Cellobiohydrolase Activity Research Articles

Influence of stem and leaf phenotypes, physiological responses and cellular ultrastructure on defoliated sugarcane cultivars

Defoliation is a primary agronomic traits, its variation depends on different plant species or cultivars. The present article assess the leaf morphological responses, oxidative metabolites and enzymatic activities at sheath base of sugarcane cultivars during defoliation stage of plant leaves. The mature leaf sheath of GT47 strongly wrapped to the stem, and no stem was exposed. The upper and lower edges of the immature fusing abscission zone were parallel, and slightly lower browning area (+ 3 to + 7 leaf position). The ROC22 cultivar was monitored highest leaf sheath-based cellulose and lignin content, followed by GT60 and GT47. Peroxidase activity was higher in leaf sheath base edge (ROC22) as compare to other cultivars. The malondialdehyde content was found highest in GT60, followed by ROC22, and GT47. The exo-β-1,4-glucanase/ cellobiohydrolase activity was found highest in the margin of GT47 than lateral and medial axis of ROC22 and GT60. The axis activity increased exponentially, and ROC22 gradually decreased from the periphery of the mid-axis and lower than GT47 and GT60 in the lateral and mid-axis of leaf. In conclusion, the mature leaves are easy to defoliate mainly loose leaf sheaths, large leaf sheath inclination angles, more deformation during the growth period of the abscission zone, early with large cracks, and slow browning process. Leaf sheaths with high fibre and lignin content showed significant hardness and thickness. The sugarcane cultivars showed positive correlation between peroxidase and malondialdehyde content with the browning process at the base of mature leaf sheaths.

Co-expression of endoglucanase and cellobiohydrolase from yak rumen in lactic acid bacteria and its preliminary application in whole-plant corn silage fermentation.

Endoglucanase (EG) and cellobiohydrolase (CBH) which produced by microorganisms, have been widely used in industrial applications. In order to construct recombinant bacteria that produce high activity EG and CBH, in this study, eg (endoglucanase) and cbh (cellobiohydrolase) were cloned from the rumen microbial genome of yak and subsequently expressed independently and co-expressed within Lactococcus lactis NZ9000 (L. lactis NZ9000). The recombinant strains L. lactis NZ9000/pMG36e-usp45-cbh (L. lactis-cbh), L. lactis NZ9000/pMG36e-usp45-eg (L. lactis-eg), and L. lactis NZ9000/pMG36e-usp45-eg-usp45-cbh (L. lactis-eg-cbh) were successfully constructed and demonstrated the ability to secrete EG, CBH, and EG-CBH. The sodium carboxymethyl cellulose activity of the recombinant enzyme EG was the highest, and the regenerated amorphous cellulose (RAC) was the specific substrate of the recombinant enzyme CBH, and EG-CBH. The optimum reaction temperature of the recombinant enzyme CBH was 60°C, while the recombinant enzymes EG and EG-CBH were tolerant to higher temperatures (80°C). The optimum reaction pH of EG, CBH, and EG-CBH was 6.0. Mn2+, Fe2+, Cu2+, and Co2+ could promote the activity of CBH. Similarly, Fe2+, Ba2+, and higher concentrations of Ca2+, Cu2+, and Co2+ could promote the activity of EG-CBH. The addition of engineered strains to whole-plant corn silage improved the nutritional quality of the feed, with the lowest pH, acid detergent fiber (ADF), and neutral detergent fiber (NDF) contents observed in silage from the L. lactis-eg group (p < 0.05), and the lowest ammonia nitrogen (NH3-N), and highest lactic acid (LA) and crude protein (CP) contents in silage from the L. lactis-eg + L. lactis-cbh group (p < 0.05), while the silage quality in the L. lactis-cbh group was not satisfactory. Consequently, the recombinant strains L. lactis-cbh, L. lactis-eg, and L. lactis-eg-cbh were successfully constructed, which could successfully expressed EG, CBH, and EG-CBH. L. lactis-eg promoted silage fermentation by degrading cellulose to produce sugar, enabling the secretory expression of EG, CBH, and EG-CBH for potential industrial applications in cellulose degradation.

Fungal Saprotrophic Promotion and Plant Pathogenic Suppression under Ditch-Buried Straw Return with Appropriate Burial Amount and Depth.

Fungi as heterotrophs are key participants in the decomposition of organic materials and the transformation of nutrients in agroecosystems. Ditch-buried straw return as a novel conservation management strategy can improve soil fertility and alter hydrothermal processes. However, how ditch-buried straw return strategies affect the soil fungal community is still unclear. Herein, a 7-year field trial was conducted to test the influences of burial depth (0, 10, 20, 30, and 40 cm) and the amount of ditch-buried straw (half, full, double) on the diversity, composition, and predicted functions of a soil fungal community, as well as the activities of carbon-degraded enzymes. Under the full amount of straw burial, the abundance of phylum Ascomycota was 7.5% higher as compared to other burial amount treatments. This further increased the activity of cellobiohydrolase by 32%, as revealed by the positive correlation between Ascomycota and cellobiohydrolase. With deeper straw burial, however, the abundance of Ascomycota and β-D-glucopyranoside activity decreased. Moreover, genus Alternaria and Fusarium increased while Mortierella decreased with straw burial amount and depth. FUNgild prediction showed that plant fungal pathogens were 1- to 2-fold higher, whilst arbuscular mycorrhizal fungi were 64% lower under straw buried with double the amount and at a depth of 40 cm. Collectively, these findings suggest that ditch-buried straw return with a full amount and buried at a depth less than 30 cm could improve soil nutrient cycles and health and may be beneficial to subsequent crop production.

Maize straw increases while its biochar decreases native organic carbon mineralization in a subtropical forest soil

Organic soil amendments have been widely adopted to enhance soil organic carbon (SOC) stocks in agroforestry ecosystems. However, the contrasting impacts of pyrogenic and fresh organic matter on native SOC mineralization and the underlying mechanisms mediating those processes remain poorly understood. Here, an 80-day experiment was conducted to compare the effects of maize straw and its derived biochar on native SOC mineralization within a Moso bamboo (Phyllostachys edulis) forest soil. The quantity and quality of SOC, the expression of microbial functional genes concerning soil C cycling, and the activity of associated enzymes were determined. Maize straw enhanced while its biochar decreased the emissions of native SOC-derived CO2. The addition of maize straw (cf. control) enhanced the O-alkyl C proportion, activities of β-glucosidase (BG), cellobiohydrolase (CBH) and dehydrogenase (DH), and abundances of GH48 and cbhI genes, while lowered aromatic C proportion, RubisCO enzyme activity, and cbbL abundance; the application of biochar induced the opposite effects. In all treatments, the cumulative native SOC-derived CO2 efflux increased with enhanced O-alkyl C proportion, activities of BG, CBH, and DH, and abundances of GH48 and cbhI genes, and with decreases in aromatic C, RubisCO enzyme activity and cbbL gene abundance. The enhanced emissions of native SOC-derived CO2 by the maize straw were associated with a higher O-alkyl C proportion, activities of BG and CBH, and abundance of GH48 and cbhI genes, as well as a lower aromatic C proportion and cbbL gene abundance, while biochar induced the opposite effects. We concluded that maize straw induced positive priming, while its biochar induced negative priming within a subtropical forest soil, due to the contrasting microbial responses resulted from changes in SOC speciation and compositions. Our findings highlight that biochar application is an effective approach for enhancing soil C stocks in subtropical forests.

Effect of substrate moisture content during cultivation of Hericium erinaceus and subsequent vermicomposting of spent mushroom substrate in a continuous feeding system

Cultivation of Hericium erinaceus depends on various factors, one of which is water content in the substrate. This parameter influences not only the growth rate of the mushroom but also enzymatic activity, which is important for substrate decomposition and for the later usage of spent mushroom substrate (SMS). This study compared parameters, such as mycelial growth, pH and enzymatic activity in substrates with different initial water content. During cultivation, the water content and pH decreased in all variants, but the activity of hydrolytic enzymes increased with time and was higher in variants with higher water content (70% and 75%); however, the activity of ligninolytic enzymes decreased during cultivation. The production of 1 kg of mushrooms generates about 5 kg of SMS. Vermicomposting is a natural method for processing SMS, as it involves a combination of earthworms, microorganisms and enzymatic activity; thus, we compared the differences between variants with and without earthworms using continuous feeding vermicomposters. The C:N ratio in the variant with earthworms radically decreased from 153.7:1 to 16.5:1. The ratio of bacteria to fungi in both variants was highest in the oldest compost layer in the vermicomposters. The variant without earthworms exhibited the highest enzymatic activity of β-D-glucosidase and Mn-peroxidase, but the highest activity of cellobiohydrolase and laccase occurred in the variant with earthworms. The vermicomposting process is ideal for this type of biowaste, as it produces a fertilizer rich in beneficial microorganisms and enzymatic activity.

Evaluation of single and mixed cover crops species in a sandy loam soil under corn production

AbstractInformed selection of cover crop species is critical for optimizing their benefits by considering the costs of adoption and potential initial negative impact on yields against the proven benefits for sustainable production. The Lower Mississippi Delta region is lagging in cover crop adoption, partly due to a paucity of this information from the area, despite being one of the major row crop‐producing regions in the United States. Common cover crop species in the region, cereal rye (CR) (Secale cereale), hairy vetch (HV) (Vicia villosa), and crimson clover (CC) (Trifolium incarnatum), and their possible two‐ and three‐combination mixes were evaluated for their impact on biomass production, enzyme activities, nutrient cycling, and corn (Zea mays) yields. HV + CC + CR and HV + CR produced the highest biomass and lowest yields compared to all treatments. HV and CC produced the least biomass but comparable yields to no cover crop. HV + CC + CR, HV + CR, CR, CC, and HV treatments had comparable total nitrogen, phosphorus, and soil organic carbon levels in the surface 0‐ to 5‐cm depth. Generally, CC alone and the HV + CR mix consistently displayed significantly higher phosphatase, N‐acetylglucosaminidase, β‐glucosidase, and cellobiohydrolase activities compared to all other treatments, while CR had the lowest. The single species of CC or HV may be the best option in the short term for initial cover crop implementation, rotating with CR a few years down the line for optimum long‐term benefits under corn production in this region.

Improved consolidated bioprocessing for itaconic acid production by simultaneous optimization of cellulase and metabolic pathway of Neurospora crassa

Lignocellulose was directly used in itaconic acid production by a model filamentous fungus Neurospora crassa. The promoters of two clock control genes and cellobiohydrolase 1 gene were selected for heterologous genes expression by evaluating different types of promoters. The effect of overexpression of different cellulase was compared, and it was found that expression of cellobiohydrolase 2 from Trichoderma reesei increased the filter paper activity by 2 times, the cellobiohydrolase activity by 4.5 times, and that the itaconic acid titer was also significantly improved. A bidirectional cis-aconitic acid accumulation strategy was established by constructing the reverse glyoxylate shunt and expressing the transporter MTTA, which increased itaconic acid production to 637.2 mg/L. The simultaneous optimization of cellulase and metabolic pathway was more conducive to the improvement of cellulase activity than that of cellulase alone, so as to further increase itaconic acid production. Finally, through the combination of fermentation by optimized strains and medium optimization, the titers of itaconic acid using Avicel and corn stover as substrate were 1165.1 mg/L and 871.3 mg/L, respectively. The results prove the potential of the consolidated bioprocessing that directly converts lignocellulose to itaconic acid by a model cellulase synthesizing strain.

Long‐term continuous maize: Impacts on the soil microbiome and implications for residue management

AbstractContinuous maize (Zea mays L.) (CM) cropping has been proposed to increase soil organic carbon stocks through greater residue return to soils. These residues, however, can contribute to a yield decrease known as the continuous maize yield penalty (CMYP). The objectives of this research were to (1) evaluate the efficacy of residue management practices to mitigate the CMYP when compared to a maize–soybean [Glycine max (L.) Merr.] (MS) rotation and (2) determine effects of long‐term rotation or residue sizing on soil microbial communities and carbon‐cycling enzyme activities. Two long‐term sites (17 and 19 years) with replicated blocks of CM and MS rotation were used. The yield response to management was similar at both sites, with an average CMYP of 2570 kg ha−1 with no residue management, while chopping the residue along with broadcast ammonium sulfate (AMS) reduced the CMYP by 728 kg ha−1 (28.3%). The CMYP was further reduced when a microbial blend was applied with AMS to the sized residues, reducing the CMYP by a total of 1303 kg ha−1 (50.7%). Soil bacterial communities differed by site but were unchanged by crop rotation or residue sizing. Soil fungal assemblage, particularly arbuscular mycorrhizal fungi, was influenced by rotation and site. Sizing of residues resulted in higher soil cellobiohydrolase activity for CM, but not for MS. These findings indicate that the CMYP was not directly associated with the soil bacterial community, and that management to mitigate the CMYP may be aided by elevated levels of fungal diversity under CM.

Do soil enzyme activities explain stimulated carbon mineralization following liming?

Losses of soil organic carbon (C) following liming have been proposed to result from stimulated C mineralization, which could occur through a variety of mechanisms including soil enzymes. Given the pH-sensitivity of enzyme activities, liming could impact catalysis of C mineralization by extracellular enzymes independently of microbial response. To this end, we evaluated the responses of C mineralization as CO2 flux, permanganate-oxidizable C (POXC), and the activities of C-hydrolytic enzymes to liming of a Haplic Ferralsol (Typic Kandiudox) in western Kenya under three differing 11-year soil fertility managements: unfertilized (UNF), mineral fertilized (MIN), and organic fertilized (ORG). Five rates of Ca(OH)2 (1.5, 3.0, 4.5, 6.0, and 7.5 t ha−1) and an unlimed control were used to establish a pH gradient of 4.6–6.4. Soil C mineralization rates assessed as CO2 production peaked within 5 d for high liming rates, and converged to a similar rate as unlimed soils after 21 d. At 28 d, activities of β-glucosidase and cellobiohydrolase decreased with increasing pH, increased for β-glucosaminidase, and were unaffected for β-galactosidase. POXC generally increased with liming rate for fertilized soils, more so in ORG and less in MIN soils, with relative increases of 18%, 5%, and 1% for ORG, MIN and UNF soils, respectively, at 7.5 relative to 0 t ha−1 liming. This study identifies potentially rapid albeit short-lived stimulation of C mineralization following addition of a highly soluble liming agent. Notably, decreases in activities of soil enzymes that catalyze the first and last step of the cellulosic C depolymerization suggests that short-term losses of soil C were not driven by enzyme activities, and may occur in spite of lowered C-hydrolytic enzyme activity. The enhanced C mineralization observed could reflect augmentation of labile C pools via non-enzymatic processes (e.g., desorption) in the short-term.

Specific activity and utility of recombinant cellobiohydrolase II (Cel6A) produced in maize endosperm.

Cellobiohydrolase II (CBH II) is an exo-glucanase that is part of a fungal mixture of enzymes from a wood-rot fungus, Trichoderma reesei. It is therefore difficult to purify and to establish a specific activity assay. The gene for this enzyme, driven by the rice Os glutelin promoter, was transformed into High II tissue culture competent corn, and the enzyme accumulated in the endosperm of the seed. The transgenic line recovered from tissue culture was bred into male and female elite Stine inbred corn lines, stiff stalk 16083-025 (female) and Lancaster MSO411 (male), for future production in their hybrid. The enzyme increases its accumulation throughout its 6 generations of back crosses, 27-266-fold between T1 and T2, and 2-10-fold between T2 and T3 generations with lesser increases in T4-T6. The germplasm of the inbred lines replaces the tissue culture corn variety germplasm with each generation, with the ultimate goal of producing a high-yielding hybrid with the transgene. The CBH II enzyme was purified from T5 inbred male grain 10-fold to homogeneity with 47.5% recovery. The specific activity was determined to be 1.544 units per µg protein. The corn-derived CBH II works in biopolishing of cotton by removing surface fibers to improve dyeability and increasing glucose from corn flour for increasing ethanol yield from starch-based first-generation processes.

SsdchA is a novel secretory cellobiohydrolase driving pathogenicity in Sclerotinia sclerotiorum

The necrotrophic fungus, Sclerotinia sclerotiorum, employs an array of cell wall-degrading enzymes (CWDEs), including cellulase, to dismantle host cell walls. However, the molecular mechanisms through which S. sclerotiorum degrades cellulose remain elusive. Here, we unveil a novel secretory cellobiohydrolase, SsdchA, characterized by a signal peptide and a Glyco_hydro_7 (GH7) domain. SsdchA exhibits a robust expression of during early infection stages. Interestingly, colony morphology and growth rates remain unaffected across the wild-type, SsdchA deletion strains and SsdchA overexpression strains on potato dextrose agar (PDA) medium. Nevertheless, the pathogenicity and cellobiohydrolase activity decreased in the SsdchA deletion strains, but enhanced in the SsdchA overexpression strains. Moreover, the heterologous expression of SsdchA in Arabidopsis thaliana leads to reduced cellulose content and heightened susceptibility to S. sclerotiorum. Collectively, our data underscore the pivotal role of the novel cellobiohydrolase SsdchA in the pathogenicity of S. sclerotiorum.

Nitrogen deposition-induced stimulation of soil heterotrophic respiration is counteracted by biochar in a subtropical forest

Both atmospheric nitrogen (N) deposition and biochar application can markedly impact soil heterotrophic respiration (RH), an important component of the global carbon cycle. However, the interactive effects of N deposition and biochar application on soil RH in subtropical forest ecosystems remain unclear. Here, we conducted a three-year (2019–2022) field trial within a bamboo forest in subtropical China to examine the responses of soil physicochemical and microbial properties to N deposition and biochar application, and to elucidate how biochar regulates N deposition-induced change in soil RH. Nitrogen deposition stimulated soil RH by 8.1–9.8 % annually over three years compared to the control, and this stimulation was mitigated (by 8.1–8.9 % annually) with biochar addition. In the context of N deposition, the decrease of soil RH by biochar application was not through changing soil temperature, moisture or labile organic carbon content. Biochar treatment reduced the abundances of bacterial glycoside hydrolase family 48 gene (GH48) and fungal glycoside hydrolase family 7 cellobiohydrolase I gene (cbhI) and the activities of β-glucosidase and cellobiohydrolase (CBH), but increased the abundance of cbbL gene and activity of RubisCO enzyme. Furthermore, the RH was correlated positively (P < 0.01) with β-glucosidase and CBH activities and negatively (P < 0.01) with RubisCO enzyme activity. Structural equation modeling revealed that the biochar-induced reduction of soil RH under N deposition was associated with decreases in the abundance of cbhI gene and the activity of CBH in soils. We highlight that management practices can mitigate soil carbon loss in forests through modulating soil microbial functions under atmospheric N deposition, and that biochar application in Moso bamboo forests has the potential to reduce RH by approximately 7.6 × 106 t CO2 yr−1 under atmospheric N deposition.

Culture of Trichoderma sp. with biochar to produce high-activity cellulase in a laboratory

Biochar (BC) was used in Trichoderma sp. culture to produce high-activity cellulase on a laboratory scale. The biochar was added into the flask before being applied to the fermenter to identify the enhancement effect and to determine the best amount of addition and the most suitable incubation period. Cellulase production was performed with a working volume of 4 L, and enzymatic hydrolysis was conducted to evaluate the saccharification ability of the enzyme. During incubation, the activities of three enzymes (Endoglucanase (EG), β-glucosidase (BGL), and cellobiohydrolase (CBH)) were measured for three days, and the cellulase activity was determined using a filter paper unit (FPU). In flask scale, EG, BGL, and CBH activities were increased by 1.4, 2.1, and 1.8 folds, respectively, and the incubation period was shortened by adding BC. In the fermenter scale, EG, BGL, and CBH activities were noticeably enhanced by 12.1, 5.8, and 7.2 folds, respectively, and FPU was 42.1 (9.8 folds). Additionally, the conversion rates of cellulose and steam exploded softwood and hardwood were 109.4%, 75.4%, and 87.3%, which were similar to a commercial enzyme (Cellic CTecⅡ). This study demonstrated that biochar could be used to produce high-activity cellulase in a shorter period and suggests a novel method for effective cellulase production.

Effects of stand ages on soil enzyme activities in Chinese fir plantations and natural secondary forests.

Forest type and stand age are important biological factors affecting soil enzyme activities. However, the changes in soil enzyme activities across stand ages and underlying mechanisms under the two forest restoration strate-gies of plantations and natural secondary forests remain elusive. In this study, we investigated the variations of four soil enzyme activities including cello-biohydrolase (CBH), β-1,4-glucosidase (βG), acid phosphatase (AP) and β-1,4-N-acetylglucosaminidase (NAG), which were closely associated with soil carbon, nitrogen, and phosphorus cycling, across Cunninghamia lanceolata plantations and natural secondary forests (5, 8, 21, 27 and 40 years old). The results showed that soil enzyme activities showed different patterns across different forest types. The acti-vities of AP, βG and CBH in the C. lanceolata plantations were significantly higher than those in the natural secon-dary forests, and there was no significant difference in the NAG activity. In the plantations, AP activity showed a decreasing tendency with the increasing stand ages, with the AP activity in the 5-year-old plantations significantly higher than other stand ages by more than 62.3%. The activities of NAG and CBH decreased first and then increased, and βG enzyme activity fluctuated with the increasing stand age. In the natural secondary forests, NAG enzyme activity fluctuated with the increasing stand age, with that in the 8-year-old and 27-year-old stand ages being significantly higher than the other stand ages by more than 14.9%. βG and CBH enzyme activities increased first and then decreased, and no significant difference was observed in the AP activity. Results of the stepwise regression analyses showed that soil predictors explained more than 34% of the variation in the best-fitting models predicting soil enzyme activities in the C. lanceolata plantations and natural secondary forests. In conclusion, there would be a risk of soil fertility degradation C. lanceolata plantations with the increasing stand age, while natural secondary forests were more conducive to maintaining soil fertility.

A detailed sensitivity analysis identifies the key factors influencing the enzymatic saccharification of lignocellulosic biomass

Corn stover is the most abundant form of crop residue that can serve as a source of lignocellulosic biomass in biorefinery approaches, for instance for the production of bioethanol. In such biorefinery processes, the constituent polysaccharide biopolymers are typically broken down into simple monomeric sugars by enzymatic saccharification, for further downstream fermentation into bioethanol. However, the recalcitrance of this material to enzymatic saccharification invokes the need for innovative pre-treatment methods to increase sugar conversion yield. Here, we focus on experimental glucose conversion time-courses for corn stover lignocellulose that has been pre-treated with different acid-catalysed processes and intensities. We identify the key parameters that determine enzymatic saccharification dynamics by performing a Sobol's sensitivity analysis on the comparison between the simulation results from our complex stochastic biophysical model, and the experimental data that we accurately reproduce. We find that the parameters relating to cellulose crystallinity and those associated with the cellobiohydrolase activity are predominantly driving the enzymatic saccharification dynamics. We confirm our computational results using mathematical calculations for a purely cellulosic substrate. On the one hand, having identified that only five parameters drastically influence the saccharification dynamics allows us to reduce the dimensionality of the parameter space (from nineteen to five parameters), which we expect will significantly speed up our fitting algorithm for comparison of experimental and simulated saccharification time-courses. On the other hand, these parameters directly highlight key targets for experimental endeavours in the optimisation of pre-treatment and saccharification conditions. Finally, this systematic and two-fold theoretical study, based on both mathematical and computational approaches, provides experimentalists with key insights that will support them in rationalising their complex experimental results.

Fe‐modified biochar improved the stability of soil aggregates and organic carbon: Evidence from enzymatic activity and microbial composition

AbstractBiochar modifications are used to improve soil organic carbon (SOC) content, while its effects on soil structure stability and carbon (C) mineralization are less known especially in saline–alkaline soils. A 5 years field experiment was arranged with organic amendments addition in the Yellow River Delta, including (i) NPK, only 255, 56, and 190 kg ha−1 N, P, and K each year, (ii) RS, NPK + rice straw, (iii) BC, NPK + straw‐derived biochar, and (iv) FeBC, NPK + biochar modified with ferric chloride. Relative to NPK treatment, the mean weight diameter was significantly increased with organic amendments addition, which was the highest in FeBC treatment. Meanwhile, SOC content in the soil added with organic amendment was increased by 2%–18%. Compared with the RS and BC, FeBC addition increased the content of stable humin (HU), crystalline Fe oxides (Fed), and amorphous Fe oxides (Feo). There was a positive correlation between HU and Feo/Fed, indicating HU and Fe oxides might form organic mineral complexes to limit SOC biodegradation. While the mineralization rate of SOC in FeBC treatment was decreased by more than 30.4% than that in BC treatment. This might be due to the decrease of soil β‐glucosidase and cellobiohydrolase activities, as well as the abundance of Gammaproteobacteria and Actinobacteria. These results were the mechanism of soil enzyme activity and bacterial community regulating C stability. Therefore, Fe‐modified biochar is a better organic amendment to improve the stability of aggregates structure and SOC in saline–alkaline paddy soil.

Effects of Mycorrhizal and Extraradical Hyphae of Subtropical Native Tree Species on Soil Enzyme Activities and Their Stoichiometric Ratios

We aimed to study the effects of mycorrhizal and extraradical hyphae on soil physical and chemical properties and enzyme activity characteristics in a subtropical plantation and to explore its indicative effect on the effectiveness of soil nutrients. In this study, three native afforestation tree species, Cunninghamia lanceolata, Schima superba, and Liquidambar formosana, with different biological characteristics, root functional traits, and nutrient acquisition strategies in subtropical regions were selected as the research objects. Based on the method of in-growth soil cores, the nylon mesh with different pore sizes was used to limited the root system and hypha into the soil column. The soil physical and chemical properties of five kinds of hydrolase related to the carbon (C), nitrogen (N), and phosphorus (P) cycles were determined in this study. The correlation of different tree species, roots, and mycelia with soil physicochemical properties, enzyme activity, and stoichiometric ratios was analyzed. The results revealed that mycorrhizal treatment significantly affected the soil total carbon (TC) and pH but had no significant effect on hydrolase activity and its stoichiometric ratio. Tree species significantly affected soil physical and chemical properties, soil β-1,4-N-acetylglucosaminidase (NAG), β-1,4-glucosidase (βG), and cellobiohydrolase (CB) activities and soil enzyme stoichiometric ratios. The soil enzyme activity and stoichiometric ratio of the Chinese fir forest had higher values than in monoculture broad-leaved stands of both Schima superba and Liquidambar formosana. There was no significant interaction effect of mycorrhizal treatments and tree species on all soil properties, enzyme activities, and stoichiometric ratios. In addition, the soil enzyme activity and stoichiometric characteristics were mainly affected by the pH. In this study, the soil enzyme activity ratios In(BG + CB):In(AP) and In(NAG + LAP):In(AP) were lower values than the global scale, while the ratios of In(βG + CB):In(NAG + LAP) were higher than the average, indicating that the soil microorganisms in this area were limited by C and P. Moreover, the soil enzyme activity and chemical metrology characteristics were mainly affected by the pH change. In conclusion, differences in litter quality and root functional traits of tree species affected the soil enzyme activity and its stoichiometric characteristics through the shaping of the forest environment by organic matter input, and the influence of pH was the main regulating factor.

Effect of inoculating thermophilic bacterial consortia on compost efficiency and quality

The objective of this study was to investigate the potential effects of thermophilic bacterial consortia on compost efficiency and quality. The application of bacterial consortia resulted in an earlier onset of the thermophilic period (THP), an increased upper temperature limit, and an extended duration of the THP by 3–5 days compared to the control group (CK). Microbial inoculation significantly improved the efficiency of organic matter degradation, as well as the content of water-soluble nitrogen (WSN) and humic acid-carbon (HAC). In the case of consortium Ⅱ inoculation (T2), the activities of cellobiohydrolase, β-glucosidase, and protease were increased by 81.81 %, 70.13 %, and 74.09 % at the THP respectively compared to CK. During the maturation stage, T2 also exhibited the highest PV, n/PIII, n value (1.33) and HAC content (39.53 mg·g−1), indicating that inoculation of consortium Ⅱ effectively promoted substrate maturity and product quality. Moreover, this inoculation effectively optimized the bacterial communities, particularly the growth of Planococcus, Chelatococcus, and Chelativorans during the composting, which were involved in carbon and nitrogen conversion or HAC synthesis. Carbohydrate and amino acid metabolism, and membrane transport were predominant in the consortia-inoculated samples, with an increased gene abundance, suggesting that inoculation contributed to promoting the biodegradation of lignocellulose and the exchange of favorable factors. In conclusion, this study demonstrates that inoculating thermophilic bacterial consortia has a positive impact on enhancing the resource utilization efficiency of agricultural waste and improving the quality of compost products.

Slow soil enzyme recovery following invasive tree removal through gradual changes in bacterial and fungal communities

Abstract Biological invasions of plants have profound effects on ecosystem functioning by directly and indirectly altering soil microbiota, especially when invasive plants co‐invade with their associated microbiomes. Ecosystem functions may recover slowly following invader removal, with implications for restoration. We investigated the recovery of soil ecosystem function (measured as soil enzymes) following the removal, at different densities and times, of invasive Pinus spp. in New Zealand, and how different enzymatic activities responded to pine legacies. Enzymatic activities were driven by pine legacies via both abiotic (soil nutrients) and biotic (fungi and bacteria) soil properties, with different enzymes showing distinct patterns. The activity of the enzymes cellobiohydrolase (cellulose degrading), β‐glucosidase (cellulose degrading), N‐acetyl‐glucosaminidase (chitin degrading), laccase (lignin oxidising) and acid phosphatase (organic phosphate hydrolysing) were influenced by time since pine removal and by pine density at removal via effects on biotic communities. In comparison, Mn‐peroxidase (lignin oxidising) was positively correlated with density of pines at removal and was negatively correlated with time since removal and was only influenced by fungal communities. Synthesis. The recovery of soil enzymatic function following invasive species removal is slow and dependent on pine legacies through the gradual changes in fungal and bacterial communities. The cascading effects of these changes suggest potential implications for the success of future plant establishment and restoration of co‐invaded ecosystems.

Genomic analysis of lignocellulolytic enzyme producing novel Streptomyces sp.MS2A for the bioethanol applications

The conversion of lignocellulosic waste to energy offers a cost-effective biofuel. The current study discusses the utilization of cellulose in rice husks by lichen-associated Streptomyces sp. MS2A via carbohydrate metabolism. Out of 39 actinobacteria, one actinobacterial strain MS2A, showed CMCase, FPase, and cellobiohydrolase activity. The whole genome analysis of Streptomyces sp. MS2A showed maximum similarity with Streptomyces sp. CCM_MD2014. The genome analysis confirmed the presence of cellulose-degrading genes along with xylan-degrading genes that code for GH3, GH6, GH9, GH11, GH43, GH51, and 15 other GH families with glycosyl transferase, carbohydrate-binding modules, and energy metabolism groups. Protein family analysis corroborates the enzyme family. Among the 19,402 genes of Streptomyces sp. MS2A, approximately 70 GH family codes for lignocellulose degradation enzymes. The structure of cellulase was modeled and validated. Scanning electron microscopy and gas chromatography–mass spectrometry (GCMS) was performed to analyze the lignocellulosic degradation of rice husk and the end product bioethanol.