Formation of a Meat-Like Flavor by Submerged Cultivated Laetiporus montanus.

Basidiomycota are natural sources of aroma compounds. When grown in submerged cultures, the fungus Laetiporus montanus (LMO) forms a spicy and meat-like aroma. It thus represents an interesting candidate for the production of natural savory flavors. To identify the key aroma compounds of LMO grown submerged in malt extract peptone medium, the volatiles were isolated by means of automated solvent assisted flavor evaporation (aSAFE). An aroma extract dilution analysis was performed by means of gas chromatography-olfactometry coupled with a flame ionization detector (GC-FID-O). In the aSAFE extract of LMO, 24 aroma-active compounds were detected. 5-Butyl-2(5H)-furanone (FD 4096), perceived as coconut-like, was determined as the compound with the highest FD factor. (E,E)-2,4-Decadienal, (E,Z)-2,4-decadienal, and sotolon were identified as responsible key compounds for the spicy odor of the submerged cultures. Moreover, supplementation of the cultures of LMO, Laetiporus sulphureus, and Laetiporus persicinus with 13C-labeled thiamine hydrochloride resulted in the formation of 2-methyl-3-(methylthio)furan (MMTF), a compound with a pronounced meaty flavor. The concentrations of MMTF were further increased to 19-27 µg L-1 by additional supplementation of the cultures with ascorbic acid. The results of this study indicate potential for the biotechnological production of a meat-like flavor by Laetiporus species.

Enhancing structural complexity: An experiment conducted in the Black Forest National Park, Germany.

We report on a structural complexity enhancement (SCE) experiment that was designed to test ecological restoration measures in the Black Forest National Park, Germany. The main goal was to understand as to whether the creation of standing and downed deadwood within previously managed, single-layered Norway spruce (Picea abies L.) forests accelerates the development of forest structure, richness, and diversity of a range of taxonomic groups. Here we introduce the experimental design and describe the development of stand structure including abundance and richness of tree-related microhabitats (TreMs) within 5 years after initiation of the experiment in October 2016. To enhance structural complexity in treatment plots, 10 trees per plot were toppled using a skidder winch, and another 10 trees were ring barked at a height of around 60 cm above ground level with a chainsaw. To monitor stand structure, we collected data on common forest attributes such as diameter at breast height (DBH), tree height, and TreMs of all trees in the six experimental and six control plots measuring 0.25 ha in size before the treatments were carried out in 2016 and again in 2020/21. We analyzed the abundance and richness of TreMs using generalized linear mixed models with DBH and treatment vs. control as predictors. The SCE treatment resulted in a significant increase in deadwood volumes (4.2 vs. 439.5 m3) as well as in TreM abundance and richness (increase of 0.74 TreMs per tree). This indicates that the SCE treatment was effective to increase biodiversity-relevant structures such as deadwood and TreMs, in previously managed Norway spruce-dominated stands. The ongoing monitoring of a range of taxonomic groups (birds, bats, small mammals, coleoptera, fungi, mosses, and vascular plants) in this experiment will demonstrate to what extent the enhancement in structural complexity will lead to an enrichment in species richness and diversity.

Formation of Diastereomeric Dihydromenthofurolactones by Cystostereum murrayi and Aroma Dilution Analysis Based on Dynamic Headspace Extraction.

Submerged cultures of the basidiomycota Cystostereum murrayi emit an intensive coconut-like, sweetish, and buttery smell. For identification of the key aroma compounds, an aroma dilution analysis using dynamic headspace was performed by adjusting the split ratio of the GC inlet system. Flavor dilution (FD) factors varied from 22 up to ≥218, whereby the largest class of compounds represented terpenoids, including two rare stereoisomers of 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran (dill ether, ee ≥ 99.9). By means of nuclear magnetic resonance spectroscopy, the substances with the highest FD factors (29, 212, and 218) were identified as diastereomers of 3,6-dimethyl-3a,4,5,6,7,7a-hexayhydro-3H-1-benzofuran-2-one (dihydromenthofurolactone) and as its corresponding C3-unsaturated lactone. The latter two compounds have not been described for Cystostereum murrayi or for any other basidiomycota previously. Supplementation studies using 2-13C-d-glucose indicated that these lactones as well as the two stereoisomers of dill ether and other terpenoids were formed de novo by the fungus.

Diversity and taxonomy of Tricholoma species from Yunnan, China, and notes on species from Europe and North America.

Although taxonomic knowledge on Tricholoma (Agaricales, Basidiomycota) is fairly comprehensive in northwest Europe, knowledge of the global diversity and distribution of Tricholoma spp. is still sparse. In this study, the diversity and distribution of some Tricholoma spp. are analyzed by morphological and molecular methods based on 70 collections from Yunnan, China, 45 from central Europe, 32 from Colorado, USA, 9 from Japan, and 3 from Ukraine. A Holarctic distribution is suggested for several species, based on collections and nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS) sequences. Six species new to science are formally described from Yunnan: five in existing sections, Tricholoma forteflavescens, T. olivaceoluteolum, T. melleum, T. olivaceum, and T. sinoportentosum, and one, T. muscarioides, in the newly described section Muscaria alongside several previously described species. Additional putatively new species cannot be formally described because they lack sufficient material. Tricholoma foliicola is recognized as a species of the genus Gerhardtia.

Species diversity, distribution patterns, and substrate specificity of Strobilurus.

The fungal genus Strobilurus belongs to Physalacriaceae and contains approximately 11 species worldwide. Species of this genus grow and reproduce on cones of various conifers, seed pods or fruits of Magnolia and Liquidambar, and branches and wood of conifers. Previous studies focused mainly on samples from Europe and North America. And no genus-specific phylogenetic analysis has been carried out to date. The monophyly, degree of species diversity and substrate specificity, and overall distribution patterns are addressed here using morphological and molecular evidence. The authors collected samples of Strobilurus from much of its known distribution ranges and carried out morphological observations and multilocus phylogenetic analyses using five molecular markers. The results show that Strobilurus is a monophyletic group but may exclude one species, S. ohshimae. A total of 13 species was identified, with two, S. orientalis and S. pachycystidiatus, described as new from China. Several species were shown to be specific to certain substrates, whereas a few less so. Biogeographic analyses indicated that historical exchanges of species between East Asia, Europe, and North America, later vicariance events, and substrate specificity have contributed jointly to diversification of Strobilurus.

Out of Asia: Biogeography of fungal populations reveals Asian origin of diversification of the Laccaria amethystina complex, and two new species of violet Laccaria.

Purple Laccaria are ectomycorrhizal basidiomycetes associated with temperate forests all over the Northern Hemisphere in at least two taxa: Laccaria amethysteo-occidentalis in North America, and L. amethystina complex in Eurasia, as shown by Vincenot et al. (2012). Here, we combine a further study of the genetic structure of L. amethystina populations from Europe to southwestern China and Japan, using neutral Single Sequence Repeat (SSR; microsatellite) markers; and a systematic description of two novel Asian species, namely Laccaria moshuijun and Laccaria japonica, based on ecological, morphological, and molecular criteria (rDNA sequences). Population genetics provides evidence of the ancient isolation of three regional groups, with strong signal for speciation, and suggests a centre of origin of modern populations closest to present-day Chinese populations. Phylogenetic analyses confirm speciation at the molecular level, reflected in morphological features: L. moshuijun samples (from Yunnan, China) display strongly variable cheilocystidia, while L. japonica samples (from Japan) present distinctive globose to subglobose spores and clavate cheilocystidia. This study of a species complex primarily described with an extremely wide ecological and geographical range sheds new light on the biodiversity and biogeography of ectomycorrhizal fungi.