A review on the valorization of lignin from sugarcane by-products: from extraction to application

The sugarcane industry generates several by-products including the harvest residue (straw) and the fibrous fraction following juice extraction (bagasse). The conversion of sugarcane industry by-products into value-added products is of paramount importance from a sustainable circular economy perspective. Also, the increase of second-generation bioethanol production has triggered the development of approaches to convert residues into functional bioproducts thus increasing the overall sustainability of the process. Lignin is the major biopolymer in nature, and one of the three main components of sugarcane bagasse (SCB) and straw (SCS) biomasses. Due to the potential of lignin as natural antioxidant, antimicrobial, and ultraviolet protector, lignin-based research and new product development have significantly increased. Therefore, this review aims at updating the progress on the valorization of SCS and SCB, and emphasizing their main potential bioactivities and applications, thus serving as a valuable reference material for the academy and industry. A brief introduction of the sugarcane and sugar industry in terms of by-products generation and current end-uses is presented. Recent research studies on SCB and SCS delignification techniques, lignin purification/separation and the main physical-chemical differences between SCS and SCB are covered. The most reported biological activities for sugarcane lignin and their potential applications in the cosmetic and materials fields are also detailed in this review.