1 Associate Professor & Head, 2 Former Professor and Head, 3 Professor, 4 Associate Professor, 5 Asscoiate Professor, 6 Scientist (Microbiology), 7 Associate Professor (Biochemistry) Potential of Sodium Hydroxide Pre treatment of Prosopis juliflora for Fermentable Sugar Production Vijayakumar Palled 1 *, M. Anantachar 2 , M. Veerangouda 3 , K.V. Prakash 4 , C.T. Ramachandra 5 , Nagaraj M. Naik 6 and R.V. Beladadhi 7 University of Agricultural Sciences, Raichur 584 104, Karnataka, India (Received 19 June, 2021; Accepted 11 August, 2021) ABSTRACT The present study aimed at investigating the potential of sodium hydroxide (NaOH) as a viable alkaline reagent for lignocellulosic pre treatment considering its various benefits of pre treatment. Prosopis juliflora was pre treated with different NaOH concentrations of 1–3 % for varying treatment times of 15–60 min at temperatures of 100, 120 and 140 °C in an autoclave. Maximum lignin reductions at different temperatures were all obtained at the combinations of highest NaOH concentrations and longest treatment times, which indicated a close relationship between pre treatment severity and lignin reduction. The highest carbohydrate retention of 65.09 per cent was observed in the sample pre treated at 120 °C with 2% NaOH and 60 min. Three pre treatment conditions were selected for subsequent enzymatic hydrolysis with Cellic CTec2® enzyme complex for fermentable sugar production along with untreated biomass as control to study the soaking effect. The biomass pretreated with 2.0 % NaOH for 1 h at 120 °C and loaded with 30% enzyme was determined to be the most effective as it resulted in generation of 583.9 mg sugar/g biomass for a corresponding carbohydrate conversion of 90.86 %. Key words : Acid insoluble lignin, Enzymatic hydrolysis, Fermentable sugars, NaOH, Prosopis juliflora Introduction Lignocellulose-to-ethanol conversion has been in- vestigated intensively around the world over the last two decades. Lignocellulosic biomass is a com- plex substrate that typically contains 50–80 % [dry basis (db)] carbohydrates that are polymers of 5C and 6C sugar units (Carlo et al., 2005). Lignocellu- losic materials have been considered as alternative energy sources because they can capture CO 2 during growth so that their combustion does not generate net CO 2 (Klass, 1998). Cellulose and hemicellulose are polysaccharides that can be used for ethanol pro- duction, while lignin is a complex aromatic polymer that stiffens and surrounds the fibres of polysaccha- rides (Fan et al., 1987). The conversion of lignocellu- losic biomass to ethanol involves three main steps: pretreatment, the hydrolysis of carbohydrate com- ponents present in pretreated biomass to ferment- able sugars, and the fermentation of the sugars to ethanol. However, recalcitrant structure of lignocel- lulosic material necessitates a pretreatment step to break it up, thus making cellulose and hemicellulose more accessible to hydrolytic enzymes for ferment- able sugar production (Xu, 2009). Pretreatment methods can be roughly divided into different categories: physical (milling and grinding), physicochemical (steam pretreatment/ autohydrolysis, hydrothermolysis, and wet oxida- tion), chemical (alkali, dilute acid, oxidizing agents, Eco. Env. & Cons. 28 (February Suppl. Issue) : 2022; pp. (S412-S424) Copyright@ EM International ISSN 0971–765X DOI No.: http://doi.org/10.53550/EEC.2022.v28i02s.065