Abstract
The genus Aspergillus encompasses several species with relevant lignocellulose-degrading capacity, and a novel species, denominated A. olivimuriae, was recently discovered after its isolation from table olive brine. The acquisition of insight into this species and the assessment of its potential relied on a bioinformatics approach, based on the CAZy database, associated with enzymatic activity profiles in solid-state cultures on four different types of waste, including residual thistle biomass (RTB), spent coffee grounds (SCG), digestate solid fraction and barley straw. The CAZy analysis of A. olivimuriae genome showed that the number of predicted genes for each family was close to that of other Aspergillus species, except for cellobiose dehydrogenase, acetyl xylan esterase and polygalacturonases. In A. olivimuriae solid-state cultures, hemicellulose degradation outperformed that of cellulose, and lignin removal did not occur, regardless of the growth substrate. This is in line with its CAZy content and the extent of hemicellulolytic, and ligninolytic activities detected in its solid-state cultures. RTB and barley straw were the substrates enabling the best glycosyl hydrolase production levels. The exception was SCG, the hemicellulose composition of which, mainly made of glucomannans and galactomanans, led to the highest β-mannanase and β-mannosidase production levels (3.72 ± 0.20 and 0.90 ± 0.04 IU g−1 substrate, respectively).
Highlights
The characterization of new isolates and strains from public culture collections is essential for knowledge implementation and to provide the research and biotechnological industry with helpful information for conducting screenings to find microbial strains of potential interest
The choice of wheat bran (WB) was made due to the inclusion, in this investigation, of spent coffee grounds (SCG), a matrix that, owing to its constituent particles’ fine granulometry, has low porosity, making gas exchanges problematic
The integrated use of different procedures made it possible to acquire information regarding the lignocellulolytic attitudes of Aspergillus olivimuriae, a recently described species
Summary
The characterization of new isolates and strains from public culture collections is essential for knowledge implementation and to provide the research and biotechnological industry with helpful information for conducting screenings to find microbial strains of potential interest. There is a global abundance of lignocellulosic residues, for instance, lignocellulolytic fungi are acquiring an ever-increasing role in biorefinery-based applications aiming to upgrade biomass through the production of value-added products [1]. Owing to the structural heterogeneity and complexity that characterize plant biomass, fungi need to produce a wide set of glycosyl hydrolase activities to perform the breakdown of plant polysaccharides into their monomeric constituents [2,3]. Several studies suggest that this database might be a robust tool, affording insights into the carbohydrate-degrading aptitude of a given fungal species and supporting the classification and functional prediction of novel genes [2,4,5]. The CAZy database enables predicting Auxiliary Activity (AA) families involving lignin-modifying enzymes such as laccases (AA1) and ligninolytic peroxidases (lignin peroxidase, manganese peroxidases and versatile peroxidases) (AA2) [6]
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