Continuous hydrogen production by immobilized Enterobacter cloacae IIT-BT 08 using lignocellulosic materials as solid matrices

Abstract

A process was developed for continuous hydrogen production using immobilized Enterobacter cloacae IIT-BT 08 on environmentally friendly lignocellulosic solid matrices. Among the three lignocellulosic carriers used, SM-C (coir) was found to be the best in terms of cell retention (0.44 g dry cell/g dry carrier), packing density (100 g/liter reactor volume), cell loading (44 g dry cell/liter reactor volume) and hydrogen production rate (62 mmol/liter h). Gas hold-up was a major problem in tubular bioreactor with immobilized cells. The tapered and rhomboid bioreactors gave better performance in terms of both the rate of hydrogen production and the gas hold up. The gas hold-up was reduced by 67% using the rhomboid bioreactor as compared to tubular one. The maximum hydrogen production rate achieved was 75.6 mmol/liter h at a dilution rate of 0.93 h −1 and recirculation ratio of 6.4. The substrate conversion efficiency was increased by 15% at these conditions as compared to the system with no recycling. There was no substrate inhibition for hydrogen production up to 1.0% glucose concentration. The μ max and k s for immobilized cells were 1.25 h −1 and 9.31 g/liter respectively. The maximum rate of hydrogen production was found to be 2.1 times higher than that of batch system. The process was found more efficient as compared to other continuous hydrogen production processes using packed bed reactor.