Production, optimization and membrane diffusion studies of nanocellulose obtained from gluconacetobacter sp. bczm 1

Abstract

Bacterial nanocellulose (BNC) has displayed significant advantages over cellulose obtained from plants due to the absence of lignin, hemicellulose, pectin and other contaminating materials of animal origin. Hence, it possesses a high degree of purity, crystallinity index, and biocompatibility. In this study, nanocellulose-producing bacteria were isolated from the environmental samples and screened for their ability to produce nanocellulose. The best among the selected bacteria were identified and characterised using 16S rRNA gene sequences analysis. Physicochemical factors affecting BNC production were identified using One-Factor-At-a-Time (OFAT). Statistical optimization of the BNC production was carried out using Central Composite Design (CCD). Purification of the BNC was achieved using 0.1 M NaOH at 80 °C. The BNC dried film was characterised to determine its morphological, structural, chemical and thermal properties. Furthermore, biomedical application of BNC for transdermal delivery of crocin as a model drug using vertical Franz cells diffusion was determined and presented. The isolated bacterium was able to produce nanocellulose on the surface of the culture medium under static condition at 30 °C. Maximum concentration of 4 g/L of dried BNC was obtained at the end of the fermentation. The bacterium was identified as Gluconacetobacter sp. BCZM 1 by 16S RNA gene sequencing method using universal 27F and 1492R primers. Based on OFAT study, the pH, temperature, incubation time, and inoculum size were the significant factors affecting BNC production by the bacterium. CCD analysis conducted on the significant factors showed optimum condition for BNC production with a maximum BNC concentration of 6.7 g/L. The regression model of the ANOVA was found to be significant with p<0.0001 and R2 value of 0.9963. Characterization of the dried BNC membranes based on Fourier transformed infrared (FTIR) spectrum showed strong absorption peaks at 3335.36 and 2901.40 cm-1 representing band signature for pure nanocellulose. Scanning electron microscopy (SEM) revealed its morphological characteristics as an interwoven network structure. Thermogravimetric (TG) analysis had confirmed the BNC produced was thermally stable with degradation temperature above 340 °C. Analysis on BNC-crocin film showed a uniform distribution of the crocin into the BNC membranes. Dissolution studies on the BNC-crocin film displayed significant release of crocin (80-90 %) into the phosphate buffer solution within 40 minutes. Diffusion studies conducted with Franz cells showed that the incorporation of crocin into the BNC membrane provided a slow release pattern with an average flux of 0.53 µg cm-2 min-1. Moreover, the production and purification steps adopted had displayed significant influence on BNC unique properties. The high swelling ratio of 33.47 for BNC dry film had indicated a high water absorbing capacity as an important quality for wound dressing materials. The release profile and simple preparation and incorporation of drug – loaded (BNC-crocin) membranes clearly indicated the potentials of using BNC membranes for transdermal application of the active compound. The findings of the current research have revealed the potential of local bacteria for the efficient production of BNC as a value added product with wider biotechnological potential and suitable for biomedical applications. This will further offer a robust platform for future direction in the area of research and innovations.