Huperziacrassifolia (Lycopodiaceae), a new species from China based on morphological characters and molecular evidence.

A new species of the firmoss from China, Huperziacrassifolia sp. nov., is described and illustrated based on morphological characters and molecular evidence. The new species resembles species associated with the H.javanica complex, in particular H.javanica based on leaf shape and serrations, but can be easily distinguished by elliptic lanceolate and thick coriaceous leaves, well differentiated seasonal constriction zones, and reflexed leaf margins when get dried. Phylogenomic reconstruction using whole chloroplast genome sequences recovered H.crassifolia as sister to H.sutchueniana and only distantly related to morphological similar species H.javanica, H.nanlingensis, and H.serrata. The genome size 2C = 17.2 pg indicated the new species to be a tetraploid, whereas diploid H.javanica had a genome size of 8.7 pg. Morphological characters, distribution, and conservation status of the new species are also presented.

The Possible Earliest Allopolyploidization in Tracheophytes Revealed by Phylotranscriptomics and Morphology of Selaginellaceae.

Selaginellaceae, originated in the Carboniferous and survived the Permian-Triassic mass extinction, is the largest family of lycophyte, which is sister to other tracheophytes. It stands out from tracheophytes by exhibiting extraordinary habitat diversity and lacking polyploidization. The organelle genome-based phylogenies confirmed the monophyly of Selaginella, with six or seven subgenera grouped into two superclades, but the phylogenetic positions of the enigmatic Selaginella sanguinolenta clade remained problematic. Here, we conducted a phylogenomic study on Selaginellaceae utilizing large-scale nuclear gene data from RNA-seq to elucidate the phylogeny and explore the causes of the phylogenetic incongruence of the S. sanguinolenta clade. Our phylogenetic analyses resolved three different positions of the S. sanguinolenta clade, which were supported by the sorted three nuclear gene sets, respectively. The results from the gene flow test, species network inference, and plastome-based phylogeny congruently suggested a probable hybrid origin of the S. sanguinolenta clade involving each common ancestor of the two superclades in Selaginellaceae. The hybrid hypothesis is corroborated by the evidence from rhizophore morphology and spore micromorphology. The chromosome observation and Ks distributions further suggested hybridization accompanied by polyploidization. Divergence time estimation based on independent datasets from nuclear gene sets and plastid genome data congruently inferred that allopolyploidization occurred in the Early Triassic. To our best knowledge, the allopolyploidization in the Mesozoic reported here represents the earliest record of tracheophytes. Our study revealed a unique triad of phylogenetic positions for a hybrid-originated group with comprehensive evidence and proposed a hypothesis for retaining both parental alleles through gene conversion.

A new mountain pitviper of the genus Ovophis Burger in Hoge & Romano-Hoge, 1981 (Serpentes, Viperidae) from Yunnan, China.

Based on a molecular phylogenetic analysis and morphological comparison, a new species of mountain pitviper, Ovophisjenkinsi sp. nov., is described. The new species was collected in Yingjiang County, Yunnan Province, China. It can be distinguished from congeneric species by the following characters: (1) internasals in contact or separated by one small scale; (2) second supralabial entire and bordering the loreal pit; (3) dorsal scales in 23 (25)-21 (23, 25)-19 (17, 21) rows; (4) 134-142 ventrals; (5) 40-52 pairs of subcaudals; (6) third supralabial larger than fourth in all examined specimens of Ovophisjenkinsi sp. nov.; (7) deep orange-brown or dark brownish-grey markings on dorsal head surface; (8) background color of dorsal surface deep orange-brown or dark brownish-grey; (9) both sides of dorsum display dark brown trapezoidal patches; (10) scattered small white spots on dorsal surface of tail.

Primulaweiliei (Primulaceae), a new species from Hubei, Central China.

In this study, we describe and illustrate a new species, Primulaweiliei L.S.Yang, Z.K.Wu & G.W.Hu, from the Shennongjia Forestry District, Hubei Province in Central China. It is morphologically assigned to Primulasect.Aleuritia based on its dwarf and hairless habit, long petiole, fruits longer than calyx and covered by farina on the scape. This new species is similar to P.gemmifera and P.munroisubsp.yargongensis in the same section, but it can be distinguished by its smaller calyxes, homostylous flowers, corolla tube throat without annular appendage and only 1-2 flowers in each inflorescence. Based on the assessment conducted according to the IUCN Red List criteria, we propose that P.weiliei be classified as a Critically Endangered (CR) species.

The simultaneous removal of methylene blue (MB) and Ca2+ by recyclable adsorbents based the scales derived from coal gasification system.

The transformation of solid wastes from industrial production into effective adsorbents could significantly contribute to wastewater treatment. In this study, after acidizing and burning soft scale (SS) from coal gasification system, two magnetic adsorbents (mag-ASS and mag-BASS) were prepared via the combination of magnetite with ultrasonic, respectively. The treatment effects of mag-ASS and mag-BASS were then investigated for simulated wastewater containing macromolecular organic matter [i.e., methylene blue (MB)] and Ca2+. The results indicated that the pseudo second order kinetic, Elovich, Freundlich, Langmuir and Temkin model could well describe the adsorption behavior of MB and Ca2+ onto mag-ASS and mag-BASS. The maximum adsorption capacities of mag-ASS for MB and mag-BASS for Ca2+ were 600.53 mg/g and 102.54 mg/g, respectively. Surprisingly, the adsorption abilities of mag-ASS for MB and mag-BASS for Ca2+ show significantly higher than the others. The adsorption mechanisms of MB mainly included electrostatic interaction, π-π conjugate interaction and cation exchange, while those of Ca2+ were mainly electrostatic interaction and cation exchange. The diffusion of MB and Ca2+ onto the magnetic adsorbents might be controlled by the combined effects of intraparticle and liquid film diffusion. There was no significant reduction in adsorption capacity after 8 cycles of adsorption and desorption, indicating that SS-based magnetic adsorbents had good recyclability and stability. Moreover, the removal efficiency of mag-BASS for total hardness and total organic carbon in real coal gasification gray water (CGGW) was 82.60 and 64.10%, respectively. The treatment of CGGW and the resource of wastes would significantly promote the reasonable disposal of coal gasification scales.

Can Sb(III)-oxidizing prokaryote also oxidize As(III) under aerobic and anaerobic conditions, and vice versa?

Sb(III) and As(III) share similar chemical features and coexist in the environment. However, their oxidase enzymes have completely different sequences and structures. This raises an intriguing question: Could Sb(III)-oxidizing prokaryotes (SOPs) also oxidize As(III), and vice versa? Regarding this issue, previous investigations have yielded unclear, incorrect and even conflicting data. This work aims to address this matter. First, we prepared an enriched population of SOPs that comprises 55 different AnoA genes, lacking AioAB and ArxAB genes. We found that these SOPs can oxidize both Sb(III) and As(III) with comparable capabilities. To further confirm this finding, we isolated three cultivable SOP strains that have AnoA gene, but lack AioAB and ArxAB genes. We observed that they also oxidize both Sb(III) and As(III) under both anaerobic and aerobic conditions. Secondly, we obtained an enriched population of As(III)-oxidizing prokaryotes (AOPs) from As-contaminated soils, which comprises 69 different AioA genes, lacking AnoA gene. We observed that the AOP population has significant As(III)-oxidizing activities, but lack detectable Sb(III)-oxidizing activities under both aerobic and anaerobic conditions. Therefore, we convincingly show that SOPs can oxidize As(III), but AOPs cannot oxidize Sb(III). These findings clarify the previous ambiguities, confusion, errors or contradictions regarding how SOPs and AOPs oxidize each other's substrate.

Microwave-assisted esterification and electro-enhanced solid-phase microextraction of omega-3 polyunsaturated fatty acids in eggs.

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs), a type of fatty acid that has many health benefits, are of increasing concern. Herein, we developed a method for the rapid esterification and enrichment of ω-3 PUFAs in eggs, which includes microwave-assisted esterification (MAE) and electrically enhanced solid-phase microextraction (EE-SPME). Combined with gas chromatographic, efficient detection of ω-3 PUFAs was achieved in eggs. Under microwave radiation, the esterification efficiency exhibited a significant increase ranging from 5.06 to 10.65 times. The EE-SPME method reduced extraction time from 50 to 15 min. In addition, improvements in extractive fiber coating materials were explored, which ensured efficient extraction of ω-3 PUFAs. Under the optimal conditions, the method displayed a low detection limit (1.01-1.54 µg L-1), good recoveries (85.82%-106.01%), and wide linear range (7.5-1000 µg L-1), which was successfully applied to determine ω-3 PUFAs in real egg samples.

Functional features of a novel Sb(III)- and As(III)-oxidizing bacterium: Implications for the interactions between bacterial Sb(III) and As(III) oxidation pathways.

Antimony (Sb) and arsenic (As) share similar chemical characteristics and commonly coexist in contaminated environments. It has been reported that the biogeochemical cycles of antimony and arsenic affect each other. However, there is limited understanding regarding microbial coupling between the biogeochemical processes of antimony and arsenic. Here, we aimed to solve this issue. We successfully isolated a novel bacterium, Shinella sp. SbAsOP1, which possesses both Sb(III) and As(III) oxidase, and can effectively oxidize both Sb(III) and As(III) under aerobic and anaerobic conditions. SbAsOP1 exhibits greater aerobic oxidation activity for the oxidation of As(III) or Sb(III) compared to its anaerobic activity. SbAsOP1 also significantly catalyzes the oxidative mobilization of solid-phase Sb(III) under aerobic conditions. The activity of SbAsOP1 in oxidizing solid Sb(III) is 3 times lower than its activity in oxidizing soluble form. It is noteworthy that, in the presence of both Sb(III) and As(III) under aerobic conditions, either As(III) or Sb(III) significantly inhibits the oxidation of Sb(III) or As(III), respectively. In comparison, under anaerobic conditions and in the coexistence of Sb(III) and As(III), As(III) significantly inhibits Sb(III) oxidation, whereas Sb(III) almost completely inhibits As(III) oxidation. These findings suggest that under both aerobic and anaerobic conditions, SbAsOP1 demonstrates a partial preference for Sb(III) oxidation. Additionally, bacterial oxidations of Sb(III) and As(III) mutually inhibit each other to varying degrees. These observations gain a novel understanding of the interplay between the biogeochemical processes of antimony and arsenic.

Colorectal image analysis for polyp diagnosis.

Colorectal polyp is an important early manifestation of colorectal cancer, which is significant for the prevention of colorectal cancer. Despite timely detection and manual intervention of colorectal polyps can reduce their chances of becoming cancerous, most existing methods ignore the uncertainties and location problems of polyps, causing a degradation in detection performance. To address these problems, in this paper, we propose a novel colorectal image analysis method for polyp diagnosis via PAM-Net. Specifically, a parallel attention module is designed to enhance the analysis of colorectal polyp images for improving the certainties of polyps. In addition, our method introduces the GWD loss to enhance the accuracy of polyp diagnosis from the perspective of polyp location. Extensive experimental results demonstrate the effectiveness of the proposed method compared with the SOTA baselines. This study enhances the performance of polyp detection accuracy and contributes to polyp detection in clinical medicine.

Biological oxidation of As(III) and Sb(III) by a novel bacterium with Sb(III) oxidase rather than As(III) oxidase under anaerobic and aerobic conditions.

Sb and As are chemically similar, but the sequences and structures of Sb(III) and As(III) oxidase are totally distinct. It is thus interesting to explore whether Sb(III) oxidase oxidizes As(III), and if so, how microbial oxidations of Sb(III) and As(III) influence one another. Previous investigations have yielded ambiguous or even erroneous conclusions. This study aimed to clarify this issue. Firstly, we prepared a consortium of Sb(III)-oxidizing prokaryotes (SOPs) by enrichment cultivation. Metagenomic analysis reveals that SOPs with the Sb(III) oxidase gene, but lacking the As(III) oxidase gene are predominant in the SOP community. Despite this, SOPs exhibit comparable Sb(III) and As(III)-oxidizing activities in both aerobic and anaerobic conditions, indicating that at the microbial community level, Sb(III) oxidase can oxidize As(III). Secondly, we isolated a representative cultivable SOP, Ralstonia sp. SbOX with Sb(III) oxidase gene but without As(III) oxidase gene. Genomic analysis of SbOX reveals that this SOP strain has a complete Sb(III) oxidase (AnoA) gene, but lacks As(III) oxidase (AioAB or ArxAB) gene. It is interesting to discover that, besides its Sb(III) oxidation activities, SbOX also exhibits significant capabilities in oxidizing As(III) under both aerobic and anaerobic conditions. Moreover, under aerobic conditions and in the presence of both Sb(III) and As(III), SbOX exhibited a preference for oxidizing Sb(III). Only after the near complete oxidation of Sb(III) did SbOX initiate rapid oxidation of As(III). In contrast, under anaerobic conditions and in the presence of both Sb(III) and As(III), Sb(III) oxidation notably inhibited the As(III) oxidation pathway in SbOX, while As(III) exhibited minimal effects on the Sb(III) oxidation. These findings suggest that SOPs can oxidize As(III) under both aerobic and anaerobic conditions, exhibiting a strong preference for Sb(III) over As(III) oxidation in the presence of both. This study unveils a novel mechanism of interaction within the Sb and As biogeochemical cycles.

Effects of Tao Hong Si Wu decoction on IncRNA expression in rats with occlusion of middle cerebral artery / 中国药理学通报

Aim To screen and study the expression of long non-coding RNA (IncRNA) in rats with middle cerebral artery occlusion (MCAO) with MCAO treated with Tao Hong Si Wu decoction (THSWD) and determine the possible molecular mechanism of THSWD in treating MCAO rats. Methods Three cerebral hemisphere tissue were obtained from the control group, MCAO group and MCAO + THSWD group. RNA sequencing technology was used to identify IncRNA gene expression in the three groups. THSWD-regulated IncRNA genes were identified, and then a THSWD-regu-lated IncRNA-mRNA network was constructed. MCODE plug-in units were used to identify the modules of IncRNA-mRNA networks. Gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) were used to analyze the enriched biological functions and signaling pathways. Cis- and trans-regulatory genes for THSWD-regulated IncRNAs were identified. Reverse transcription real-time quantitative pol-ymerase chain reaction (RT-qPCR) was used to verify IncRNAs. Molecular docking was used to identify IncRNA-mRNA network targets and pathway-associated proteins. Results In MCAO rats, THSWD regulated a total of 302 IncRNAs. Bioinformatics analysis suggested that some core IncRNAs might play an important role in the treatment of MCAO rats with THSWD, and we further found that THSWD might also treat MCAO rats through multiple pathways such as IncRNA-mRNA network and network-enriched complement and coagulation cascades. The results of molecular docking showed that the active compounds gallic acid and a-mygdalin of THSWD had a certain binding ability to protein targets. Conclusions THSWD can protect the brain injury of MCAO rats through IncRNA, which may provide new insights for the treatment of ischemic stroke with THSWD.

Integrated approach to hydrogeochemical appraisal of groundwater quality concerning arsenic contamination and its suitability analysis for drinking purposes using water quality index.

Arsenic (As), contamination in drinking groundwater resources is commonly environmental problem in many developing countries including Pakistan, with significant human health risk reports. In order to examine the groundwater quality concerning As contamination, its geochemical behavior along with physicochemical parameters, 42 samples were collected from community tube wells from District Bahawalpur, Punjab, Pakistan. The results showed the concentration of elevated As, its source of mobilization, and associated public health risk. The As concentration detected in groundwater samples varied from 0.12 to 104 µg/L with an average value of 34.7 µg/L. Among 42 groundwater samples, 27 samples were beyond the permitted limit of 10 µg/L recommended by World Health Organization (WHO), for drinking purposes. Statistical analysis result show that the groundwater cations values are in decreasing order such as: Na+ > Mg2+ > Ca2+ > K+, while anions were HCO3- > SO42- > Cl- > NO3-. Hydrochemical facies result depict that the groundwater samples of the study area, 14 samples belong to CaHCO3 type, 5 samples belong to NaCl type, 20 samples belong to Mixed CaMgCl type, and 3 samples belong to CaCl2 type. It can be accredited due to weathering and recharge mechanism, evaporation processes, and reverse ion exchange. Gibbs diagram shows that rock water interaction controls the hydrochemistry of groundwater resources of the study area. Saturation Index (SI) result indicated the saturation of calcite, dolomite, gypsum, geothite, and hematite mineral due their positive SI values. The principal component analysis (PCA) results possess a total variability of 80.69% signifying the anthropogenic and geogenic source of contamination. The results of the exposure-health-risk-assessment method for measuring As reveal significant potential non-carcinogenic risk (HQ), exceeding the threshold level of (> 1) for children in the study area. Water quality assessment results shows that 24 samples were not suitable for drinking purposes.

Unusual paranasal sinus solitary neurofibroma and literature review.

Neurofibroma (NF) is a common benign peripheral neurogenic tumor that is rarely encountered in the paranasal sinus tract. In this report, we present a 55-year-old female who serendipitously discovered a maxillary sinus NF during a medical examination for a pulmonary nodule. The purpose of this article is to enhance medical practitioners' comprehension of paranasal sinus solitary NF by exploring cases, summarizing occurrences located in the paranasal sinus tract and conducting an organized review of paranasal sinus tract NF.

Staminal hairs increase pollinator attraction and pollination accuracy in Tradescantia fluminensis (Commelinaceae).

Staminal hairs are the particular appendages of stamens, which may affect pollinator foraging behaviour and pollen transfer. However, experimental evidence of the functions of staminal hairs in pollination remains scarce. Here, we conducted staminal hair manipulation experiments in Tradescantia fluminensis (Commelinaceae) to investigate their effects on visitation and pollen transfer by bees. Our observations revealed that both visitation rates and visit duration of honeybees (Apis cerana) to control flowers were significantly higher than that of hairless flowers. Moreover, removing the staminal hairs significantly decreased pollen deposition by honeybees (A. cerana), but did not affect pollen removal. The staminal hair was similar in length to the stamen and the pistil of T. fluminensis. The staminal hairs provide more footholds for honeybees, and they lay prone on the staminal hairs to collect pollen, which increased the accuracy of pollination through the consistent pollen placement and pick-up on the ventral surface of honeybees. These results showed that the staminal hairs in T. fluminensis may represent an adaptation to attract pollinators and enhance pollination accuracy.

Contradictory Impacts of Nitrate on the Dissimilatory Arsenate-Respiring Prokaryotes-Induced Reductive Mobilization of Arsenic from Contaminated Sediments: Mechanism Insight from Metagenomic and Functional Analyses.

Dissimilatory arsenate-respiring prokaryotes (DARPs) are considered to be a key impetus of the reductive dissolution of solid-phase arsenic. However, little is known about the interaction between nitrate and DARPs so far. In this study, we showed that nitrate either inhibited or promoted the DARP population-catalyzed reductive mobilization of As in sediments. Metagenomic analysis of the microbial communities in the microcosms after seven days of As release assays suggested that microbes mainly consisted of: Type-I DARPs having potential to reduce NO3- into NO2- and Type-II DARPs having potential to reduce NO3- to NH4+. We further isolated two cultivable DARPs, Neobacillus sp. A01 and Paenibacillus sp. A02, which represent Type-I and -II DARPs, respectively. We observed that nitrate suppressed A01-mediated release of As(III) but promoted A02-mediated release of As(III). Furthermore, we demonstrated that this observation was due to the fact that nitrite, the end product of incomplete denitrification by Type-I DARPs, suppressed the arrA gene expression per cell and growth of all DARPs, whereas ammonium, the end product of dissimilatory nitrate reduction to ammonium (DNRA) by Type-II DARPs, enhanced the arrA gene expression per cell and significantly promoted the growth of all DARPs. These findings suggest that the actual effects of nitrate on DARP population-catalyzed reductive mobilization of arsenic, largely depend on the ratio of Type-I to Type-II DARPs in sediments.

Repression of rRNA gene transcription by endothelial SPEN deficiency normalizes tumor vasculature via nucleolar stress.

Human cancers induce a chaotic, dysfunctional vasculature that promotes tumor growth and blunts most current therapies; however, the mechanisms underlying the induction of a dysfunctional vasculature have been unclear. Here, we show that split end (SPEN), a transcription repressor, coordinates rRNA synthesis in endothelial cells (ECs) and is required for physiological and tumor angiogenesis. SPEN deficiency attenuated EC proliferation and blunted retinal angiogenesis, which was attributed to p53 activation. Furthermore, SPEN knockdown activated p53 by upregulating noncoding promoter RNA (pRNA), which represses rRNA transcription and triggers p53-mediated nucleolar stress. In human cancer biopsies, a low endothelial SPEN level correlated with extended overall survival. In mice, endothelial SPEN deficiency compromised rRNA expression and repressed tumor growth and metastasis by normalizing tumor vessels, and this was abrogated by p53 haploinsufficiency. rRNA gene transcription is driven by RNA polymerase I (RNPI). We found that CX-5461, an RNPI inhibitor, recapitulated the effect of Spen ablation on tumor vessel normalization and combining CX-5461 with cisplatin substantially improved the efficacy of treating tumors in mice. Together, these results demonstrate that SPEN is required for angiogenesis by repressing pRNA to enable rRNA gene transcription and ribosomal biogenesis and that RNPI represents a target for tumor vessel normalization therapy of cancer.

The first homosporous lycophyte genome revealed the association between the recent dynamic accumulation of LTR-RTs and genome size variation.

The contrasting genome size between homosporous and heterosporous plants is fascinating. Different from the heterosporous seed plants and mainly homosporous ferns, the lycophytes are either heterosporous (Isoetales and Selaginellales) or homosporous (Lycopodiales). Many lycophytes are the resource plants of Huperzine A (HupA) which is invaluable for treating Alzheimer's disease. For the seed-free vascular plants, several high-quality genomes of heterosporous Selaginella, homosporous ferns (maidenhair fern, monkey spider tree fern), and heterosporous ferns (Azolla) have been published and provided important insights into the origin and evolution of early land plants. However, the homosporous lycophyte genome has not been decoded. Here, we assembled the first homosporous lycophyte genome and conducted comparative genomic analyses by applying a reformed pipeline for filtering out non-plant sequences. The obtained genome size of Lycopodium clavatum is 2.30 Gb, distinguished in more than 85% repetitive elements of which 62% is long terminal repeat (LTR). This study disclosed a high birth rate and a low death rate of the LTR-RTs in homosporous lycophytes, but the opposite occurs in heterosporous lycophytes. we propose that the recent activity of LTR-RT is responsible for the immense genome size variation between homosporous and heterosporous lycophytes. By combing Ks analysis with a phylogenetic approach, we discovered two whole genome duplications (WGD). Morover, we identified all the five recognized key enzymes for the HupA biosynthetic pathway in the L. clavatum genome, but found this pathway incomplete in other major lineages of land plants. Overall, this study is of great importance for the medicinal utilization of lycophytes and the decoded genome data will be a key cornerstone to elucidate the evolution and biology of early vascular land plants.

Phylogenomic analysis, cryptic species discovery, and DNA barcoding of the genus Cibotium in China based on plastome data.

Germplasm resources are the source of herbal medicine production. The cultivation of superior germplasm resources helps to resolve the conflict between long-term population persistence and growing market demand by consistently producing materials with high quality. The fern species Cibotium barometz is the original plant of cibotii rhizoma ("Gouji"), a traditional Chinese medicine used in the therapy of pain, weakness, and numbness in the lower extremities. Long-history medicinal use has caused serious wild population decline in China. Without sufficient understanding of the species and lineage diversity of Cibotium, it is difficult to propose a targeted conservation scheme at present, let alone select high-quality germplasm resources. In order to fill such a knowledge gap, this study sampled C. barometz and relative species throughout their distribution in China, performed genome skimming to obtain plastome data, and conducted phylogenomic analyses. We constructed a well-supported plastome phylogeny of Chinese Cibotium, which showed that three species with significant genetic differences are distributed in China, namely C. barometz, C. cumingii, and C. sino-burmaense sp. nov., a cryptic species endemic to NW Yunnan and adjacent regions of NE Myanmar. Moreover, our results revealed two differentiated lineages of C. barometz distributed on the east and west sides of a classic phylogeographic boundary that was probably shaped by monsoons and landforms. We also evaluated the resolution of nine traditional barcode loci and designed five new DNA barcodes based on the plastome sequence that can distinguish all these species and lineages of Chinese Cibotium accurately. These novel findings on a genetic basis will guide conservation planners and medicinal plant breeders to build systematic conservation plans and exploit the germplasm resources of Cibotium in China.

The spatio-temporal diversity and succession of microbial community and its environment driving factors during stacking fermentation of Maotai-flavor baijiu.

Stacking fermentation is an important stage of microbial expansion and enrichment in the brewing process of Maotai-flavor baijiu and has an important impact on quality. However, the structure and succession of microbial communities at different spatial points of fermented grains, as well as the key environmental factors driving community assembly, remain unclear. Here, we analyzed spatio-temporal similarities and differences in the microbial community structure and succession during 1-6 rounds of stacking fermentation of Maotai-flavor baijiu. The microbial diversity and richness in the pile center were higher than those at the pile surface. The dominant bacterial genus changed from Lactobacillus to Acetobacter, while the dominant fungal genus Pichia was gradually replaced by Candida, however, some microorganisms (Acetobacter, Thermoascus) could not occupy community dominance in both the pile surface and the pile center of fermented grains. Most of the biomarkers (Kroppenstedtia, Thermomyces, etc.) of the pile surface showed thermostable or thermophilic characteristics, while most biomarkers (Aspergillus, Hyphopicia, etc.) of the pile center were functional microorganisms. Furthermore, pH and moisture were the main environmental driving factors of community construction at the pile surface and the pile center, respectively, with starch and reducing sugars having a greater impact on the microbial community assembly of the pile center than that of the pile surface. The main differences in the metabolic pathways of the dominant bacterial genera of the pile surface and the pile center were concentrated around cell growth and death, amino acids, leading to enrichment and growth of microbial communities at the pile surface and nitrogen utilization at the pile center, respectively. This study reveals the spatio-temporal differences in microbial community structure, succession and corresponding environmental driving factors during stacking fermentation, which will provide guidance for regulating the microbial community diversity to produce high-quality Maotai-flavor baijiu.

Comprehensive identification of key compounds in different quality grades of soy sauce-aroma type baijiu by HS-SPME-GC-MS coupled with electronic nose.

In the production of soy sauce-aroma type baijiu (SSAB), the quality of base liquor significantly affects the finished liquor's quality. Moreover, low-quality liquor may cause health problems. The different quality grades of base liquor were analyzed to investigate the relationship between the quality and the key compounds in SSAB. In this study, samples were evaluated by the sensory and further analyzed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) coupled with electronic nose (E-nose). First, by sensory evaluation, the sauce, floral and fruity, fermented aromas and taste indicators (softness, fullness, harmony, purity and persistence) were positively correlated with the quality grade of the base liquor. The E-nose could distinguish the different quality grades of base liquor well. Second, differential compounds were identified via untargeted metabolome based on the HS-SPME-GC-MS. 16 common differential compounds were shared in the base liquor from different fermentation rounds, including 11 esters, 1 alcohol, 2 aldehydes and 2 ketones. It was found that the higher the quality grade of the base liquor, the richer the content of aromatics, alcohols, aldehydes and ketones. The principal component analysis (PCA) biplots of the differential compounds in the different quality grades of base liquor indicated that the superior-grade base liquor has a strong fruity aroma. By correlation analysis of the differential compounds and sensors responses of E-nose, furfuryl ethyl ether, butanoic acid ethyl ester, isopentyl hexanoate, nonanoic acid ethyl ester and 3-methyl-1-butanol had a significant effect on the response intensity of E-nose sensors. In the present study, the key differential compounds between the different quality grades of base liquor were identified, and the sensory differences between the base liquor were digitized.