Simultaneous production of lignocellulolytic enzymes and extraction of antioxidant compounds by solid-state fermentation of agro-industrial wastes

Abstract

In recent years, the interest to find alternative extraction methods has increased. Extraction of natural phenolics by enzymes produced during solid-state fermentation (SSF) is a useful and novel technique environmentally friendly. On the other hand, agro-industrial wastes are an excellent source of natural antioxidants as phenolics. The aim of the work was to evaluate the increase of antioxidant compounds extraction from agro-industrial wastes after SSF and to relate it to the production of lignocellulolytic enzymes. Several filamentous fungi were evaluated as candidates to increase the extraction of antioxidant compounds by solid-state fermentation of wineries, olive mill and brewery wastes. Fermented and unfermented agro-industrial wastes were extracted with water and lignocellulolytic enzymes, total phenolic compounds and antioxidant activity were determined in the extract. The maximum xylanase and cellulase activities were achieved by A. ibericus strains using brewer´s spent grain (BSG) as substrate and ranged from 300 to 313 U xylanase/g and 51-62 U cellulase/g. The best producer of β-glucosidase was A. niger CECT2088 using BSG as substrate (94 ± 4 U/g). The results of extraction of phenolic compounds revealed a higher extraction by SSF in olive mill wastes followed by winery wastes. In the same form, the maximum increase of antioxidant activity was achieved by SSF of exhausted olive pomace by Rhizopus oryzae MUM 10.260, increasing 12.9-fold in relation to unfermented waste. In addition, the production of enzymes, the extraction of phenolic compounds and the increase of antioxidant activity were related by principal component analysis. The first component grouped the BSG along with maximum enzymes production, the second component related positively the production of enzymes and the extraction of phenolic compounds and the increase of antioxidant activity. SSF proved to be an innovative environmentally friendly process that can improve the extraction of antioxidant compounds and simultaneously to produce lignocellulolytic enzymes from different agro-industrial wastes.

Optimization of Extraction Conditions to Improve Phenolic Content and In Vitro Antioxidant Activity in Craft Brewers’ Spent Grain Using Response Surface Methodology (RSM)

“…This positive correlation has also been reported by previous authors in wheat grains [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. However, ABTS was not significantly correlated with DPPH (see Table 3 ), which is agreement with results reported by Zhang et al [ 30 ], but is not consistent with results by Socaci et al [ 9 ].…”

“…Todaro et al [ 28 ] observed that the increase in the liquid/solid ratio only improved the yield for phenols (anthocyanins) in the case of acidified methanol, but not for tartaric and malic acids aqueous solutions. In contrast, some authors observed that TPC increased as the solid/liquid ratio increased from 1:10 to 1:50 (g/mL) in fruit extracts, though organic solvents were used instead of water [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Ryu et al [ 29 ] did not observe a significant effect of the solid/liquid ratio when applying water extraction in black soy beans.…”

“…In addition, water is a polar solvent and it is suitable for extraction of polar compounds as phenols [ 6 ]. Water has been used as an alternative for the recovery of phenolic compounds from potato, apple pomace [ 11 ], and from fermented BSG [ 12 ].…”

Optimization of Protease and Amylase Production by Rhizopus oryzae Cultivated on Bread Waste Using Solid-State Fermentation

“…Solid-state fermentation (SSF), an environmentally friendly technique, which uses solid substrates at low moisture levels, requires suitable solid substrate among agroindustrial materials [20]. Various raw materials are used for SSF, for example, winery and brewery waste, olive mill waste, sunflower cake, sugarcane bagasse, fruit's peels and pulps, cereal brans, and BW [21][22][23][24][25]. In this process, microorganisms grow and produce a wide variety of products such as mushrooms [26], aroma [21,27], microbial oil [28,29], preservatives like fumaric acid [30,31], enzymatic production of wax esters [32], and enzymes [14,27], thus reducing the cost of production, as reported by these studies.…”

Biodegradation potential of indigenous litter dwelling ligninolytic fungi on agricultural wastes

“…The enzymes were extracted from fermented and unfermented solid substrates according to the procedure of Leite et al (2019) with slight modification. The decomposed substrate (10 g) was suspended in 50 mL of sodium acetate buffer (50 mM pH 5.0) and gently shaken for 30 min at 150 rpm.…”