Abstract
Bacterial nanocellulose (BNC) is a unique product of microbiological synthesis, having a lot of applications among which the most important is biomedicine. Objective complexities in scaling up the biosynthesis of BNC are associated with the nature of microbial producers for which BNC is not the target metabolite, therefore biosynthesis lasts long, with the BNC yield being small. Thus, the BNC scale-up problem has not yet been overcome. Here we performed biosynthesis of three scaled sheets of BNC (each having a surface area of 29,400 cm2, a container volume of 441 L, and a nutrient medium volume of 260 L and characterized them. The static biosynthesis of BNC in a semisynthetic nutrient medium was scaled up using the Medusomyces gisevii Sa-12 symbiotic culture. The experiment was run in duplicate. The BNC pellicle was removed once from the nutrient medium in the first experiment and twice in the second experiment, in which case the inoculum and glucose were not additionally added to the medium. The resultant BNC sheets were characterized by scanning electron microscopy, capillary viscosimetry, infrared spectroscopy, thermomechanical and thermogravimetric analyses. When the nutrient medium was scaled up from 0.1 to 260 L, the elastic modulus of BNC samples increased tenfold and the degree of polymerization 2.5-fold. Besides, we demonstrated that scaled BNC sheets could be removed at least twice from one volume of the nutrient medium, with the yield and quality of BNC remaining the same. Consequently, the world’s largest BNC sheets 210 cm long and 140 cm wide, having a surface area of 29,400 cm2 each (weighing 16.24 to 17.04 kg), have been obtained in which an adult with burns or vast wounds can easily be wrapped. The resultant sheets exhibit a typical architecture of cellulosic fibers that form a spatial 3D structure which refers to individual and extremely important characteristics of BNC. Here we thus demonstrated the scale-up of biosynthesis of BNC with improved properties, and this result was achieved by using the symbiotic culture.
Highlights
The scaled cultivation resulted in three pearl-white bacterial nanocellulose (BNC) sheets
We demonstrated that two BNC sheets could be taken out of one volume of the nutrient medium
How the biosynthesis of the second BNC sheet can be explained if the initial glucose concentration was 5.9 g/L? As is well known, cellulose fibrils are synthesized by microbial producers through the formation of intermediates: glucose 6-phosphate is isomerized to glucose 1-phosphate which reacts with uridine triphosphate (UTP), forming uridine-50 -diphosphate-α-D-glucose (UDP-glucose)
Summary
Worldwide interest in bacterial nanocellulose (BNC) continues unabated and is due to its properties such as a 3D porous structure with nanosized fibers, high purity, high crystallinity and water-holding capacity, considerable mechanical strength and elasticity, high degree of polymerization, and excellent biocompatibility [1]. It is because of these properties that BNC has found a wide spectrum of applications, ranging from the food industry to medicine. BNC can be used either as a component of food products or as a food packaging material [2]. BNC is demanded most of all in medicine to improve health and save human lives. BNC is used as artificial skin, vascular grafts, dental implants, artificial bones and cartilages, a sorbent for targeted delivery of drugs, proteins and hormones, as well as for sorption and pinpoint use of stem cells [3]
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