Enhanced production of reducing sugars from paragrass using microwave-assisted alkaline pretreatment

Abstract

The main aims of this study were to examine the effectiveness of pretreatment methods for enhancing the conversion of Brachiara mutica (paragrass) lignocellulose into valuable reducing sugars by enzymatic hydrolysis. The pretreatments studied included alkali alone, microwave-assisted alkali, acid alone, and microwave-assisted acid. It was found that the application of microwave irradiation during alkaline pretreatment with an alkali-to-biomass ratio of 5% (w w−1) for 30 min at 120 °C markedly increased the total reducing sugar (TRS) yield after enzymatic hydrolysis from 316 mg g−1 dry pretreated paragrass without microwave irradiation to 750 mg g−1 dry pretreated paragrass with microwave irradiation. In particular, the microwave-assisted alkaline pretreatment markedly increased xylose production and enhanced the enzymatic digestibility of cellulose. The concentrations of 5-hydroxymethylfurfural (HMF) and furfural after the microwave-assisted pretreatment were well below 1.0 kg m−3, the suggested threshold concentration of furfurals where yeast inhibition may begin.