Boosting lignocellulosic bioethanol production: fermentation of corn stalk using a lignin-reduced brown midrib 2...

The recalcitrance of lignin is a major bottleneck in the efficient conversion of lignocellulosic biomass to bioethanol. Genetic reduction of lignin content represents a key strategy to overcome this barrier. This study focuses on characterizing the brown midrib2 (bm2) maize mutant to assess its potential for improving bioethanol production.

Using a near-isogenic line (BC₄F₅) harboring the bm2 mutation, an 8.01% reduction in acid-insoluble lignin content in stalks was observed, with no significant change in cellulose or hemicellulose. This lignin reduction led to a 25.17% increase in glucose release upon sulfuric acid pretreatment. Most importantly, the bm2 mutant showed significantly higher lignocellulosic bioethanol yields: 3.05 g/L Ethanol 1 from the pretreatment hydrolysate (fermentation via Pichia stipites) and 25.88 g/L Ethanol 2 from the cellulose residue (fermentation via Saccharomyces cerevisiae), corresponding to 59.07% and 38.58% increases over the wild-type control, respectively.

Our results provide direct evidence that the bm2 mutation enhances lignocellulosic ethanol production by reducing lignin content and improving saccharification efficiency. This work underscores the value of bm2 in breeding specialized corn varieties for sustainable biofuel feedstock.