In situ production of bacterial nanocellulose-activated carbon composites from pear juice industry wastewater by two new Komagataeibacter intermedius and Komagataeibacter xylinus isolates for heavy metal removal

Fruit juice industry generates a large amount of wastewater, which contains substantial waste activated carbon for juice turbidity removal. Due to the low concentrations of useful compounds in the wastewater, the cost for the extraction is extremely high. Two new bacterial nanocellulose (BNC) producing strains were isolated and identified. These strains produced 6.11 and 1.38 folds BNC from pear juice wastewater than from a conventional medium, respectively. BNC spontaneously encapsulated the suspended waste activated carbon particles during the fermentation, flocculating and collecting the particles without additional filtration or centrifugation processes. FE-SEM, FT-IR, TGA and XRD showed that the fiber diameters, chemical structure, thermal stability and crystallinity of BNC produced from the pear juice wastewater supernatant was similar to that from the conventional medium. FE-SEM revealed the three-dimensional package structure of the BNC-activated carbon composite, and XRD showed that the crystallinity of the composite was improved up to 86%. The BNC-activated carbon composite exhibited excellent adsorption performance towards heavy metals, and the maximum adsorption capacities for Cu2+ and Zn2+ were 20.71 mg/g and 76.92 mg/g within 60 min, respectively. Especially, compared to activated carbon, the adsorption capacity of the composite for Zn2+ was improved for 25.01%. This study utilized pear juice wastewater as an alternative medium to produce BNC at lower cost, and reduced BOD and wastewater treatment costs. Additionally, BNC encapsulated residual activated carbon left over in the wastewater, preventing dust pollution and enabling recycling of the waste activated carbon, and formed a composite with excellent heavy metal absorption capacity.