From bread waste to bacterial cellulose nanostructures: Development of a novel rotating disk bioreactor

A novel rotating disk bioreactor was designed and manufactured to produce bacterial cellulose (BC) using Komagataeibacter rhaeticus. Optimal conditions-45 % disk submersion, mechanically etched disks with rotation speed of 20 rpm, spacing of 35 mm and 0.5 vvm air supply- achieved a yield of 1020 mg BC/disk with commercial glucose. Bread waste enzymatic hydrolysates improved BC production by 133.3 %, highlighting the potential of waste valorization in sustainable biopolymer production. BC was further modified into nanostructures (BNCs) using H₂SO₄ (BNC1), H₂SO₄- HCl (BNC2), and cellulases (BNC3). FTIR spectra of BC and BNCs revealed typical cellulose vibration-bands while dynamic light scattering showed bimodal or trimodal size distributions (hydrodynamic radiuses of 60-2969 nm). TEM imaging of BNC1 and BNC2 demonstrated rodlike/needlelike nanostructure with widths of 33.1 ± 18.2 nm and 24.8 ± 14.2 nm respectively. BNC3 presented buddle of flat ribbons (width of 56.4 ± 26.3 nm). The maximum degradation temperature of BC (295 °C) decreased after its ex-situ modification (271-294 °C). The enhanced production and tailored structural modifications of BC highlight its potential for diverse applications in materials science. This transformative approach that integrates bread waste valorization and innovative bioreactor design paves the way for high-value advancements in biotechnology and environmental sustainability.