Bioprospecting Saccharification of Alkali Pretreated Paddy Straw Through Statistically Designed Parameters for Biofuel Production

Abstract

Gradual increase in energy demand, global warming and fleet industrialization have served as the lashing forces for the development of efficient, safe, clean, renewable and sustainable energy source having the potential of replacing fossil fuels. Current research has been focused towards the exploitation of lignocellulosic biomass (LCB) for biofuel production. Pretreatment plays an important role in efficient enzymatic saccharification of LCB. In present study, effectiveness of chemical pretreatment with alkaline hydrogen peroxide (H₂O₂, pH 11.5) and sodium hydroxide (NaOH) was investigated for increasing enzymatic hydrolysis of paddy (rice) straw. Face-centered Central Composite Design (FCCD) was used to optimize the pretreatment conditions with respect to solid loading (%, w/v), time (min), temperature (^oC) and concentration (% v/v) of NaOH and H₂O₂ (pH 11.5). The optimized values of all the parameters were obtained as solid loading 16.76 %; time 15 min; temperature 120.97^oC; and H₂O₂ concentration 2 %, and obtained the reducing sugar concentration of 35.29 g L⁻¹ (352.9 g reducing sugar kg⁻¹ dry biomass) after saccharification at 50°C using cellulases Cellic Ctec2 at 10 % solid loading of pretreated biomass and enzyme loading of 60 mg protein g⁻¹ pretreated biomass on dry basis. Similarly, in case of NaOH pretreatment, the optimized values were obtained as solid loading 20.00%; time 42.51 min; temperature 84.79^oC; and NaOH concentration 0.5 % with reducing sugar concentration of 36.93 g L⁻¹ (369.3 g reducing sugar kg⁻¹ dry biomass). Pretreatment with NaOH was found to be better than alkaline H₂O₂ in terms of concentration, temperature, solid loading and reducing sugars obtained. This is the first study for comparative statistical standardization of alkaline pretreatment variables along with their interactive study.