Integrated alkaline pretreatment and surfactant-assisted hydrolysis for high-yield Manno-oligosaccharides production from spent coffee grounds

In this study, a process optimization strategy was established to enhance the efficiency of manno-oligosaccharides (MOS) production from spent coffee grounds (SCG), using a sequential approach of aqueous ammonia pretreatment and surfactant-assisted enzymatic hydrolysis. Aqueous ammonia pretreatment (25 % NH₃·H₂O, 70 °C, 48 h) significantly disrupted the lignocellulosic matrix, achieving 67.1 % lignin removal and resulting in more than a threefold increase in MOS yield. The addition of non-ionic surfactants (Tween 80 and PEG 6000) further improved MOS yields by mitigating the non-specific binding of mannanase to lignin. Among them, Tween 80 exhibited superior performance, increasing the MOS yield to 62.3 % at a concentration of 5 mg/mL. This integrated strategy provides a practical and effective means of valorizing SCG into functional oligosaccharides through optimized chemical and enzymatic processes.