Combined hydrothermal pre-treatment and enzymatic hydrolysis of corn fibre: Production of ferulic acid extracts and assessment of their antioxidant and antiproliferative properties

Abstract Ferulic acid may be used as a nutraceutical ingredient or as a substrate to produce bio-vanillin. There is an increasing market demand for ferulic acid obtained from natural sources such as low-cost agro-industrial by-products, due to its potential applications as nutraceutical ingredient and as a substrate to produce bio-vanillin. This work aims to study ferulic acid recovery from corn fibre (one of the most abundant natural sources of ferulic acid), involving an integrated process of hydrothermal pre-treatment followed by enzymatic hydrolysis. The objective is primarily to produce natural extracts with a maximum ferulic acid recovery yield, but it is also to assess their antioxidant and antiproliferative properties and their cytotoxicity. Different commercial enzyme preparations were tested for release of ferulic acid from corn fibre. The best results were obtained for Ultraflo ®XL in a concentration of 2 % (wenzyme preparation/w dry corn fibre) at a pH of 5 and at 55 °C, presenting a recovery yield of esterified ferulic acid of 7.83 ± 1.35 % (wrecovered ferulic acid/wtotal esterified ferulic acid), which corresponds to 0.13 ± 0.02 % (wferulic acid/w dry corn fibre). When using a hydrothermal pre-treatment at a temperature of 140 °C for 40 min, prior to the use of the same enzymatic hydrolysis procedure, the recovery yield of esterified ferulic acid increased to 28.94 ± 2.40 % (w recovered ferulic acid/ wtotal esterified ferulic acid), which corresponds to 4.9 ± 0.3 % (wferulic acid/wdry corn fibre). The use of this pre-treatment leads not only to the highest yield of ferulic acid, but also to the lowest concentration of furfural and hydroxymethylfurfural, without the formation of formic and levulinic acid (not detected). All pre-treatments tested led to an improved quality of the extract in terms of bioactivity.