Understanding the Xylan Content for Enhanced Enzymatic Hydrolysis of Individual Bamboo Fiber and Parenchyma Cells

To enhance the understanding of the effect of xylan removal on the cellulose ultrastructure and subsequent enzymatic hydrolysis, the top-down influence of xylan content on the cell wall, cellulose microfibrils, and crystal structure of individual bamboo fiber and parenchyma cells were investigated. The results indicated that partial xylan removal (27.49%–37.46% for the fiber and 19.03%–27.98% for the parenchyma) significantly improved the cellulose digestibility due to larger crystal size and greater microfibril exposure while retaining the cell wall structure intact. However, excessive xylan degradation resulted in cell wall swelling and deformation, cellulose microfibril coalescence, and smaller crystal size, leading to a lower conversion yield of cellulose. The optimal content of xylan removal for fiber and parenchyma were 37.46% and 27.98%, respectively, at which the cellulose conversion yields were ∼99%. During the successive extraction of xylan, the parenchyma showed a larger crystal size and lower crystallinity index and thus resulted in a higher conversion yield of cellulose than the fiber. Notably, a sugar yield over 90% was achieved within only 6 h of saccharification in the parenchyma cells, indicating that parenchyma cells are competitive as a biofuel feedstock by using less hydrolysis time for high sugar yield.