Extracellular Enzyme Activities Research Articles

Impact of short-term pasture development on soil aggregation, temperature sensitivity of soil organic carbon, and functional diversity in semi-arid ecosystem

Pasture development could be a viable option to restore degraded land in semi-arid region. New knowledge on soil functional diversity, aggregation, and temperature sensitivity (Q 10) of soil organic carbon (SOC) after pasture development would assist to accomplish the scope of global pastureland management for climate change mitigation and land restoration. To understand the impact of pasture development on soil aggregation, SOC stock, and its Q 10, research was undertaken at three development sites (RS1, RS2, RS3) in India with seeding of Cenchrus ciliaris, Megathyrus maximus, and Stylosanthes seabrana (at a line-ratio of 2:2:1). After three years, biomass productivity and for SOC, aggregation, enzyme activities, etc. at 0–20 and 21–40 cm depths were estimated. Pasture development improved biomass productivity from 0.68 mg ha−1 in undeveloped site to 3.62–4.64 mg ha−1. Pasture development enhanced SOC stock from 5.85 to 7.31 mg C ha−1 at the surface layer with an annual accumulation rate of 28–112 kg SOC ha−1 year−1. Greater activities of extracellular enzymes were observed at the surface soil layer in pasture development sites over undeveloped control. The mean weight diameter was ∼23–38% higher at pasture development sites over undeveloped sites. The Q 10 being controlled by the labile carbon was significantly higher (13–29%) at the pasture development sites over undeveloped site. Hence, short-term pasture development could improve the SOC stocks at the surface layer only, but the stocks were vulnerable to C loss at higher temperature. However, long-term pasture development could have a great potential to accrue C to mitigate climate change.

Influence of Arbuscular Mycorrhizal Fungi on Nitrogen Dynamics During Cinnamomum camphora Litter Decomposition

Arbuscular mycorrhizal fungi (AMF) can preferentially absorb the released ammonium (NH4+) over nitrate (NO3−) during litter decomposition. However, the impact of AMF’s absorption of NH4+ on litter nitrogen (N) decomposition is still unclear. In this study, we investigated the effects of AMF uptake for NH4+ on litter N metabolic characteristics by enriching NH4+ via AMF suppression and nitrification inhibition in a subtropical Cinnamomum camphora forest. The results showed that AMF suppression and nitrification inhibition significantly decelerated litter decomposition in the early stage due to the repression of NH4+ in extracellular enzyme activity. In the late stage, when soil NH4+ content was low, in contrast, they promoted litter decomposition by increasing the extracellular enzyme activities. Nitrification inhibition mainly promoted the utilization of plant-derived N by promoting the degradation of the amide I, amide II, and III bands by increasing protease activity, and it promoted ammonification by increasing urease activities, whereas it reduced the utilization of microbial-derived N by decreasing chitinase activity. On the contrary, AMF suppression, which significantly reduced the ammonification rate and increased the nitrification rate, only facilitated the degradation of the amide II band. Moreover, it intensified the microbial-derived N decomposition by increasing chitinase activity. The degradation of the amide I and II bands still relied on the priming effects of AMF on soil saprotrophs. This was likely driven by AMF-mediated phosphorus (P) mineralization. Nutrient acquiring, especially P by phosphatase, were the main factors in predicting litter decomposition and protein degradation. Thus, AMF could relieve the end-product repression of locally enriched NH4+ in extracellular enzyme activity and promote early-stage litter decomposition. However, the promotive effects of AMF on litter protein degradation and NH4+ release rely on P mineralization. Our results demonstrated that AMF could alleviate the N limitation for net primary production via accelerating litter N decomposition and reducing N loss. Moreover, they could restrict the decomposition of recalcitrant components by competing with saprotrophs for nutrients. Both pathways will contribute to C sequestration in forest ecosystems, which advances our understanding of AMF’s contribution to nutrient cycling and ecosystem processes in subtropical forests.

Long-term climate establishes functional legacies by altering microbial traits.

Long-term climate history can influence rates of soil carbon cycling but the microbial traits underlying these legacy effects are not well understood. Legacies may result if historical climate differences alter the traits of soil microbial communities, particularly those associated with carbon cycling and stress tolerance. However, it is also possible that contemporary conditions can overcome the influence of historical climate, particularly under extreme conditions. Using shotgun metagenomics, we assessed the composition of soil microbial functional genes across a mean annual precipitation gradient that previously showed evidence of strong climate legacies in soil carbon flux and extracellular enzyme activity. Sampling coincided with recovery from a regional, multi-year severe drought, allowing us to document how the strength of climate legacies varied with contemporary conditions. We found increased investment in genes associated with resource cycling with historically higher precipitation across the gradient, particularly in traits related to resource transport and complex carbon degradation. This legacy effect was strongest in seasons with the lowest soil moisture, suggesting that contemporary conditions-particularly, resource stress under water limitation-influences the strength of legacy effects. In contrast, investment in stress tolerance did not vary with historical precipitation, likely due to frequent periodic drought throughout the gradient. Differences in the relative abundance of functional genes explained over half of variation in microbial functional capacity-potential enzyme activity-more so than historical precipitation or current moisture conditions. Together, these results suggest that long-term climate can alter the functional potential of soil microbial communities, leading to legacies in carbon cycling.

Nonlinear response of soil organic carbon sequestration to deadwood decomposition in a subtropical–temperate ecotonal forest

Abstract The decomposition of deadwood is a crucial process for the accumulation and sequestration of soil organic carbon (SOC) in forest ecosystems. Yet, the response of SOC to various classes of deadwood decay and the underlying mechanisms remain unclear. Here, we investigated the dynamics of SOC, soil properties, extracellular enzyme activities, and phospholipid fatty acid biomarkers across five decay classes (defined from 1 to 5) of Masson pine (Pinus massoniana Lamb.) downed deadwood in a subtropical-temperate ecotone forest in Central China. Results showed a nonlinear response pattern of SOC along the deadwood decomposition gradient, with the maximum value at the decay class 4. Soil available nitrogen content, bacterial biomass, fungal biomass, the ratio of fungal to bacterial biomass, cellulase, and ligninase all increased, whereas soil pH decreased along with the intensification of deadwood decay. Increases in SOC content were associated with a direct positive effect of bacteria, and direct and indirect positive effects of fungi via cellulase, but ligninase showed no significant relationship with SOC content. These findings suggest that cellulose and microbial biomass determine soil C formation and sequestration during deadwood decomposition. This study highlights the importance of the nonlinear response of SOC to deadwood decay intensification, thus helping to predict future C–climate feedbacks.

Rooting for microbes: impact of root architecture on the microbial community and function in top- and subsoil

Abstract Background and aims Climate change and associated weather extremes pose major challenges to agricultural food production, necessitating the development of more resilient agricultural systems. Adapting cropping systems to cope with extreme environmental conditions is a critical challenge. This study investigates the influence of contrasting root system architectures on microbial communities and functions in top- and subsoil. Methods A column experiment was performed to investigate the effects of different root architectures, specifically deep (DRS) and shallow (SRS) root systems of wheat (Triticum aestivum L.) on microbial biomass, major microbial groups, and extracellular enzyme activities in soil. We focused on β-glucosidase (BG) activity, which is an indicator for microbial activity, during different plant growth stages, using destructive and non-destructive approaches. Results We found that the DRS promoted microbial biomass and enzyme activity in subsoil, while the SRS increased the microbial biomass and enzyme activity in topsoil. In-situ soil zymography provided fine-scale spatial insights, highlighting distinct patterns of BG activity near root centers and formation of enzyme activity hotspots, which were defined as regions where enzyme activity exceeds the mean activity level by 50%. Temporal changes in BG activity further underscored the dynamic nature of root-microbe interactions. Extracellular enzyme activities indicated varying carbon, nitrogen and phosphorus acquisition strategies of rhizosphere microorganisms between top- and subsoil. Conclusion This study underscores the need to consider root system architecture in agricultural strategies, as it plays a crucial role in influencing microbial communities and enzyme activities, ultimately affecting carbon and nutrient cycling processes in top- and subsoil.

Isolation optimization and screening of halophilic enzymes and antimicrobial activities of halophilic archaea from the high-altitude, hypersaline Da Qaidam Salt Lake, China.

The aim of this study is to increase the diversity of culturable halophilic archaea by comparing various isolation conditions and to explore the application of halophilic archaea for enzyme-producing activities and antimicrobial properties. We systematically compared the isolation performance of various archaeal and bacterial media by isolating halophilic archaea from the Da Qaidam Salt Lake, a magnesium sulfate subtype hypersaline lake on the Qinghai-Tibet Plateau, China, using multiple enrichment culture and gradient dilution conditions. A total of 490 strains of halophilic archaea were isolated, which belonged to five families and 11 genera within the order Halobacteriales of the class Halobacteria of the phylum Euryarchaeota. The 11 genera consisted of nine known genera and two potentially new genera, the former including Halorubrum, Natranaeroarchaeum, Haloplanus, Haloarcula, Halorhabdus, Halomicrobium, Halobacterium, Natrinema, and Haloterrigene. Halorubrum was the dominant genus with a relative abundance of 78.98%. By comparing different culture conditions, we found that bacterial media 2216E and R2A showed much better isolation performance than all archaeal media, and enrichment culture after 60 d and dilution gradients of 10-1 and 10-2 were best fitted for halophilic archaea cultivation. The screening of 40 halophilic archaeal strains of different species indicated that these halophilic archaea had great extracellular enzyme activities, including amylase (62.5%), esterase (50.0%), protease (27.5%), and cellulase (15.0%), and possessed great antimicrobial activities against human pathogens. A total of 34 strains exhibited antimicrobial activity against four or more pathogens, and 19 strains exhibited antimicrobial activity against all six pathogens. The diversity of culturable halophilic archaea was significantly increased by enrichment culture and selection of bacterial media, and screening of representative strains showed that halophilic archaea have multiple extracellular enzyme activities and broad-spectrum antimicrobial activity against human pathogens.

Diversity, Extracellular Enzyme Activity and Growth Promoting Potential of Fungal Isolates from the Roots of Coleus aromaticus Benth.

ABSTRACT: Coleus aromaticus Benth. a member of Lamiaceae family is a herbaceous plant with numerous medicinal properties. The present study was aimed at the isolation, characterization, extracellular enzyme activity and growth promoting ability of endophytic fungi from the roots of C. aromaticus collected from different parts of Palakkad, Kerala, India. A total of nine cultures grouped into five morphotypes including one non-sporulating taxa mostly belonging to Ascomycota were isolated. Their colonization rate and diversity index was determined. Extracellular enzyme activity and plant growth promotion studies were also carried out. Amylase activity was exhibited by all isolates, while none of them showed tyrosinase, protease, or laccase activity. Among the isolates, Fusarium sp. exhibited significant root and shoot length promotion in Vigna radiata seedlings, and its identification was confirmed through sequence analysis as Fusarium solani. The results indicated that the endophytic association has a positive role in promoting plant growth and revealed diverse mycoflora in the roots of Coleus aromaticus with various biological activities, highlighting the potential for further research into endophytes and their metabolites as a promising field.

Comparative Genomics and Biosynthetic Cluster Analysis of Antifungal Secondary Metabolites of Three Strains of Streptomyces albidoflavus Isolated from Rhizospheric Soils.

Streptomyces is a genus of Gram-positive bacteria with high GC content. It remains attractive for studying and discovering new antibiotics, antifungals, and chemotherapeutics. Streptomyces genomes can contain more than 30 cryptic and expressed biosynthetic gene clusters (BGC) encoding secondary metabolites. In this study, three Streptomyces strains isolated from jungle rhizospheric soil exhibited supernatants that can inhibit sensitive and fluconazole-resistant Candida spp. The genomes of the strains Streptomyces sp. A1, J25, J29 ori2 were sequenced, assembled de novo, and analyzed. The genome assemblies revealed that the size of the genomes was 6.9 Mb, with linear topology and 73.5% GC. A phylogenomic approach identified the strains with high similitudes between 98.5 and 98.7% with Streptomyces albidoflavus SM254 and R-53649 strains, respectively. Pangenomic analysis of eight genomes of S. albidoflavus strains deposited in the Genomes database recognized 4707 core protein orthogroups and 745 abundant accessory and exclusive protein orthogroups, suggesting an open pangenome in this species. The antiSMASH software detected candicidin and surugamide BGC-encoding polyene and octapeptide antifungal secondary metabolites in other S. albidoflavus. CORASON software was used to compare the synteny, and the abundance of genes harbored in the clusters was used. In conclusion, although the three strains belong to the same species, each possesses a distinct genome, as evidenced by the different phenotypes, including antifungal and extracellular enzymatic activities.

Spatio-temporal distribution and biotechnological potential of culturable yeasts in the intertidal sediments and seawater of Aoshan Bay, China.

Marine yeasts play a crucial role in marine microbial ecology, facilitating the biogeochemical cycling of carbon and nitrogen in marine ecosystems, while also serving as important reservoirs of bioactive compounds with extensive applications in pharmaceuticals, agriculture, and various industries. Intertidal flats, characterized by their complex ecological dynamics, are postulated to harbor a wealth of yeast resources. This study employed a culture-dependent approach to assess the diversity, spatio-temporal distribution, and biotechnological potential of yeast communities residing within the intertidal sediments and seawater of Aoshan Bay. A total of 392 yeast strains were identified from 20 distinct genera, encompassing 43 recognized species and four candidate novel species. Notably, 17 of these species were identified as novel occurrences in marine environments, underscoring the rich yeast biodiversity of the Aoshan Bay ecosystem, with Candida emerging as the dominant genus in both sedimentary and aqueous habitats. Yeast community composition exhibited significant spatial and temporal variation, with peak diversity and abundance observed in autumn, the subtidal zone, and the surface soil layer. No clear pattern, however, emerged linking these shifts to specific changes in community composition, highlighting the complex interactions between microbial communities, environmental variables, and anthropogenic disturbance. Although several yeast species isolated here have been previously recognized for their biotechnological potential, their diverse and abundant extracellular enzyme profiles were characterized, further highlighting their crucial role in organic matter decomposition and nutrient cycling within the tidal ecosystem, as well as their potential applicability in the food, fine chemical, textile, and pharmaceutical industries.IMPORTANCEThis study presents groundbreaking insights into the yeast diversity of Aoshan Bay, offering invaluable information on their spatial and temporal distribution patterns, as well as their biotechnological potential in the tidal environment. The findings reveal that the eutrophic intertidal flat is a rich repository of yeasts with abundant extracellular enzymatic activity and an important role in nutrient cycling and decomposition processes. Also, these yeasts serve as crucial indicators of ecosystem health and function and are excellent candidates for biotechnological and industrial applications. Collectively, this study not only expands our knowledge of the diversity and distribution of intertidal yeasts but also highlights their promising potential for biotechnological applications.

Soil health improvements under cover crops are associated with enhanced soil content of cytokinins.

Cytokinins (CKs) are phytohormones produced by plants and other soil life. including bacteria, fungi, insects, and earthworms. These organisms can release CKs to the soil, which may have positive implications for soil health and plant growth. However, no studies have examined phytohormones as soil health indicators. In custom-designed rhizo-pots that separated rhizosphere and bulk soils, the cover crops tillage radish and cereal rye were used to manipulate soil health parameters: soil pH, soil organic matter, soil active carbon, soil microbial community diversity, and extracellular enzyme activities involved in C, N and P cycling. Data were compared to impacts of cover crops on CKs that were purified from the complex soil and measured with HPLC-HRMS/MS. From soil we detected free base-CKs (trans-zeatin (tZ), isopentenyladenine (iP)), riboside-CKs (RB-CKs), cis-zeatin riboside (cZR), isopentenyladenosine (iPR) and four methylthiolated CKs: 2-methylthio-zeatin (2MeSZ), 2-methylthio-zeatin ribosides (2MeSZR), 2-methylthio-isopentenyladenine (2MeSiP), and 2-methylthio-isopentenyladenine riboside (2MeSiPR). These CK levels were significantly enhanced in cover cropped soil compared to uncultivated soil, and reflect a positive relationship between soil CK profiles and other soil health parameters - notably, between total CK and active C levels and soil microbial community diversity. This is the first detailed soil CK analysis and assessment of its potential use as a novel, reliable, short-term soil health parameter. The increased CK concentrations in cover cropped soils likely reflects the activity levels of soil life (plants, microbes, animals) and provides a rationale to use CKs as tools to evaluate soil health as influenced by agricultural management strategies.

Ground cover management enhances soil extracellular enzyme activities across Chinese orchards.

The impacts of ground cover management (GCM) on orchard soil properties have been extensively studied. However, the quantitative assessment of soil extracellular enzyme activities (EEAs) in mulch agriculture remains understudied. In this study, we investigated EEAs related to GCM to assess microbial metabolic activity, soil health, and nutrient status, based on 81 studies focusing on orchards in China. Our findings show that GCM significantly increases carbon acquisition (C-acq, 37%), nitrogen acquisition (N-acq, 34%), phosphorus acquisition (P-acq, 26%), and oxidative decomposition (OX, 14%) enzymes compared to continuous clean tillage. A subgroup analysis and a random forest model were conducted to further identify the effects and potential mechanisms through which soil EEAs respond to GCM in orchards under various moderators. The significant changes in EEAs induced by GCM vary with experimental and environmental factors. Tree age, climate conditions, and soil depth are the primary contributors to the variation in soil EEAs. Overall, our results suggest that the implementation of GCM positively affects EEAs, thereby enhancing microbe-mediated soil ecosystem functions and soil fertility. This meta-analysis provides comprehensive evidence of GCM-induced effects on hydrolase and oxidase activity, improving our understanding of the underlying mechanisms by which orchard mulching impacts soil nutrient cycling.

Bioavailability of dissolved organic matter (DOM) derived from seaweed Gracilaria lemaneiformis meditated by microorganisms

Seaweed Gracilaria lemaneiformis, a significant oceanic primary producer, releases substantial dissolved organic matter (DOM) during growth and decay, potentially impacting coastal organic carbon reservoirs and microbial communities. This study aimed to investigate the bioavailability of Gracilaria-derived DOM and its interactions with microbial communities. Laboratory experiments introduced Gracilaria-derived DOM into natural seawater, tracking variations in DOM composition, microbial structure, and eight extracellular enzyme activities over 168 h. The results indicated a rapid breakdown of dissolved organic carbon, nitrogen, and phosphorus, representing 48 % to 90 % of their total concentrations within 168 h, highlighting the high DOM bioavailability. Tryptophan substances were identified as the primary components of Gracilaria-derived DOM, being highly labile and utilized by microorganisms. Within the initial 0–12 h of DOM influx, Proteobacteria significantly increased and dominated in bacterial community, while after 48 h, as DOM decomposed, Desulfobacterota became the dominant group. The labile DOM stimulated bacteria, particularly Proteobacteria, to release substantial extracellular enzymes that peaked within the first 12 h. Subsequent substrate depletion led to decreased enzyme activities. Positive correlations were observed among bacterial abundance, enzyme activities, and tryptophan substances, emphasizing the intricate interplay among microbial communities, labile DOM, and extracellular enzymes. This study underscores the high bioavailability of Gracilaria-derived DOM and its interactions with microbial communities in nearshore environments.

Organic Matter Composition and Water Stoichiometry Are Main Drivers of Heterotrophic Nitrate Uptake in Mediterranean Headwater Streams

AbstractHeterotrophic bacteria can contribute to improve stream water quality by taking up nitrate (NO3−) from the water column, although microbial demand for this nutrient is usually lower than for other inorganic nitrogen (N) forms, such as ammonium. Heterotrophic NO3− uptake has been related to the availability of dissolved organic carbon (DOC) relative to nutrients (i.e., DOC: nutrients ratios). Yet, how dissolved organic matter (DOM) composition and specific microbial assemblages influence NO3− uptake remains poorly understood. We conducted laboratory incubations to investigate heterotrophic NO3− uptake kinetics in 9 Mediterranean freshwater ecosystems, primarily headwater streams, exhibiting wide variation in DOC:NO3 ratios (from 1.5 to 750). Moreover, we characterized DOM composition using spectroscopic indexes and its degradation via a reactivity continuum model approach. Microbial community composition and functioning were assessed by analyzing extracellular enzymatic activities and the potential abundance of N‐cycling genes. Our results revealed that NO3− uptake rates (kNO3) were positively related with DOC:NO3 ratios (r2 = 0.4) and to NO3:SRP ratios as well (r2 = 0.6). Furthermore, kNO3 was negatively correlated to the humification index (r2 = 0.7), suggesting that a higher proportion of humic‐like compounds slow down heterotrophic NO3− uptake. A partial least squares regression model (PLS) pinpointed that DOC and nutrient stoichiometry, DOM composition and reactivity, and microbial composition and activity collectively contributed to explain the variability in kNO3 observed across treatments. Our findings suggest that heterotrophic NO3− uptake may show significant responsiveness to shifts toward more labile DOM sources and nutrient imbalances induced by global change.

TAXONOMIC COMPOSITION AND PHYSIOLOGICAL AND BIOCHEMICAL PROPERTIES OF CULTIVATED MICROORGANISMS ISOLATED FROM KUDURITE ROCKS OF THE PRIMORSKY KRAI AND THE REPUBLIC OF ALTAI (RUSSIA)

The reason for the consumption of rocks (kudurits) by wild animals has not yet been identified. One of the hypotheses of geophagy is a microbiological factor, i.e. rocks can be a source of microorganisms useful for wild animals. In this work, the composition of cultured microorganisms of kudurits of Primorsky Krai and the Altai Republic, as well as some physiological and biochemical properties of the isolated bacteria were studied using molecular genetic analysis of the 16S RNA gene. It has been shown that the studied breeds contain a high amount of physiological groups of bacteria (saprophytic, ammonifying, nitrifying, silicate, hydrolytic) and yeasts (106-109 cells/ml) useful for animals. Among the isolated culturable microorganisms in the curls of Primorsky Krai, representatives of the genus Pseudomonas, Bacillus, Rhodotorula, Paenibacillus, and Stenotrophomonas predominated. The bacteria of the genus Bacillus, Chryseobacterium, and Streptomyces dominated in the edible soils of Altai. Among the isolates, non-pigmented, motile (35-70%) catalase-positive (86-91%) and oxidase-negative (68-76%) rods (67-90%) predominated. All cultures were characterized by a high level of extracellular enzymatic activity, especially in relation to such substrates as casein (57-75%), starch (57-60%), urea (43-45%). The isolated microorganisms are able to develop in a wide range of temperatures (5-500C), pH (5-12), NaCl concentration (1-18%) and utilize a wide range of carbohydrates and alcohols. It has been established that the microorganisms and biologically active compounds they produce can be a factor that encourages animals to instinctively consume rocks. High antibiotic activity of the isolated cultures has been noted against opportunistic bacteria Staphylococcus aureus, Micrococcus luteus and phytopathogenic fungi Fusarium oxysporum.

Nearly 30a shrub introduction in desert steppes has led to an increase in saprotrophic fungi, accelerating the degradation of carbon compounds and nitrate reduction

Clarifying how soil microbial communities respond to shrub introduction after overgrazing in desert steppe and their potential functions is crucial for understanding the biogeochemical processes involved in vegetation transformation and sustainability of desert grasslands. However, the dynamics of microbial communities remain poorly understood. We selected enclosed grasslands (20a), overgrazed grasslands, and shrublands (6a, 15a, and 25a) to explore how shrubs introduced influence soil microbial structure and functional groups over the long term after desert grassland degradation. The results showed that overgrazing and shrub introduction (Caragana korshinskii) had more significant impacts on microbial β diversity than on α diversity. Fungal communities were more sensitive to grassland degradation. In contrast, introducing shrubs affected both fungal and bacterial communities, and an increase in shrub age drove the synergistic effects of fungal species. Soil nitrate and microbial biomass nitrogen were the key factors affecting bacterial and fungal communities. Compared with enclosed grasslands, overgrazing and introducing shrubs significantly increased soil nitrate reduction, ectomycorrhizals, and endophytes. The introduction of shrubs after overgrazing in desert steppe further enhanced the decomposition of carbon compounds and reduced processes such as denitrification. During shrub introduction, total phosphorus, nitrate–nitrogen, and N-acetylglucosaminidase were key factors affecting carbon, nitrogen, and fungal functional groups. Variations in microbial diversity and functional groups, through their influence on extracellular enzymes activity and the availability of microbial biomass nutrients, ultimately explained 85%, 42%, and 34% the observed variations in soil carbon, nitrogen, and phosphorus content, respectively. This study aimed to investigate the long-term effects of anthropogenic shrub expansion on the structure and function of soil microbial communities in degraded desert steppes, provide a scientific basis for steppe restoration and management, and further understand their significance for ecosystem sustainability.

A comprehensive study on fermentation and aroma contributions of Torulaspora delbrueckii in diverse wine varieties: Insights from pure and co-fermentation studies

As a well-commercialized and utilized non-Saccharomyces yeast, Torulaspora delbruineckii is gaining increasing relevance in the winemaking industry. However, its ability to produce distinctive aromas in wine has been inconsistently reported in the literature. This study aimed to evaluate the fermentation performance and aroma properties of T. delbrueckii isolates through pure and co-fermentation with Saccharomyces cerevisiae across eight different wine varieties: Merlot, Zidaifu, Petit Verdot, Marselan, Italian Riesling, Sauvignon Blanc, Ugni Blanc, and Petit Manseng. A comprehensive analysis using HS-SPME-GC–MS, OPLS-DA, and Spearman’s correlation analysis was conducted. Key findings include: (1) The strain T. delbrueckii R12 exhibited higher extracellular enzyme activity compared to S. cerevisiae CECA and demonstrated superior sugar tolerance compared to six other native T. delbrueckii strains. (2) T. delbrueckii R12 exhibited strong fermentative capability, completing fermentation in 23 days across the eight wines, producing lower levels of acetic acid (0 ∼ 0.8 g/L reduction) and ethanol (0.1 ∼ 4.0 % v/v reduction), and higher levels of glycerol (0.1 ∼ 0.9 g/L increase) in the majority of wines. (3) Co-fermentation with T. delbrueckii and S. cerevisiae altered glycosidase activity, enhancing the varietal aroma intensity and complexity of the eight wines by releasing C6 compounds, terpenes and esters, and reducing higher alcohols and fatty acids. (4) The aroma contribution of T. delbrueckii R12 was variety-dependent, with isobutyl alcohol, isopentyl alcohol, 1-pentanol, and 1-propanol prevalent in red wines, and (Z)-2-hexen-1-ol more associated with white wines. Additionally, T. delbrueckii R12 consistently enhanced aromas in all eight experimental wines by increasing levels of 1-hexanol, farnesyl alcohol, linalool, citronellol, ethyl acetate, isobutyric acid and decanoic acid, while decreasing 1-pentanol, octanoic acid, isoamyl acetate, and ethyl laurate. Seven of the increased compounds were identified as signature aromas of T. delbrueckii R12, potentially contributing grass, floral, muscat, rose, fruit, caramel and buttery notes to the wines. This study confirms the significant role of T. delbrueckii in winemaking and wine aroma, resolving previous discrepancies in the literature. It provides new knowledge for innovating and diversifying wine production across various grape varieties.

Sequential pretreatment with hydroxyl radical and manganese peroxidase for the efficient enzymatic saccharification of corn stover

BackgroundWhite rot fungi produce various reactive oxygen species and ligninolytic enzymes for lignocellulose deconstruction. However, their interactions during the deconstruction of lignocellulosic structural barriers for efficient enzymatic saccharification remain unclear.ResultsHerein, the extracellular enzyme activities and secretomic analysis revealed the sequential expression of hydroxyl radical (⋅OH) and manganese peroxidases (MnPs) for lignocellulose deconstruction by the white rot fungus Irpex lacteus. Subsequently, in vitro functional studies found that ⋅OH possessed the ability to disrupt the smooth surface structure of corn stover, resulting in increased enzymatic saccharification and cellulose accessibility. Purified recombinant MnPs from I. lacteus were able to cleave the β-O-4 bond in phenolic and non-phenolic lignin model dimers without the help of any mediators. Furthermore, the sequential pretreatment of corn stover with ⋅OH and MnP exhibited significant synergistic effects, increasing enzymatic saccharification and cellulose accessibility by 2.9-fold and 1.8-fold, respectively.ConclusionsThese results proved for the first time the synergistic effects of ⋅OH and MnP pretreatment in improving the enzymatic saccharification and cellulose accessibility of corn stover. These findings also demonstrated the potential application of ⋅OH and MnP pretreatment for the efficient enzymatic saccharification of corn stover.Graphical

Higher Soil Mesofauna Abundance and Microbial Activities Drive Litter Decomposition in Subtropical Forests

Soil fauna play an important role in litter decomposition and affect the “home-field advantage” (HFA) of litter decomposition. However, how this effect is modulated by the microenvironment needs further investigation. We conducted a reciprocal transplant experiment of litter decomposition using different mesh-size litterbags across litter and soil layers in subtropical coniferous (Pinus massoniana) and broad-leaved (Quercus variabilis) forests. Our results revealed a pronounced HFA in P. massoniana. P. massoniana litter decomposed faster in its home habitat by 40.6% in the litter layer and 10.2% in the soil layer in coarse mesh bags and by 21.8% in the litter layer and 21.4% in the soil layer in fine mesh bags. However, Q. variabilis litter showed faster decomposition in its home soil layer by 10.8% and 4.3% for coarse and fine mesh bags, whereas in the litter layer it decomposed faster in the away habitat by 16.7% and 20.6% for coarse and fine mesh bags, respectively. Higher soil mesofauna abundance and microbial activities in the coniferous forest compared to the broad-leaved forest drive the observed HFA of litter decomposition. Especially in the litter layer, the abundance of mesofauna was 89.8% higher in the coniferous forest. Coarse mesh bags generally facilitated a higher decomposition rate across litter and soil layers, likely due to a better interaction between soil mesofauna and extracellular enzyme activity. The HFA index exhibited distinct seasonal fluctuations, peaking in October for coarse mesh bags and in April for fine mesh bags within the litter layer, while soil layer peaks occurred in August and April. Notably, an increase in Acarina abundance strongly correlated with enhanced decomposition and HFA effects in the litter layer during October. This study revealed the sensitivity of HFA to the soil layer and soil fauna and underscores the complex role of the microclimate in shaping interactions among soil microorganisms, litter quality, and mesofauna, thereby enriching our understanding of litter decomposition dynamics in forest ecosystems.

In Situ Galacto-Oligosaccharides Synthesis in Whey Powder Fortified Milk by a Modified β-Galactosidase and Its Effect on the Techno-Functional Characteristics of Yogurt.

In situ galacto-oligosaccharide (GOS) synthesis in milk using β-galactosidases is an effective method for developing prebiotic dairy products. However, the low lactose concentration in milk (∼4.6%, w/w) reduces the GOS yield. In this study, a modified β-galactosidase from Bacillus circulans (mBgaD-D) with enhanced transglycosylation activity at low lactose concentration was developed through directed evolution and saturation mutagenesis. The GOS yield by mBgaD-D increased from 22.8% (wild type) to 30.8% in 50 g/L lactose (phosphate buffer). Pmgut was a strong sorbitol-inducible promoter from Bacillus subtilis. The expression of mBgaD-D in B. subtilis, coupled with the Pmgut promoter, resulted in a 6.4-fold increase (compared to the P43 promoter) in extracellular enzyme activity. Additionally, adding whey powder to boost the initial lactose concentration further improved the GOS yield, which reached 43% under the optimized conditions. Combining mBgaD-D and whey powder enhanced milk sweetness, producing no sugar-added, GOS-enriched yogurt (GOSY). The GOS content in GOSY was 4.1/100 g, providing an appropriate level of sweetness and yielding a yogurt that is elastic as well as firm. GOSY also increased the population of Bifidobacterium spp. during a 24 h in vitro fecal fermentation. Thus, fortifying yogurt with mBgaD-D and whey powder can enhance its technological properties and health benefits.

Microbial Life in Playa-Lake Sediments: Adapted Structure, Plastic Function to Extreme Water Activity Variations

Saline shallow lakes in arid and semi-arid regions frequently undergo drying episodes, leading to significant variations in salinity and water availability. Research on the impacts of salinity and drought on the structure and function of biofilms in hypersaline shallow lakes is limited. This study aimed to understand the potential changes of biofilms in playa-lake sediments during the drying process. Sediments were sampled at different depths (surface, subsurface) and hydrological periods (wet, retraction, and dry), which included a decrease in water activity (aw, the availability of water for microbial use) from 0.99 to 0.72. aw reduction caused a greater effect on functional variables compared to structural variables, indicating the high resistance of the studied biofilms to changes in salinity and water availability. Respiration and hydrolytic extracellular enzyme activities exhibited higher values under high aw, while phenol oxidase activity and prokaryote biomass increased at lower aw. This shift occurred at both depths but was more pronounced at the surface, possibly due to the more extreme conditions (up to 0.7 aw). The increased levels of extracellular polymeric substances and carotenoids developed at low aw may help protect microorganisms in high salinity and drought environments. However, these harsh conditions may interfere with the activity of hydrolytic enzymes and their producers, while promoting the growth of resistant prokaryotes and their capacity to obtain C and N sources from recalcitrant compounds. The resilience of biofilms in hypersaline lakes under extreme conditions is given by their resistant biochemichal structure and the adaptability of their microbial functioning.