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

The pulp of açaí palm fruits ( Mart.) is a valuable export commodity in Brazil. Its production generates 1.6 million tons/year of açaí seeds, a resource largely wasted. The seeds consist mainly of linear β-mannan, offering potential for prebiotic β-mannan-derived oligomers and mannose production. However, the crystalline structures of β-mannan hinder enzymatic hydrolysis. This study aimed to discover and characterize fungal enzymes targeting açaí seed β-mannan using a palm β-mannanase (Man5A) as a guide. Recombinant expression, enzyme optimization, kinetics, substrate specificity, and structural modeling were performed. The two fungal enzymes, Man5A and Man5A, were found to be specific for unsubstituted mannan, showing no activity toward galacto- and glucomannan. Among them, Man5A showed the highest activity on açaí seed β-mannan (∼24 U/mg) and other unsubstituted mannan substrates, likely due to its greater thermal robustness. These results provide valuable insights into β-mannan specificity contributing to the sustainable valorization of açaí seeds.