Enhancing the bioconversion of winery and olive mill waste mixtures into lignocellulolytic enzymes and animal feed by Aspergillus uvarum using a packed-bed bioreactor

Abstract

Wineries and olive oil industries are dominant agro-industrial activities in southern European regions. Olive pomace, exhausted grape marc and vine shoot trimmings are lignocellulosic residues generated by these industries, which could be valued biotechnologically. In the present work these residues were used as substrate to produce cellulases and xylanases through solid-state fermentation using Aspergillus uvarum. For that, two factorial designs (32) were first planned to optimize substrate composition, temperature and initial moisture level. Subsequently, the kinectics of cellulolytic enzymes production, fungal growth and fermented solid were characterized, Finally, the process was performed in a packed-bed bioreactor. The results showed that cellulase activity improved with the optimization processes, reaching 33.56 U/g, and with the packed-bed bioreactor aeration of 0.2 L/min, reaching 38.51 U/g. The composition of fermented solids indicated their potential use for animal feed because cellulose, hemicellulose, lignin and phenolic compounds were partially degraded 28.08, 10.78, 13.3 and 28.32% respectively, crude protein was increased from 8.47% to 17.08%, and, the mineral contents meet the requirements of main livestock.