Comparison Between Separate Hydrolysis and Fermentation and Simultaneous Saccharification and Fermentation Using Dilute Acid Pretreated Lignocellulosic Biomass

Abstract

In the present study, two different processes, separate hydrolysis and fermentation (SHF), and simultaneous saccharification and fermentation (SSF) were compared. Three different lignocellulosic biomass viz. rice straw (RS), wheat straw (WS), and sugarcane bagasse (SB) were pretreated with dilute acid at two different concentrations (2 and 4 % H2SO4 w/v) and at two different time intervals, i.e., 30 and 60 min. RS, WS, and SB with 4 % H2SO4 at 121 °C for 30 min yielded maximum reducing sugars (110, 90, and 95 g l−1). Delignification of the solid residues were carried out with 0.5 % NaOH, at 121 °C for 30 min. In-house cellulase produced by Aspergillus terreus was used for separate hydrolysis studies at 10 % solid loading and 9 FPU g−1 substrate enzyme loading for 0–48 h at 42 °C. Maximum yield of reducing sugars from RS, WS, and SB were 266, 242, and 254 mg g−1 substrate, respectively. Acid and enzymatic hydrolysates from RS, WS, and SB produced 5.1, 4.9, 5.2 g l−l, and 14.0, 13.9, 12.9 g l−1 of ethanol with Pichia stipitis and Saccharomyces cerevisiae in 24 and 36 h, respectively. Whereas SSF at 10 % solid loading and 9 FPU g−1 substrate enzyme loading for different time intervals 0–72 h at 42 °C was carried out using in-house thermotolerant yeast strain Kluyveromyces sp. RS, WS, and SB yielded maximum ethanol of 23.23, 18.29, and 17.91 g l−1, respectively. Ethanol yield was enhanced by addition of Tween 80 1 % (v/v) by 8.39, 9.26, and 8.14 % in RS, WS and SB, respectively.