Cellulose is a biopolymer that can be produced by several species such as plants, algae and some bacterial genera such as Rococo’s (Tanskul et al., 2013), Acetobacter, Rhizobium, Agrobacterium, Aerobacter, Achromobacter, Azotobacter, Salmonella, Escherichia and Sarcina (Islam et al., 2017; Ullah et al., 2016).
First described in 1886 by Brown, bacterial cellulose (BC) proved to be a biopolymer of great interest for application in several industrial and medical areas, due to its structural characteristics, which prove to be advantageous in relation to plant cellulose (PC) (Cacicedo et al., 2016; Shah et al., 2013; Ul-Islam et al., 2012a). Although its structure is identical to that of PC, consisting of β-(1→4) glycosidic bonds, BC is devoid of lignin, pectin and hemicellulose, which gives it a high degree of purity(Kumar et al., 2019). A special emphasis has been given to the cellulose produced by bacteria of the Acetobacteraceae family mainly of the Gluconacetobacter (Cacicedo et al., 2016) genus, later named G. xylinus and G. hansenii, and currently classified in the genus Komagataeibacter (Yamada, 2014), using a variety of natural and synthetic culture media, with different carbon sources (Iguchi et al., 2000; Lazarini et al., 2018, 2016; Lustri et al., 2015; Shah et al., 2013; Ul-Islam et al., 2012b, 2012a)
Hydrated BC membranes have a high capacity for adsorption of different ionic and molecular species or even particle stabilization, as they have a highly hydrated structure of nanometric fibers forming a highly porous system (Eichhorn et al., 2010; Iguchi et al., 2000). Due to high mechanical resistance, hypoallergenicity, biocompatibility and high degree of liquid absorption(Lazarini et al., 2018, 2016), the BC are widely studied as controlled drug delivery systems, by our research group (de Oliveira Barud et al., 2016; Lazarini et al., 2018, 2016; Machado et al., 2018) and many international groups (Badshah et al., 2018; Fontes et al., 2017; Juncu et al., 2016; Mohd Amin et al., 2014; Negut et al., 2018; Treesuppharat et al., 2017; Ullah et al., 2016; Urbina et al., 2020).
The BC production can be performed using a static, agitated, or using a bioreactor fermentation method. In the static culture method, the BC is obtained in as a film at the air-liquid interface, promoting thinner three-dimensional network structures and excellent mechanical properties(Wang et al., 2019). In the agitated culture method, BC is produced in the form of fibrous granules or threads with a lower degree of polymerization, mechanical resistance, and crystallinity than the films formed in static fermentation. However, agitated culture is widely used for commercial purposes because it produces BC in less time, as well as possesses economic viability and desired applications (Shah et al., 2013), such as drug release (Wang et al., 2018). Bioreactor using method, which can employ both static and agitated cultures, being an alternative method classified in terms of the use of oxygen-enriched air, a rotating disc, or biofilm support, equipped with a rotating filter or a silicone membrane (Islam et al., 2017; Wang et al., 2018).
Czaja et al. (Czaja et al., 2004) proposed that the continuous shear force during agitation caused the cellulose ribbons to intertwine with each other to form the sphere-like structure.
BC membrane has widely acknowledged as biopolymer with large surface area and 3D nano-pores structure that promotes high capacity for absorbing liquids (Lin et al., 2013; Meng et al., 2019b). Compared with BC membranes, sphere-like BC (SBC) cultured under agitated conditions showed great advantages for adsorption due to its larger surface area (Diaz-Ramirez et al., 2021; Iguchi et al., 2000; Meng et al., 2019b).
Hoshi et al. (Hoshi et al., 2018) and Wang et al. (Wang et al., 2019) reported that the formation of SBC depends on the bacterial strain used, that is, not all species are capable of producing spheres in an agitated medium and the agitation speed promotes great interference in the formation of fiber networks. Thus, depending on the speed, obtaining more homogeneous spheres can be easily acquired, presenting perfect applicability for drug release.
Study, performed by Meng et al. (Meng et al., 2019a) using various bacterial culturing parameters were assessed with the goal of assembling uniform SBC which has advantages owing to its unique morphology and increased surface areas. The results showed that the uniform SBC was synthesized when the ratio of culture medium to flask volumes (M/F value) was kept at 50%, while the diameter of these uniform SBC could be adjusted by changing the agitation speed and flask volume.
Therefore, SBC could hold huge potential for many high value applications such as slow drug release (Abeer et al., 2014; Meng et al., 2019a). However, the control of properties shape, diameter, moisture content, adsorption ability, surface area and its uniformity of the SBC are a challenge to be overcome (Meng et al., 2019b).
In addition to different BC production methods, it is interesting to evaluate the effects of using different carbon sources for BC production (Fernandes et al., 2020). Several culture media are reported in the literature for the production of BC as Hestrin-Schramm (HS) (Hestrin and Schramm, 1954), Zhou (Z) (Zhou et al., 2007) and Yamanaka (Y) (Yamanaka et al., 1989). The BC production in this different culture media showed different dry mass yield and physical-chemical characteristics (Mohammadkazemi et al., 2015).
RIF, a semisynthetic antibiotic obtained from rifamycin (Sutradhar and Zaman 2021) which has bactericidal activity by inhibiting bacterial RNA polymerase and with capacity to penetrate through the biofilm (Alifano et al., 2014; Politano et al., 2013), is used as a first line treatment for tuberculosis, as well as in the treatment of other infectious diseases (Sutradhar and Zaman, 2021) and constitute one of the most potent and broad-spectrum antibiotics against others bacterial infection, as endocarditis caused by Gram-positive methicillin-susceptible or resistant Staphylococcus spp, pneumonia, particularly ventilator-associated, caused by S. aureus and Gram-negative bacilli such as Pseudomonas aeruginosa and Enterobacteriaceae and Acinetobacter spp. (Lee et al., 2017).
Conventional dosage forms for immediate local drug release, such as solutions, creams, ointments, gels and adhesives do not significantly interfere with the release of therapeutic agents. However, controlled and sustained release systems are products with advanced therapeutic performance, modulating the release and controlling the time and place in which the drugs are released (Carvalho et al., 2021). Thus, reservoir or matrix systems, where drugs are dispersed, contained in a nucleus, or fixed to the surface, have aroused interest (Carvalho et al., 2021, 2020) .
The present work had as aims the production and characterization of SBC, by K. hansenii ATCC 23769, using culture media with different compositions and concentrations of carbon and nitrogen sources (FRU, and MS1) compared to culture media already used in BC production (HS, Y, and Z) to study the influence on the physicochemical properties of the SBC produced and its possible relationship with the ability to retention and sustained release of the antibiotic RIF, a broad spectrum antibiotic, to future use in medicine. The obtained SBC were characterized by Field emission gun-scanning electron microscopy (FEG-SEM), Fourier transform spectroscopy (FTIR), X-ray diffraction (XRD) and Thermogravimetric and derived thermogravimetry (TGA/DTG) analysis, and the RIF sustained release capacity was evaluated by method and diffusion release kinetics by Franz cells.