Structural features and enzymatic digestibility of Napier grass fibre treated with aqueous ammonia

• Aqueous ammonia treatment selectively removed lignin in Napier grass.
• Solid recovery was rich in cellulose content, with an open fibrous matrix.
• Combination of cellulase and and xylanase gave 80% glucan-to-glucose conversion.
• Supplementation of cellulase with xylanase improved final extent of hydrolysis.

We characterised the structural changes of Napier grass after treatment with aqueous ammonia (27%, w/w) at a solid:liquid ratio of 1:12 for 14 days at ambient temperature and evaluated its enzymatic digestibility. This treatment protected carbohydrates in the fibre and greatly reduced lignin content (58.7% lignin removal), resulting in the deconstruction of the fibrous matrix. Although the relative cellulose content increased, the degree of crystallinity of the treated fibre increased only marginally from 42.9 to 50.0%, which can be attributed to the partial disruption of the cellulose crystal structure. Aqueous ammonia treatment markedly promoted the enzymatic cellulose digestibility, increasing from 18 to 53% with an enzyme loading of 30 FPU/g biomass. Supplementation of cellulase with xylanase (30 FPU cellulase + 100 XU xylanase/g biomass) improved the final extent of hydrolysis and greatly enhanced the final glucose yield, approaching to 80% glucan conversion.

Figure optionsDownload as PowerPoint slide