Acid and alkali pretreatment are the most commonly employed strategy in a lignocellulosic biorefinery. The main objective of the study was to evaluate the chemical implications of acid and alkali on the lignin structure and subsequently on the adhesive performance. The study also aimed to investigate the effect of complete replacement of phenol and formaldehyde in the commercial wood adhesive with phenolic lignin and glyoxal, respectively. The phenolic lignin was derived from the two differentially pretreated sugarcane bagasse, i.e., acid and alkali. The isolated lignin was characterized and utilized for the synthesis of lignin-based glyoxal resin. The resins were comparatively evaluated for their mechanical properties as wood adhesives. Adhesives derived from acid pretreated sugarcane bagasse were found to be superior to lignin derived from alkali pretreated sugarcane bagasse in terms of mechanical properties and shear strength. Graphical abstract