Dynamic composting actuated by a Caldibacillus thermoamylovorans isolate enables biodecomposability and reusability of Cinnamomum camphora garden wastes

Electric field as an activator of inoculated Bacillus clausii enhances humification during electric field-assisted aerobic composting

A novel electric field-assisted aerobic composting (EAC) method effectively facilitates compost disposal by applying a low electric field to conventional aerobic composting (CAC). The humification effect of inoculation with Bacillus clausii in the EAC system was better than that in the CAC system, so this study focused on the enhancement effect of microbial inoculation in the EAC system. Compared with EAC, EAC with microbial inoculation (AMI-EAC) increased the degradation of cellulose, hemicellulose, and lignin. Furthermore, AMI-EAC improved the humification index by 42.89 % relative to EAC. AMI-EAC also increased the relative abundance of Bacillus, enriched thermophilic and electroactive microorganisms, and enhanced the activity of associated degradative enzymes, which promoted the decomposition and humification of organic matter. Partial least squares-path model analysis showed that Bacillus inoculation during AMI-EAC enhanced the direct positive effect of microorganisms on enzyme activity and strengthened the positive impacts of substance degradation and enzyme activity on compost maturation. This study provided new insights for inoculating microbial agents to enhance composting efficiency in future engineering applications of EAC.

Lignocellulolytic Bacterial Engineering for Tailoring the Microstructure of Hard Carbon as a Sodium-Ion Battery Anode with Fast Plateau Kinetics

Lignocellulosic biomass-derived pyrolysis hard carbon (LCB-HC) shows promising commercial potential as an anode material for sodium-ion batteries (SIBs). LCB compromises multiple biopolymer carbon sources, including cellulose, hemicellulose, and lignin, which influence the formation and microstructure of pyrolysis HC. However, the poor plateau kinetics of LCB-HC is one of the main obstacles that severely limits its energy density with high power density, which could be attributed to the narrow interlayer distance and the lack of abundant closed pores for the intercalation/filling of Na+. Herein, we proposed a bottom-up approach to tailoring the microstructure of LCB-HC by regulating the components of the LCB precursor at the molecular level using bioenzymes secreted by lignocellulolytic bacteria. This mild and efficient enzymatic hydrolysis pathway partially depolymerized the biopolymers of basswood specifically, thereby enabling the construction of a small curved-graphite domain architecture with increased closed pores and an enlarged interlayer distance of LCB-HC, benefiting the low-voltage plateau Na+ storage with accelerated kinetics. As a result, the basswood-derived HC delivers a reversible capacity of 366.4 mAh g-1 and performed remarkable plateau capacity retainability with a high proportion of 74.3% even with increased current density to 1000 mA g-1. Such a microbial-chemistry-assisted approach provided insights into tailoring the microstructure of LCB-HC to construct high-performance SIB anode materials.

Thermophilic bacteria contributing to humus accumulation in hyperthermophilic aerobic fermentation of mushroom residue

The purpose of this study is to clarify the roles of thermophilic bacteria in humification during hyperthermophilic composting (HTC) of organic wastes mainly composed of mushroom residue. Results showed that HTC with a long hyperthermophilic (>80°C) period lasting for 18 days produced 83 mg/g of humus in compost on day 27, significantly higher than that of thermophilic composting (TC, 9.7 mg/g). Machine learning models identified that the dominant thermophiles belonging to Bacillaceae, Sporolactobacillaceae, Thermaerobacteraceae, Paenibacillaceae families and the unique thermophiles (Thermus and Calditerricola) in HTC played important roles in accumulating stubborn and soluble humus including humic acid and fulvic acid. Hyperthermophilic fermentation not only recruited and enriched these thermophilic bacteria to rapidly degrade organic matter into bioavailable nutrients, but also upregulated the metabolic pathways relevant to the generation and oxidation of precursors including amino acids that would be polymerized into humus, thus efficiently converting organic waste into humus-rich compost.

Recycled calcium polypeptides modulate microbial dynamics and enhance bioconversion in kitchen waste-garden waste co-composting system

The kitchen waste and garden waste (KW-GW) co-composting system provides an effective method for recycling these two types of municipal solid waste; however, further improvements are needed to enhance bioconversion performance. This study investigates a novel composting additive, calcium polypeptides (CPPs), derived from waste animal and plant proteins, which can enhance the bioconversion capacity of biomass in the KW-GW co-composting system. As a pH regulator and an available nitrogen source, CPPs significantly increase the compost matrix pH, prolong the thermophilic phase, and reduce emissions of exhaust gases such as CH4, N2O, NH3, and H2S by 52.5%, 37.9%, 17.5%, and 41.3%, respectively. Moreover, the addition of CPPs to the compost product resulted in a 32.6% increase in humic substance content, while the germination index reached 108.5%, significantly promoting the growth of ryegrass. Microbial diversity analysis revealed that CPPs significantly altered microbial richness and diversity in the KW-GW co-composting system. During the heating phase, CPPs positively correlated with the abundance of thermophilic and lignocellulose-degrading species, such as Bacillus, Corynebacterium, and Aspergillus, along with composting temperature, pH, and electrical conductivity. Conversely, CPPs negatively correlated with the abundance of acidogenic and methanogenic species like Lactobacillus, Streptococcus, and Weissella. In the maturation phase, CPPs positively correlated with the abundance of lignocellulose-degrading and humus-forming species, including Pseudoxanthomonas, Sphingobacterium, and Aspergillus, as well as with the germination index. These results indicate that recycled CPPs improve the microenvironment, boosting biomass conversion in the KW-GW co-composting system, providing a viable approach for resourceful waste biomass reuse.

Cattle manure composting driven by a microbial agent: A coupled mechanism involving microbial community succession and organic matter conversion

Aerobic composting has been used as a mainstream treatment technology for agricultural solid waste resourcing. In the present study, we investigated the effects and potential mechanisms of the addition of a microbial agent (LD) prepared by combining Bacillus subtilis, Bacillus paralicheniformis and Irpex lacteus in improving the efficiency of cattle manure composting. Our results showed that addition of 1.5 % LD significantly accelerated compost humification, i.e., the germination index and lignocellulose degradation rate of the final compost product reached values of 92.20 and 42.29 %, respectively. Metagenomic sequencing results showed that inoculation of cattle manure with LD increased the abundance of functional microorganisms. LD effectively promoted the production of humus precursors, which then underwent reactions through synergistic abiotic and biotic pathways to achieve compost humification. This research provides a theoretical basis for the study of microbial enhancement strategies and humus formation mechanisms in the composting of livestock manure.

From waste to protein: a new strategy of converting composted distilled grain wastes into animal feed

Distilled grain waste (DGW) is rich in nutrients and can be a potential resource as animal feed. However, DGW contains as much as 14% lignin, dramatically reducing the feeding value. White-rot fungi such as Pleurotus ostreatus could preferentially degrade lignin with high efficiency. However, lignin derivatives generated during alcohol distillation inhibit P. ostreatus growth. Thus, finding a new strategy to adjust the DGW properties to facilitate P. ostreatus growth is critical for animal feed preparation and DGW recycling. In this study, three dominant indigenous bacteria, including Sphingobacterium thermophilum X1, Pseudoxanthomonas byssovorax X3, and Bacillus velezensis 15F were chosen to generate single and compound microbial inoculums for DGW composting to prepare substrates for P. ostreatus growth. Compared with non-inoculated control or single microbial inoculation, all composite inoculations, especially the three-microbial compound, led to faster organic metabolism, shorter composting process, and improved physicochemical properties of DGW. P. ostreatus growth assays showed the fastest mycelial colonization (20.43 μg·g-1 ergosterol) and extension (9 mm/d), the highest ligninolytic enzyme activities (Lac, 152.68 U·g-1; Lip, 15.56 U·g-1; MnP, 0.34 U·g-1; Xylanase, 10.98 U·g-1; FPase, 0.71 U·g-1), and the highest lignin degradation ratio (30.77%) in the DGW sample after 12 h of composting with the three-microbial compound inoculation when compared to other groups. This sample was relatively abundant in bacteria playing critical roles in amino acid, carbohydrate, energy metabolism, and xenobiotic biodegradation, as suggested by metagenomic analysis. The feed value analysis revealed that P. ostreatus mycelia full colonization in composted DGW led to high fiber content retention and decreased lignin content (final ratio of 5% lignin) but elevated protein concentrations (about 130 g·kg-1 DM). An additional daily weight gain of 0.4 kg/d was shown in cattle feeding experiments by replacing 60% of regular feed with it. These findings demonstrate that compound inoculant consisting of three indigenous microorganisms is efficient to compost DGW and facilitate P. ostreatus growth. P. ostreatus decreased the lignin content of composted DGW during its mycelial growth, improving the quality of DGW for feeding cattle.

Efficient remediation of di-(2-ethylhexyl) phthalate and plant-growth promotion with the application of a phosphate-solubilizing compound microbial agent

The ecotoxic endocrine-disrupting chemical di-(2-ethylhexyl) phthalate (DEHP) is ubiquitous in agricultural soil, posing a serious threat to human health. Here, we report efficient soil-borne DEHP degradation and plant growth promotion by a microbial organic fertilizer GK-PPB prepared by combining a recycled garden waste-kitchen waste compost product with ternary compound microbial agent PPB-MA, composed of Penicillium oxalic MB08F, Pseudomonas simiae MB751, and Bacillus tequilensis MB05B. The combination of MB08F and MB751 provided synergistic phosphorus solubilization, and MB05B enhanced the DEHP degradation capacity of MB08F via bioemulsification. Under optimal conditions (25.70 °C and pH 7.62), PPB-MA achieved a 96.81 % degradation percentage for 1000 mg L-1 DEHP within 5 days. The degradation curve followed first-order kinetics with a half-life of 18.24 to 24.76 h. A complete mineralization pathway was constructed after identifying the degradation intermediates of 2H-labeled DEHP. Evaluation in Caenorhabditis elegans N2 showed that PPB-MA eliminated the ecological toxicity of DEHP. A pakchoi (Brassica chinensis L.) pot experiment demonstrated that GK-PPB promoted phosphorus solubilization and plant growth, reduced soil DEHP residue, and decreased DEHP accumulation in pakchoi, suggesting its potential practical utility in environmentally responsible and safe cultivation of vegetables.

Effects of Bacillus-based inoculum on odor emissions co-regulation, nutrient element transformations and microbial community tropological structures during chicken manure and sawdust composting

This study aims to evaluate whether different doses of Bacillus-based inoculum inoculated in chicken manure and sawdust composting will provide distinct effects on the co-regulation of ammonia (NH3) and hydrogen sulfide (H2S), nutrient conversions and microbial topological structures. Results indicate that the Bacillus-based inoculum inhibits NH3 emissions mainly by regulating bacterial communities, while promotes H2S emissions by regulating both bacterial and fungal communities. The inoculum only has a little effect on total organic carbon (TOC) and inhibits total sulfur (TS) and total phosphorus (TP) accumulations. Low dose inoculation inhibits total potassium (TK) accumulation, while high dose inoculation promotes TK accumulation and the opposite is true for total nitrogen (TN). The inoculation slightly affects the bacterial compositions, significantly alters the fungal compositions and increases the microbial cooperation, thus influencing the compost substances transformations. The microbial communities promote ammonium nitrogen (NH4+-N), TN, available phosphorus (AP), total potassium (TK) and TS, but inhibit nitrate nitrogen (NO3--N), TP and TK. Additionally, the bacterial communities promote, while the fungal communities inhibit the nitrite nitrogen (NO2--N) production. The core bacterial and fungal genera regulate NH3 and H2S emissions through the secretions of metabolic enzymes and the promoting or inhibiting effects on NH3 and H2S emissions are always opposite. Hence, Bacillus-based inoculum cannot regulate the NH3 and H2S emissions simultaneously.