Simultaneous use of two-step fermentation and in-situ addition of chitosan oligosaccharide improving bacterial cellulose pellicle in the synthesis and various behaviors

Low productivity, high cost, and imbalance between swelling behavior and mechanical properties have limited extensive applications of bacterial cellulose pellicles (BCPs). To remove the drawbacks, two-step fermentation and in-situ modification of chitosan oligosaccharide (COS) were jointly used to improve the yield and mechanical properties of BCPs in this work. Based on the optimization of the culture components, a higher yield of 5.5 g/L, which is 1.9-fold of the control produced under static fermentation, was achieved at the agitation speed of 220 rpm for 3 h (total incubation time 10 d), revealing that high agitation speed in the early incubation can promote BCP production and shorten the production time. In-situ addition of COS can induce the self-assembly of bacterial nanofibers to form a compact network of BCPs through intermolecular H-bond instead of intramolecular H-bond, increasing the yield and mechanical properties. The yield increased to 10.8 g/L, approximately 2.0-fold that of the control. The Young's modulus, toughness, yield strength, and resilience of BCP were increased by 5.7, 2.9, 3.1, and 4.0 folds, respectively. COS modification significantly improved BCP production and balanced the swelling behavior and mechanical properties, which removed the drawbacks of BCP production to a certain degree and would promote an extensive application of BCPs.