Combined steam explosion and optimized green-liquor pretreatments are effective for complete saccharification to maximize bioethanol production by reducing lignocellulose recalcitrance in one-year-old bamboo

Bamboo is a fast-growing perennial plant rich at lignocellulose convertible for biofuels and biochemical production. Despite various physical and chemical pretreatments have been implemented for bamboo biomass utilization, it becomes essential to explore optimal technology for complete biomass saccharification to maximize bioethanol production in the desirable bamboo substrates. In this study, the steam explosion followed with optimized green-liquor pretreatments were conducted in different-year-old bamboo samples using response surface methodology. Compared to the older samples, the one-year-old bamboo (PhY1) showed a complete biomass enzymatic saccharification with hexoses yield of 100.0% (% cellulose), leading to the highest bioethanol yield of 20.3% (% dry biomass) achieved among all previously-reported bamboo processes. Notably, those combined pretreatments could not only cause an effective co-extraction of hemicellulose-lignin complexes, but also distinctively modify major wall polymer features (cellulose DP and accessibility, hemicellulosic Xyl/Ara and lignin S/G) for significantly reduced lignocellulose recalcitrance, which should lead to an integrated enhancement to biomass enzymatic saccharification in the PhY1 bamboo sample. Therefore, this study has demonstrated a powerful strategy for a green-like biomass process, providing an applicable technology to achieve maximum bioethanol production in bamboo and other lignin-rich bioenergy crops.