Growth and enzymatic activity of Leucoagaricus gongylophorus, a mutualistic fungus isolated from the leaf‐cutting ant Atta mexicana, on cellulose and lignocellulosic biomass

Abstract

A mutualistic fungus of the leaf-cutting ant Atta mexicana was isolated andidentified as Leucoagaricus gongylophorus. This isolate had a close phylogeneticrelationship with L. gongylophorus fungi cultivated by other leaf-cutting ants asdetermined by ITS sequencing. A subcolony started with ~500 A. mexicanaworkers could process 2 g day-1of plant material and generate a 135 cm3 fungus garden in 160 days. The presence of gongylidia structures of ~35 lmwas observed on the tip of the hyphae. The fungus could grow without ants onsemi-solid cultures with a-cellulose and microcrystalline cellulose and in solid state cultures with grass and sugarcane bagasse, as sole sources of carbon. Themaximum CO2production rate on grass (Vmax= 17.5mgCO2Lg -1day -1)was three times higher than on sugarcane bagasse (Vmax= 6.6mgCO2Lg-1day-1). Recoveries of 32.9mgglucose gbiomass-1and 12.3mgglucose gbiomass-1were obtained from the fungal biomass and the fungus garden, respectively.Endoglucanase activity was detected on carboxymethylcellulose agar plates.This is the first study reporting the growth of L. gongylophorus fromA. mexicana on cellulose and plant material.