Lignocellulose-degrading fungi newly isolated from central Morocco are potent biocatalysts for olive pomace valorization
Arch Microbiol. 2022 Nov 13;204(12):704. doi: 10.1007/s00203-022-03318-6.
The investigation of lignocellulolytic catalysts is an important feature to face the challenges of lignocellulosic biomass valorization. In central Morocco, fungi were isolated from decaying wood, soil, olive crushing by-products and their compost. One hundred fifty-five isolates were submitted to a selective screening, which served to distinguish 83% of lignocellulolytic isolates. Then, a collection of 56 fungi was subjected to morphological and molecular identification with the ITS5 and ITS4 primers. This approach showed that 45% of the fungal population belonged to the genus Penicillium, followed by Aspergillus 14%, and Fusarium 11%. Alternaria, Trichoderma, Paecilomyces, Cladosporium, Trichocladium, Circinella, and Doratomyces genera are founded with a minority occurrence. Finally, validation of the enzymatic profile was done for 20 isolates, by testing their enzymatic performance on a liquid medium in the presence of cellulose, lignin, and olive pomace. The maximum protein production of 788 µg ml-1 was reached by an Alternaria strain, which produced also 10.6 IU ml-1 of endoglucanase. Thus, a β-glucosidase activity of 5.1 IU ml-1 was obtained by a Penicillium strain isolated from decaying wood. Regarding ligninolytic activities, olive pomace was the most suitable substrate to detect these activities. Decaying wood strains presented the most remarkable results with 1.1 IU ml-1, 0.7 IU ml-1 et 0.3 IU ml-1 for laccase, LiP and MnP, respectively. The use of the selected fungi and olive pomace as local biomass are important factors for the development of green processes targeting the valorization of this by-product into high-value molecules.