High-efficient cellulosic butanol production from deep eutectic solvent pretreated corn stover without detoxification

Authors: LIN, XIAOQING - Guangdong University; LIU, YAO - Guangdong University; ZHENG, X - Guangdong University; Qureshi, Nasib

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2021
Publication Date: 1/22/2021
Citation: Lin, X., Liu, Y., Zheng, X., Qureshi, N. 2021. High-efficient cellulosic butanol production from deep eutectic solvent pretreated corn stover without detoxification. Industrial Crops and Products. 162. Article 113258. https://doi.org/10.1016/j.indcrop.2021.113258.
DOI: https://doi.org/10.1016/j.indcrop.2021.113258

Interpretive Summary: Butanol is an important transportation fuel that contains more energy than ethanol on per gallon basis. It can be used in existing gasoline supply and distribution lines, has higher octane number, and can be mixed with gasoline in any proportion. It is also a valuable chemical. Butanol can be produced from annual crops such as corn, rice, barley and other starchy corps. However, due to prohibitive cost of these grains and cereals, use of lignocellulosic residues such as corn stover (CS) is recommended. CS is abundantly produced in the mid-western region of the United States. Production of butanol from CS, requires its treatment using either steam or chemicals such as dilute acid or alkali followed by breaking down to simple sugars using enzymes. Then the sugar solution is fermented to butanol employing microbial cultures. Treatment of CS by steam or acid/alkali is cost prohibitive (as acid/alkali cannot be recycled & generate inhibitory chemicals). Hence, we used a chemical (DES or Deep Eutectic Solvent) that can be recycled thus reducing treatment cost significantly. Additionally, we used a low concentration of enzymes for CS hydrolysis followed by efficient fermentation. Successful and economic development of this process for biofuel butanol production will benefit farmers, butanol producing industry, and the United States public.

Technical Abstract: Background: Currently, exploring and utilizing renewable agricultural and forestry waste to produce biofuels and platform chemical has been receiving worldwide attention, which can improve both energy and environmental sustainability. There are two major biofuels: bio-ethanol and bio-butanol. Compared with bio-ethanol, bio-butanol is preferred as a sustainable transport biofuel, possessing superior fuel characteristics such as high energy density, hydrophobicity, low flammability, no or low corrosiveness, and good miscibility with gasoline. How to produce concentrated fermentable sugars without any detoxification is a key challenge in the economic and environmental sustainability production of cellulosic butanol. Results: This study has developed a rapid and low energy biomass process that includes deep eutectic solvent (DES) pretreatment, enzymatic saccharification, and Clostridium fermentation for the production of concentrated fermentable sugars and high-titer bio-butanol. The pretreatment conditions were evaluated for 90 min at various temperatures (80-140 deg C). The proposed process desirably retained most of the cellulose after pretreatment of corn stover (CS; 87.71-99.24%). The scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier transform infrared (FT-IR) spectroscopy results consistently suggested that the structure of CS were disrupted by the removal of lignin and xylan during the pretreatment process. The total sugars released from treated CS at 120 oC were 37.94 g L-1 (30.59 g L-1 glucose and 7.35 g L-1 xylose) at an enzyme loading of 7.5 filter paper unit (FPU) g-1 pretreated CS which is much lower than other reports. Furthermore, the treated CS hydrolysate was successfully used to produce butanol by Clostridium beijerinckii P260 without any detoxification, with a titer of 12.39-13.65g L-1 total acetone-butanol-ethanol (ABE), a productivity of 0.41-0.68 g L-1 h-1, and yield of 0.38 g g-1. Conclusions: DES is an effective solvent for pretreatment of lignocellulosic biomass for production of bio-butanol with high productivity and yield.