Potential Use of Crude Coffee Silverskin Oil in Integrated Bioprocess for Fatty Acids Production

Oil from coffee silverskin (CS) is a potential source of fatty acids with promising applications in several industries. Thus, CS crude oil extraction processes were investigated for further enzymatic hydrolysis for fatty acids production. Firstly, Soxhlet (with 150 mL hexane for 8 hours at 70 °C) and ultrasound-assisted (three times in sequential with 50 mL of hexane for 30 min at 30 °C) extractions were carried out to extract CS oil (3.8% and 3.1%, respectively). The fatty acid profiles obtained by both extraction methods presented a similar composition, shows palmitic (16:0: 32.6–34.4%) and linoleic acids (18:2: 31.5–36.1%) as the main. Then, CS oil extracted by Soxhlet was used as the feedstock for fatty acids production by enzymatic hydrolysis using four commercial lipases. Among the lipases studied, Candida rugosa lipase (CRL) displayed a higher hydrolytic activity (1143.70 U g⁻¹), with a maximum hydrolysis degree of 51.94% (acid value of the CS oil increased from 13.4 to 37.5 mg KOH g⁻¹) after 180 min of reaction. Molecular docking analysis showed that interactions between the CRL active site (Ser209 and His449) and palmitic acid, the fatty acid of highest concentration in CS oil (≈35%), lead to higher hydrolytic activity. The integrated process developed is an advance in fatty acid production and valorization of coffee industry waste, since there is still a promising approach yet to be explored that aims at the utilization of residual CS oil.