Effects of seaweed fertilizer on enzyme activities, metabolic characteristics, and bacterial communities during maize straw composting

A red seaweed Kappaphycus alvarezii-based biostimulant (AgroGain®) improves the growth of Zea mays and impacts agricultural sustainability by beneficially priming rhizosphere soil microbial community

The overuse of chemical-based agricultural inputs has led to the degradation of soil with associated adverse effects on soil attributes and microbial population. This scenario leads to poor soil health and is reportedly on the rise globally. Additionally, chemical fertilizers pose serious risks to the ecosystem and human health. In this study, foliar sprays of biostimulant (AgroGain/LBS6) prepared from the cultivated, tropical red seaweed Kappaphycus alvarezii increased the phenotypic growth of Zea mays in terms of greater leaf area, total plant height, and shoot fresh and dry weights. In addition, LBS6 improved the accumulation of chlorophyll a and b, total carotenoids, total soluble sugars, amino acids, flavonoids, and phenolics in the treated plants. LBS6 applications also improved the total bacterial and fungal count in rhizospheric soil. The V3-V4 region of 16S rRNA gene from the soil metagenome was analyzed to study the abundance of bacterial communities which were increased in the rhizosphere of LBS6-treated plants. Treatments were found to enrich beneficial soil bacteria, i.e., Proteobacteria, especially the classes Alphaproteobacteria, Cyanobacteria, Firmicutes, Actinobacteriota, Verrucomicrobiota, Chloroflexi, and Acidobacteriota and several other phyla related to plant growth promotion. A metagenomic study of those soil samples from LBS6-sprayed plants was correlated with functional potential of soil microbiota. Enrichment of metabolisms such as nitrogen, sulfur, phosphorous, plant defense, amino acid, co-factors, and vitamins was observed in soils grown with LBS6-sprayed plants. These results were further confirmed by a significant increase in the activity of soil enzymes such as urease, acid phosphatase, FDAse, dehydrogenase, catalase, and biological index of fertility in the rhizosphere of LBS6-treated corn plant. These findings conclude that the foliar application of LBS6 on Z. mays improves and recruits beneficial microbes and alters soil ecology in a sustainable manner.

Low-cost and efficient strategy for brown algal hydrolysis: Combination of alginate lyase and cellulase

Brown algae are rich in biostimulants that not only stimulate the overall development and growth of plants but also have great beneficial effects on the whole soil-plant system. However, alginate, the major component of brown algae, is comparatively difficult to degrade. The cost of preparing alginate oligosaccharides (AOSs) is still too high to produce seaweed fertilizer. In this work, the marine bacterium Vibrio sp. B1Z05 is found to be capable of efficient alginate depolymerization and harbors an extended pathway for alginate metabolism. The B1Z05 extracellular cell-free supernatant exhibited great potential for AOS production at low cost, which, together with cellulase, can efficiently hydrolyze seaweed. The brown algal hydrolysis rates were significantly greater than those of the commercial alginate lyase product CE201, and the obtained seaweed extracts were rich in phytohormones. This work provides a low-cost but efficient strategy for the sustainable production of desirable AOSs and seaweed fertilizer.

Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition

To enhance the efficiency of composting agricultural organic waste (AOW), this study aimed to examine the impact of inoculating tomato straw compost with two distinct microbial agents: ZymoZone (ZZ), a composite microbial agent derived from the straw compost and Effective Microorganisms (EM), a commercial microbial agent. Furthermore, in order to reactivate the microorganisms within the compost during the initial high temperature phase, 10% brown sugar was introduced as a carbon source. The objective of this addition was to assess its influence on the composting process. The findings revealed that compared to the control (CK) group, the ZZ and EM treatments extended the first high-temperature phase by 2 and 1 day, respectively. Furthermore, with the addition of 10% brown sugar, the ZZ and EM treatments remained in the second high-temperature phase for 8 and 7 days, respectively, while the CK treatment had already entered the cooling stage by then. Notably, the inoculation of microbial agents and the addition of brown sugar substantially augmented the activity of lignocellulose-related hydrolases, thereby promoting the degradation of lignocellulose in the ZZ and EM treatment groups. This was confirmed by FTIR analysis, which demonstrated that the addition of microbial agents facilitated the degradation of specific substances, leading to reduced absorbance in the corresponding spectra. XRD analysis further indicated a notable reduction in cellulose crystallinity for both the ZZ (8.00%) and EM (7.73%) treatments. Hence, the incorporation of microbial agents and brown sugar in tomato straw compost effectively enhances the composting process and improves the quality of compost products.

Waste seaweed compost and rhizosphere bacteria Pseudomonas koreensis promote tomato seedlings growth by benefiting properties, enzyme activities and rhizosphere bacterial community in coastal saline soil of Yellow River Delta, China

This study investigated the effects of waste seaweed compost and rhizosphere bacteria Pseudomonas koreensis HCH2-3 on the tomato seedlings growth in coastal saline soils and chemical properties, enzyme activities, microbial communities of rhizosphere soil. Microcosmic experiment showed that the seaweed compost and rhizosphere bacteria (SC + HCH2-3) significantly alleviated the negative effects of salinity on the growth of tomato seedlings. SC + HCH2-3 amendment significantly increased the plant height and root fresh biomass of tomato seedling by 105.59% and 55.60% in the coastal saline soils, respectively. The soil properties and enzyme activities were also dramatically increased, indicating that the nutrient status of coastal saline soil was improved by SC + HCH2-3 amendment. In addition, Proteobacteria, Actinobacteriota and Firmicutes were the dominant phyla in the rhizosphere soil after adding seaweed compost and rhizosphere bacteria P. koreensis HCH2-3. The relative abundances of Massilia, Azospira, Pseudomonas and Bacillus increased in treatment SC + HCH2-3. Especially, the beneficial bacteria genera, such as Pseudomonas, Bacillus and Azospira, were significantly correlated with the increases of contents of total nitrogen, nitrate nitrogen and ammonium nitrogen in tomato rhizosphere soil samples. Consequently, adding waste seaweed compost and rhizosphere bacteria P. koreensis HCH2-3 into coastal saline soil was suggested as an effective method to relieve salt stress of tomato plants.

Combinations of waste seaweed liquid fertilizer and biochar on tomato (Solanum lycopersicum L.) seedling growth in an acid-affected soil of Jiaodong Peninsula, China

Biochar application is an effective strategy for improving soil degradation and productivity. However, the effects of the combination of biochar and other fertilizers to improve seedling growth in abiotic stress-affected soils remains unknown. We investigate the effect of biochar derived from reed straw (RBC) and waste seaweed liquid fertilizer (SLF) on tomato (Solanum lycopersicum L.) seedling growth in an acid-affected soil of Jiaodong Peninsula, China. The results revealed RBC, SLF, and the combination of RBC with SLF (RBC+SLF) significantly elevated the dry weight of tomatoes by 23.33 %, 29.93 %, and 63.66 %, respectively. The malondialdehyde content in the tomato seedling roots, stems, and leaves was significantly lower in the RBC+SLF treatment, which might be related to the enhanced contents of proline, soluble sugar, and soluble protein. The synthesis and accumulation of zeatin riboside, indole-3-acetic acid, and gibberellic acid 3 in tomato under RBC+SLF amendment may be attributed to the enhanced plant growth. Moreover, RBC, SLF, and RBC+SLF improved the soil status (including ammonium nitrogen, nitrate nitrogen, laccase, and urease) in the acid-affected soil. Biochar and waste seaweed liquid fertilizer significantly increased the relative abundance of Pseudomonas and Azospira (beneficial bacteria) in tomato rhizosphere. The microbial amino acid metabolism was associated with changes in soil properties and enzyme activities. Consequently, biochar and waste seaweed liquid fertilizer are viable soil conditioners for acid-affected soil.

Current application of seaweed waste for composting and biochar: A review

To address the origins of ocean acidification, seaweed aquaculture is emerging as a key biosequestration strategy. Nevertheless, seaweed biomass is involved in developing food and animal feed, whereas seaweed waste from commercial hydrocolloid extraction is dumped in landfills, which together limit the carbon cycle and carbon sequestration. This work sought to evaluate the production, properties, and applications of seaweed compost and biochar to strengthen the "carbon sink" implications of aquaculture sectors. Due to their unique characteristics, the production of seaweed-derived biochar and compost, as well as their existing applications, are distinct when compared to terrestrial biomass. This paper outlines the benefits of composting and biochar production as well as proposes ideas and perspectives to overcome technical shortcomings. If properly synchronized, progression in the aquaculture sector, composting, and biochar production, potentially promote various Sustainable Development Goals.

Response characteristics of Flax retting liquid addition during chicken manure composting: Focusing on core bacteria in organic carbon mineralization and humification

To explore the applicability of flax retting liquid (FRL) addition, the physicochemical properties, microbial community structure and function, carbon conversion and humus (HS) formation were assessed during chicken manure (CM) aerobic composting. Compared with the control group, the addition of FRL increased the temperature at thermophilic phase, while the microbial mass carbon content (MBC) in SCF and FRH groups raised to 96.1±0.25 g/Kg and 93.33±0.27 g/Kg, respectively. Similarly, FRL also improved the concent of humic acid (HA) to 38.44±0.85 g/Kg, 33.06±0.8 g/Kg, respcetively. However, fulvic acid (FA) decreased to 30.02±0.55g/Kg, 31.4±0.43 g/Kg, respectively and further reduced CO₂ emissions. FRL influenced the relative abundance of Firmicutes at thermophilic phase and Ornithinimicrobium at maturity phase. Additionally, FRL strengthen the association among flora and reduce the number of bacteria, which was negative correlated with HA and positive with CO₂ during composting. These findings offer powerful technological support for improving agricultural waste recycling.

Disentangling the coupling relationships between functional denitrifiers and nitrogen transformation during cattle-manure and biochar composting: A novel perspective

This study explored the coupling relationships between denitrifiers and N-transformation using multi-level (DNA, RNA and enzyme) and multi-aspect (abundance, diversity, structure, key community, network pattern, and functional module) analyses during cattle-manure (CM) and biochar (CMB) composting. Amino sugar-N (ASN, 0.914) and hydrolysable unknown-N (-0.724) were main organic-N components mediating NH₄⁺-N in CM and CMB, respectively. Biochar lowered nirK, nirS, and nosZ genes copies, up-regulated nir gene transcripts, and inhibited nitrite reductase (NIR) activity. For nirK-denitrifiers, Luteimonas was predominant taxa influencing NO₂^--N and amino acid-N (AAN). Unclassified_k_norank_d_Bacteria and unclassified_p_Proteobacteria regulated NO₃^--N and ASN, respectively. These three genera played crucial roles in mediating NIR activity and nosZ/nirK. For nirS-denitrifiers, Paracoccus and Pseudomonas mediated NH₄⁺-N and AAN, respectively, and they were vital genera regulating NO₃^--N, ASN and NIR activity. Furthermore, nirK-denitrifiers was major contributor to denitrification. Overall, functional denitrifiers might simultaneously participate in multiple N-transformation processes.

Membrane-covered composting significantly decreases methane emissions and microbial pathogens: Insight into the succession of bacterial and fungal communities

In this study, the effects of semipermeable membrane-covered on methane emissions and potential pathogens during industrial-scale composting of the solid fraction of dairy manure were investigated. The results showed that the oxygen concentration in the membrane-covered group (CT) was maintained above 10 %, and the cumulative methane emission in CT was >99 % lower than that in the control group (CK). Microbial analysis showed that the bacterial genus Thermus and the fungal genus Mycothermus were dominant in CT, and the richness and diversity of the bacterial community were greater than those of the fungal community. At the end of the composting, the relative abundance of potential bacterial pathogens in CT was 32.59 % lower than that in CK, and the relative abundance of potential fungal pathogens in each group was <2 %. Structural equation models revealed that oxygen concentration was a major factor influencing the bacterial diversity in CT, and the increase of oxygen concentration could limit methane emissions by inhibiting the growth of anaerobic bacteria. Therefore, membrane-covered composting could effectively improve compost safety and reduce methane emissions by regulating microbial community structure.

Land-use change alters the bacterial community structure, but not forest management

Deforestation has a large impact on soil fertility, especially on steep slopes, but by applying sustainable management practices, local communities in Oaxaca (Mexico) have tried to avoid the most negative effects on the forest ecosystems they manage. In this study, the characteristics and bacterial community structure were investigated from soil sampled in triplicate (n = 3) with different land use, i.e., arable, natural forest, sustainable managed, and reforested soil. The pH was significantly higher in the arable (6.2) than in the forest soils (≤ 5.3), while the organic matter was > 2 times higher in the natural forest (80.4 g/kg) and sustainable managed soil (86.3 g/kg) than in the arable (36.8 g/kg) and cleared and reforested soil (39.3 g/kg). The higher organic matter content in the first two soils was due to leaf litter, absent in the other soils. The species richness (q = 0), the typical (q = 1) and dominant bacteria (q = 2) were not affected significantly by land use. The beta diversity, however, showed a significant effect of land use on species richness (p = 0.0029). Proteobacteria (40.135%) and Actinobacteria (20.15%) were the dominant bacterial phyla, and Halomonas (14.50%) and the Verrucomicrobia DA101 (3.39%) were the dominant genera. The bacterial communities were highly significantly different in soil with different land use considering the taxonomic level of genus and OTUs (p ≤ 0.003). It was found that the sustainable managed forest provided the local community with sellable wood while maintaining the soil organic matter content, i.e., sequestered C and without altering the bacterial community structure.

Optimization of vegetable waste composting and the exploration of microbial mechanisms related to fungal communities during composting

The application of additives to regulate the microbial functional composition during composting has attracted much research attention. However, little is known about the succession and role of the fungal community in the laboratory-scale composting of vegetable waste supplemented with pig manure and microbial agents. The purpose of this study was to identify effective additives for improving vegetable waste composting performance and product quality, and to analyze the microbial community succession during composting. The results showed that the combined addition of pig manure and microbial agents (T2 treatment) accelerated the pile temperature increase, enhanced total organic carbon degradation (23.36%), and promoted the maturation of the compost. Furthermore, the T2 treatment increased the activities of most enzymes, reshaped the microbial community, and reduced the relative abundance of potential animal (1.60%) and plant (0.095%) pathogens. The relative abundance of Firmicutes (71.23%) increased with the combined addition of pig manure and microbial agents in the thermophilic stage. In the middle and late stages, Saccharomonospora, Aspergillus, and Thermomyces, which were related to C/N and total phosphorus, were enriched in the T2 treatment. Network analysis demonstrated that the complexity and stability of the fungal network were more evidently increased in the T2 treatment, and Saccharomonospora, Aspergillus, and Microascus were identified as keystone taxa. The keystone taxa associated with extracellular enzymes contributed significantly to compost maturation. These results provide a reference for the application of additives to improve compost safety in pilot-scale composting.

Treatment and novel resource-utilization methods for shale gas oil based drill cuttings - A review

The oil exploration and production (E&P) industry has made outstanding contributions to gross domestic product (GDP) growth in many countries. In recent years, the gap between energy supply and demand has widened, and, simultaneously, demand for clean energy has gradually increased. As an emerging clean energy source, shale gas has received extensive attention. However, the environmental problems caused by oil and gas extraction and production should not be underestimated. Oil-based drill cuttings (OBDC) are typical hazardous solid wastes produced during oil/gas exploration and production processes. In addition, oil-based drill cuttings ash (OBDCA) is the main product of treated OBDC and should be further utilized to avoid pollution and waste of resources. This review describes relevant policies and regulations for the OBDC. The main treatment methods for OBDC have been systematically summarized. Compared to the standard method for resource utilization of OBDCA, a novel approach was proposed to utilize OBDCA as an environment-friendly functional material for environmental remediation. The future development prospects for OBDC were envisioned to achieve sustainable development goals.

Dynamic succession patterns and interactions of phyllospheric microorganisms during NOx exposure

The phyllosphere plays a role in alleviating air pollution, potentially leveraging the native microorganisms for further enhancement. It remains unclear how phyllospheric microorganisms respond to nitrogen oxide (NO_x) pollution and participate in abatement. Here, we exposed Schefflera octophylla to NO_x to reveal microbial succession patterns and interactions in the phyllosphere. During exposure, phyllospheric ammonium (NH₄⁺-N) significantly increased, with different alpha diversity changes between bacteria and fungi. Community successions enclosed core taxa with relatively excellent tolerance, represented by bacterial genera (Norcardiodes, Aeromicrobium) and fungal genera (Talaromyces, Acremonium). The exposure eliminated specific pathogens (e.g., Zymoseptoria) and benefitted plant growth-promoting populations (e.g., Talaromyces, Exiguobacterium), which might favor plant disease control, improve plant health and thus buffer NO_x pollution. Cooccurrence networks revealed more negative correlations among bacteria and closer linkages among fungi during exposure. Our results also showed a functional shift from the predominance of pathotrophs to saprotrophs. Our study identified microbial successions and interactions during NO_x pollution and thus enlightened prospective taxa and potential roles of phyllospheric microorganisms in NO_x remediation.

Effects of straw mulching on predatory myxobacterial communities in different soil aggregates under wheat-corn rotation

Crop straw mulching is an important organic supplement in sustainable agriculture; however, the effect of increased organic matter on the diversity of micropredators such as myxobacteria and the correlation between myxobacteria and microorganisms have been little explored. In the current investigation, high-throughput sequencing was performed to analyze the myxobacterial community composition in a wheat-corn rotation experimental field with 6-year straw mulching and fertilization treatments. The results reveal no significant influence of straw mulch application on myxobacterial α-diversity (P < 0.05). NMDS (nonmetric multidimensional scaling) and perMANOVA results indicate the significant influence of straw mulching application on myxobacterial community composition (P < 0.05), and several groups, including Haliangiaceae, Polyangiaceae, and Archangiaceae, also varied in soil aggregates. RDA (redundancy analysis) results show that TOC (total organic carbon) was the most important factor affecting the myxobacterial community structure. In addition, RDA and random forest analysis results show the contribution of myxobacterial community structure to soil bacterial community α- and β-diversity, especially in the 0.25-1 mm and < 0.25 mm soil aggregate fractions. In conclusion, we suggest that the variation in myxobacterial community structure may be a driver of bacterial α- and β-diversity in soil microhabitats and might be a cause of soil microbial community changes. Our results are fruitful for finding more efficient ways to use straw from waste for the betterment of sustainable agriculture by analyzing changes in myxobacterial community structure.

Effects of Microbial Inoculation with Different Indigenous Bacillus Species on Physicochemical Characteristics and Bacterial Succession during Short-Term Composting

Bacillus accelerates lignocellulose degradation, promotes the stabilization and resource utilization of compost by secreting enzymes, and plays an important role in compost formation and quality control. This study evaluated enzyme activity, lignocellulosic degradation, and bacterial succession in composting inoculated with different microbial Bacillus agents. They were identified as B. licheniformis, B. subtilis, B. thermoamylovorans, B. thermoruber, and B. hisashii. Four treatments were established, including a CK (uninoculated microorganisms), A (B. licheniformis, B. subtilis, B. thermoamylovorans,and B. hisashii), B (B. subtilis, B. thermoamylovorans, B. thermoruber, and B. hisashii), and C (B. subtilis, B. thermoamylovorans, and B. hisashii), and the composting lasted 7–14 days. Lignin and cellulose degradation rates in B during composting were 17.1% and 36.7% at the cooling stage, respectively. Redundancy analysis showed that degradation of lignocellulose in the thermophilic stage was mainly related to the secretion of lignocellulose-degrading enzymes after microbial inoculation. 16S rRNA sequencing revealed that Bacillus (20.3%) and Thermobifida (20.2%) were the dominant genera. Inoculation with a combination including B. thermoruber was a feasible way to increase lignocellulose degradation and promote maturity in sewage sludge composting.

Ventilation induced evolution pattern of archaea, fungi, bacteria and their potential roles during co-bioevaporation treatment of concentrated landfill leachate and food waste

To obtain a favorable aeration type in co-bioevaporation treatment of concentrated landfill leachate and food waste, and to deeply understand the co-bioevaporation mechanisms, the temporal evolution differences of archaea, fungi and bacteria as well as the related microbial metabolism genes and functional enzymes under intermittent ventilation (IV) and continuous ventilation (CV) were investigated. Results through metagenomics analysis showed that the less sufficient oxygen and longer thermophilic phase in IV stimulated the vigorous growth of archaea, while CV was beneficial for fungal growth. Even genes of carbohydrates and lipids metabolism and ATP-associated enzymes (enzyme 2.7.13.3 and 3.6.4.12), as well as peptidoglycan biosynthesis enzyme (enzyme 3.4.16.4), were more abundant in CV, IV hold better DNA repair ability, higher microbial viability, and less dehydrogenase sensitivity to temperatures due to the critical contribution of Pseudomonas (3.1-45.9%). Furthermore, IV consumed a similar amount of heat for water evaporation with nearly half of the ventilation of CV and was a favorable aeration type in the practical application of co-bioevaporation.

Biochar regulates bacterial-fungal diversity and associated enzymatic activity during sheep manure composting

Aimed to evaluate the coexistence of bacterial and fungal diversity and their correlation with enzymatic activity in response to biochar. This study performed aerobic composting based on typical agricultural wastes of sheep manure with additive apple tree branch biochar at distinct concentration (0, 2.5, 5, 7.5, 10 and 12.5% corresponding from T1 to T6). The result demonstrated that appropriate amendment of biochar enriched bacterial diversity (1646-1686 OTUs) but interestingly decreased fungal diversity (542-630 OTUs) compared to control (1444 and 682 OTUs). Biochar addition enhanced all enzymatic activities and its correlation with bacterial was more complex than fungal community (786 and 359 connect edges). The dominant microbes comprised of Firmicutes (45.2-35.2%), Proteobacteria (14.0-17.5%), Basidiomycota (32.4-49.5%) and Ascomycota (11.3-37.5%) among all the treatments. Overall, biochar regulates the composting microenvironment by influencing the microbial diversity and associated enzymatic activities.

Response of constructed wetland for wastewater treatment to graphene oxide: Perspectives on plant and microbe

The wide application of graphene oxide (GO) increases its release into environment with less known on environmental effects. This work investigated 120-day interaction between GO (500 and 5000 μg/L) and constructed wetlands (CWs) planted with Iris pseudacorus. CWs showed the effective retention for GO via mature biofilm but less biodegradation. GO significantly induced enzyme activities (urease, neutral phosphatase, and catalase), which was attributed to increases in ecological association and enzyme abundance. GO decreased microbial biomass on day 30, but it had no impacts on day 120. The microbial community showed gradual self-adaption with time due to protection of antioxidant defense system (L-ascorbate oxidase, superoxide reductase, and glutathione related enzyme). The antioxidant enzymes (superoxide dismutase and peroxidase) and lipid peroxidation of Iris pseudacorus were increased by GO, accompanied by reduction on chlorophyll biosynthesis. Overall, the separate effects of GO on micro-regions and individual bodies in CWs were obvious, but it was acceptable that variations in pollutant removal were not evident due to synergetic role of plant-substrate-microbe. Organic matter and phosphorus removals reached to above 93%, and ammonia and total nitrogen removals in GO groups were reduced by 7-8% and 9-13%, respectively.

Structural and Predicted Functional Diversities of Bacterial Microbiome in Response to Sewage Sludge Amendment in Coastal Mudflat Soil

The study investigated the influence of sewage sludge application at rates of 0 (CK), 30 (ST), 75 (MT), and 150 (HT) t ha−1 to mudflats on bacterial community diversity and predicted functions using amplicon-based sequencing. Soils under sewage sludge treatments, especially the HT treatment, exhibited lower pH, salinity and higher nutrient contents (C, N, and P). Moreover, restructured bacterial communities with significantly higher diversities and distinct core and unique microbiomes were observed in all sewage sludge-amended soils as compared to the control. Specifically, core bacterial families, such as Hyphomicrobiaceae, Cytophagaceae, Pirellulaceae Microbacteriaceae, and Phyllobacteriaceae, were significantly enriched in sewage sludge-amended soils. In addition, sewage sludge amendment significantly improved predicted functional diversities of core microbiomes, with significantly higher accumulative relative abundances of functions related to carbon and nitrogen cycling processes compared to the unamended treatment. Correlation analyses showed that modified soil physicochemical properties were conducive for the improvement of diversities of bacterial communities and predicted functionalities. These outcomes demonstrated that sewage sludge amendment not only alleviated saline–sodic and nutrient deficiency conditions, but also restructured bacterial communities with higher diversities and versatile functions, which may be particularly important for the fertility formation and development of mudflat soils.

Beer lees and ceramsite amendments enhance the two-stage co-composting of green waste

Composting is a major way to process green waste (GW), and amendments are important in GW composting. In this study of the two-stage co-composting of GW, beer lees (0, 25, 30%) and/or ceramsite (0, 10, 15%) were assessed as amendments. Changes in bulk density, porosity, temperature, pH, gaseous emissions, dissolved organic carbon (DOC) and nitrogen (DON), lignocellulose degradation, microbial abundances, and phytotoxicity were assessed during GW composting with the amendments. Treatments with a combination of beer lees and ceramsite had positive effects, and 25% beer lees and 15% ceramsite optimized all compost parameters. The optimal combination of amendments extended the thermophilic phase, enhanced the lignocellulose decomposition, and generated a stable and mature product in 20 days. Consequently, the best final compost was not phytotoxic (germination index: 164%), was mature (void space ratio: 48.48, pH: 7.20, and DOC/DON ratio: 0.51), and nutrient-rich (especially for N: 5.13%, P: 1.84%, and K: 0.68%).

Compositional and functional succession of bacterial and fungal communities is associated with changes in abiotic properties during pig manure composting

While both bacteria and fungi are important for the degradation and humification of organic matter during composting, it is unclear to what extent their roles are associated with abiotic compost properties. This study evaluated changes in abiotic compost properties and the succession of bacterial and fungal communities during pig manure composting for 90 days. The compost rapidly reached thermophilic phase (>58 ℃), which lasted for 15 days. Both bacterial and fungal community compositions changed drastically during composting and while bacterial diversity increased, the fungal diversity decreased during the thermophilic phase of composting. Two taxa dominated both bacterial (Bacillales and Clostridiales) and fungal (Eurotiales and Glomerellales) communities and these showed alternating abundance fluctuations following different phases of composting. The abundance fluctuations of most dominant bacterial and fungal taxa could be further associated with decreases in the concentrations of fulvic acid, cellulose, hemicellulose and overall biodegradation potential in the compost. Moreover, bacterial predicted metabolic gene abundances dominated the first three phases of composting, while predicted fungal saprotrophic functional genes increased consistently, reaching highest abundances towards the end of composting. Finally, redundancy analysis (RDA) showed that changes in abiotic compost properties correlated with the bacterial community diversity and carbohydrate metabolism and fungal wood saprotrophic function. Together these results suggests that bacterial and fungal community succession was associated with temporal changes in abiotic compost properties, potentially explaining alternating taxa abundance patterns during pig manure composting.

Soil properties and microbial community in the rhizosphere of Populus alba var. pyramidalis along a chronosequence

By maintaining soil structure and quality, soil microbial communities usually play important role in many forest ecosystem processes, including ecological succession. Understanding changes in the microbial communities of areas afforested with stands of different ages is of interest in ecology. Populus alba var. pyramidalis Bunge has been widely planted in Northwest China for ecological restoration. Rhizospheric soil samples were collected from 4-, 9-, 15-, 25- and 30-year-old plantations of P. alba to measure soil characteristics and soil microbial community diversity using Illumina MiSeq sequencing. The soil nutrition concentration and enzymatic activities decreased with depth of soil layer increased. In terms of stand age, alkaline phosphatase and dehydrogenase and the contents of nitrate N, available P and soil organic content (SOC) increased gradually. According to Illumina MiSeq sequencing results, the fungal and bacterial community structure varied with stand age, and diversity of fungi was less than bacteria. With increasing stand age, fungal community diversity indexes first increased and then decreased, peaked at 25y or 30y. RDA results suggested that soil available P and nitrate N were the most important factors governing fungal community structure, while available P contributed significantly to the variance of the bacterial community. Structural equation modelling (SEM) results indicated soil available P, nitrate N and SOC contents largely explained the shift in the microbial community structure along the cultivation chronosequence, and soil enzyme activities were related with changes in microbial community. Our results illustrated that the successional changes in microbial communities in the P. alba plantations can largely be attributed to changes in soil nutrition level along the chronosequence.

Succession of the microbial communities and function prediction during short-term peach sawdust-based composting

Short-term composting of raw materials for preparing oyster mushroom cultivation media is widely used in China, and its microbial mechanism needs to be further studied. 11-days' peach sawdust-based composting was performed to evaluate material conversion and microbial succession using physicochemical analysis and 16S rRNA and ITS sequencing. Composting bacteria demonstrated much higher abundance than fungi. Firmicutes, Actinobacteriota, and Proteobacteria were the dominant bacterial phyla, while most of fungal species belonged to Ascomycota. Moisture was the key factor at the beginning, while total nitrogen, temperature, and lignin became main influencing factors for composting maturity. Actinobacteriota, Firmicutes, and Proteobacteria of bacterial phyla, Eurotiomycetes and Sordariomycetes of fungal classes involved in lignocellulosic degradation. Bacterial function prediction analysis showed that carbohydrate metabolism and amino acid metabolism were the main metabolic pathways. These results confer a better understanding of material and microbial succession during short-term composting and also provide valuable utilization in mushroom industry.

Studying Microbial Communities through Co-Occurrence Network Analyses during Processes of Waste Treatment and in Organically Amended Soils: A Review

Organic wastes have the potential to be used as soil organic amendments after undergoing a process of stabilization such as composting or as a resource of renewable energy by anaerobic digestion (AD). Both composting and AD are well-known, eco-friendly approaches to eliminate and recycle massive amounts of wastes. Likewise, the application of compost amendments and digestate (the by-product resulting from AD) has been proposed as an effective way of improving soil fertility. The study of microbial communities involved in these waste treatment processes, as well as in organically amended soils, is key in promoting waste resource efficiency and deciphering the features that characterize microbial communities under improved soil fertility conditions. To move beyond the classical analyses of metataxonomic data, the application of co-occurrence network approaches has shown to be useful to gain insights into the interactions among the members of a microbial community, to identify its keystone members and modelling the environmental factors that drive microbial network patterns. Here, we provide an overview of essential concepts for the interpretation and construction of co-occurrence networks and review the features of microbial co-occurrence networks during the processes of composting and AD and following the application of the respective end products (compost and digestate) into soil.

Acetobacter orientalis XJC-C with a high lignocellulosic biomass-degrading ability improves significantly composting efficiency of banana residues by increasing metabolic activity and functional diversity of bacterial community

Banana residues are an important energy resource after fruit harvesting. The optionally dumping and burning causes severely environmental problems. Traditional compost efficiency was limited by lignocellulosic composition of banana residues. Inoculation with cellulase-producing microbes provides an efficient strategy for improving degradation of lignocellulosic materials. In our study, a newly isolated cellulolytic bacterium Acetobacter orientalis XJC-C with a salt and high temperature resistance was identified from a marine soft coral. By contrast, the strain can biodegrade different lignocellulosic agricultural residues, especially banana straw. The highest cellulolytic and ligninolytic enzyme activities were detected during composting at 40 days. Compared with the negative and positive control groups, the lignin degradation rate reached 76.24% in the A. orientalis XJC-C group, increased by 47.08% and 21.85%, respectively. Moreover, the strain improved significantly the metabolic activity and functional diversity of bacterial community. Hence, A. orientalis XJC-C will be a promising candidate for degrading lignocellulosic agricultural residues.

Efficient bio-degradation of food waste through improving the microbial community compositions by newly isolated Bacillus strains

This study aims to screen high-degradability strains and develop a novel microbial agent for efficient food waste degradation. The effects of the novel microbial agent on organic matter degradation, enzyme activity, and bacterial succession during the in-situ reduction of food waste were evaluated and compared with other two microbial agents previously developed. Results showed that the novel agent containing four Bacillus strains received maximum organic degradation rates, volatile solid removal (46.91%) and total mass reduction (76.16%). Pyrosequencing analysis revealed that there was a significant difference in the microbial community structure of the matrix among the three biodegradation systems, and the novel agent greatly improved the stability of in-situ reduction process that Bacillus was the dominant genus (>98%) since day 4. These results indicated that the inoculant containing only Bacillus was more stable and cost-effective in FW in-situ reduction.

Effects of urease inhibitors on enzymatic activities and fungal communities during the biosolids composting

This study evaluated the influences of urease inhibitors (UIs) on nitrogen conversion, enzyme activities, and fungal communities during aerobic composting. Results showed that UI addition reduced NH₃ emissions by 22.2% and 21.5% and increased the total nitrogen (TN) content by 9.7% and 14.3% for the U1 (0.5% UI of the dry weight of the mixture) and U2 (1% UI of the dry weight of the mixture) treatments, respectively. The addition of UI inhibited the enzyme activity during thermophilic stage while increased enzyme activity during the cool and maturity stages. Ascomycota, Basidiomycota and unclassified fungi were the main phyla, and Ascomycota increased significantly during the maturity period. Network analysis showed that Aspergillus, Penicillium, Trichoderma, Talaromyces, Peseudeurotium, and Exophiala were the main “connecting” genera. The redundancy analysis (RDA) showed that the fungal community was mainly influenced by temperature, DOC, pH, and urease. The results suggested that UI was an effective additive for nitrogen conservation and the increase of enzyme activity reduce nitrogen loss and promote enzyme activity during biosolids composting.

Adding UI was effective for nitrogen conservation and the increase of enzyme activity during biosolid composting.

Composting of seaweed waste: Evaluation on the growth of Sarcocornia perennis

Composting represents a suitable and cheap method for handling and processing seaweeds accumulated on the coast. Within this framework, two seaweed composts were prepared, one with Undaria pinnatifida accumulated in spring-summer and other with a mixture of seaweeds accumulated in autumn-winter, both from Central Patagonian beaches. The effect of these two composts was evaluated experimentally as an amendment for the growth of Sarcocornia perennis (chickenclaws), a plant species dominating Patagonian salt marshes. Both composts were applied at 75, 50, and 25% doses with perlite. The analysis of the compost properties (phytotoxicity test, C/N, electrical conductivity, pH, and metal content) allowed characterizing both composts as matures and stables. The growth results showed that both composts allow the growth of S. perennis in all doses tested; however, Undaria compost was better in the stimulation of vegetative growth when applied in dose 50%, followed by 75% of both composts. For these reasons, both composts from seaweed waste accumulated on Patagonian coasts could be used in the growth of S. perennis and potentially other plant species, giving value to the seaweeds that currently are considered a waste that disturb these coasts and are discarded without use.

Stable isotopes reveal the formation diversity of humic substances derived from different cotton straw-based materials

Humic substances (HS) are essential in environment processes and carbon (C) sequestration in soils. In this study, organic materials such as cotton straw and its derived compost and biochar were added to the soil on a C-equivalent basis and incubated for 30 and 180 days in order to investigate the different forms of plant biomass derived C sequestration in HS. The C distribution in humic acid (HA), fulvic acid (FA), and humin (Hu) derived from organic materials was investigated using the ¹³C isotope method, while the catalase, sucrose, and β-glucosidase activities were also determined. The results showed that C3 distribution of Hu derived from straw, compost and biochar increased from 40.94% to 67.12%, 74.47% and 80.75%, respectively. In addition, the increase of C3 distribution of HA or FA derived from straw, compost and biochar were 4.69%, 10.09% and 1.49%, respectively. There were significantly positive correlations between catalase, sucrase and β-glucosidase activities and C3 derived HA and FA. The principal component analysis showed that catalase, sucrase and β-glucosidase were explained mainly by the first principal component indicating a significant correlation. These findings suggest that straw, compost and biochar are mainly sequestrated in Hu. Comparatively, the straw and compost are more likely to contribute to the formation of HA and FA in soil, but biochar favors the Hu, which helps in soil C sequestration. The formation of HA and FA derived from organic materials was supported by catalase, sucrase and β-glucosidase activities.

Composting pig manure and sawdust with urease inhibitor: succession of nitrogen functional genes and bacterial community

Understanding the relationship between nitrogen (N) cycle and N transformation-related functional genes is crucial to reduce N loss during composting process. Urease inhibitor (UI) is widely used to reduce N loss in agriculture. However, the effects of UI on N transformation and related N functional genes during composting have not been well investigated. The goal of this study was to investigate the effects of a urease inhibitor (UI) on N functional genes and bacterial community succession during pig manure composting. Results showed that the addition of UI decreased the ammonium N content during the thermophilic stage and notably increased the total N and nitrite N contents of the final compost. The UI significantly decreased the abundances of amoA, nirS, nirK, and nosZ during the initial composting stage, while the opposite trend was observed at the maturation stage. Bacterial community richness and diversity were increased after the UI amendment, but the relative abundance of the phyla Firmicutes and Proteobacteria significantly decreased compared with control during the thermophilic stage. Redundancy analysis indicated that the evaluated environmental factors and bacterial community showed a cumulative 94.7% contribution to the total variation in N functional genes. In summary, UI addition is a recommended method for N conservation during composting, but the added forms of UI, such as delayed addition, combined with adsorbing materials, or microorganism inoculant, should be further evaluated.

Effects of Different Fertilizer Treatments on Rhizosphere Soil Microbiome Composition and Functions

Fertilization influences the soil microbiome. However, little is known about the effects of long-term fertilization on soil microbial metabolic pathways. In this study, we investigated the soil microbiome composition and function and microbial participation in the N cycle according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene ontology (GO) functional annotation of different genes in a metagenomic analysis after long-term fertilization. Fertilizer application significantly changed the soil C/N ratio. Chemical fertilizer (NPK) treatment decreased soil pH, and chemical fertilizer combined with straw (NPK+S0.5) treatment increased ammonium nitrogen (NH4+-N) but decreased nitrate nitrogen (NO3−-N). NPK, NPK+S0.5 and S0.5 applications did not change the soil microbiome composition or dominant phylum but changed the relative abundances of microbiome components. Moreover, fertilizer significantly influenced metabolic processes, cellular processes and single-organism processes. Compared with a no-fertilizer treatment (CK), the NPK treatment resulted in more differentially expressed gene (DEG) pathways than the NPK+S0.5 and S0.5 treatments, and these pathways significantly correlated with soil nitrate nitrogen (NO3−-N), available phosphorus (AP) and the moisture content of soil (MC). KEGG analysis found that fertilizer application mainly affected the ribosome, photosynthesis and oxidative phosphorylation pathways. S0.5 and NPK+S0.5 increased microbial nitrogen fixation, and NPK and NPK+S0.5 decreased amoA and amoB and accelerated denitrification. Thus, organic fertilizer increased N fixation and nitrification, and inorganic N fertilizer accelerated denitrification. We found that the function of the soil microbiome under different fertilizer applications could be important for the rational application of fertilizer and for environmental and sustainable development.

Hydrolyzing Laminaria japonica with a combination of microbial alginate lyase and cellulase

A novel seaweed-hydrolyzing strain designated as Pseudoalteromonas sp. Alg6B was isolated from the surface of brown seaweed (Laminaria japonica). The activity of crude alginate lyase produced by Alg6B was 54.5 U/ml and the main products of hydrolyzing alginate were disaccharide and tetrasaccharide. The hydrolysis rate of seaweed reached up to 97% after combining 3% (v/v) Alg6B and 0.2% (w/v) solid cellulase. In kelp hydrolysate, the contents of nutrients are much more than raw seaweed. Alg6B grows quickly and has the ability of producing alginate oligosaccharides with low molecular weight (MW) (≤2 kDa). Furthermore, this study demonstrates that a combination of microbial alginate lyase and cellulase could almost hydrolyze seaweed completely. This research indicated that Alg6B could provide a feasible pathway to produce alginate oligosaccharides (AOS), and the synergistic effect of alginate lyase and cellulase on seaweed bioconversion can potentially pave the way to the sustainable production of seaweed fertilizer.

Effects of microbial inoculation on enzyme activity, available nitrogen content, and bacterial succession during pig manure composting

This study evaluated enzyme activity, available nitrogen, and bacterial succession during pig manure composting with and without microbial inoculation (ABB and CK, respectively). ABB reached the thermophilic stage 2 days than CK. Cellulose, urease, phosphatase, and sucrase activities were higher in ABB than in CK on days 12-24 of composting, but catalase activity was lesser in ABB than in CK throughout composting. NH4+-N and NO3--N were significantly increased in ABB at the maturity stage. 16S rRNA sequencing revealed Nocardiopsaceae, Bacillaceae, Streptosporangiaceaec, Flavobacteriaceae, and Caldicoprobacteraceae as the dominant bacteria at the family level. Metabolism function analysis revealed that human diseases were reduced and carbohydrate metabolism was increased in ABB. Correlation analysis revealed that urease, sucrose, and phosphatase were significantly correlated with bacteria at the species level, whereas NH4+-N and NO3--N were not significantly correlated. These results indicated that microbial inoculation accelerated the composting process and significantly regulated microbial functions.

Genetic and Metabolic Diversity of Soil Microbiome in Response to Exogenous Organic Matter Amendments

Loss of organic matter content of cultivated soils is observed in many regions of Europe. The possibility of using organic waste as a soil additive that enriches the soil with organic matter and essential components is important in soil quality protection and waste management. This research concerned the influence of six organic wastes—two industrial composts, three digestates and meat bone meal—on soil microbial properties. The study of functional microbial diversity concerns the determination of the catabolic capacity of bacterial, fungal and anaerobic communities in relation to carbon substrates in metabolic profiling plates (Biolog® ECO, FF, AN (Biolog Inc., Hayward, CA, USA)). The assessment of genetic diversity was made on the basis of analysis of the restriction profile of ammonia-oxidizing archaea. Additionally, soil dehydrogenases activity was determined. The research showed that the type of organic waste used had an influence on the microbiological parameters. The application of exogenous organic matter caused increases in functional and genetic microbial diversity. The nature of the noted changes was short term and periodic. The values of the microbiological parameters in soils with organic waste were similar to those of the control samples. This indicates an improved microbiological balance and stability of the soil environment after the application of exogenous organic matter.

Effect of biochar and bacterial inoculum additions on cow dung composting

The present study evaluates the effectiveness of different types of biochar additives and bacterial inoculation on gaseous emission, nutrient preservation, and relevant functional bacterial community during cow manure composting. The result revealed that biochar and bacterial consortium inoculation effectively inhibited gaseous emission and improved carbon and nitrogen sequestration, remarkably enriching the abundance of the functional bacteria community. Notably, superior efficacy was found in 12% wheat straw biochar and bacterial consortium amendment composting of T6 with the lowest cumulative CO₂-C and NH₃-N (308.02 g and 12.71 g, respectively), minimal total C and N losses, and the highest bacterial population. Additionally, gaseous emission exhibited a strong correlation between physicochemical properties with intersection of 66.78% and a unique substrate utilizing bacterial communities. Consequently, the integrated application of biochar and bacterial consortium inoculation was suggested as an efficient method to adjust microbial activity and facilitate cellulose-rich waste degradation, enabling efficient management of organic waste from cow manure and wheat straw by composting.

Assessment of bacterial and fungal communities in a full-scale thermophilic sewage sludge composting pile under a semipermeable cover

Bacterial and fungal communities in a full-scale composting pile were investigated, with sewage sludge and a vegetal bulking agent as starting materials. Bacillales and Actinomycetales were predominant throughout the process, showing significant abundance. Ascomycota was the predominant fungal phylum during the thermophilic phase, with a shift to Basidiomycota at the end of the process. The bulking material was the principal contributor to both communities by the end of the process, with a signal above 50%. The presence of genera, such as Pedomicrobium, Ureibacillus and Tepidimicrobium at the end of the process, and Chaetomium and Arthrographis in the maturation phase, showed an inverse correlation with indicators of organic matter stabilisation. A semipermeable cover was an effective technology for excluding pathogens. These results indicate that changes in the microbial population and their interrelation with operational variables could represent a useful tool for monitoring composting processes.