Changes in fibrolytic enzyme activity during vermicomposting of maize stover by an anecic earthworm Amynthas hupeiensis

Multidimensional effects of green waste vermicomposting on cadmium contaminated soil ecosystems: From physicochemical properties to microbial communities

Soil heavy metal pollution and green waste accumulation have emerged as two major environmental challenges, necessitating the development of sustainable remediation and management technologies. This study investigated the remediation effects of vermicomposted green waste (JE) on cadmium (Cd)-polluted soil. Batch adsorption tests and soil microcosm experiments were conducted to examine the impact of JE on soil quality, microbial community structure, and Cd biotransformation. Results demonstrated that, compared with untreated green waste, JE significantly increased the Cd2+ adsorption capacity by 55.94 %. This enhancement was attributed primarily to increased surface functional groups and altered crystal structure through vermicomposting. JE treatment effectively improved the soil physicochemical properties, increased the nutrient content and elemental exchangeability, and increased soil enzyme activities. At the microbial level, JE drove the assembly and modification of soil microbial communities, increasing their diversity and abundance, particularly those of beneficial bacterial groups. Environmental matrix analysis revealed complex interactions among soil properties, enzyme activities, and soil microbial communities in terms of Cd biotransformation. Overall, vermicomposted green waste rapidly improved the Cd adsorption efficiency and, upon its soil application, effectively enhanced the Cd-polluted soil quality while optimizing soil microbial community structure and function. This ultimately led to Cd immobilization and inert transformation in the soil. This study provides a solid theoretical and practical foundation for the safe utilization and sustainable remediation of heavy metal-polluted agricultural soils, as well as the resource utilization of green waste.

Optimization of Eisenia fetida stocking density for biotransformation during green waste vermicomposting

Appropriate stocking density plays an important role in ensuring the stability and improving the overall efficiency of the vermicomposting system. Although some studies have shown that earthworms can degrade lignocellulosic materials, relatively few studies have been conducted on the effect of earthworm stocking density on the degradation of a single green waste (GW) with high lignocellulosic content. Therefore, this study investigated the degradation effect of earthworms on GW at different stocking densities, and assessed the stability and maturity of the whole vermicomposting by comprehensively analysing the changes in physicochemical and biological properties of earthworms during vermicomposting, and by combining the growth of earthworms with a multi-dimensional assessment of the stability and maturity of the whole vermicomposting. In this study, six stocking densities (CK-T5) were set up, namely, no earthworms, 10, 20, 30, 40, and 50 worms/kg. The results showed that compared with the CK (without earthworms), when there were 30 earthworms per kg of GW (i.e. T3), the total nitrogen, total phosphorus, total potassium, organic matter decomposition, bacterial and fungal numbers, and germination index of earthworm compost products increased by 14 %, 29 %, 32 %, 35 %, 42 %, 94 %, and 125 %, respectively. T3 also enhanced the activities of cellulase and alkaline phosphatase. The results were further supported by principal component analysis. Finally, we conclude that when the stocking density of earthworms is appropriate (T3), it not only favours the growth of earthworms, but also positively affects the physicochemical properties of the vermicomposting process, which in turn significantly improves the biodegradation efficiency of GW.

The temporal profile of GH1 gene abundance and the shift in GH1 cellulase-producing microbial communities during vermicomposting of corn stover and cow dung

Vermicomposting is a promising method for corn stover management to achieve bioresource recovery and environmental protection. Most β-glucosidases, which limit the cellulose degradation rate during vermicomposting of corn stover, belong to glycoside hydrolase family 1 (GH1). This study was conducted with different earthworm densities to quantify the GH1 gene abundance and investigate the evolution of GH1 cellulase-producing microbial communities using qPCR and pyrosequencing. The results showed that β-glucosidase activity, GH1 gene abundance, TOC, and microbial communities carrying the GH1 gene were affected by processing time and earthworm density. After introducing earthworms, β-glucosidase activity increased to 1.90-2.13 U/g from 0.54 U/g. The GH1 gene abundance of treatments with earthworms (5.82E+09-6.70E+09 copies/g) was significantly higher than that of treatments without earthworms (2.48E+09 copies/g) on Day 45. Earthworms increased the richness of microbial communities. The relative abundances of Sphingobium and Dyadobacter, which are dominant genera harboring the GH1 gene, were increased by earthworms to peak values of 23.90% and 11.20%, respectively. Correlation analysis showed that Sphingobium, Dyadobacter, Trichoderma, and Starkeya were positively associated with β-glucosidases. This work sheds new light on the mechanism of cellulose degradation during vermicomposting at the molecular level.

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.

Vermicomposting: A Valorization Alternative for Corn Cob Waste

As vermicomposting has become a viable alternative for the valorization of organic waste; the objectives of this research were to (1) assess the feasibility of said process for corn cob waste (corn cobs and corn husks) and (2) evaluate the operation conditions for the biodegradation of different mixtures with load material (LM). LM did not include animal excreta as a nitrogen source, a practice widely used in a range of studies. The experiment consisted of an initial phase of pre-composting in order to obtain a partially stabilized substrate. Subsequently, four separate mixtures were made consisting of corn cob waste mixed with consistent load material (LM) containing vegetable waste and eggshells (CR, M1, M2, M3) to obtain a balance substrate able to facilitate degradation using Eisenia fetida earthworms. The following parameters were analyzed during the control process: temperature, pH, humidity, organic material (OM), total organic carbon (TOC), total nitrogen (TN) and carbon/nitrogen (C/N) ratio. The analysis of the final values of the stabilized mixtures showed that vermicomposting is indeed a feasible alternative for the degradation of corn cob waste for use as a soil improver.

A Review on Bacterial Contribution to Lignocellulose Breakdown into Useful Bio-Products

Discovering novel bacterial strains might be the link to unlocking the value in lignocellulosic bio-refinery as we strive to find alternative and cleaner sources of energy. Bacteria display promise in lignocellulolytic breakdown because of their innate ability to adapt and grow under both optimum and extreme conditions. This versatility of bacterial strains is being harnessed, with qualities like adapting to various temperature, aero tolerance, and nutrient availability driving the use of bacteria in bio-refinery studies. Their flexible nature holds exciting promise in biotechnology, but despite recent pointers to a greener edge in the pretreatment of lignocellulose biomass and lignocellulose-driven bioconversion to value-added products, the cost of adoption and subsequent scaling up industrially still pose challenges to their adoption. However, recent studies have seen the use of co-culture, co-digestion, and bioengineering to overcome identified setbacks to using bacterial strains to breakdown lignocellulose into its major polymers and then to useful products ranging from ethanol, enzymes, biodiesel, bioflocculants, and many others. In this review, research on bacteria involved in lignocellulose breakdown is reviewed and summarized to provide background for further research. Future perspectives are explored as bacteria have a role to play in the adoption of greener energy alternatives using lignocellulosic biomass.

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.

Pre-Composting and Vermicomposting of Pineapple (Ananas Comosus) and Vegetable Waste

In the last few years, pineapple (Ananas comosus) has grown to be considered one of the most important fruits worldwide due to its high production and consumption. However, inadequate disposal of the waste it generates, which represents up to 67% of its total weight, can have environmental impacts. Therefore, this study focuses on the degradation of organic waste produced in the industrialized processing of pineapple waste (rinds, crowns and cores), which undergo a process of vermicomposting at a laboratory level. The methodology used included the pre-composting process and vermicomposting through Californian red worms using mixes tested in three different proportions of pineapple waste (PR) and load material (LM) made up of vegetable waste and eggshells. Testing revealed that the pre-composting process for this waste was feasible as a first stage of the degradation process; the characteristics of the pre-composted material allowed a favorable adaptation for both the worms and general degradation. It also showed efficiencies in the removal of organic carbon between 36.40% and 45.78%. Results also showed the total nitrogen content remained between 1.2% and 2.2% and the carbon/nitrogen relation (C/N) had values under 20 as required for high-quality vermicompost.

Alkyl polyglycoside and earthworm (Eisenia fetida) enhance biodegradation of green waste and its use for growing vegetables

Managing municipal green waste is a challenge to municipalities, partly because of the slow rate of decomposition of green waste during composting due to its high lignin and cellulose contents. Hence, this study evaluated the effect of alkyl polyglycoside (APG), a biosurfactant, and the earthworm Eisenia fetida on the composting process. Addition of APG and E. fetida significantly increased total bacteria, cellulolytic fungi, phosphate solubilizing bacteria and nitrogen fixing bacteria populations, and the activities of cellulase, urease and alkaline phosphatase in composts as compared with the control. The APG and earthworm treatments also increased surface roughness and porosity of the green waste; Compared with control, APG and earthworm addition increased the degradation rate of TOC, lignin and cellulose by 5.9-17.9, 10.3-32.0 and 10.8-18.8%, respectively, and resulted in better compost quality, as was reflected in the neutral pH, higher cation exchange capacity (CEC) and nutrient concentrations (N, P, K, Ca, Mg, Fe, Cu, Zn, Mn). Final germination percentage and growth rate of tomato, eggplant and pepper seedlings were higher (P < 0.05) or similar in all composts produced with the addition of APG and earthworm, while plant growth was lower (P < 0.05) in the compost produced with the control than in peat substrate. The combination of APG+E. fetida enhanced the decomposition of green waste and improved final compost quality the most. Further research is needed to determine the best level of APG addition and optimum earthworm density for composting green waste.

Impacts of urbanization and landscape patterns on the earthworm communities in residential areas in Beijing

Earthworms play an important role in soil processes and functions. However, few studies have focused on their community patterns in perturbed systems, especially in an urban environment with a high turnover rate of land cover. In this study, we collected and identified the earthworms in the residential areas in metropolitan Beijing. We further investigated the effects of urban soil properties, urbanization and landscape patterns on the earthworm communities. The results showed that both the abundance and biomass of earthworms in residential areas in metropolitan was relatively low. The abundance of earthworms was negatively correlated with soil organic carbon (SOC) in this study. Soil moisture and pH could be considered as the most important edaphic variables that affected earthworm communities. The construction age of residential areas significantly influenced the earthworm abundance. Moreover, the earthworm community composition responded differently to urban landscape features at different scales. The percentage of impervious and green space surface, the amount of landscape cover types, patch density and landscape fragment significantly affected the earthworm assemblages. Our result discovered that the edaphic properties, urbanization as well as landscape patterns might be the potential factors that influenced the earthworm community patterns.