Investigation of properties of bacterial cellulose for wound dressing applications

Abstract

Bacterial cellulose (BC), an exo-polysaccharide produced by Acetobacter xylinum, shows numerous properties such as purity, nano size, higher mechanical strength, absorbancy, crystallinity and mouldability than plant cellulose. Hence it exhibits number of applications in medical and industrial fields. In this study, Acetobacter xylinum species isolated from Kombucha, a mixed culture was identified and isolated by streak plate method, Gram staining, morphology and formation of HALO area on CaCO3 added differential media. It was confirmed by its ability to form pure cellulose in static fermentation. Optimum storing temperature of Acetobacter xylinum was found to be – 70 °C, retaining its activity and purity. In media optimization, control sample showed a dry yield of 1.08 g/l/cm2 at pH 5.0 which was comparable with the yields of BC in coconut water supplemented with different carbon and nitrogen sources. Chemical structure of BC fibrils biosynthesized in different media confirmed a structure similar to pure cellulose by FTIR spectroscopy and SEM confirmed nano size and network structure. Mechanical tests revealed increased tensile strain from 0.09 to 0.339, decreased tensile stress from 52.89 to 10.93 Nm-2 and Young’s modulus from 588.93 to 32.3 MPa when moisture content of BC was increased from 0 to 25 %. Fluid re-absorption in 24 hours decreased with increasing moisture content from 1342.83 % to 175.83 % and 919.72 % to 114.88 % in deionized water and saline respectively. Therefore dried BC could hold 7-8 times fluid capacity than wet BC. Mechanical test applied on dried (2-3 % moisture) and wet (25-30 % moisture) BC at swollen state in deionized water and saline at 24 hours confirmed Young’s modulus and fluid re-absorption tend to decrease with increasing moisture content. This study confirms coconut water by itself as a nutriently rich substrate for BC production. Further, investigations proved the ability to produce cellulose based biomaterial consisting nano-scale fibre structure with considerable strength as appropriate for wound dressing applications. Key words: bacterial cellulose, Acetobacter xylinum, coconut water, wound dressing