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, <i>tef</i>1-α, <i>tub</i>2, <i>rpb</i>2, <i>act</i>, and/or <i>cal</i> sequences. Among the identified taxa, two new <i>Trichoderma</i> species within the Harzianum clade, namely <i>Trichoderma amurcicola</i> (phylogenetically related to <i>T. simile</i> and <i>T. guizhouense</i>) and <i>Trichoderma olivarum</i> (phylogenetically related to <i>T. simmonsii</i>), were described following a multilocus phylogenetic analysis combined with a study of their morphoanatomical features. A rather high phylogenetic divergence was detected in <i>Candida boidinii</i>, <i>Pleurostoma richardsiae,</i> and <i>Mucor circinelloides</i>, while <i>Cladosporium limoniforme</i>, <i>Mucor pseudolusitanicus</i>, <i>Stagonosporopsis ailanthicola,</i> and <i>Talaromyces nanjingensis</i> 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 <i>Cladosporium limoniforme</i>, <i>C. ramotenellum</i>, <i>Fuscoporia ferrea, Peniophora lycii</i>, and <i>Pseudophlebia setulosa</i>. Fungi detected in TPOMW are promising biotechnological tools to be exploited in the frame of circular economy applications.