Occurrence of Cellulose-Producing Gluconacetobacter spp. in Fruit Samples and Kombucha Tea, and Production of the Biopolymer

Cellulose producing bacteria were isolated from fruit samples and kombucha tea (a fermented beverage) using CuSO4 solution in modified Watanabe and Yamanaka medium to inhibit yeasts and molds. Six bacterial strains showing cellulose production were isolated and identified by 16S rRNA gene sequencing as Gluconacetobacter xylinus strain DFBT, Ga. xylinus strain dfr-1, Gluconobacter oxydans strain dfr-2, G. oxydans strain dfr-3, Acetobacter orientalis strain dfr-4, and Gluconacetobacter intermedius strain dfr-5. All the cellulose-producing bacteria were checked for the cellulose yield. A potent cellulose-producing bacterium, i.e., Ga. xylinus strain DFBT based on yield (cellulose yield 5.6 g/L) was selected for further studies. Cellulose was also produced in non-conventional media such as pineapple juice medium and hydrolysed corn starch medium. A very high yield of 9.1 g/L cellulose was obtained in pineapple juice medium. Fourier transform infrared spectrometer (FT-IR) analysis of the bacterial cellulose showed the characteristic peaks. Soft cellulose with a very high water holding capacity was produced using limited aeration. Scanning electron microscopy (SEM) was used to analyze the surface characteristics of normal bacterial cellulose and soft cellulose. The structural analysis of the polymer was performed using C-13 solid-state nuclear magnetic resonance (NMR). More interfibrillar space was observed in the case of soft cellulose as compared to normal cellulose. This soft cellulose can find potential applications in the food industry as it can be swallowed easily without chewing.