Microwave assisted alkaline pretreatment to enhance enzymatic saccharification of catalpa sawdust

•Catalpa sawdust was pretreated by microwave to enhance biofuel yield.•Hemicellulose and lignin were solubilized after microwave-alkali pretreatment.•Reducing sugar yield increased by 682.15% after microwave-Ca(OH)2 pretreatment.•Catalpa sawdust with microwave-Ca(OH)2 pretreatment is promising for enzymolysis.

Catalpa sawdust, a promising biofuel production biomass, was pretreated by microwave-water, -NaOH, and -Ca(OH)2 to enhance enzymatic digestibility. After 48 h enzymatic hydrolysis, microwave-Ca(OH)2 pretreated sample showed the highest reducing sugar yield. The content of hemicellulose and lignin in catalpa sawdust decreased after microwave-alkali pretreatment. SEM observation showed that the catalpa sawdust surface with microwave-Ca(OH)2 pretreatment suffered the most serious erosion. Crystallinity index of catalpa sawdust increased after all three kinds of pretreatment. The optimum conditions of microwave-Ca(OH)2 pretreatment were particle size of 40 mesh, Ca(OH)2 dosage of 2.25% (w/v), microwave power of 400 W, pretreatment time of 6 min, enzyme loading of 175 FPU/g, and hydrolysis time of 96 h, and the reducing sugar yield of microwave-Ca(OH)2 pretreated catalpa sawdust reached 402.73 mg/g, which increased by 682.15% compared with that of raw catalpa sawdust. The catalpa sawdust with microwave-Ca(OH)2 pretreatment is promising for biofuel production with great potential.