellulose from the complex matrices in which cellulose participates to form a though, intercalated plant network with other biopolymers like lignin, pectin, and hemicellulose. Strong acids, alkali, or particular solvents are required to break down this complex plant matrix, which makes these methods inconvenient for environmental and economic reasons. Bacterial nanocellulose (BNC), an exopolysaccharide resulted as a secondary product from kombucha production by fermentation of tea broth with a symbiotic culture of acetic acid bacteria and yeast (SCOBY). BNC is one of the most intensively studied biopolymers at the moment due to its appealing properties like fine network structure, high tensile strength, high surface area, chemical stability, hydrophilicity, crystallinity, transparency, biocompatibility, magnetic and electric susceptibility, proton conductivity, rich surface chemistry, and availability. It has unique structural and mechanical properties, can be obtained in higher purity, and exhibits a higher degree of polymerization and crystallinity index as compared to plant cellulose. It also has the higher water holding capacity (WHC), and water release rate (WRR) than that of plant cellulose, making it more suitable raw material for producing high fidelity acoustic speakers, high-quality paper, and dessert foods. In this study, BNC produced, separated and purified from kombucha was evaluated and characterized by employing Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The yield and properties of BNC produced were investigated after 14 days of fermentation in currant tea sweetened with sucrose (60 to 120 g/L) and Hestrin-Schramm (HS) based media containing glucose, maltose, fructose or glycerol as carbon sources. The highest BNC yield was obtained using sucrose and glucose, 300 g/L and 151 g/L, respectively. The thickness and yield of BC increased with fermentation time and correspondingly with the increase of surface area and depth of media up to 144%. Obtained results showed that the sample had a higher percentage of amorphous regions than crystalline regions. Findings from this study suggest that the yield of BNC depends on many factors that need to be optimized to achieve maximum yield. Results of investigations offer significant improvements the yield of BNC, simplicity in operation, cost efficiency and green aspects, avoiding toxic catalysts and minimizing the generation of waste.

bacterial nanocellulose production, kombucha fermentation, morphology, physical properties

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