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

Microbial agents obtained from tomato straw composting effectively promote tomato straw compost maturation and improve compost quality

Appropriate management of agricultural organic waste (AOW) presents a significant obstacle in the endeavor to attain sustainable agricultural development. The proper management of AOW is a necessity for sustainable agricultural development. This can be done skillfully by incorporating microbial agents in the composting procedure. In this study, we isolated relevant bacteria strains from tomato straw AOW, which demonstrated efficient degradation of lignocellulose without any antagonistic effects in them. These strains were then combined to create a composite microbial agent called Zyco Shield (ZS). The performance of ZS was compared with a commercially effective microorganism (EM) and a control CK. The results indicate that the ZS treatment significantly prolonged the elevated temperature phase of the tomato straw pile, showing considerable degradation of lignocellulosic material. This substantial degradation did not happen in the EM and CK treatments. Moreover, there was a temperature rise of 4-6 ℃ in 2 days of thermophilic phase, which was not the case in the EM and CK treatments. Furthermore, the inoculation of ZS substantially enhanced the degradation of organic waste derived from tomato straw. This method increased the nutrient content of the resulting compost and elevated the enzymatic activity of lignocellulose-degrading enzymes, while reducing the urease enzyme activity within the pile. The concentrations of NH4+-N and NO3--N showed increases of (2.13% and 47.51%), (14.81% and 32.17%) respectively, which is again very different from the results of the EM and CK treatments. To some extent, the alterations observed in the microbial community and the abundance of functional microorganisms provide indirect evidence supporting the fact that the addition of ZS microbial agent facilitates the composting process of tomato straw. Moreover, we confirmed the degradation process of tomato straw through X-ray diffraction, Fourier infrared spectroscopy, and by scanning electron microscopy to analyze the role of ZS microbial inoculum composting. Consequently, reinoculation compost strains improves agricultural waste composting efficiency and enhances product quality.

Shifts in bacterial diversity characteristics during the primary and secondary fermentation stages of bio-compost inoculated with effective microorganisms agent

Microbial inoculation was an effective way to improve product quality of composting and solve traditional composting shortage. However, the effect mechanism of microbial inoculation on compost microorganisms remains unclear. Here, Shifts in bacterial community, metabolic function and co-occurrence network during the primary and secondary fermentation stages of bio-compost inoculated with effective microorganisms (EM) agent were analyzed by high-throughput sequencing and network analysis. Microbial inoculation promoted organic carbon transformation in early stage of secondary fermentation (days 27 to 31). The beneficial biocontrol bacteria were main dominant genera at the second fermentation stage. Microbial inoculation can be good for the survival of beneficial bacteria. Inoculation with microbes promoted amino acid, carbohydrate and lipid metabolism, and inhibited energy metabolism and citrate cycle (TCA cycle). Microbial inoculation could enhance complexity of bacterial network and enhance mutual cooperation among bacteria during composting.

Humification process enhancement through relative abundance promotion of Talaromyces and Coprinopsis by inoculated Phanerochaete chrysosporium during the secondary fermentation of composting

To explore the mechanism of Phanerochaete chrysosporium (P. chrysosporium) inoculation driving the humification process of maize straw composting, the treatments without P. chrysosporium inoculation (T1) and that with P. chrysosporium inoculation (T2) were carried out separately during the secondary fermentation of the co-composting of maize straw and rapeseed cake. The key microorganisms were determined by evaluating the succession of the fungal community and its relationship with humification process parameters. The results showed that P. chrysosporium inoculation (T2) reduced fungal diversity but increased the relative abundance of Coprinopsis and Talaromyces. At the end of the composting (day 36), the relative abundance of Talaromyces and Coprinopsis in T2 increased by 1223.7% and 30.2%, respectively, compared with T1. Combined CCA and SEMs analyses demonstrated the microbially driven mechanisms that enhance the humification process of composting, that is, P. chrysosporium inoculation promoted lignin continuous degradation by promoting the relative abundance of Talaromyces and Coprinopsis during the secondary fermentation of composting; meanwhile, P. Chrysosporium inoculation further intensified the biological process of humification in composting.

Evaluating differences in humic substances formation based on the shikimic acid pathway during different materials composting

This study aimed to evaluate differences in humic substance (HS) formation based on the shikimic acid pathway (SAP) during five different materials composting. The results showed that compared with other three materials, gallic acid, protocatechuic acid and shikimic acid of the SAP products in lawn waste (LW) and garden waste (GW) compost decreased significantly. Furthermore, as important indicators for evaluating humification, humic acid and degree of polymerization increased by 39.4%, 79.5% and 21.8%, 87.9% in LW and GW, respectively. Correlation analysis showed that SAP products were strongly correlated with HS fractions in LW and GW. Meanwhile, network analysis indicated that more core bacteria associated with both SAP products and HS were identified in LW and GW. Finally, the structural equation model proved that SAP had more significant contribution to humification improvement in LW and GW. These findings provided theoretical foundation and feasible actions to improve compost quality by the SAP.

Lignocellulosic depolymerization induced by ionic liquids regulating composting habitats based on metagenomics analysis

The application of ionic liquids with sawdust and fresh dairy manure was studied in composting. The degradation of organic matter (OM), dissolved organic matter (DOM), and lignocellulose was analyzed. The DOM decreased by 14.25 mg/g and 11.11 mg/g in experimental group (ILs) and control group (CK), respectively. OM decreased by 7.32% (CK) and 8.91% (ILs), respectively. The degradation rates of hemicellulose, lignin, and cellulose in ILs (56.62%, 42.01%, and 23.97%) were higher than in CK (38.39%, 39.82%, and 16.04%). Microbial community and carbohydrate-active enzymes (CAZymes) were analyzed based on metagenomics. Metagenomic analysis results showed that ionic liquids enriched Actinobacteria and Proteobacteria in composting. Compared with CK, the total abundance values of GH11, GH6, AA6, and AA3_2 in ILs increased by 13.98%, 10.12%, 11.21%, and 13.68%, respectively. Ionic liquids can improve the lignocellulosic degradation by regulating the environmental physicochemical parameters (temperature, pH, C/N) to promote the growth of Actinobacteria and Proteobacteria and carbohydrate-active enzymes (CAZymes) abundance. Therefore, ionic liquids are a promising additive in lignocellulosic waste composting.

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.

Study on dynamic changes of microbial community and lignocellulose transformation mechanism during green waste composting

There are few reports on the material transformation and dominant microorganisms in the process of greening waste (GW) composting. In this study, the target microbial community succession and material transformation were studied in GW composting by using MiSeq sequencing and PICRUSt tools. The results showed that the composting process could be divided into four phases. Each phase of the composting appeared in turn and was unable to jump. In the calefactive phase, microorganisms decompose small molecular organics such as FA to accelerate the arrival of the thermophilic phase. In the thermophilic phase, thermophilic microorganisms decompose HA and lignocellulose to produce FA. While in the cooling phase, microorganisms degrade HA and FA for growth and reproduction. In the maturation phase, microorganisms synthesize humus using FA, amino acid and lignin nuclei as precursors. In the four phases of the composting, different representative genera of bacteria and fungi were detected. Streptomyces, Myceliophthora and Aspergillus, maintained high abundance in all phases of the compost. Correlation analysis indicated that bacteria, actinomycetes and fungi had synergistic effect on the degradation of lignocellulose. Therefore, it can accelerate the compost process by maintaining the thermophilic phase and adding a certain amount of FA in the maturation phase.

Combined System of Organic Substrate and Straw-Degrading Microbial Agents Improved Soil Organic Matter Levels and Microbial Abundance in a Rice-Wheat Rotation

Rice-wheat rotation is one of the most intensive agricultural planting modes in China and is pivotal to develop optimized straw-returning management in situ to improve soil fertility and productivity in agricultural ecosystems. Previous studies have mainly focused on the effects of straw return with a single application of organic fertilizers. The integrated management of different fertilizers in improving the management of straw return in situ is not well known. In this study, a field experiment was conducted from 2017 to 2019 to explore the effects of a combined system of modified organic substrate (MOS) and straw-degrading compound microbial agent (CMA) on soil physiochemical properties, labile organic carbon, microbial activities, and soil microbial community composition under the background of direct crop straw return and chemical fertilizer utilization. Four treatments were designed: (1) control check; (2) CMA; (3) MOS; and (4) MOS + CMA. The results showed that the MOS + CMA treatment had the combined advantages of soil organic matter (SOM) accumulation, soil nutrient increase and soil microbial community alteration, which may be more suitable for improving the quality and fertility of sandy loam soil. This study provides novel insights for further understanding the effects of organic substrates and composite microbial agents on SOM changes and microbial community composition and function in the field, which has important implications for sustainable crop production and agricultural development.