An integrated process for conversion of spent coffee grounds into value-added materials

Abstract

Spent coffee grounds (SCG) are inexpensive materials with a complex composition that makes them promising feedstocks for a biorefinery.Here, conversion of SCG into a wide range of high value-added products (coffee oil, bio-ethanol, D-mannose, manno-oligosaccharide (MOS), cafestol and kahweol) using a novel integrated system was evaluated. The process involves oil extraction, MOS production by mannanase obtained from Penicillium purpurogenum, NaOH (Na) and hydrogen peroxide (HP) pretreatment for the degradation of lignin and phenolic compounds, diterpenes extraction, enzymatic hydrolysis, and fermentation, which can be performed using environmentally friendly technologies. Approximately 97 mL of coffee oil, 164 g of D-mannose, 102 g of MOS, 99 g of bioethanol and a dash of cafestol/kahweol were produced from 1 kg of dry SCG. Producing high-value co-products from SCG using an integrated approach as demonstrated here may be an efficient strategy to reduce waste generation, while improving the economics of the biorefinery production process.

Keywords: D-mannose; Integrated biorefinery process; Manno-oligosaccharide; Spent coffee grounds; Value-added products.