Application of crude enzyme extracts produced in solid-state fermentation by Trichoderma harzianum on coffee waste for the hydrolysis of pretreated waste

Abstract

Residues from the coffee industry are an important source of organic matter to produce hydrolytic enzymes by solid-state fermentation (SSF) using filamentous fungi and Trichoderma harzianum. SSF was performed with sterilized (SR) and nonsterilized (nSR) residues with particle sizes between 1.68 mm and 2.37 mm. In the aqueous crude enzyme extracts from SSF-SR, a xylanase activity of 7.59 ± 1.18 IU/g dry of coffee residues mix was detected after 8 days, as well as CMCase activity, 3.4 ± 0.2 IU/g, after 6 days. In SSF-nSR, FPase activity, was 29.65 ± 3.14 IU/g, at 8 days of fermentation. Subsequently, SSF was carried out with pretreated residue with ultrasound-assisted aqueous extraction (SSF-pUAA) and with residues no-pretreatment; in both cases, a particle size between 1 mm-1.68 mm was used. The highest CMase activity with 9.4 ± 1.36 IU/g CRM was detected in the SSF-pUAA. Finally, the crude enzymatic extract obtained with buffer was used to hydrolyze residues treated by ultrasound-assisted organosolv testing different residue:enzyme extract ratios. In the best hydrolysis ratio (1:15), the highest presence of galactose was observed at 10.78 ± 0.84 mg/g, which can indicate hydrolysis, preferably of the hemicellulose present in the pretreated residues.