2‑Hydroxy-1,4-naphthoquinone (Lawsone) as a Redox Catalyst for the Improvement of the Alkaline Pretreatment of Sugarcane Bagasse

This study evaluated the use of a new redox catalyst (2-hydroxy-1,4-naphthoquinone, HNQ) in order to contribute to the preservation of the carbohydrate fraction and to increase delignification of sugarcane bagasse (SB) subjected to soda pretreatment, without inhibiting enzyme activity during saccharification. The effects of HNQ were compared to the well-known redox catalyst anthraquinone (AQ). A 25‑1 fractional design and a 22 central composite design were used for optimization of the soda-HNQ pretreatment of SB. The use of HNQ promoted preservation of 76.4% cellulose and 86.2% hemicelluloses, as well as 86.1% delignification of raw SB, showing a superior performance than AQ. The optimized pretreatment conditions were 150 °C, 60 min, 15% (w w–1) NaOH, 0.4% (w w–1) HNQ, and a liquid-to-solid ratio of 9.6 mL g–1. Saccharification of SB pretreated by soda-HNQ yielded higher overall glucose (74.0%) and xylose (74.3%) yields compared to SB pretreated by AQ (64.9% glucose, 67.3% xylose).