Simultaneous saccharification and fermentation of sequential dilute acid-alkali pretreated cotton (Gossypium hirsutum L.) stalk for cellulosic ethanol production

BACKGROUND Cotton stalk (CS) was deconstructed by sequential dilute acid-alkali pretreatment (DALP) using sulfuric acid (1%, v/v) and sodium hydroxide (3%, w/v). The enzymatic hydrolysis of DALP-CS by cellulase was optimized by Taguchi method, employing factors like solid loading, enzyme dose, tween 80, and pH as main process variables. For bioethanol production, pretreated CS was subjected to simultaneous saccharification and fermentation (SSF) using a newly identified yeast strain Kluyveromyces marxianus JKSG-6. RESULTS Sequential pretreatment of CS resulted in 66% and 42% removal of hemicellulose and lignin, respectively. The same was evident from the changes in the fourier transforming infrared (FT-IR) spectroscopy absorption spectrum. Under optimized conditions, the enzymatic hydrolysis of DALP-CS released 375.50 +/- 0.04 mg g(-1) of glucose. Further, by employing K. marxianus JKSG-6 under SSF at 42 degrees C, the strain produced an ethanol titer of 26.10 +/- 0.05 g L-1 from pretreated CS. CONCLUSION Sequential dilute acid-alkali pretreatment rendered CS, a highly recalcitrant LCB feedstock for bioethanol, more accessible for hydrolysis by cellulase. SSF of the effectively pretreated CS was successfully carried out for bioethanol production by employing a newly identified yeast K. marxianus JKSG-6. (c) 2021 Society of Chemical Industry (SCI).