Spent coffee grounds are the most abundant waste generated during the preparation of coffee beverages, amounting to 60 million tons per year worldwide. Excessive food waste production has become a global issue, emphasizing the need for waste valorization through the bioprocess of solid-state fermentation (SSF) for high added-value compounds. This work aims to identify the operational conditions for optimizing the solid-state fermentation process of spent coffee grounds to recover bioactive compounds (as polyphenols). An SSF process was performed using two filamentous fungi (Trichoderma harzianum and Rhizopus oryzae). An exploratory design based on the Hunter & Hunter method was applied to analyze the effects of key parameters such as inoculum size (spores/mL), humidity (%), and temperature (°C). Subsequently, a Box–Behnken experimental design was carried out to recovery of total polyphenols. DPPH, ABTS, and FRAP assays evaluated antioxidant activity. The maximum concentration of polyphenols was observed in treatment T3 (0.279 ± 0.002 TPC mg/g SCG) using T. harzianum, and a similar result was obtained with R. oryzae in the same treatment (0.250 ± 0.011 TPC mg/g SCG). In the Box–Behnken design, the most efficient treatment for T. harzianum was T12 (0.511 ± 0.017 TPC mg/g SCG), and for R. oryzae, T9 (0.636 ± 0.003 TPC mg/g SCG). These extracts could have applications in the food industry to improve preservation and functionality.

The coffee industry is an industry that generates a large amount of agroindustrial waste as it is the second-largest commodity in the world. The main residues of this commodity are coffee pulp, which represents 40–45% of the fruit’s dry weight, husk coffee, which represents 50% of the weight of the dry fruit, and the spend coffee grounds (SCG) represent 65% in weight of the roasted coffee. This last residue is obtained during the brewing process and generates around 6 million tons per year derived from the consumption of coffee. Its composition is rich in proteins, lipids, mainly fatty acids, cellulose, lignin, tannins, antioxidant compounds of the anthocyanin type, hydroxycinnamic acids, and monosaccharides, such as arabinose, galactose, and mannose. These compounds can be exploited as a source of biological compounds, thus decreasing the environmental pollution generated by these 150residues from the coffee industry. This chapter explores the composition of this residue and the main bio-products that can be obtained from this material using biotechnological strategies. <!----> <!----> <!----> <!---->