Densifying Lignocellulosic biomass with alkaline Chemicals (DLC) pretreatment unlocks highly fermentable sugars for bioethanol production from corn stover

Abstract

Cellulosic ethanol has attracted much attention as it is of great benefit to social and environmental sustainability. However, the adverse properties of lignocellulosic biomass (i.e. low bulk density, fluffy/difficult to handle, and being easily contaminated by microbes), and issues related to biomass pretreatment (i.e. high energy consumption, difficulty in scale-up and low fermentability of pretreated biomass), largely impede the commercialization of cellulosic ethanol. To address these issues, we invented a novel pretreatment method, Densifying Lignocellulosic biomass with alkaline Chemicals (DLC), and studied DLC on corn stover (CS). DLC-CS has high density and high durability, with contamination prevented and sugar fully preserved, which greatly facilitates biomass logistics. DLC-CS showed high enzymatic digestibility and high fermentability after storage. DLC-CS containing calcium hydroxide yielded 21.4 g of ethanol per 100 g of CS, which was further enhanced to 25.3 g of ethanol per 100 g of CS using a regular steam autoclave. An ethanol titer as high as 70.6 g L⁻¹ was achieved, for the first time, without washing or detoxification of the pretreated biomass. These promising results demonstrated the great potential of DLC pretreatment for lignocellulosic biofuel production.