Diversity of Culturable Fungi in Two-Phase Olive Mill Waste, a Preliminary Evaluation of Their Enzymatic Potential, and Two New Trichoderma Species

This study investigates the diversity and provides a preliminary evaluation of the enzymatic potential of culturable fungi present in two-phase olive mill waste (TPOMW), a lignocellulose- and phenolic-rich agro-industrial by-product generated in large quantities in olive oil-producing countries. Ninety-four isolates, representing 31 species of the phyla Ascomycota, Basidiomycota, and Mucoromycota, were obtained and identified by using ITS, 28S, tef1-α, tub2, rpb2, act, and/or cal sequences. Among the identified taxa, two new Trichoderma species within the Harzianum clade, namely Trichoderma amurcicola (phylogenetically related to T. simile and T. guizhouense) and Trichoderma olivarum (phylogenetically related to T. simmonsii), were described following a multilocus phylogenetic analysis combined with a study of their morphoanatomical features. A rather high phylogenetic divergence was detected in Candida boidinii, Pleurostoma richardsiae, and Mucor circinelloides, while Cladosporium limoniforme, Mucor pseudolusitanicus, Stagonosporopsis ailanthicola, and Talaromyces nanjingensis were recorded for the first time in TPOMW. A preliminary screening revealed 29 species with cellulolytic and/or xylanolytic activities; 26 species displayed dye decolorization capacity, while ligninolytic and laccase activities were restricted to a few taxa. The most promising degraders of lignocellulosics included strains of Cladosporium limoniforme, C. ramotenellum, Fuscoporia ferrea, Peniophora lycii, and Pseudophlebia setulosa. Fungi detected in TPOMW are promising biotechnological tools to be exploited in the frame of circular economy applications.