Enhancing Antioxidants Extraction from Agro-Industrial By-Products by Enzymatic Treatment

Abstract

Nowadays, agro-industrial by-products are of increasing interest as a source of antioxidant compounds. Thus, alternative green techniques to extract antioxidant compounds have been pursued. The use of enzymes to release bioactive compounds through antioxidant activity reduces the environmental impact caused by traditional extraction systems using organic solvents. A crude enzymatic extract containing carbohydrolases was produced by solid-state fermentation (SSF) of an olive pomace and brewery spent-grain combination. The crude extract was evaluated at different temperatures and pH values and its thermostability was studied. Results showed that β-glucosidase and cellulase were more stable than xylanase, particularly cellulase, which kept 91% of its activity for 72 h at 45 °C. The extract was also applied in enzymatic treatments (ET) to liberate antioxidant compounds from winery, olive mill and brewery by-products under optimal conditions for enzymatic activities. The highest antioxidant activity was found in extracts obtained after enzymatic treatment of exhausted olive pomace (EOP). Enzymatic crude extract produced by SSF was successfully applied in the extraction of antioxidant compounds from winery, olive mill and brewery by-products. Thus, integrating SSF and enzymatic technologies is a valuable approach to implement circular economy practices in the agro-food industry.

Keywords: antioxidants; circular economy; lignocellulolytic enzymes; thermostability.

Figure 1

Effects of temperature (a) and pH (b) on xylanase activity (●), cellulase activity (▲) and β-glucosidase activity (◆). Letters in each value indicate the results of Tukey’s test (p < 0.05).

Figure 2

Thermostability of xylanase activity at 40 °C (- . -▲- . -), 45 °C (- . -■- . -) and 50 °C (- . -●- . -); cellulase activity at 40 °C (--▲--), 45 °C (--■--) and 50 °C (--●--); and β-glucosidase activity at 40 °C (△), 45 °C (□) and 50 °C (○).

Figure 3

Variation of (a) phenolic compounds and (b) antioxidant activity after ET of untreated by-products, COP (●), VTS (■), EOP (▲) and BSG (◆), using the enzymatic extract.

Figure 4

Variation of (a) phenolic compounds and (b) antioxidant activity after ET of untreated COP using the enzymatic extract with crude extract loads of 0.75 (●), 1.5 (■), 2.5 (◆) and 5 mL extract/g of substrate (▲).

Figure 5

Variation of phenolic compounds (●) and antioxidant activity (■) after sequential SSF and ET.