Hydrotropic pretreatment on rice straw for bioethanol production

•Hydrotropic pretreatment was carried out on rice straw using alkyl benzene sulfonates.•Glucose yield significantly improved after hydrotropic pretreatment.•Hydrotrope solution of sodium cumene sulfonate can be efficiently reused for five cycles.•First report on hydrotropic pretreatment on rice straw for bioethanol production.

The aim of this study was to investigate the effect of hydrotrope as a pretreatment process on rice straw for bioethanol production. Sodium cumene sulfonate and sodium xylene sulfonate (Na–X) were used as hydrotropes to delignify rice straw. Effects of biomass loading, time, temperature and hydrotrope concentration were studied for both the hydrotropes. There was no loss of cellulose & hemicellulose in the hydrotrope solution. Sodium cumene sulfonate could remove more than 50% of lignin from rice straw with 5% biomass loading at 121 °C for 1 h. Reusability of aqueous hydrotrope solution was demonstrated. Enzymatic digestibility of the hydrotrope pretreated rice straw was studied and evaluated for subsequent bioethanol production. The use of the hydrotrope for biomass pretreatment has the potential to mitigate the environmental impact of chemical pretreatment.