Search Results (90)

Soil organic carbon (SOC) responses to straw return are strongly influenced by active carbon dynamics and extracellular enzyme responses, yet how these processes vary with initial SOC status and long-term straw-return history remains unclear. To address this question, we conducted a controlled incubation experiment using soils from long-term straw removal (CK) and straw return (SR) plots at two sites with contrasting SOC levels: a carbon-poor fluvo-aquic soil in Quzhou (QZ) and a carbon-rich black soil in Gongzhuling (GZL). Three fresh-straw input levels were imposed, and CO₂ release, SOC, labile C and N pools, extracellular enzyme activities, and ecoenzymatic stoichiometry were determined. Fresh-straw input markedly stimulated carbon mineralization in both soils, but SOC responses differed substantially. In QZ, SOC increased 12.1–15.7% at day 7 (vs. T0) and remained 6.7–12.1% above the control at day 90 under the long-term straw-return background. In contrast, GZL showed only minor early SOC responses, and doubled straw input reduced SOC 4.9–9.5% at day 90 despite a stronger dissolved organic carbon (DOC) pulse and greater cumulative CO₂ release. Enzyme responses also differed between soils: higher straw input in QZ enhanced β-cellobiohydrolase (CBH), β-xylosidase (BX), and especially L-leucine aminopeptidase (LAP), accompanied by lower ecoenzymatic C:P and higher vector angle, whereas GZL showed later activation of CBH, BX, and NAG with only slight changes in vector angle. Overall, our results indicate that initial SOC status and long-term straw-return history jointly regulate whether fresh-straw input promotes net SOC accumulation or enhanced mineralization. Full article

Plant cell walls provide structural integrity and defense against biotic and abiotic stresses. In rice (Oryza sativa), xylan is the major hemicellulose, and β-xylosidase hydrolyzes xylan by removing xylose residues from non-reducing ends. We analyzed a transgenic rice line (OsXylGH3-1-FOX) that constitutively overexpresses a GH3-family β-xylosidase (Os03g0749100) under the maize ubiquitin promoter. Following inoculation with M. oryzae, OsXylGH3-1-FOX leaves exhibited increased lesion numbers and disease indices, indicating reduced resistance, whereas leaf sheaths showed fewer fungal penetrations, suggesting enhanced resistance. To investigate these organ-specific responses, we quantified cell wall components. In leaves, xylose and arabinose decreased by ~33%, and galacturonic acid (pectin) by ~50%. In leaf sheaths, xylose and arabinose were unchanged, while galacturonic acid and cellulose increased by ~50% and ~70%, respectively. Histochemical staining confirmed reduced pectin in leaves and stronger, organized cellulose and pectin in leaf sheaths. These findings suggest that decreased pectin weakens cell adhesion, facilitating pathogen ingress in leaves, whereas increased pectin and cellulose reinforce wall integrity in leaf sheaths. Thus, pectin and cellulose abundance strongly correlate with organ-specific blast resistance, while hemicellulose plays a secondary role. Full article

β-D-xylosidase (BXL) is a key enzyme involved in xylan degradation and plays crucial roles in plant development and stress responses. However, its functional roles in potato (Solanum tuberosum) remain poorly understood. In this study, we performed a genome-wide identification of the StBXL gene family and identified eight StBXL genes distributed across five chromosomes. A phylogenetic analysis classified these genes into four groups. Conserved motif and domain analyses indicated functional conservation among StBXL proteins. Analyses of cis-acting elements in the promoters and expression profiles of StBXL genes in various plant tissues under different stress treatments revealed their spatiotemporal expression patterns, as well as potential roles in phytohormone signaling and stress responses. Alkali stress significantly inhibited the expression of StBXL4 and StBXL5. The overexpression of StBXL4 enhanced the sensitivity of potato seedlings to alkali stress, whereas the overexpression of StBXL5 showed no significant phenotypic differences under the same conditions. These results suggest that StBXL4 acts as a negative regulator of the alkali stress response in potato. This study fills the research gap regarding the potato StBXL gene family and provides valuable insights for the molecular breeding of alkali-tolerant potato varieties. Full article

Intensive land use in the Argentine Pampas has led to soil degradation, yet links between soil organic matter (SOM) composition, enzyme activity, and fungal communities remain unclear. This study compared contrasting ecoregions and land uses: pristine (PI), pasture (PA), crop rotation with cover crops (RO), and monoculture (MO). Infrared spectra showed that PI soils in Anguil had higher absorbance in hydroxyl/amine (3400 cm⁻¹: 0.90 ± 0.08) and carbonyl (1750 cm⁻¹: 0.52 ± 0.12) bands than MO soils (0.47 ± 0.30 and 0.35 ± 0.06; p < 0.05), indicating greater SOM diversity. Pergamino soils showed smaller differences, reflecting site-specific effects. Enzyme activities also responded to land use. In Anguil, xylosidase, β-1,4-N-acetylglucosaminidase, and phosphatase peaked under PI (40, 127, and 443 nmol g⁻¹ h⁻¹). In Pergamino, xylosidase and β-1,4-N-acetylglucosaminidase were higher under PA and PI, indicating enhanced microbial functionality under low disturbance. Fungal composition varied with land use and location: Mortierellomycetes dominated in Pergamino, while Leotiomycetes and Agaricomycetes were more abundant in PI and PA, and Dothideomycetes increased in MO and RO. Despite compositional shifts, fungal diversity changed little. Integrating chemical, biochemical, and molecular indicators revealed how land-use intensification modifies SOM and microbial processes in Pampas soils. Full article

The present study investigated the impact of genetic engineering strategies to produce a cell-free xylanase for applications in the baking industry. The xynA1 gene from the nonpathogenic bacterium Caulobacter vibrioides was integrated into the pAS22 vector with a xylose-inducible promoter and introduced back into the bacteria, resulting in the creation of the BS-xynA1. This construct exhibited substantial secreted xylanase 1 (XynA1) activity, reaching 17.22 U/mL, and a specific activity of 278.64 U/mg after an 18 h growth period with 0.3% (v/v) xylose plus 0.2% (w/v) corn straw. RT-qPCR analysis confirmed that higher xylanase activity in C. vibrioides cells was correlated with increased transcription of the xynA1 gene in the induction medium. Moreover, BS-xynA1 cells coexpress other enzymes, including xylanase 2 (XynA2), cellulase, pectinase, α-amylase, β-glucosidase, β-xylosidase, and α-L-arabinosidase, at low levels (≤2 U/mL). In vitro comparison of cell-free xylanases from BS-xynA1 with three commercially available xylanase-containing mixtures commonly utilized in baking protocols revealed its superior specific activity (163.4 U/mg) across a broad temperature range (30–100 °C), with optimal performance at 50 °C. In practical baking tests, the addition of cell-free XynA1 led to a reduction in dough kneading time and increase in bread height compared to those of the control. Notably, the incorporation of XynA1 resulted in enhanced alveolar structure formation within the bread crumb. Specifically, the following changes were observed in the mass parameters compared to those of the control: an increase in extensibility, elasticity, and deformation energy, and subsequent improvements in strength. Additionally, XynA1 addition led to a reduction in toughness and toughness/elasticity index, indicating a reduction in the mass stiffness of the enzyme-treated bread. To date, this is the first successful application of recombinant XynA1 from C. vibrioides in biotechnological processes related to baking, underscoring the potential and prospects in the food industry. Full article

β-D-xylosidases (BXLs) are pivotal enzymes in xylan degradation, playing essential roles in plant development and stress responses. In this study, we identified 29 GmBXL genes in soybean through homolog alignment. Phylogenetic analysis classified these genes into three groups, with Group III being legume-specific. The GmBXLs are unevenly distributed across 15 chromosomes, with their expansion driven by both tandem and segmental duplications. Conserved motif and domain analyses revealed functional conservation, particularly in family 3 of glycoside hydrolase domains. Promoter regions of GmBXLs are enriched with hormone-responsive and stress-related cis-elements, indicating their involvement in diverse biological processes. Tissue-specific expression analysis revealed differential GmBXLs expression across leaves, roots, flowers, and seeds, with GmBXL13 and GmBXL26 exhibiting notably high transcript levels in pods and seeds. Under salt stress, 26 GmBXLs exhibited significant expression changes, with 20 genes up-regulated in both leaves and roots, highlighting their roles in salt tolerance. These findings enhance our understanding of the evolutionary and functional characteristics of GmBXLs, providing valuable insights for molecular breeding of salt-tolerant soybean varieties. Full article

The fungi belonging to the genus Pleurotus can be cultivated in different substrates and represent excellent producers of several extracellular enzymes. In this study, we analyzed eleven hydrolytic enzymes of the P. eryngii and P. ostreatus secretomes, which were collected at three different growth stages after 23 days (mycelial colonization of about 50% of the substrate), 34 days (100% colonization of the substrate) and 50 days (after the first flush). Mushrooms were axenically cultivated on the same substrate. The results demonstrate that proteases, lipases, amylases, α-glucosidase, cellulases (endoglucanase, β-cellobiohydrolase and β-glucosidase) and hemicellulase (xylosidase, glucuronidase, arabinosidase and mannosidase) activities were higher in the secretomes from P. eryngii than those from P. ostreatus. Time course analysis revealed for both species a similar enzymatic activity profile, in which in the early stages of mycelium development, both species use starch as the main carbon source. Protease and lipase activities increased and remained constant during the subsequent formation of fruiting bodies, whereas cellulase and hemicellulase activities decreased after the complete mycelial colonization of the substrate. The zymographic analysis suggested the presence in the secretomes of proteolytic activities belonging to different classes. In conclusion, both mushroom species released into the secretomes a broad spectrum of hydrolytic enzymes potentially useful in various biotechnological fields. Full article

Prebiotics are food ingredients that result in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefits upon host health. Xylooligosaccharides (XOS) are prebiotic fibers made from xylan. Commercial XOS are mixtures of oligosaccharides containing β-1,4–linked xylose residues. Though they are widely added to foods at different doses, the molecular mechanisms of the catabolism and growth promotion of XOS in the innate gut microbes Lactobacillus spp. remain unknown. In this study, we evaluated the growth-promoting effect using a human fecal isolate, Lactiplantibacillus plantarum strain B20 (Lb. plantarum B20). Assays of bacterial growth and lactic acid production showed stronger growth promotion of XOS than other oligosaccharides did, in a dose- and fraction-dependent pattern. Using the Lb. plantarum strain SK151 genome as a reference, bioinformatic analysis failed to identify any previously characterized genes responsible for the uptake and catabolism of XOS. However, transcriptomic analysis of Lb. plantarum B20 yielded numerous differentially expressed genes (DEGs) during fermentation of XOS. Among these, an oligopeptide ABC transporter (RS03575-03595, composed of five proteins) and a hydrolase (RS06170) were significantly upregulated. Molecular docking analysis indicated that the substrate-binding protein RS03575 may mediate the import of XOS into the cell. Enzymatic assays further demonstrated that RS06170 possesses β-xylosidase activity and can effectively degrade XOS. In addition, functional enrichment analysis suggested that the growth-promoting effect of XOS may be attributed to the upregulation of genes involved in cellular component biogenesis and cell division, potentially through modulation of ribosome function and carbohydrate metabolism in Lb. plantarum B20. These results provide valuable insights into the mechanisms by which XOS promote growth and highlight potential targets for enhancing prebiotic–probiotic interactions. Full article

Establishing a suitable and useful soil quality (SQ) assessment tool is imperative for the accurate evaluation of the effect of environmental changes on SQ. This study constructed four soil quality indexes (SQIs) based on different minimum data sets and weighted additive models to evaluate the influence of grassland degradation on SQ in northwest Guizhou, China. A total of 19 soil properties, including six physical properties, six chemical properties, and seven microbial properties, were measured at soil depths 0–20 cm to construct the SQIs. Results showed that 18 soil indicators were selected as the potential SQ indicators in the total data set. Based on the principal component analysis, four indicators, soil organic carbon (SOC), mean weight diameter, α-glucosidase, and β-acetylglucosaminidase, were selected in the minimum data set (MDS). However, six indicators, SOC, pH, β-1,4-xylosidase, β-acetylglucosaminidase, Clay, and Bulk Density, were selected for the selective MDS. Despite the notable inter-correlation among the four established SQIs, the SQI derived from the selective MDS and weighted additive model demonstrated heightened sensitivity and capacity for differentiation with respect to grassland degradation because of the high values of F and CV. Grassland degradation significantly reduced the SQ, and the value of SQ under severely degraded grassland was reduced by 51% compared with that under non-degraded grassland. Under the lightly degraded grassland, the reduction in soil physical quality was the primary reason for the total SQ decline, while the reduction in soil microbial and chemical reduction resulted in a significant decline in total SQ under the severely degraded grassland. In conclusion, greater attention should be paid to the SQ reduction resulting from grassland degradation in the study area, and the SQI established by selective MDS and weighted additive model should be used as a suitable and useful SQ assessment tool to evaluate the influence of environmental changes on SQ in Southwest China and other similar areas. Full article

Decreasing precipitation frequency (DPF) has the potential to alter soil microbial community structure, enzyme activity, and the stoichiometry of microbial biomass in grassland ecosystems. Grasslands have undergone degradation, often driven by anthropogenic activities such as overgrazing, which further intensifies their sensitivity to environmental changes such as altered precipitation. Changes in soil microbial communities can in turn impact the soil organic carbon pool (SOCP) and its stability, particularly in degraded grasslands shaped by agricultural practices. Here, we evaluated how DPF affects different types of soil carbon pools, soil microbial community structure, the stoichiometry of microbial biomass, and the potential activity of exoenzymes related to microbial nutrient acquisition in three steppe grasslands representing a degradation gradient (from light to moderate to severe degradation). We also developed a systematic model linking microbial stoichiometry, community structure, enzyme activity, and the SOCP and its stability. Our results showed that DPF significantly reduced the soil total carbon pool (STCP), SOCP, and dissolved organic carbon pool (DOCP) in all degraded grasslands, while it increased the DOCP/SOCP ratio in the grasslands with light to moderate degradation, indicating lower stability of the SOCP. Decreased precipitation frequency reduced microbial biomass in grasslands with light to moderate degradation but had the opposite effect on grasslands with severe degradation. Additionally, the promoting effects of DPF on the fungi/bacteria ratio and β-1,4-xylosidase activity diminished with increasing grassland degradation. The fungi/bacteria ratio, microbial biomass carbon/nitrogen ratio, and β-1,4-xylosidase activity were identified as the main predictors for the SOCP and its stability. In lightly and moderately degraded grasslands, decreased soil water content (SWC) and increased soil moisture variation induced by lower precipitation frequency promoted β-1,4-xylosidase activity by decreasing the microbial biomass carbon/nitrogen ratio. The lower stability of the SOCP in degraded grasslands under altered precipitation frequency highlights the challenges posed by climate change regarding soil carbon sequestration in these fragile ecosystems. Our results also stress the importance of targeted water management for soil carbon sequestration in agriculture and livestock management, which could be achieved by altering soil microbial activity and stoichiometry, For example, fertilization increases nutrient availability, enhances microbial growth, and shifts C/N/P ratios, promoting carbon allocation to biomass over respiration and thus enhancing soil carbon retention. Full article

The GH43 family of glycosidases represents an important class of industrial enzymes that are widely utilized across the food, pharmaceutical, and various other sectors. In this study, we identified a GH43 family glycoside hydrolytic enzyme, Xyaf313, derived from the plant endophytic fungus Chaetomium globosum DX-THS3, which is capable of transforming several common ginsenosides. The enzyme function analysis reveals that Xyaf313 exhibits dual functionality, displaying both α-L-arabinofuranosidase and β-D-xylosidase activity. When acting as an α-L-arabinofuranosidase, Xyaf313 achieves optimal enzyme activity of 23.96 U/mg at a temperature of 50 °C and a pH of 7. In contrast, its β-D-xylosidase activity results in a slight reduction in enzyme activity to 23.24 U/mg, with similar optimal temperature and pH conditions to those observed for the α-L-arabinofuranosidase activity. Furthermore, Xyaf313 demonstrates considerable resistance to most metal ions and common chemical reagents. Notably, while the maximum enzyme activity of Xyaf313 occurs at 50 °C, it maintains high activity at room temperature (30 °C), with relative enzyme activity exceeding 90%. Measurements of ginsenoside transformation show that Xyaf313 can convert common ginsenosides Rc, Rb₁, Rb₂, and Rb₃ into Rd, underscoring its potential for pharmaceutical applications. Overall, our findings contribute to the identification of a new class of bifunctional GH43 glycoside hydrolases, highlight the significance of plant endophytic fungi as a promising resource for the screening of carbohydrate-decomposing enzymes, and present new candidate enzymes for the biotransformation of ginsenosides. Full article

The importance of urban forest management and carbon cycle research has increased amidst ongoing urbanization. Understanding the potential impact of fine woody debris (FWD) retention as a management strategy on the soil organic carbon (SOC) levels and stability in urban forests is crucial. In this study, four FWD retention treatments (no retention, CK; low retention, LR; medium retention, MR; and high retention, HR) were implemented in Harbin urban Picea koraiensis Nakai plantations to investigate the stability of the SOC pool in response to these treatments. The FWD retention treatment had no significant effect on the soil’s physical and chemical properties and SOC concentration, but significantly reduced the total potassium and NO₃⁻ concentrations. The FWD retention treatment increased active SOC fractions and carbon-degrading enzyme activities, while reducing leucine aminopeptidase, polyphenol oxidase enzyme activities, and the stability of the SOC pool. The random forest model showed that FWD retention, particulate organic carbon, cellobiohydrolases, and β-xylosidase enzyme activities were factors that significantly affected the stability of the SOC pool. These findings suggest that retaining a large amount of FWD in northeast China can benefit the soil carbon cycle in urban plantations by accelerating the turnover of active SOC fractions. Full article

Valorization of agri-food residues has garnered significant interest for obtaining value-added compounds such as enzymes or bioactive molecules. Rice milling by-products, such as rice bran, have limited commercial value and may pose environmental challenges. Filamentous fungi are recognized for their ability to grow on residues and for their capacity to produce large amounts of metabolites and enzymes of industrial interest. Here, we used filamentous fungi to produce enzyme cocktails from rice bran, which, due to its polysaccharide composition, serves as an ideal substrate for the growth of fungi producing cellulases and xylanases. To this end, sixteen fungal strains were isolated from rice bran and identified at the species level. The species belonged to the genera Aspergillus, Penicillium, and Mucor. The Aspergillus species displayed the highest efficiency in cellulase and xylanase activities, especially A. niger var. phoenicis and A. amstelodami. A. terreus, A. tritici, and A. montevidensis stood out as xylanolytic isolates, while P. parvofructum exhibited good cellulase activity. A. niger var. phoenicis followed by A. terreus showed the highest specific enzymatic activities of α- and β-D-galactosidase, α-L-arabinofuranosidase, α- and β-D-glucosidase, and β-D-xylosidase. Additionally, proteomic analysis of A. terreus, A. niger var. phoenicis, and P. parvofructum exoproteomes revealed differences in enzyme production for rice bran degradation. A. niger var. phoenicis had the highest levels of xylanases and cellulases, while P. parvofructum excelled in proteases, starch-degrading enzymes, and antifungal proteins. Finally, two Penicillium isolates were notable as producers of up to three different antifungal proteins. Our results demonstrate that filamentous fungi can effectively valorize rice bran by producing enzyme cocktails of industrial interest, along with bioactive peptides, in a cost-efficient manner, aligning with the circular bio-economy framework. Full article

The impact of nitrogen and phosphorus deposition alternations, as well as apoplastic litter quality and quantity, on soil nutrient cycling and soil carbon pool processes in forest ecosystems is of considerable importance. Soil ecological enzyme chemistry is a powerful tool for elucidating the nutrient limitations of microbial growth and metabolic processes. In order to explore the responding mechanisms of soil ecological enzyme chemistry to the simultaneous changes in apoplast input and nitrogen and phosphorus deposition in temperate coniferous and broad-leaved mixed forests, an outdoor simulating experiment was conducted. The results demonstrate that the treatments involving apoplastic material and nitrogen and phosphorus additions had significantly impacted soil nutrient levels across different forest types. Apoplastic treatments and N-P additions had a significant effect on the soil total organic carbon (TOC), dissolved organic carbon (DOC), soil total soluble nitrogen (TSN), soil available phosphorus (SAP), soil total nitrogen (TN), soil total phosphorus (TP), and microbial biomass carbon (MBC). However, the effects on soil microbial biomass (MBN) and microbial biomass phosphorus (MBP) were insignificant. The apomictic treatments with N and P addition did not result in a statistically significant change in soil C-hydrolase activities (β-1,4-glucosidase BG, β-1,4-xylosidase BX, cellobiohydrolase CBH, phenol oxidase POX, and peroxidase PER), N-hydrolase activities (β-1,4-N-acetylglucosaminidase NAG and L-leucine aminopeptidase LAP), or P-hydrolase activities (Acid phosphatase AP). Although the apomictic treatments did not yield a significant overall impact on carbon hydrolase activity, they influenced the activity of specific enzymes, such as CBH, LAP, and PER, to varying degrees. The effects on BG, BX, CBH, AP, and C-hydrolase activities were significant for different stand types. The impact of apomictic treatments and N-P additions on soil nitrogen hydrolase activities was inconsequential with a minimal interactive effect. The highest correlation between PER, LAP, and N-hydrolase activities was observed in conjunction with elevated levels of nitrogen and phosphorus addition (N3L0, original litter treatment, and high amounts of N and P addition). These findings may provide a theoretical foundation for the management of ecosystem function in broad-leaved Korean pine forests. Full article

Litter decomposition is a crucial biochemical process regulated by microbial activities in the forest ecosystem. However, the dynamic response of the fungal community during litter decomposition to vegetation changes is not well understood. Here, we investigated the litter decomposition rate, extracellular enzyme activities, fungal community, and nutrient cycling-related genes in leaf and twig litters over a three-year decomposition period in a pure Liquidamabar formosana forest and a mixed L. formosana/Pinus thunbergii forest. The result showed that during the three-year decomposition, twig litter in the mixed forest decomposed faster than that in the pure forest. In both leaf litter and twig litter, β-cellobiosidase and N-acetyl-glucosamidase exhibited higher activities in the mixed forest, whereas phosphatase, β-glucosidase, and β-xylosidase were higher in the pure forest. The fungal α-diversity were higher in both litters in the pure forest compared to the mixed forest, with leaf litter showing higher α-diversity than twig litter. Fungal species richness and α-diversity within leaf litter increased as decomposition progressed. Within leaf litter, Basidiomycota dominated in the mixed forest, while Ascomycota dominated in the pure forest. Funguild analysis revealed that Symbiotroph and ectomycorrhizal fungi were more abundant in the mixed forest compared to the pure forest. In the third-year decomposition, genes related to phosphorus cycling were most abundant in both forests, with the pure forest having a higher abundance of cex and gcd genes. Fungal community structure, predicted functional structure, and gene composition differed between the two forest types and between the two litter types. Notably, the fungal functional community structure during the first-year decomposition was distinct from that in the subsequent two years. These findings suggest that dominant tree species, litter quality, and decomposition time all significantly influence litter decomposition by attracting different fungal communities, thereby affecting the entire decomposition process. Full article