Ultrasound-assisted alkaline pretreatment of Parthenium hysterophorus for fermentable sugar production using a response surface approach

Parthenium hysterophorus is a lignocellulosic material with a high potential for fermentable sugar production due to its high availability and adaptability. The current investigation aims at studying the effectiveness of KOH-assisted ultrasonication on the pretreatment of P. hysterophorus biomass. Ultrasonication is a new hydrolysis technology that can provide a higher fermentable sugar yield in less time and at a lower temperature while using less alkali. The combination of KOH and ultrasound has been applied with a detailed study into the effects of various parameters such as sonication time (operating range of 10–50 min), KOH concentration (0.5–2.5%), and temperature (20–50 °C). A higher reducing sugar yield (128.15±0.06 mg/g) was obtained in US-KOH-pretreated biomass as compared with that of the KOH-pretreated biomass. The optimised pretreatment (using a 1:10 bath ratio, 1% (w/v) KOH, and 15-min sonication times) reduced lignin content (delignification) by 58.72% (w/w) and increased the available cellulose content (27.97% w/w) over untreated biomass, which was confirmed by compositional analysis of treated biomass. Further US-KOH-pretreatment was investigated for the liberation of maximum reducing sugar (325.51 mg/g) using the response surface methodology (RSM) approach. Following statistical optimization using response surface methodology, the yield of enzymatic hydrolysis was increased by 3.2-fold compared to the control. According to the investigations, P. hysterophorus can be used as a promising and affordable biomass source for the production of commercial bioethanol.