Enhancing the Bioconversion of Winery and Olive Mill Waste Mixtures into Lignocellulolytic Enzymes and Animal Feed byAspergillus uvarumUsing 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 MUM 08.01. For that, two factorial designs (3(2)) were first planned to optimize substrate composition, temperature, and initial moisture level. Subsequently, the kinectics of cellulolytic enzyme 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.

Ultrasounds pretreatment of olive pomace to improve xylanase and cellulase production by solid-state fermentation

“…The enzyme activities achieved by SSF with low cost nutrients (cellulase activity: 9.99 ± 1.39 U/g; xylanase activity: 19.44 ± 3.85 U/g) were lower than the activities achieved using commercial nutrients. Salgado et al (2015) observed a positive effect of urea and vinasses as nutrient supplement in SSF carried out with mixtures of olive pomace, exhausted grape marc and vine trimming shoots.…”

“…According to Giannoutsou et al (2012) this slight increase may be the result of the degradation of polyphenols to smaller phenolic compounds that may be an indication that the microorganism could use the specific substrate for its growth. Salgado et al (2015) also studied the course of the compounds over fermentation time and proved the depletion of the sugars, the increase of the proteins percentage from 8.47% to 17.98% after 6 days of fermentation and the degradation of phenol compounds, obtaining 28.32% reduction of phenols after 10 days of fermentation. The decrease in activity with increasing incubation time may be due to the production of by products resulting from microbial metabolism, as well as nutrient depletion, inhibiting fungal growth and enzyme formation (Shafique et al, 2009).…”

“…The use of olive pomace as solid substrate for cellulase and xylanase production was barely studied. Only in a preview own studies were identified their production after SSF (Salgado et al, 2014b(Salgado et al, , 2015 The results were analysed by one-way ANOVA followed by a multiple comparison test, Tukey's Multiple Comparison Test. The differences observed between the cellulases and xylanases activities for the three fungi on EOP and COP were statistically significant (P-value < 0.0001), but differences in xylanase activities were not significant between A. uvarum on EOP and A. ibericus on EOP.…”

“…After this, the activity decreased, maybe due to proteolysis. Salgado et al (2015) refer that low proteolytic activity can be an advantage when developing SSF processes, it may avoid inactivation of other secreted enzymes and benefit the accumulation of those in the substrate, improving production yields. The maximum cellulases activity (35 ± 5 U/g solid subtract) was achieved after 11 days.…”

“…organic load, presence of antimicrobial compounds such phenols and lipids, low pH value and low nutrients concentration (Morillo et al, 2009). These barriers can be overcome in biotechnology processes by mixing with other wastes (Salgado et al, 2014a(Salgado et al, , 2015Oliveira et al, 2016) or by pre-treatments (Gianico et al, 2013).…”