Abstract
Knufia chersonesos is an ascomycotal representative of black fungi, a morphological group of polyextremotolerant melanotic fungi, whose ability to resort to recalcitrant carbon sources makes it an interesting candidate for degradation purposes. A secretome screening towards polyesterases was carried out for the fungus and its non-melanized mutant, grown in presence of the synthetic copolyester Polybutylene adipate terephthalate (PBAT) as additional or sole carbon source, and resulted in the identification of 37 esterolytic and lipolytic enzymes across the established cultivation conditions. Quantitative proteomics allowed to unveil 9 proteins being constitutively expressed at all conditions and 7 which were instead detected as up-regulated by PBAT exposure. Protein functional analysis and structure prediction indicated similarity of these enzymes to microbial polyesterases of known biotechnological use such as MHETase from Ideonella sakaiensis and CalA from Candida antarctica. For both strains, PBAT hydrolysis was recorded at all cultivation conditions and primarily the corresponding monomers were released, which suggests degradation to the polymer’s smallest building block. The work presented here aims to demonstrate how investigations of the secretome can provide new insights into the eco-physiology of polymer degrading fungi and ultimately aid the identification of novel enzymes with potential application in polymer processing, recycling and degradation.
Highlights
Synthetic polymeric materials such as polyesters are ubiquitously present in our daily life because of their numerous applications[1,2]
When cultivated in absence and presence of the polyester Polybutylene adipate terephthalate (PBAT), the amount of protein secreted by K. chersonesos appeared to be strictly linked to the nutrient availability in the media and quite unrelated to the presence of the polymer, as visualised by SDSPAGE
For the first time, a secretome screening of the black fungus Knufia chersonesos and its non-melanised mutant exposed to PBAT was carried out for the detection of polyesterases with a role in PBAT breakdown
Summary
Synthetic polymeric materials such as polyesters are ubiquitously present in our daily life because of their numerous applications[1,2]. The bioremediation potential of some species was recognized, along with the ability of species isolated from oligotrophic environments to resort to recalcitrant carbon sources spurned by other microorganisms[29,30,31] Such a nutritional physiology, as demonstrated in the rock-associated Knufia chersonesos[32], can translate into the aptitude to tolerate and grow on monoaromatic compounds and to possibly feed on other types of alternative carbon sources. As demonstrated in the rock-associated Knufia chersonesos[32], can translate into the aptitude to tolerate and grow on monoaromatic compounds and to possibly feed on other types of alternative carbon sources The screening of this and other black fungi species might hold great potential in view of the biodegradation of synthetic polyesters. Their abundance patterns, predicted functions and role in the polymer breakdown were investigated
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