Liquid ammonia pretreatment optimization for improved release of fermentable sugars from sugarcane bagasse

Alkali pretreatment of biomass is a widely accepted method for efficient delignification causing significant recovery of pentoses and hexoses to be utilized for second generation ethanol production. Present study is investigated to optimize the conditions of liquid ammonia pretreatment of sugarcane bagasse using statistical design of response surface methodology with respect to liquid ammonia concentration (15–25% v/v), solid loading (5–20% w/v), temperature (70–100 °C) and retention time (16–24 h) for maximum recovery of sugars during enzymatic hydrolysis. Optimized conditions for liquid ammonia pretreatment were found as 15.64% (v/v) ammonia; 10.51% (w/v) solid loading; 84.9 °C temperature; and 23.95 h retention time. The reducing sugar yield of 545.57 ± 7.1 g/kg of raw biomass corresponding to 75.41 ± 1% of maximum theoretical sugars was achieved after 72 h of saccharification using Cellic CTec 2 (20 FPU/g pretreated biomass). Biophysical techniques further validated the efficiency of process via deeper understanding of structural and compositional changes of pretreated as well as saccharified biomass imprinted by optimized pretreatment conditions used in the study. [Display omitted] •Efficient recovery of C5 and C6 sugars is achieved in the present study.•Process parameters for combined sugar yield have been optimized using RSM.•The total reducing sugar yield (RSY) of 545.57 ± 7.1 g/kg of raw bagasse is achieved.