Solid state fermentation of lignocellulose containing plant residues withSporotrichum pulverulentum Nov. andDichomitus squalens (Karst.) Reid.

Summary

The fermentation profiles ofSporotrichum pulverulentum andDichomitus squalens showed distinct differences.D. squalens digested the substrate more slowly thanSporotrichum pulverulentum. The relative degradation rates of total organic matter and lignin also differed considerably.

Whereas withS. pulverulentum the ratio was about the same throughout the whole observation period, withDichomitus squalens it altered in favour of lignin degradation.

WithSporotrichum pulverulentum an optimum digestion in vitro of 40%–50% was achieved after 20 days of incubation. WithDichomitus squalens the best value (about 60%) was reached after 30 days of incubation. Increasing incubation temperatures enhanced the degradation of the substrate.

As found with wheat straw, all other substrates tested (straw of rape and barley, glumes of rice) were degraded more slowly byDichomitus squalens than bySporotrichum pulverulentum. The degradation rates for oak, spruce and beech sawdust were very low compared to those for straw.

Small amounts of ammonium nitrate stimulated the degradation of straw byS. pulverulentum whereas higher concentrations had an inhibitory effect. The optimum water content of the substrate, measured by decomposition of total organic matter and lignin and by in vitro digestibility, was between 50 and 100 ml of water/25 g substrate. Higher and lower water contents had an unfavourable effect.

Varying the pore size of the substrate by using milled straw of defined particle size had no influence on the 6 parameters tested under the given experimental conditions.

The best method to supress potential competitors was to heat the substrate to 90°C for 24 h.