Comparison of hydrodynamic characteristics of Tulsion and Siran immobilised beads in a fluidised bed bioreactor

Abstract

The fluidised bed reactors are successfully utilised in various bioprocesses to produce high value products using immobilised cells and enzymes. The present work aims at evaluating hydrodynamic characteristics of a three phase fluidised bed bioreactor using Tulsion® A-1X MP, Tulsion® ADS-400 and Tulsion® ADS-800, polystyrene and polyacrylic based three types of free and immobilised cells solid carriers viz. and comparing their performance with Siran® SIKUG41 glass beads. The hydrodynamic parameters such as particle density (cells and beads), drag coefficient, minimum and maximum fluidisation velocity, particle settling velocity were estimated and compared in water and biological media (E2 and MSM) having varying rheological properties. The relationships between drag coefficient (CD)–Reynolds numbers (NRe), superficial liquid velocity (Uf)–void fraction(ε), expansion index(n)–NRe were obtained.The scanning electron microscopy studies revealed that the pore sizes of Tulsion beads (20–300 nm) were significantly smaller compared to Siran carriers (7–120 μm) leading to cells growth only on the surface of the beads. The biomass grown was estimated to be 0.75–1.2 mgCDW/g for Tulsion beads and 1.27–1.3 mgCDW/g for Siran beads with immobilised cells of P. putida and R. erythropolis, respectively. As per the results obtained, the reactor could be operated as a fluidised bed reactor with Tulsion and Siran beads at ε>0.4 and ε>0.6. The cell immobilised Tulsion and Siran beads have shown higher drag co-efficient in E2 and MSM media compared to water. The empirical correlations describing beads properties in falling (NRe) and fluidisation conditions in the form of Archimedes Number (NAr) were developed for ε in the range of 0.3–0.8 at 0.3<NRe<100 and 10<NAr<1000. The experimental data was statistically analysed using percentage mean relative error ± standard deviation and values were found to be at 95% confidence level.The evaluation of hydrodynamic characteristics of Tulsion and Siran carriers could be used to set up an operating window for three phase fluidised bed reactor for a bioprocess.