Improved lignocellulolytic enzyme production and antioxidant extraction using solid‐state fermentation of olive pomace mixed with winery waste

Abstract

Olive pomace is characterized by its low nutritional value and high phenolic content, which hinders its direct use as animal feed, fertilizer, or as a substrate in bioprocesses such as solid-state fermentation (SSF). A possible strategy for bioprocessing olive pomace by SSF is the mixture of olive mill wastes with other wastes produced in the same region, such as winery wastes. This may improve the production of bioactive compounds like enzymes and antioxidant phenolics. A simplex-centroid design was used to evaluate the use of olive mill and winery wastes alone or in combination as a substrate for SSF with Aspergillus niger and Aspergillus ibericus. Synergistic effects of combinations of crude olive pomace (COP), exhausted olive pomace (EOP), vine trimming shoots (VTS), and exhausted grape marc (EGM) were observed in the production of xylanases, cellulases, β-glucosidases, and in the variation in total phenolics and antioxidant activity of SFF extracts. A multiple response optimization was carried out, leading to the following optimal mixture of substrates: for A. niger, 23% (w/w) COP, 30% EGM, 33% VTS, 14% EOP; for A. ibericus, 30% EGM, 36% VTS, 34% EOP. The scale-up to tray bioreactor with optimal substrate made it possible to achieve the maximum xylanase, cellulase, and β-glucosidase production of 189.1 ± 26.7, 56.3 ± 2.1 and 10.9 ± 0.8 U/g, respectively. The antioxidant activity of fermented wastes was also improved 2.2-fold as compared with unfermented wastes. Thus, a combination of olive mill and winery wastes in SSF is a potential strategy to increase their value and to develop a circular strategy in these industries.

Comparative study on laccase activity of white rot fungi under submerged fermentation with different lignocellulosic wastes

“…Laccase activity depends on the type of fungal species or strains (Elisashvili et al 2008;Janusz et al 2015;An et al 2016aAn et al , 2018Han et al 2017Han et al , 2018Han et al , 2020. The secretion of laccase from fungi is affected by many factors, including the concentration, ratio and complexity of carbon and nitrogen sources, fermentation method, the type and concentration of metal ions, pH, temperature, co-cultivation of different fungi, and aromatic compounds (Stajić et al 2006;Elisashvili and Kachlishvili 2009;Janusz et al 2015;Metreveli et al 2017;Filipe et al 2019;Rajavat et al 2020).…”

A Comprehensive Review on Valorization of Agro-Food Industrial Residues by Solid-State Fermentation

“…AFIRs are a source of carbon, nitrogen, and nutrients and can therefore serve as solid carriers suitable for nutrient absorption and biomass growth [ 71 ]. Sometimes it is necessary to combine several different residues according to their chemical composition and to use such a mixture as a substrate to ensure sufficient nutrients for the optimal growth of microorganisms [ 11 ]. For SSF, the moisture content of the substrate is one of the most important operating parameters that affects the whole fermentation process.…”

“…The term filamentous fungi is used in contrast to yeasts, which are essentially unicellular fungi [ 8 ]. Filamentous fungi have great potential for the production of enzymes with high commercial value and/or many different valuable compounds by SSF as a result of enzymatic activity ( Table 3 ) [ 5 , 11 , 80 ].…”

“…The methods used for this are acid hydrolysis, which is environmentally unacceptable, and enzymatic hydrolysis, which is economically inconvenient [ 82 ]. On the other hand, phenolic compounds can be recovered by SSF, during which the microorganisms synthesize enzymes involved in breakdown of complex lignocellulosic material and release of these valuable compounds [ 11 ] ( Table 7 ).…”

“…According to numerous studies, SSF is one of the most suitable techniques to obtain the desired biomolecules from lignocellulosic materials. SSF has been extensively studied for potential applications in fuel, food, and feed, as well as in the chemical and pharmaceutical industries [ 11 , 12 ].…”