Physiological aspects of immobilised Aspergillus niger cells producing polymethylgalacturonase

Abstract

Conidia of Aspergillus niger 26 spores were immobilised in 3% Ca-alginate beads and some intrinsic kinetic characteristics including growth, polymethylgalacturonase (PMG) production and specific oxygen uptake rates determined. A negative correlation between the specific growth rate and specific PMG production indicated a non-growth-associated enzyme formation. Immobilisation did not change the model of PMG synthesis even in repeated replacement cultures and leads under certain conditions to an enhanced PMG production. The immobilised mycelium was concentrated at the surface layer of the alginate beads and the fungal hyphae could not be found in the central part of the gel. The dense growth of the mycelia on the outer bead surface allowed the formation of a fur-like mycelium coat, which had a large surface for oxygen uptake. This growth behaviour is a reason why the effectiveness factor increased during incubation from 0.54 to 0.93.