Discovery and Characterization of Mannan-Specialized GH5 Endo-1,4-β-mannanases: a Strategy for Acai (Euterpe oleracea Mart.) Seeds Upgrading

The pulp of acai palm fruits (Euterpe oleracea Mart.) is a valuable export commodity in Brazil. Its production generates 1.6 million tons/year of acai seeds, a resource largely wasted. The seeds consist mainly of linear beta-mannan, offering potential for prebiotic beta-mannan-derived oligomers and mannose production. However, the crystalline structures of beta-mannan hinder enzymatic hydrolysis. This study aimed to discover and characterize fungal enzymes targeting acai seed beta-mannan using a palm beta-mannanase (EgMan5A) as a guide. Recombinant expression, enzyme optimization, kinetics, substrate specificity, and structural modeling were performed. The two fungal enzymes, JaMan5A and SlMan5A, were found to be specific for unsubstituted mannan, showing no activity toward galacto- and glucomannan. Among them, SlMan5A showed the highest activity on acai seed beta-mannan (similar to 24 U/mg) and other unsubstituted mannan substrates, likely due to its greater thermal robustness. These results provide valuable insights into beta-mannan specificity contributing to the sustainable valorization of acai seeds.