Degradation of formaldehyde in packed-bed bioreactor by kissiris-immobilized Ralstonia eutropha

Abstract

The ability of the Ralstonia eutropha cells to utilize formaldehyde (FA) as the only source of carbon and energy was studied in the kissiris-immobilized cell bioreactor (KICB) in batch-recirculation and continuous modes of operation. In batch-recirculation experiments, the test bacterium could tolerate concentrations of FA up to 1,400 mg/L at 30°C and aeration rate equal to 0.75 vvm (rS = 7.25 mg/L/h, qS = 0.019 gFA/gcell/h). However, further increase of initial FA concentration resulted in degradation reaction of FA to stop at 1,600 mg/L. Results of continuous mode experiments showed that the biodegradation performance of the KICB was dependent on both feed flow rate and inlet FA concentration parameters. The optimum feed flow rate which corresponded to the highest biodegradation rate (rS = 240.3 mg/L/h) was observed at Q = 18 mL/min when KICB did not operate under the external mass transfer limiting regime. Substrate inhibition kinetics (Edwards and Luong equations) were used to describe the experimental specific degradation rates data. According to the Luong model, the values of the maximum specific degradation rate (qmax), half-saturation coefficient (KS), the maximum allowable FA concentration (Sm), and the shape factor (n) were 0.178 gFA/gcell/h, 250.9 mg/L, 1,600 mg/L, and 1.86, respectively.