Comparative study and characterization of water-treated bacterial cellulose produced by solid or liquid inoculum of Komagateibacter sucrofermentans

Structural and physicochemical properties of two types of bacterial cellulose (BC) produced by Komagateibacter sucrofermentans strain DSM 15973 T after 7 days through either immobilized bacteria (solid inoculum) forming BCS 7 or free bacteria (liquid inoculum) forming BCL 7 , followed by a water-based purification as a chem-free alternative treatment, were investigated in this study. SEM verifies the effectiveness of the water-based purification on BC network and reveals the insufficient interfibrillar space of BCS 7 compared to BCL 7 . BCL 7 was generally proved to be superior to BCS 7 regarding degree of purification, BC yield, overall higher porosity, water swell ability, and water holding capacity (WHC), exhibiting higher hydrophilicity. However, thermally resistant BCS 7 reveals a 35% residual up to 800 ºC compared to BCL 7 (15%) and prevailed in terms of water retention rate. Both water-treated BC 7 were proved to be Iα-rich cellulose type and exhibited a typical type IV(a) isotherm with an H3 type of hysteresis loop, a similar pore distribution, crystallinity index (~77%), crystallite size (~7.5 cm), same levels of moisture content (~98%) and the same poor levels of rehydration after the freeze-drying process. During BCL kinetics in 20 mL of HS medium over 7 days, K . sucrofermentans , 2D pellicle formation was observed until day 3 and then 3D. The highest WHC was obtained on day 4 (116 g water/g cellulose), while the lowest on day 1 (19 g water/g cellulose). Overall, we discussed the preparation and characterization of two different BCs water-treated for purification as an eco-friendly alternative method towards functional, and sustainable application. Graphical Abstract