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

Abstract

AbstractBacterial 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 were identified as Acinetobacterlowffii and Candida krusei, respectively. The symbiotic culture was 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). The highest BCNF production was achieved using BT medium with 0.2% tea and 6.0% commercial sugar (with dry weight 4.77–4.61 g/l and productivity 68.14% and 65.85%, 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 spectrum of BCNF from sugared water (SW), HS and BT showed similar structure with high purity. As a conclusion, gamma irradiation has no effect on the BCNF structure while showed different effects on its crystallinity index and size with the different doses. The changes in CrI were ranged between (17 and 23.5%), while the crystallinity size (Cs) was affected by gamma irradiation in a positive relationship where the crystalline size was decreased (33%) by exposure to 5 kGy then increased by increasing the dose of radiation reaching 25.7% at 25 kGy. SEM graphs showed the morphology of microbial culture and its symbiotic relationship in addition to the ultrafine structure of non-irradiated and irradiated BCNF. Graphical abstract