Formic acid-facilitated hydrothermal pretreatment of raw biomass for co-producing xylo-oligosaccharides, glucose, and lignin

A large number of bamboo waste is produced from bamboo processing industries. Bamboo waste, with high biomass yield and rich in xylan and glucan, is a promising material for the coproduction of xylo-oligosaccharides and glucose. In this work, a formic acid-facilitated hydrothermal pretreatment of bamboo was investegated to increase the yield of xylo-oligosaccharides by controlling the severity factor (SF) and formic acid concentration. The maximum xylo-oligosaccharides yield was 68.04 % (of initial xylan) and the concentrations of X2, X3, X4, and X5 were 4.56, 3.08, 2.30 and 2.58 g/L, respectively. The highest enzymatic hydrolysis yield reached 93.05 % at 45 FPU/g cellulase dosage. Additionally, lignin isolated after formic acid pretreatment (FA-lignin), and lignin from alkali extraction (AE-lignin) had better thermal stability than milling wood lignin (MWL), which could be used in fire-retardant material applications. The techno-economic analysis predicts a revenue of 118.86 USD by processing 100 kg of waste bamboo combined with enzyme cost analysis. To conclude, xylo-oligosaccharides (12.56 kg), xylose (4.81 kg), glucose (22.37 kg) and lignin (13.28 kg) were produced from bamboo (100 kg, 18.37 % xylan, 44.29 % glucan, 27.23 % lignin). The results can give insights into establishing an efficient acid pretreatment of bamboo waste to produce xylo-oligosaccharides, glucose and lignin.