Chemical modifications of kombucha SCOBY bacterial cellulose films by citrate and carbamate cross-linking

Bacterial cellulose films prepared by purification of kombucha SCOBY pellicle was chemically modified in an attempt to improve the properties of the films. Two different approaches were tested including cross-linking with citric acid and carbamate groups. Citric acid cross-linking resulted a decrease in tensile strength. Whereas carbamate cross-linking with hexamethylene, toluene, methylene di-p-phenyl and 4,4′-methylene-bis(cyclohexyl) linking groups by treatments with corresponding diisocyanates resulted improvements in tensile strength, thermal stability and reduction in water retention properties in kombucha bacterial cellulose films. The highest improvement in tensile strength was observed in toluene group cross-linked films showing a tensile strength of 51.3 ± 5.4 MPa, in comparison to untreated films of 25.3 ± 1.8 MPa. Carbamate cross-linking increased the bacterial cellulose decomposition onset temperatures by 38–100 °C in comparison to untreated bacterial cellulose films and the highest increase of 100 °C was observed with cross-coupling through methylene di-p-phenyl groups