Flowthrough Pretreatment Enhanced Cellulose Digestibility Compared to Batch Pretreatment

Flowthrough pretreatment is capable of removing high quantities of hemicellulose and lignin from plant biomass than batch pretreatment. Hence, the team of Samarthya Bhagia from University of California Riverside compared these two pretreatments in terms of sugar yields and lignin removal in hopes of gaining insights into lignocellulosic biomass deconstruction.

The team applied flowthrough and batch pretreatments using either liquid hot water (LHW) or extremely diluted acid (EDA) to poplar at two temperatures (140°C and 180°C). The solid composition, sugar yields, and lignin removal from pretreatment and enzymatic hydrolysis were analyzed.

LWH flowthrough pretreatment of poplar removed between 63-69% lignin, while batch pretreatments removed about 20-33% lignin at similar conditions. EDA slightly enhanced lignin removal in flowthrough pretreatment. Close to 100% total sugar yields were also measured from LHW and EDA flowthrough pretreatments. The high lignin removal by flowthrough pretreatment enhanced cellulose digestibility compared to batch pretreatment, consistent with lignin being a key contributor to biomass recalcitrance.

Results show that flowthrough pretreatment removes about 65–70% of lignin before it can form lignin rich fragments that deposit on the biomass surface in batch operations and hinder enzyme action. However, the leftover 30–35% lignin in poplar is still a key player in biomass recalcitrance to enzymatic deconstruction and might be harder to remove from the biomass with low temperature pretreatment.