Cell dispersion culture for the effective growth of Humicola insolens and efficient enzyme production.

ABSTRACT

We have developed a method for the effective growth of Humicola insolens conducive to efficient enzyme production using a medium containing glucose as a carbon source and extruded soybean meal (ExSBM) as a nitrogen source. Enzymes from Humicola sp. hold promise for biomass degradation, especially of lignocellulosic materials such as rice straw, wood chips, and corn stover. The strain, however, is hard to disperse, so an aggregated form of the fungus in a liquid culture media is generally used, resulting in poor control of the growth process and low enzyme production. This has greatly limited the utilization of this strain, in spite of its potential as an enzyme producer. Surprisingly, the addition of ExSBM improves mycelium dispersion and enzyme production of H. insolens, and the dispersive effect is applicable to other fungi such as Trichoderma and Aspergillus sp. In contrast, defatted soybean meal not treated with an extrusion process has little effect on mycelium cohesion. It therefore appears that the specific three-dimensional structure of ExSBM arising from the extrusion process provides a favorable environment for cell growth, since the composition of ExSBM and soybean meal is essentially identical. The optimum medium for cell dispersion culture essentially consisted of 5% glucose and 0.3% ExSBM.