Biosynthesis of bacterial cellulose nanofibrils in black tea media by a symbiotic culture of bacteria and yeast isolated from commercial kombucha beverage

Abstract

Abstract Bacterial cellulose has drawn the attention for its unique properties and applications including; medicine, pharmacy, food, agricultural, textile and electronics. The present study focused on the production of bacterial cellulose nanofibrils (BCNF) from black tea as cost effective alternative medium in addition to study the effect of gamma radiation on BCNF properties. A symbiotic culture of bacteria and yeast (SCOBY) were isolated from commercial Kombucha beverage and used for production of BCNF on Hestrin- Schramm (HS), black tea (BT) and modified BT media. BCNF was purified (0.5 N NaOH) and quantified by dry weight, yield and productivity determination. Characterization and effect of gamma radiation (5–25 kGy) on BCNF were studied using Scanning Electron Microscope (SEM), Fourier transform infrared (FTIR) and X-Ray Diffraction (XRD). Bacterial and yeast isolates were identified as Acinetobacter lowffii and Candida krusei (synonymous: Pichia kudriavzevii), respectively. The highest BCNF production was achieved using BT medium with 0.2 and 6.0% tea and sucrose concentrations (4.77 and 4.61g/l, respectively). Supplementation of BT medium with 1% ethanol,0.27% Na2HPO4 and 0.5% yeast extract individually, enhanced the BCNF production (7.85, 6.84 and 5.73 g/l), respectively. FTIR and XRD spectrum of BCNF from sugared water (SW), HS and BT showed similar structure with high purity. Gamma irradiation have no effect on the BCNF structure while showed increasing in its crystallinity with increasing the doses (5–25 kGy). SEM illustrated the morphology of microbial culture and its symbiotic relationship in addition to the ultrafine structure of non-irradiated and irradiated BCNF.