Towards a cleaner process for furfural production and pectin extraction from brewery and winery residues

The production of furfural and pectin extraction from brewer's spent grain (BSG) and grape marc (GM) represents a sustainable strategy for valorizing agro-industrial residues either through the recovery or the transformation into high-value compounds. Furfural, a versatile platform molecule with broad industrial applications, and pectin, widely used in the pharmaceutical and food industries, were extracted using an environmentally benign method combining phosphoric acid, thermal treatment, and ultrasound. A Box–Behnken experimental design was employed to evaluate the influence of pH, extraction time, and temperature on product yields. Mathematical models were developed to describe the relationships between the experimental conditions and extraction efficiency, and multi-objective optimization using genetic algorithms was applied to simultaneously maximize furfural concentration and pectin yields. BSG outperformed GM due to its higher hemicellulose and pectin content, yielding greater product concentrations. Optimal simultaneous production of furfural and pectin extraction conditions for BSG were 74.5 °C, 45.1 min, and pH 1.7, resulting in 103.26 mg g⁻¹ dry weight (dw) of furfural and 2.83 % (28.3 mg g⁻¹ dw) pectin. The combination of ultrasound and phosphoric acid effectively disrupted the lignocellulosic matrix, enhancing the recovery of these valuable bioproducts. This approach aligns with the principles of green chemistry and circular economy, offering a promising pathway for the integrated valorization of agro-industrial by-products.