Bacterial nanocellulose-based hydrogel from Bacillus subtilis W7 for a sustainable adsorption of tetracycline from wastewater

The production of nanocellulose using microbes has been gained interest across wide range of industries due to its flexible characteristics and advantages as compared to plant cellulose. The most active producers of bacterial nanocellulose were acetobacteraceae. The present study was conducted with the aim to isolate and characterize bacterial nanocellulose for the production of nanocellulose based hydrogels for removal of tetracycline from wastewater. The bacterial nanocellulose producing bacterias were isolated and screened from Awash winery waste (Ethiopia) using Hestrin-Schramm media. Analysis of the 16S rRNA gene sequence revealed that the bacterial isolate W7 shows 98.12% similarity with Bacillus subtilis strain T13 and isolate W4 shows 99.93% similarity with Bacillus subtilis strain 9-1-2.The highest bacterial nanocellulose yield of 5.15 ± 0.13 g/L was obtained from bacterial isolate W7 in Hestrin-Schramm culture media and the yield was further improved to 5.88 ± 0.25 g/L by using molasses as a main carbon source. The bacterial nanocellulose hydrogel was synthesised from bacterial nanocellulose by using glutaraldehyde as cross-linking agent. The synthesised bacterial nanocellulose based-hydrogel was tested for its tetracycline removal efficiency using a batch adsorption method at different experimental conditions. The maximum adsorption capacity (q_e) and removal efficiency (R%) was observed in the experimental conditions of pH 7 (59.52 ± 1.3 mg/g and 59.52 ± 1.3%), 60min contact time(54.97 ± 0.57 mg/g and 54.97 ± 1.5%), 50 mg adsorbent dose (128.39 ± 1.3 mg/g and 64.19 ± 1.30%), and 50 mg/L adsorption concentration (75.24 ± 1.09 mg/g and 56.69 ± 0.9%). Pore-filling effect, hydrogen bonding, hydrophilic, electrostatic and π-π interactions attributed to the adsorption of tetracycline. The result indicated that cellulose from Bacillus subtilis strain W7 is a promising adsorbent for the removal of tetracycline from waste water.