Novel airlift reactor fitting for hairy root cultures: developmental and performance studies

In vitro growth of Solanum chrysotrichum hairy roots was carried out in three different types of reactors: shake flasks, a glass-draught internal-loop 2-L basic design airlift reactor (BDR), and a novel modified mesh-draught with wire-helixes 2-L reactor (MR). In each of them, the growth patterns were different, as well as some of the dynamic parameters. The specific growth rates were 0.08, 0.067, and 0.112 d(-1) for shake flasks, BDR, and MR, respectively. In shake flasks and in the MR, growth followed first-order kinetics. In the MR without roots, superficial liquid velocity in the riser and downcomer ranged from 2.1 to 2.7 and 1.4 to 1.7 cm s(-1), respectively (nearly the same as the BDR values). After 42 days in culture, tissue density in the MR was twice that found in the BDR and about the same as that found in the shake flasks. At the tissue densities reached at 42 days, superficial liquid velocities in the MR and BDR downcomers were 4-5 and 7-8 times lower, and mixing times were 11 and 18 times longer than those observed without roots. Tissue densities measured at three points in the MR's downcomer and riser ranged from 10.21 to 12.17 and 4.94 to 5.24 gDW L(-1) respectively. Dynamic gas hold-up dropped faster when roots grew radially in the mesh-draught. In addition, root cultures were scaled-up in a 10-L MR reactor in which some geometric relations were maintained, such as the Q/V radio. Growth in 10-L MR followed first-order kinetics, but despite this, specific growth velocity was 0.09 d(-1) and overall tissue density diminished slightly with respect to that of the 2-L MR. Tissue inoculation, distribution, and harvest were more easily accomplished in the MRs.