Characterization of bacterial nanocellulose cultivated on polyethylene terephthalate (PET) monomers via raman and fourier transform infrared spectroscopy.

The potential of Komagataeibacter (K.) sucrofermentans to valorize polyethylene terephthalate (PET) monomers - ethylene glycol (EG) & disodium terephthalate (Na2-TPA) - and glucose into bacterial nanocellulose (BNC) membranes was investigated using Raman and Fourier transform infrared (FT-IR) spectroscopy. Gravimetric analysis indicated higher BNC yields for K. sucrofermentans nurtured with EG (2.54 g L− 1) compared to pure glucose (2.00 g L− 1) and TPA (1.54 g L− 1). Scanning Electron Microscopy (SEM) images showed that BNC derived from glucose had a dense interconnected fibrillar matrix with uniform porosity, whereas EG and TPA displayed a network structure with less uniform fiber packing. The Segal approach from X-ray diffraction (XRD) showed a lower crystallinity for EG (CrI 62.3%) and substantially lower for TPA (CrI of 18%) than for the commonly known values of glucose (CrI around 70%). Raman spectra of BNC showed that bands between 1050 cm− 1 and 1150 cm− 1 were shifted towards lower wavenumbers compared to AVICEL cellulose, indicating an increased strain on the glycosidic linkages. The Raman spectrum of BNC with TPA as a feedstock showed additional bands at 629, 861, 1125, and 1425 cm− 1 indicating that not all TPA was valorized. FT-IR spectra of the BNC with EG and TPA as feedstocks showed minor transmission and bands at 447, 560, 687, 730, 862, plus between 1500 and 1600 cm− 1 that are typically assigned to PET monomers. The absorption ratio A ~ 1430/ A ~ 897, a measure of crystallinity, gave the values glucose = 1.02, TPA = 0.63, EG = 0.53 showing that glucose as a feedstock produced the highest BNC crystallinity. In the case of glucose and EG, well-structured cellulose membranes were produced, whereas for TPA a composite membrane was produced, paving the way to use PET monomers as a feedstock for biodegradable BNC production.