Simplifying cellulase production by using environmental selection pressures and recycling substrate.

The production of crude cellulase in solid-state fermentation was simplified by using environmental selection pressures as an alternative to specialized strains and by re-using cellulose-to-ethanol fermentation substrate for cellulase production. The performance of wild strains of Trichoderma viride isolated from wheat and bark were found not to differ significantly from a 'cellulase-enhanced' strain of Trichoderma reesei. The filter paper activity of a strain of Aspergillus niger isolated in the laboratory was more than two times higher than the specialized T. reesei at 10 days. Activities of enrichment cultures obtained from compost and horse manure were more than double T. reesei after 10 days. Using the solid residue of previous simultaneous saccharification and fermentations of wheat straw to ethanol as substrate for cellulase production brought forward the onset of cellulase production and increased cellulase levels by 50%. The findings may help to simplify the on-site manufacture of cellulase for cellulose-to-ethanol conversion and reduce the amount of substrate required for the overall process.