Characterization of microbial community succession during vermicomposting of medicinal herbal residues

Reuse of composted food waste from rural China as vermicomposting substrate: effects on earthworms, associated microorganisms, and economic benefits

ABSTRACTAerobic composting of food waste (FW) from rural China using a composting device results in a substantial financial burden on the government. This study aimed to assess the feasibility of mitigating this cost using vermicomposting of composted FW. The specific aims were to elucidate the effects of composted FW on earthworm growth and reproduction, reveal the changes in the physical and chemical properties of earthworm casts during vermicomposting, identify the microbial community structure associated with vermicomposting, and perform a financial analysis based on the yield of earthworms and earthworm casts. Mixing composted FW and mature cow dung in an equal ratio achieved the highest earthworm reproduction rate, where 100 adult earthworms produced 567 juvenile earthworms and 252 cocoons in 40 d. Earthworms reduce salt content of vermicomposting substrates by assimilating Na+ and promoting humification by transforming humin into humic and fulvic acid, thus producing earthworm casts with a high generation index > 80%. When composted FW was added to a vermicomposting substrate, a distinctive microbial community structure with alkaliphilic, halophilic, and lignocellulolytic microorganisms dominated the microflora. The dominant bacterial species was Saccharopolyspora rectivirgula, and the dominant fungal species changed from Kernia nitida to Coprinopsis scobicola. Furthermore, microbial genes for refractory organic matter and fat degradation were observed in Vibrio cholerae, Kernia nitida, and Coprinopsis scobicola. Financial analysis showed that vermicomposting has the potential to reduce the cost associated with FW disposal from $ 57 to $ 18/t.

Changes in the content of emerging pollutants and potentially hazardous substances during vermi/composting of a mixture of sewage sludge and moulded pulp

Processing sewage sludge can be problematic due to its potential environmental toxicity. It may contain high concentrations of pharmaceuticals, polycyclic aromatic hydrocarbons, and heavy metals, as well as pathogenic microorganisms. However, it is a good source of organic matter and rich in microbial communities and enzymatic activity. This study deals with composting and vermicomposting of pre-composted mixtures of two different kinds of sewage sludge blended with moulded pulp in an operating composting plant. Of the total number and concentration of pollutants detected in individual piles, a large percentage of them were reduced by the composting process. The composting 2 process resulted in the greatest reduction in contaminating substances--a total of 19 substances by 4.39-90.4%. Some pharmaceuticals accumulated in earthworm bodies during vermicomposting; a total of 11 substances were detected. Atorvastatin showed the highest percentage reduction in compost 2 (90.4%), vermicompost 1 (65.2%) and vermicompost 2 (97.3%). Both composting and vermicomposting appeared to be effective for removal of heavy metals. A higher content of microbial phospholipid fatty acids (PLFAs) was found in composts than vermicomposts. There was a significant reduction in the content of pathogenic microorganisms in both processes, but the reduction in enterococci was not significant.

How do earthworms affect the pathway of sludge bio-stabilization via vermicomposting?

The synergy effects between earthworms and microorganisms promote nitrogen mineralization and enhance stabilization of organic matters in a vermicomposting system. However, the stabilization pathways of vermicomposting in the system remain unknown. The aim of this study was to investigate the effect of earthworms on the stabilization pathway and associated microbial population of waste activated sludge recycled by vermicomposting. The treatment of sludge with and without earthworms was conducted at 20 °C for 60 days. The trends in organic matter (OM), dissolved organic carbon (DOC), NH4+-N, electrical conductivity (EC), microbial biomass carbon (MBC), and dehydrogenase activity (DHA) were similar in both systems over time. At the end of the treatment, OM and DOC were significantly lower (p < 0.05), and EC, NH4+-N, and NO3--N were significantly higher (p < 0.05) in the vermicomposting group than in the control. Based on the statistical results of principal component analysis (PCA), it was proposed that the stabilization pathway in both treatment systems required a sequence of reactions characterized by the degradation of organic matter, accumulation of dissolved organic carbon, ammonification, and nitrification. Vermicomposting led to greater abundance and diversity (Shannon index) of 16S rDNA microbial species, but more even distribution in microbial community composition (Simpson index) than the control. However, the opposite performance for 18S rDNA microbes was observed. Vermicomposting enhanced the abundance of microorganisms involved in organic matter degradation and nitrification, facilitating the conversion of organic matter and favoring the nitrification. In short, the pathway of sludge bio-stabilization is not altered regardless of the addition of earthworms or not, which enables us to better understand vermicomposting process of sludge.

The genus Acrophialophora: History, phylogeny, morphology, beneficial effects and pathogenicity

The genus Acrophialophora is a thermotolerant fungus, which is widely distributed in temperate and tropical zones. This fungus is classified in Ascomycota and belongs to the Chaetomiaceae family and the genera of Parathielavia, Pseudothielavia and Hyalosphaerella are closely related to Acrophialophora. For this genus have been reported 28 species so far, which two species of Acrophialophora jodhpurensis and Acrophialophora teleoafricana produce only sexual phase and other species produce asexual form. Therefore, producing both sexual and asexual forms were not reported by any species. Many applications were reported by some species in agriculture, pharmacy and industry. Production of enzymes, antimicrobial metabolites and plant growth-promoting factors were reported by some species. The species of A. nainiana is used in the industries of textile, fruit juice, pulp and paper due to extracellular enzyme production. Also, other species produce extracellular enzymes that can be used in various industries. The species Acrophialophora are used in the composting industry due to the production of various enzymes and to be thermotolerant. In addition, some species were isolated from hostile environmental conditions. Therefore has been suggested that it can be used for mycoremediation. Also, antimicrobial metabolites of Acrophialophora have been reported to be effective against human and plant pathogens. In contrast to the beneficial effects described, the Acrophialophora pathogenicity has been rarely reported. Two species A. fusispora and A. levis are opportunistic fungi and have been reported as pathogens in humans, animals and plants. Currently, the development and applications of Acrophialophora species have increased more than past. To our knowledge, there is no report with comprehensive information on the species of Acrophialophora, which include their disadvantage and beneficial effects, particularly in agriculture. Therefore, it seems necessary to pay more in-depth attention to the application of this genus as a beneficial fungus in agriculture, pharmaceutical and industry. This review is focused on the history, phylogeny, morphology, valuable roles of Acrophialophora and pathogenicity.

Network complexity of bacterial community driving antibiotic resistome in the microbiome of earthworm guts under different land use patterns

Recently, the study of antibiotic resistance in the soil animal microbiome has attracted extensive attention; however, the patterns of antibiotic resistance genes (ARGs) in soil and soil animals related to different land use types remain poorly studied. In the present study, soil and earthworms were collected from four different land-use types (farmland, hospital, park land, and mountain park), and 162 ARGs in the microbiomes of the soil and earthworms were quantified using high-throughput quantitative PCR. Our study showed that the abundance and number of ARGs were higher in soil samples than in earthworm guts, but earthworms as the living organisms created relatively isolated ambient surroundings, which allowed for a more heterogeneous ARGs profile. Meanwhile, land use significantly influenced the abundance, number and co-occurrence pattern of ARGs in the soil and earthworm samples. Furthermore, abiotic and biotic factors had significant effects on the ARGs profile, among which pH had a negative effect on the ARGs profiles of both soil and earthworm microbiomes, and bacterial network complexity had a positive effect on the earthworm ARGs profile. Our study provides new insights into the distribution and dispersal of ARGs in the soil animal gut microbiome under different land use patterns.

Comparison of the basic processes of aerobic, anaerobic, and aerobic-anaerobic coupling composting of Chinese medicinal herbal residues

Chinese medicinal herbal residues (CMHRs) are waste generated after extracting Chinese medicinal materials, and they can be used as a renewable bioresource. This study aimed to evaluate the potential of aerobic composting (AC), anaerobic digestion (AD), and aerobic-anaerobic coupling composting (AACC) for the treatment of CMHRs. CMHRs were mixed with sheep manure and biochar, and composted separately under AC, AD, and AACC conditions for 42 days. Physicochemical indices, enzyme activities, and bacterial communities were monitored during composting. Results showed that AACC- and AC-treated CMHRs were well-rotted, with the latter exhibiting the lowest C/N ratio and maximal germination index (GI) values. Higher phosphatase and peroxidase activities were detected during the AACC and AC treatments. Better humification was observed under AACC based on the higher catalase activities and lower E4/E6. AC treatment was effective in reducing compost toxicity. This study provides new insights into biomass resource utilisation.

Antibiotic resistance in soil-plant systems: A review of the source, dissemination, influence factors, and potential exposure risks

As an emerging environmental contaminant, the widespread of antibiotic resistance has caused a series of environmental issues and human health concerns. A load of antibiotic residues induced by agricultural practices have exerted selective pressure to bacterial communities in the soil-plant system, which facilitated the occurrence and dissemination of antibiotic resistance genes (ARGs) through horizontal gene transfer. As a result, the enrichment of ARGs within crops at harvest under the influence of food ingestion could lead to critical concerns of public health. In this review, the prevalence and dissemination of antibiotic resistance in the soil-plant system are highlighted. Moreover, different underlying mechanisms and detection methods for ARGs transfer between the soil environment and plant compartments are summarized and discussed. On the other hand, a wide range of influencing factors for the transfer and distribution of antibiotic resistance within the soil-plant system are also presented and discussed. In response to exposure of antibiotic residues and resistomes, corresponding hazard identification assessments have been summarized, which could provide beneficial guides of the toxicological tolerance for the general population. Finally, further research priorities for detection and management ARGs spread are also suggested.

Vermicomposting of Pleurotus eryngii spent mushroom substrates and the possible mechanisms of vermicompost suppressing nematode disease caused by Meloidogyne incognita

The mushroom industry produces a large amount of spent mushroom substrate (SMS), which requires a large geographical footprint and causes pollution. Vermicomposting is a low-cost technology for its value in recycling of organic wastes and production of beneficial organic fertilizers. In this study, the changes of physicochemical properties was characterized during vermicomposting of Pleurotus eryngii SMS with cow dung (CD) as amendment. The efficiency and possible mechanisms of vermicompost suppressing disease induced by Meloidogyne incognita was also investigated. Six combinations with different ratios of SMS and cow dung (CD) was included in the vermicomposting using Eisenia fetida. Effect of vermicompost against disease induced by M. incognita on tobacco was conducted under greenhouse condition. And the possible mechanisms of vermicompost suppressing M. incognita was investigated by evaluated the species diversity of nematode-trapping fungi (NTF) in soil, and the defense response enzymes in tobacco. The combination of 65% SMS +35% CD was more suitable for vermicomposting, in which the highest vermicompost production (57%) and earthworm biomass increment (268%) were achieved. Additionally, the reduction in pH, total organic carbon, carbon: nitrogen ratio, and the pronounced elevation in four overall nutrient status were also observed. Soil amended with vermicompost (100:1 w/w) showed 61% control efficiency against nematode disease caused by M. incognita on tobacco, which significantly higher than that of the normal compost (24%). Comparing to the normal compost, the potential mechanism of vermicompost suppressing M. incognita could be rely on promoting species diversity of NTF in soil and enhancing the activities of the defense response enzymes in tobacco plant. Our findings indicate that vermicomposting is a promising technology for recycling of P. eryngii SMS, and the resulting vermicompost as organic fertilizer can be sued for management of the diseases caused by root-knot nematodes. This study establish a sustainable avenue for P. eryngii SMS disposal and a practical manner for controlling pathogens.

The contribution of earthworms to carbon mineralization during vermicomposting of maize stover and cow dung

Vermicomposting is an eco-friendly way to manage agricultural wastes. Maize stover and cow dung were used as the substrates. Earthworm ingestion and respiration models were employed to quantify earthworm contributions to carbon mineralization. Decreased substrate C/N and slightly increased earthworm tissue C/N were observed. Earthworm biomass carbon first increased and then decreased. Bacterial biomass carbon decreased, while fungi increased and maintained a steady level until the end of the experiment. Bacteria dominated throughout the process. The earthworm feeding rate showed a decreasing trend. In the early, middle and later stages, earthworms directly led to carbon mineralization rates of 0.030, 0.032 and 0.023 g C m^-2 month^-1, and indirectly led to 0.197, 0.211 and 0.153 g C m^-2 month^-1, respectively. It indicated that the driving force exerted by earthworms on microbes was more important. This study provides some new insights into the quantification of earthworm contributions to carbon mineralization during vermicomposting.

Evaluation of fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 inoculant

The objective of this work was to evaluate the fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 (LD3) inoculant. Inoculation reduced the content of total organic carbon, moisture content, nitrate nitrogen, and nitrite nitrogen. The LD3 inoculant was able to drive the changes in the assembly of the fungal community. In particular, inoculation with LD3 not only increased the relative abundance of Ascomycota and Trichocomaceae_unclassified for lignocellulose degradation at the mesophilic and cooling stages but also reduced the relative abundances of the opportunistic human pathogen Candida. Saprotroph was the predominant fungal trophic mode in composting, and inoculation with LD3 has a better inactivation effect on animal and plant pathogenic fungi during composting. Furthermore, the variation of the fungal community after inoculation with LD3 was the largest explained by temperature (30.64%). These results implied that LD3 significantly regulated fungal composition and function of food waste composting.

Exploring the dynamic of microbial community and metabolic function in food waste composting amended with traditional Chinese medicine residues

The aim of this study was to explore the dynamic of microbial community and metabolic function in food waste composting amended with traditional Chinese medicine residues (TCMRs). Results suggested that TCMRs addition at up to 10% leads to a higher peak temperature (60.5 °C), germination index (GI) value (119.26%), and a greater reduction in total organic carbon (TOC) content (8.08%). 10% TCMRs significantly induced the fluctuation of bacterial community composition, as well as the fungal community in the thermophilic phase. The addition of 10% TCMRs enhanced the abundance of bacterial genera such as Acetobacter, Bacillus, and Brevundimonas, as well as fungal genera such as Chaetomium, Thermascus, and Coprinopsis, which accelerated lignocellulose degradation and humification degree. Conversely, the growth of Lactobacillus and Pseudomonas was inhibited by 10% TCMRs to weaken the acidic environment and reduce nitrogen loss. Metabolic function analysis revealed that 10% TCMRs promoted the metabolism of carbohydrate and amino acid, especially citrate cycle, glycolysis/gluconeogenesis, and cysteine and methionine metabolism. Redundancy analysis showed that the carbon to nitrogen (C/N) ratio was the most significant environmental factor influencing the dynamic of bacterial and fungal communities.

Co-composting with cow dung and subsequent vermicomposting improve compost quality of spent mushroom

In order to determine a feasible degrading process for spent mushroom (SMS) with high lignin content, the present work used cow dung (CD), SMS, and a mixture of CD and SMS as substrates and evaluated the effects of vermicomposting on the microflora and the quality of composting products. Bacterial (R² = 0.548, P = 0.001) and fungal (R² = 0.314, P = 0.005) community both were different between composting and vermicomposting. Vermicomposting and substrates affected enzyme activities indirectly by affecting ammonium, pH, total carbon, richness, and bacterial community composition. These results suggested that appropriate regulation of environmental factors may increase microbial activity. An increase in ion-exchange capacity (up to 139.8%), pH (6.9%), and nitrate (71.1%) and a decrease in total carbon (31.2%) and carbon/nitrogen ratio (32.1%) in vermicomposting indicated that earthworms could further improve product quality. Co-composting with CD and integrated subsequent vermicomposting efficiently promoted the maturity of SMS.

Temperature impacts fate of antibiotic resistance genes during vermicomposting of domestic excess activated sludge

Effect of temperature on antibiotic resistance genes (ARGs) during vermicomposting of domestic excess sludge remains poorly understood. Vermicomposting experiment with excess sludge was conducted at three different temperatures (15 °C, 20 °C, and 25 °C) to investigate the fate of ARGs, bacterial community and their relationship in the process. The vermicomposting at 25 °C did not significantly attenuate the targeted ARGs relative to that at 15 °C and 20 °C. The dynamics of qnrA, qnrS, and tetM genes during vermicomposting at 15 °C and 20 °C followed the first-order kinetic model. Temperature remarkably impacted bacterial diversity of the final products with the lowest Shannon index at 25 °C. The presence of the genus (Aeromonas and Chitinophagaceae) at 25 °C may contribute to the rebound of the genes (qnrA, qnrS and tetM). The study indicates that 20 °C is a suitable vermicomposting temperature to simultaneously reach the highest removal efficiency of the ARGs and the good biostability of the final product.

Eco-risk management of tylosin fermentation residues using vermicomposting

Tylosin fermentation residues (TFR) pose an ecotoxicological risk through antibiotic resistant bacteria (ARBs) and their corresponding genes (ARGs). This study evaluated the ecotoxicity of TFR to soil biological activity, and further explored the mechanisms of vermicomposting to reduce the toxicological risk. The results showed that tylosin (TYL) was moderately degradable with a half-life (t_1/2) of 37.5 d, inducing 28-44% inhibition rate of nitrogen transformation in soil, and the EC₅₀ of earthworm avoidance was 880 mg/kg. The 30-d vermicomposting reduced the pH and OM content, while increased the EC and TN content, accelerated compost maturation (C/N ratio up to 20), and enriched the microbial community. ARGs were reduced by earthworm through removal of TYL (>70% degradation, t_1/2 of <20 d), inhibiting abundance of intI1 and ARBs. We conclude that vermicomposting is an efficient method for TFR treatment and its eco-risk management.

Impact of bamboo sphere amendment on composting performance and microbial community succession in food waste composting

The purpose of this study was to find an economical and effective amendment for improving composting performance and product quality, as well as to analyze the microbial community succession in the whole phase of composting. Therefore, the effect of reusable amendment bamboo sphere on composting performance and microbial community succession during food waste composting was investigated. The results showed that 6% bamboo sphere treatment had the highest degree of polymerization (3.7) and humification index (0.18). Compared with control, 6% bamboo sphere amendment increased total nitrogen (TN), phosphorus (TP) and potassium (TK) contents by 13.61%, 19% and 17.42%, respectively. Furthermore, bamboo sphere enhanced bacterial-fungal diversity and improved microbial community composition by enhancing the relative abundance of thermo-tolerance and lignocellulolytic bacteria and fungi. The five most abundant genera in bamboo sphere composting comprised Bacillus (0-71.47%), Chloroplast-norank (0-47.17%), Pusillimonas (0-33.24%), Acinetobacter (0-27.98%) and unclassified Sphingobacteriaceae (0-22.62%). Linear discriminant analysis effect size showed that Firmicutes, Thermoascaceae and Actinobacteriota, which have a relationship with the decomposition of soluble organic matter and lignocellulose, were significantly enriched in bamboo sphere treatment. Canonical correspondence analysis illustrated that total organic carbon (TOC), TK, and TP were the most important environmental factors on microbial community succession in the two composting systems. Together these results suggest that bamboo sphere as a reusable amendment can shorten maturity period, improve humification degree, increase the contents of nutrient and contribute to the succession of microbial community during food waste composting. These findings provide a theoretical basis for improving the efficiency of food waste composting.

Improving the efficiency of vermicomposting of polluted organic food wastes by adding biochar and mangrove fungi

Vermicomposting of food waste amended with biochar and cow dung was studied during a 90-day composting period. The improvement of the vermicomposting process by adding three mangrove fungal species as additional amendments were studied. The use of mangrove fungi Acrophialophora jodhpurensis as a bio-catalytic actor during vermicomposting proved to be beneficial in terms of final compost quality (available N, P and K) and the shortening of the composting period. All three fungal species, however, reached the neutral pH at the end of the composting period and appeared to be beneficial. Heavy metal (Cd, Ni, Pb, Zn, Cu and Cr) concentrations decreased throughout the composting process. Food waste can be treated using vermicomposting with biochar, cow dung and the mangrove fungi A. jodhpurensis. The final vermicomposting product is suitable for agricultural use.

Microbial and chemical dynamics of brewers' spent grain during a low-input pre-vermicomposting treatment

The eco-sustainability of industrial processes relies on the proper exploitation of by-products and wastes. Recently, brewers' spent grain (BSG), the main by-product of brewing, was successfully recycled through vermicomposting to produce an organic soil conditioner. However, the pre-processing step there applied (oven-drying) resulted in high costs and the suppression of microbial species beneficial for soil fertility. To overcome these limitations, a low-input pre-processing step was here applied to better exploit BSG microbiota and to make BSG suitable for vermicomposting. During 51 days of pre-treatment, the bacterial and fungal communities of BSG were monitored by denaturing gradient gel electrophoresis (DGGE). Chemical (carbon, nitrogen, ammonium, nitrate content, dissolved organic carbon) and biochemical (dehydrogenase activity) parameters were also evaluated. Mature vermicompost obtained from pre-processed BSG was characterized considering its legal requirements (e.g., absence of pathogens and mycotoxins, lack of phytotoxicity on seeds), microbiota composition, and chemical properties. Results obtained showed that throughout the pre-process, the BSG microbiota was enriched in bacterial and fungal species of significant biotechnological and agronomic potential, including lactic acid bacteria (Weissella, Pediococcus), plant growth-promoting bacteria (Bacillus, Pseudomonas, Pseudoxhantomonas), and biostimulant yeasts (Pichia fermentans, Trichoderma reesei, Beauveria bassiana). Pre-processing increased the suitability of BSG for earthworms' activity to produce high-quality mature vermicompost.

The succession of GH6 cellulase-producing microbial communities and temporal profile of GH6 gene abundance during vermicomposting of maize stover and cow dung

Vermicomposting eco-friendly converts lignocellulosic wastes into bio-organic fertilizer. Cellulose is the most abundant carbohydrate in lignocellulose. Glycoside hydrolase family 6 (GH₆) plays a key role in the early step of cellulose degradation, which is essential for stabilizing lignocellulose. This study intends to quantify the abundance of GH₆ gene and to clarify the succession of GH₆ cellulase-producing microbial communities during vermicomposting. 100% of maize stover (A) and maize stover and cow dung at 60:40 ratio (B) were used. The results showed that different native genera were observed in the starting materials. Cellulomonas and Cellulosimicrobium were dominant genera harboring GH₆ gene. The peak relative abundance of Cellulomonas was 76% and 30% in B and A during vermicomposting phase, and the corresponding values of Cellulosimicrobium was 36% and 37%. Earthworms increased the abundance of GH₆ gene, which reached 1.51E + 09 from 3.46E + 08 copies/g in B. The results partially interpreted promoting effect of earthworms.

Effects of biocontrol Bacillus and fermentation bacteria additions on the microbial community, functions and antibiotic resistance genes of prickly ash seed oil meal-biochar compost

This study evaluated the effects of biocontrol Bacillus and fermenting bacteria addition on the microbial community, metabolic functions and antibiotic resistance genes (ARGs) of new prickly ash seed oil meal (PSOM)-biochar composting. The results showed that the addition of Bacillus subtilis and fermentation bacteria significantly increased the NH₄⁺-N, bacterial abundance and fungal diversity of compost while decreasing the relative abundances (RAs) of carbon metabolism genes in mature compost. NH₄⁺-N was significantly correlated with microbial abundance and diversity, and its increase was closely related to microbial amino acid metabolism. The addition of biocontrol and fermenting bacteria changed the RAs of ARGs, which was caused by changes in the potential hosts Proteobacteria, Bacteroidota and Firmicutes in the compost. Consequently, adding Bacillus and fermenting bacteria into PSOM to make composting was suggested as an effective method to promote nutrient transformation, regulate microbial activity and decrease RAs of tetracycline and vancomycin ARGs.

Earthworm activity optimized the rhizosphere bacterial community structure and further alleviated the yield loss in continuous cropping lily (Lilium lancifolium Thunb.)

The soil microbial community plays a vital role in the biogeochemical cycles of bioelements and maintaining healthy soil conditions in agricultural ecosystems. However, how the soil microbial community responds to mitigation measures for continuous cropping obstacles remains largely unknown. Here we examined the impact of quicklime (QL), chemical fungicide (CF), inoculation with earthworm (IE), and a biocontrol agent (BA) on the soil microbial community structure, and the effects toward alleviating crop yield decline in lily. High-throughput sequencing of the 16S rRNA gene from the lily rhizosphere after 3 years of continuous cropping was performed using the Illumina MiSeq platform. The results showed that Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chloroflexi and Gemmatimonadetes were the dominant bacterial phyla, with a total relative abundance of 86.15-91.59%. On the other hand, Betaproteobacteriales, Rhizobiales, Myxococcales, Gemmatimonadales, Xanthomonadales, and Micropepsales were the dominant orders with a relative abundance of 28.23-37.89%. The hydrogen ion concentration (pH) and available phosphorus (AP) were the key factors affecting the structure and diversity of the bacterial community. The yield of continuous cropping lily with using similar treatments decreased yearly for the leaf blight, but that of IE was significantly (p < 0.05) higher than with the other treatments in the same year, which were 17.9%, 18.54%, and 15.69% higher than that of blank control (CK) over 3 years. In addition, IE significantly (p < 0.05) increased organic matter (OM), available nitrogen (AN), AP, and available potassium (AK) content in the lily rhizosphere soil, optimized the structure and diversity of the rhizosphere bacterial community, and increased the abundance of several beneficial bacterial taxa, including Rhizobiales, Myxococcales, Streptomycetales and Pseudomonadales. Therefore, enriching the number of earthworms in fields could effectively optimize the bacterial community structure of the lily rhizosphere soil, promote the circulation and release in soil nutrients and consequently alleviate the loss of continuous cropping lily yield.

Evaluating the interaction of soil microorganisms and gut of soil fauna on the fate and spread of antibiotic resistance genes in digested sludge-amended soil ecosystem

Earthworms have shown their effectiveness in reducing the abundances of antibiotic resistance genes (ARGs) from solid waste. However, the mechanisms of the reduced ARGs by earthworm and whether the solid waste would affect the ARGs profile in earthworm gut were poorly understood. Herein, the patterns of ARGs and microbial communities in digested sludge-amended soil and earthworm gut after 80-day cultivation were investigated. Results show that the enrichment of ARGs (e.g., tetA, tetQ, and sulII) in soil caused by digested sludge-amendment was temporary and would recover to their original levels before amendment. In addition, earthworms could contribute to the further reduction of ARG abundances, which was mainly attributed to their gut digestion via shifting the microbial community (e.g., attenuating the anaerobes). However, the amended soil could significantly increase ARGs abundance in the earthworm gut, which may enhance the potential risk of ARGs spread via the food chain. These findings may provide a new sight on the control of ARGs occurrence and dissemination in sludge-amended soil ecosystem with consideration of earthworms.

Fate of Functional Bacterial and Eukaryotic Community Regulated by Earthworms during Vermicomposting of Dewatered Sludge, Studies Based on the 16S rDNA and 18S rDNA Sequencing of Active Cells

DNA sequencing of active cells involved in vermicomposting can clarify the roles of earthworms in regulating functional microorganisms. This study aimed to investigate the effect of earthworms on functional microbial communities in sludge by comparing biodegradation treatments with and without earthworms. PCR and high throughput sequencing based on pretreatment of propidium monoazide (PMA) were used to detect the changes in active bacterial 16S rDNA and eukaryotic 18S rDNA during vermicomposting. The results showed that the nitrate in sludge vermicomposting and control were significantly different from day 10, with a more stable product at day 30 of vermicomposting. Compared with the control, the Shannon indexes of active bacteria and eukaryotes decreased by 1.9% and 31.1%, respectively, in sludge vermicompost. Moreover, Proteobacteria (36.2%), Actinobacteria (25.6%), and eukaryotic Cryptomycota (80.3%) were activated in the sludge vermicompost. In contrast, the control had Proteobacteria (44.8%), Bacteroidetes (14.2%), Cryptomycota (50.00%), and Arthropoda (36.59%). Network analysis showed that environmental factors had different correlations between active bacterial and eukaryotic community structures. This study suggests that earthworms can decrease the diversity of bacterial and eukaryotic communities, forming a specific-functional microbial community and thus accelerating organic matter decomposition during vermicomposting of dewatered sludge.

Effects of multi-phase inoculation on the fungal community related with the improvement of medicinal herbal residues composting

Composting has become the most important way to recycle medicinal herbal residues (MHRs). The traditional composting method, adding a microbial agent at one time, has been greatly limited due to its low composting efficiency, mutual influence of microbial agents, and unstable compost products. This study was conducted to assess the effect of multi-phase inoculation on the lignocellulose degradation, enzyme activities, and fungal community during MHRs composting. The results showed that multi-phase inoculation treatment had the highest thermophilic temperature (68.2 °C) and germination index (102.68%), significantly improved available phosphorus content, humic acid, and humic substances concentration, accelerated the degradation of cellulose and lignin, and increased the activities of cellulase in the mature phase, xylanase, manganese peroxidase, and utilization of phenolic compounds. Furthermore, the non-metric multi-dimensional scaling showed that the composting process and inoculation significantly influenced fungal community composition. In multi-phase inoculation treatment, Thermomyces in mesophilic, thermophilic, and mature phase, unclassified_Sordariales, and Coprinopsis in mature phase were the dominant genus that might be the main functional groups to degrade lignocellulose and improve the MHRs composting process.

Pilot-scale vermicomposting of sewage sludge mixed with mature vermicompost using earthworm reactor of frame composite structure

To improve the efficiency of sludge vermicomposting, a new cost-effective method is provided. It uses a new earthworm reactor with a frame composite structure for vermicomposting and reuses mature vermicompost to condition the sludge. Under the optimum conditions (proportion of earthworm droppings: 15%; thickness of sludge laying: 6 cm; moisture content of initial sludge mixture: 75%), the method of continuous operation described herein works well and presents three advantages compared with the traditional vermicomposting method: the short time required for vermicomposting (20.25 h); covering a small area (5 m2/t·d); and a low cost. In addition, the vermicompost obtained from sludge vermicomposting shows better stability and maturity (C/N: 14.96; GI: 86.42%; TOC: 188.5 mg/g; ash content: 516.2 mg/g). The investigation of the associated mechanisms, including 3D-EEM, TGA, SEM and microbial community analyses, revealed that the addition of mature vermicompost can speed up the progress of decomposition and humification of organic matter in sludge. The process of vermicomposting and adding mature vermicompost significantly modified the microbial community of sewage sludge, and the changes in microorganisms in vermicompost were related to the microorganisms in the earthworm gut.

Metabarcoding analysis of the bacterial succession during vermicomposting of municipal solid waste employing the earthworm Eisenia fetida

A culture-independent DNA metabarcoding analysis of the bacterial communities was carried out throughout a complete vermicomposting cycle of municipal solid waste material using the earthworm Eisenia fetida. 16S rRNA amplicons from the initial material (0 days), an intermediate (42 days), and a final stage (84 days) were sequenced in an Illumina NGS platform and compared. A steady increase in community diversity was observed corresponding to a 2.5-fold higher taxa richness and correspondingly risen values of the Shannon and Simpson ecological indexes and the evenness parameter. A total of 49,665 operational taxonomic units (OTUs) were counted. From the qualitative standpoint, a clear successional shift was observed with an initial community dominated by putatively plant-associated groups belonging to the Rhizobiales order within the Alphaproteobacteria class, regressively leaving the scores of relative abundance (RA) to the Firmicutes phylum and in particular to the Bacilli. Vermistabilization of municipal solid waste (MSW) increased (p < 0.001) the TKN and total P content in the final vermicompost, while pH, TOC, and C/N ratio declined (p < 0.001) in the process. Likewise, a progressive decrease was noticed in β-glucosidase, acid phosphatase, and urease activity while protease and dehydrogenase showed a slight increase, followed by a steep fall. A strong positive correlation was observed among the canonical functions of physico-chemical attributes and enzyme activities. The canonical correspondence analysis (CCA) revealed that significant families did not change on the temporal scale; however, their abundance was influenced by the abiotic environmental factors. In comparison to prior studies on vermicomposting that used different earthworm species (Eisenia andrei) and different substrates, results reflect a considerable degree of substrate specificity for the earthworm species used. The results offer clues to optimize the vermistabilization of MSW along with its potential use in agriculture, to foster improved levels of the circular economy.

Vermiproductivity, maturation and microbiological changes derived from the use of liquid anaerobic digestate during the vermicomposting of market waste

Recently, it has been suggested that the liquid fraction of anaerobic digestate, derived from the treatment of wastewater and solid wastes, could be used in vermicomposting as a solution to its disposal, and even for its valorization. Nevertheless, the literature does not provide enough information about its impact on the process of vermicomposting itself and on the final quality of the end-product. In this study, the effect of different doses of digestate in the vermicomposting process treating market waste is assessed measuring earthworm population dynamics, the bacterial community succession present in the vermibeds, as well as maturation and the end-quality of the vermicompost. Our results show that the addition of liquid digestate to the vermibeds increased the earthworms biomass, i.e. 71%, 94% and 168% in control, and vermibeds with 30% and 60% digestate, respectively. Further, the increase in the amount of N in the vermicompost decreased as the digestate addition increased, i.e. 75%, 8%, 3%. The maturity achieved was high in all treatments as shown by the C/N ratio, 7.98, 7.40 and 10.20, and the high seed germination rate, above 90%. Finally, the succession of the microbial community was not disturbed and compositional stabilization was reached after 92 days.

Unraveling the environmental impacts of bioactive compounds and organic amendment from grape marc

In a society that produces large amounts of solid waste, the search for new methods of valorisation has led to the development of techniques that make it possible to obtain new products from waste. In the case of bio-waste, biological treatment such as anaerobic digestion or composting appear to be suitable options for producing bio-energy or bio-fertilizers respectively. Vermicomposting is a method of converting solid organic waste into resources through bio-oxidation and stabilization of the organic waste by earthworms. The purpose of this study is to establish the environmental impacts of a complete route for the valorisation of grape pomace in order to identify environmental hotspots. In this valorisation route, different value-added products are produced with potential application in the cosmetic, food and pharmaceutical sectors. Priority was given to the use of primary data in the elaboration of the data inventories needed to perform the life cycle assessment (LCA). The main findings from this study reported that the energy requirement of the distillation process is an important hot spot of the process. Although the valorisation route has some poor results in terms of the two environmental indicators (carbon footprint and normalised impact index), when economic revenues were included in this analysis, its environmental performance was better than that of other alternatives for bio-waste recovery.

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.

Effect of excess activated sludge on vermicomposting of fruit and vegetable waste by using novel vermireactor

This study aimed to clarify the effect of excess activated sludge (EAS) on vermicomposting of fruit and vegetable wastes (FVW). For this, a novel vermireactor consists of substrate and bed compartments was used for treating five types of FVW (banana peels, cabbage, lettuce, carrot, and potato) with and without the addition of EAS by earthworms. The EAS promoted the growth and cocoon production of earthworms, and the decomposition efficiency of FVW. The changes of dehydrogenase activity revealed that the EAS enhanced the microbial activity in all treatments except for the carrot. The organic matter content, total carbon and the C/N ratio showed a significant decrease after addition of EAS into FVW. The content of nitrogen and phosphorus was also improved in the final products after vermicomposting. This study suggested that the addition of EAS could be a feasible option to enhance the vermicomposting of FVW.

Comparative study of vermicomposting of garden waste and cow dung using Eisenia fetida

Vermicomposting is the process of composting using worms and is applied in waste management to produce high-quality organic fertilizer. Garden waste (GW) is often mixed with other raw materials for vermicomposting. In the present study, the feasibility of vermicomposting using only GW was investigated in comparison with cow dung (CD). The total nitrogen (TN), total phosphorus (TP), and total potassium (TK) contents and the electrical conductivity increased, while total organic carbon (TOC) and the C/N ratio decreased in both substrates after vermicomposting. The nutrient content (TN, TP, and TK) of the GW vermicompost was promoted less than that in CD. Scanning electron microscopy images and specific surface area analysis showed that the vermicompost was strongly disaggregated and became more compacted and fragmented compared with the raw substrates. No mortality of earthworms was observed in GW; however, the earthworms had a higher mean body weight and reproduction rate in CD than that in GW. There were higher bacterial community richness and diversity in the vermicompost than that in the raw materials, and the dominant phylum species were Proteobacteria, Actinobacteria, and Bacteroidetes. Redundancy analysis demonstrated that TN, C/N ratio, and TOC play an important role in bacterial community dynamics. These data indicate that vermicomposting is a robust process that is suitable for the management of GW.

Effect of microbial inoculation on physicochemical properties and bacterial community structure of citrus peel composting

In this study, microorganisms were inoculated during citrus peel composting for citrus waste recycling and valorisation. The physicochemical properties and the bacterial community structure of citrus peel composting inoculated microorganism were studied. The thermophilic stage of pilot-scale composting (T2) was 20 days longer than lab-scale composting (T1). C/N, organic matter, moisture, pectin and cellulose content decreased along with composing process, but the pH, soluble protein and total nutrient showed an opposite trend. The inoculation improved the richness and diversity of the bacterial community and the diversity index reached maximum on 21 days. As composting progress, Bacillus, Sphingobacterium and Saccharomonospora in inoculum became the dominant genus. Redundancy analysis showed that C/N, pectin degradation rate and temperature could explain 30.1%, 24.9% and 15.6% of the variation in bacterial genera, respectively.

Enzymatic in situ saccharification of herbal extraction residue by a medicinal herbal-tolerant cellulase

Herbel-tolerant strains exhibit considerable environmental and commercial values not only due to their harmless treatment of herbal-extraction residues (HERs) but also because of their use in preparing high-quality cellulase cocktails. In this study, three typical HERs were evaluated for enzymatic in situ saccharification performance. A HERs-tolerance fungus, identified as Penicillium oxalicum G2, can grow in 1.5% (w/v) Radix isatidis residues (RIR), thereby exhibiting the highest FPase (2.2 U/mL), carboxymethyl cellulase (13.3 U/mL), and β-glucosidase (4.6 U/mL) activities. The most effective production of cellulase cocktail was achieved via orthogonal experiment in a system with pH 6.0, 30 °C, and 96 h. Cellulase cocktail from P. oxalicum G2 can directly saccharify the extraction RIR, thereby achieving a maximum reducing sugar yield of 7.2 mg/mL, which is 1.7-fold higher than those of commercial cellulases. Results illustrate the potential of P. oxalicum G2 for enzymatic in situ saccharification.

Metaphire guillelmi gut as hospitable micro-environment for the potential transmission of antibiotic resistance genes

Earthworm gut played an important role in the transformation of various contaminants in the soil environments. With the increasing application of organic fertilizer recently, the ingestion of antibiotics, antibiotic resistance bacteria (ARB), and antibiotic resistance genes (ARGs) made the earthworm gut a potential favorable micro-environment for the transmission of ARGs in the soil. In this work, the conventional plate incubation and high-throughput sequencing methods were both employed to investigate the composition of the cultivable and overall ARB/ARGs in the Metaphire guillelmi earthworm gut. A total of 87 cultivable isolates that resisted tetracycline (TC) and/or sulfadiazine (SD) were obtained, most of which belonged to phylum Firmicutes, genus Bacillus. Meanwhile, the counts of isolates with TC-SD dual resistance were higher than those with sole SD or TC resistance. Moreover, higher ARB counts and diversity were detected in the earthworm gut by high-throughput sequencing technique than those by the classical plate cultivation. Overall, the combination of conventional cultivable bacteria isolation and high-throughput sequencing methods provided a comprehensive understanding of the ARB composition in the earthworm gut. The results demonstrate that the earthworm gut is a hospitable micro-environment for ARB colonization. The potential role of earthworm intestinal ARB and ARGs proliferation in soil environments warrants further research.

Recycling of lignocellulosic waste as vermicompost using earthworm Eisenia fetida

Present study aimed to evaluate the vermicomposting of lignocellulosic wastes employing Eisenia fetida earthworms. The study examined the effectiveness of vermicomposting for 105 days by mixing lignocellulosic waste (LW) with cattle manure (CM) in five different proportions. Results revealed that TOC and C/N ratio decreased gradually till end and in vermicomposts varied between 268-320 g/kg and 12.26-16.85, respectively. Nutrient content (NPK) in the vermicomposts increased with time in all the mixtures. Heavy metals' content also increased in vermicomposts and benefit ratio for heavy metals ranged between 0.06 and 5.1. Increase in earthworm biomass (22.38-39.64 g) and reproduction (21.27-31.60 hatchlings/worm) was also satisfactory in all the waste mixtures. Based on results, it can be inferred that lignocellulosic waste can successfully be converted into good quality manure employing earthworms.

Seaweeds as bioresources for vermicompost production using the earthworm, Perionyx excavatus (Perrier)

Fifteen days pre-decomposed seaweeds, Halimeda gracilis, Gracilaria corticata, Sargassum wightii and Sargassum swartzii spiked with cowdung (1:1) were vermicomposted using Perionyx excavatus for 60 days. The pH in the vermicompost showed insignificant reduction while electrical conductivity showed significant enhancement (P < 0.05). The reduction of organic carbon in vermicomposts ranged from -37.78 to -50.97% over worm-unworked composts. Total NPK contents showed significant increment (26.72-78.17%) in vermicompost over worm-unworked composts. The difference in percentage increase/decrease between physicochemical parameters was statistically significant (P < 0.001) and the same pattern was found between substrates. The total microbial population in vermicomposts was significantly higher than that of initial and composts of all seaweed + cowdung combinations (P < 0.001). The growth and reproduction of Perionyx excavatus in seaweed + cowdung combinations showed equivalent or higher rates when compared with cowdung signifying that Perionyx excavatus is well suited to convert seaweed and cowdung combinations into nutrient rich vermicompost.

Rapid reformation of larger aerobic granular sludge in an internal-circulation membrane bioreactor after long-term operation: Effect of short-time aeration

The investigation aimed at revealing the influence of an external disturbance on the rapid reformation of larger aerobic granular sludge (AGS) in an internal-circulation membrane bioreactor (IC-MBR) after long-term operation. The used IC-MBR was continuously operated well for more than one year, in which, the biomass was still in the state of AGS with a balanced average size at around 200 μm and an even size distribution. By providing short-time aeration to the biomass within this bioreactor, the characteristics of biomass were totally changed in a very short time, including the surface hydrophilicity, physic-chemical properties, and the structure of microbial community, which created suitable conditions for the growth of filamentous bacteria (Saccharibacteria). Such a variation was very beneficial to the reformation of larger AGS, which resulted in the average size of AGS increased to nearly 400 μm with a compact structure and clear edge in no more than one month.

Changes of quinolone resistance genes and their relations with microbial profiles during vermicomposting of municipal excess sludge

Antibiotic resistance genes abundant in municipal excess sludge reduce the agricultural value of vermicompost. However, little attention has been paid on the fate and behavior of the problem-causing agents in vermicomposting. In this study, the fate and behavior of quinolone resistance genes in excess activated sludge during vermicomposting were studied with reactors introduced with Eisenia fetida for three different densities. The substrate pile without earthworms was operated as control in parallel. The results showed that earthworms could significantly reduce the absolute abundance of quinolone resistance genes in the excess sludge, with a reduction ratio of 85.6-100% for qnr A and 92.3-95.3% for qnr S, respectively (p < 0.05). For microbial profiles, both the dehydrogenase activity and the abundance of microbes (16S rDNA) revealed a distinct decreasing trend after 7 days from the start of the experiment; however, the bacterial diversity in the final products seemed to be enriched with the emergence of the uncultured Flavobacteriales bacterium and uncultured Anaerolineaceae bacterium. Redundancy analysis revealed clearly that the qnr genes had positive correlations with the targeted indexes of microbial profiles, with the correlations with the bacterial abundance and dehydrogenase activity being more statistically significant than the bacterial diversity (p < 0.05). The results of this study suggested that earthworms could promote the attenuation of quinolone resistance genes in the excess sludge through lowering the bacterial abundance and activity, and the promotion effect could be enhanced by increasing the density of earthworms.

Effects of waste lime and Chinese medicinal herbal residue amendments on physical, chemical, and microbial properties during green waste composting

Traditional composting is time-consuming and often results in a low-quality product. The objective of this study was to determine the effects of waste lime (WL; at 0, 2.5, and 3.5%) and/or Chinese medicinal herbal residues (CMHRs; at 0, 10, and 20%) as amendments on the two-stage composting of green waste (GW). The combination of WL and CMHRs improved compost particle-size distribution and pH, decreased nitrogen loss, and increased cation exchange capacity (CEC), nutrient content, and microbial numbers. The combination of WL and CMHRs also accelerated organic matter humification and lignocellulose degradation and therefore increased the germination index of the final compost. Relative to the non-amended compost, the optimal amendment (2.5% WL and 20% CMHRs) increased the percentage of particles of ideal size from 23.8 to 66.9%, the pH from 6.69 to 7.17, the CEC from 52 to 169 cmol/kg, the humic acid to fulvic acid ratio from 1.32 to 2.49, the hemicellulose degradation rate from 42 to 87%, and the cellulose degradation rate from 20 to 61%. The treatment with addition of 2.5% WL and 20% CMHRs to GW required only 21 days to generate the highest quality compost product.

Exploring the effects of earthworms on bacterial profiles during vermicomposting process of sewage sludge and cattle dung with high-throughput sequencing

This study aims to reveal the effects of earthworms (Eisenia fetida) on bacterial profiles during the vermicomposting process of sewage sludge and cattle dung with the high-throughput sequencing technology. The earthworms could accelerate organic degradation and improve the stabilization process. Moreover, the addition of earthworms not only affected the bacterial numbers, but also increased the bacterial community diversity. The activity of earthworms had significant effects on the bacterial community structure as the bacterial community was clearly different between the vermicomposting and the control treatment. Furthermore, the earthworms affected the physical and chemical properties of substrates, thus promoting the growth of some microorganisms, such as Flavobacteria, Acidbacteria, and Planctomycetes. Earthworms largely inhibited the growth of various human pathogenic bacteria. In summary, earthworms significantly affected the bacterial community in vermicomposting and it could be applied as an authentically effective technique for the stabilization of organic wastes.