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

Abstract

Abstract The potential of Komagataeibacter (K.) sucrofermentans to valorize polyethylene terephthalate (PET) monomers - ethylene glycol (EG) & disodium terephthalate (Na 2 -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.