Control of CO2 level within a certain range is one of the most important tasks in life support systems, such as spaceship and submarine. In order to control the membrane liquid evaporation into the gas phase for the hollow fiber contained carbonic anhydrase (CA) and its buffer membrane contactor (buffer-CA HFCLM), a poly(acrylic acid-co-acrylamide) (poly(AA-co-AM)) hydrogel showing biocompatibility is synthesized for the immobilization of CA. The hollow fiber contained hydrogel-CA membrane contactor (hydrogel-CA HFCLM) is then prepared for the comparison of operating stability and CO2 removal efficiency with that of buffer-CA HFCLM. The results show that the loss of the membrane liquid is alleviated while the water-rich ambience is still retained by holding the water molecule within the network of the hydrogel. The hydrogel-CA HFCLM in combining both advantages of CO2 facilitated transport using CA and the poly(AAco-AM) hydrogel as facilitators shows higher CO2 removal capability, reducing CO2 from 0.52 vol.% in the inlet feed gas to under 0.09% while the buffer-CA HFCLM only reducing CO2 to 0.32% under the same operating conditions. Consequently, as a safer and more reliable CO2 removal system, the hydrogel-CA HFCLM deserves to be further studied. (C) 2008 Elsevier B.V. All rights reserved.