Effects of substrate particle size and alkaline pretreatment on protein enrichment by Neurospora sitophila

The effects of solid-substrate characteristics (particle size, pretreatment conditions) on microbial biomass protein production and cellulose utilization by Neurospora sitophila (ATCC 36935) were investigated. Corn stover ground to various particle size fractions (< 1 mm, 1–2 mm, 2–3 mm) was the test substrate. The pretreatment utilized sodium hydroxide (0–0.15 kg/kg substrate, at 121°C for 30 min) for delignification and hemicellulose removal. Cellulose utilization by the fungus and the crude protein production increased with decreasing substrate particle size and with increasing sodium hydroxide concentration in the pretreatment step. Under the best conditions, using < 1 mm substrate particles treated with 0.15 kg NaOH/kg substrate, approx. 90% of the initial cellulose was consumed by the fungus and the crude protein concentration in the dry product exceeded 50% by weight.