Antioxidant Profile and Biosafety of White Truffle Mycelial Products Obtained by Solid-State Fermentation

Solid-state fermentation may produce therapeutic compounds with higher biomass or better product characteristics than those generated by submerged fermentation. The objectives of this study were to analyze the antioxidant activities and biosafety of products obtained by white truffle (Tuber magnatum) solid-state fermentation in media with different ratios of soybean and red adlay. High levels of antioxidant components and high antioxidant activities such as DPPH radical scavenging, ferrous ion chelation, and reducing power were measured in 20 mg/mL water and ethanol extracts of the white truffle fermentation products. When the solid-state fermentation medium contained soybean and red adlay in a 1:3 ratio (S1A3), the fermentation product had more uniform antioxidant compositions and activities by principal component analysis (PCA). In addition, a 200 ppm water extract of the mycelial fermentation product was able to protect zebrafish embryos from oxidative stress induced by 5 mM hydrogen peroxide. Sprague–Dawley rats were fed the mycelial fermentation product for 90 consecutive days, revealing a no-observed-adverse-effect level (NOAEL) of 3000 mg/kg BW/day. Therefore, mycelial products obtained by white truffle solid-state fermentation can be used instead of expensive fruiting bodies as a good source of antioxidant ingredients.

Root-Associated Mycobiome Differentiate between Habitats Supporting Production of Different Truffle Species in Serbian Riparian Forests

Balkan lowlands bordering with the Pannonia region are inhabited by diverse riparian forests that support production of different truffle species, predominantly the most prized white truffle of Piedmont (Tuber magnatum Pico), but also other commercial species (T.macrosporum Vitt., T. aestivum Vitt.). Surprisingly, little is known about the native root-associated mycobiome (RAM) of these lowland truffle-producing forests. Therefore, in this study we aim at exploring and comparing the RAMs of three different truffle-producing forests from Kolubara river plane in Serbia. Molecular methods based on next generation sequencing (NGS) were used to evaluate the diversity of root-associated fungal communities and to elucidate the influence of environmental factors on their differentiation. To our knowledge, this is the first study from such habitats with a particular focus on comparative analysis of the RAM in different truffle-producing habitats using a high-throughput sequencing approach. Our results indicated that the alpha diversity of investigated fungal communities was not significantly different between different truffle-producing forests and within a specific forest type, while the seasonal differences in the alpha diversity were only observed in the white truffle-producing forests. Taxonomic profiling at phylum level indicated the dominance of fungal OTUs belonging to phylum Ascomycota and Basidiomycota, with very minor presence of other phyla. Distinct community structures of root-associated mycobiomes were observed for white, mixed, and black truffle-producing forests. The core mycobiome analysis indicated a fair share of fungal genera present exclusively in white and black truffle-producing forest, while the core genera of mixed truffle-producing forests were shared with both white and black truffle-producing forests. The majority of detected fungal OTUs in all three forest types were symbiotrophs, with ectomycorrhizal fungi being a dominant functional guild. Apart from assumed vegetation factor, differentiation of fungal communities was driven by factors connected to the distance from the river and exposure to fluvial activities, soil age, structure, and pH. Overall, Pannonian riparian forests appear to host diverse root-associated fungal communities that are strongly shaped by variation in soil conditions.

De novo transcriptome assembly of the Italian white truffle (Tuber magnatum Pico)

The Italian white truffle (Tuber magnatum Pico) is a gastronomic delicacy that dominates the worldwide truffle market. Despite its importance, the genomic resources currently available for this species are still limited. Here we present the first de novo transcriptome assembly of T. magnatum. Illumina RNA-seq data were assembled using a single-k-mer approach into 22,932 transcripts with N50 of 1,524 bp. Our approach allowed to predict and annotate 12,367 putative protein coding sequences, reunited in 6,723 loci. In addition, we identified 2,581 gene-based SSR markers. This work provides the first publicly available reference transcriptome for genomics and genetic studies providing insight into the molecular mechanisms underlying the biology of this important species.