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

Abstract

Structural and physicochemical properties of two types of bacterial cellulose (BC) produced by Komagateibacter sucrofermentans strain DSM 15973T after 7 days through either immobilized bacteria (solid inoculum) forming BCS7 or free bacteria (liquid inoculum) forming BCL7, 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 BCS7 compared to BCL7. BCL7 was generally proved to be superior to BCS7 regarding degree of purification, BC yield, overall higher porosity, water swell ability, and water holding capacity (WHC), exhibiting higher hydrophilicity. However, thermally resistant BCS7 reveals a 35% residual up to 800 ºC compared to BCL7 (15%) and prevailed in terms of water retention rate. Both water-treated BC7 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