Mangrove root fungal endophytes as a source of biomass degrading enzymes

Abstract

Fungal endophytes isolated from mangrove roots demonstrated strong halotolerant characteristics, as indicated by their ability to maintain growth under a wide range of NaCl concentrations (0, 1, 2, 3, and 4%). Although several fungal isolates exhibited a gradual reduction in growth performance as salinity increased, Lasiodiplodia theobromae and Pseudopestalotiopsis theae showed stable growth responses across all tested salinity levels, suggesting their high physiological adaptation to saline environments. Interestingly, Phomopsis sp. 1 exhibited enhanced growth under salt stress conditions, indicating that certain mangrove-associated endophytes may possess specific adaptive mechanisms that allow them to utilize or tolerate elevated salt concentrations. In addition to their halotolerance capability, several mangrove root endophytes demonstrated functional enzymatic activities by producing salt-induced or salt-tolerant cellulase and β-glucosidase enzymes. These fungi were also capable of producing laccase enzymes that remained active under saline conditions. The ability to maintain extracellular enzyme activity under high salinity conditions highlights the ecological importance of these fungi in mangrove ecosystems, particularly in environments characterized by fluctuating salinity and prolonged inundation. The presence of salt-tolerant lignocellulolytic enzymes suggests that mangrove root endophytes play an essential role as biological decomposers, facilitating the breakdown of complex organic materials such as cellulose and lignin derived from plant residues. Consequently, these fungi contribute significantly to nutrient mineralization and biogeochemical cycling within submerged mangrove ecosystems. Their adaptation to saline habitats also indicates potential applications as functional microbial resources for biotechnology, particularly in the development of environmentally sustainable biomass degradation processes.