Performance of a solid-state immersion bioreactor for ligninolytic enzyme production: evaluation of different operational variables

Abstract

The production of ligninolytic enzymes by the white-rot fungus Phanerochaete chrysosporium BKM-F-1767 in a solid-state immersion bioreactor, employing cubes of nylon sponge as a support, was studied. Cultivation was carried out in both batch and continuous mode, and the effect of some operational variables (aeration level, pH) was investigated. Batch operation at an aeration level of 0.5 vvm led to maximum manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP) activities of 574 and 116 U l −1, respectively. The results were compared with those obtained at a higher aeration level (1 vvm), reported in a previous work, and it appeared that LiP productivity increased with aeration rate, while MnP was not significantly affected. Continuous operation showed much lower MnP activities (around 60 U l −1) and similar LiP activities (about 132 U l −1). However, in terms of productivity the difference between batch and continuous operation for MnP was less remarkable (239 and 150 U day −1, respectively), whereas LiP productivity was ten-fold higher in continuous operation than in batch mode. This could be attributed to the influence of operation pH on ligninolytic enzyme activities. The study of the kinetic characteristics of the biocatalysts supported this hypothesis.