The co-inoculation of Trichoderma viridis and Bacillus subtilis improved the aerobic composting efficiency and degradation of lignocellulose

New insights into Peniophora crassitunicata and its co-inoculation with commercial microbial inoculant accelerating lignocellulose degradation and compost maturation during orchard wastes composting

Lignocellulosic composting has been widely promoted in the utilization of agricultural wastes, while few focus on orchard lignocellulosic wastes in the fruit industry. Peniophora is a laccase hyper-producer highly efficient in lignin degradation, yet its application in lignocellulosic composting has not been investigated. Here, an aerobic composting experiment was conducted to investigate the effects of inoculation with Peniophora crassitunicata and a commercial microbial inoculant (mainly Bacillus and Aspergillus) on grape (Vitis Vinifera L.) orchard lignocellulosic wastes degradation and the underlying mechanisms. The inoculation with P. crassitunicata, both individually (H) and in combination with the commercial microbial inoculant (HS), enhanced lignocellulose degradation efficiency. Notably, the co-inoculation exhibited higher lignocellulose degradation ratios and higher lignocellulosic enzyme activities compared to other treatments. The compost piles with co-inoculation experienced a more rapid temperature rise, a longer duration (15 days) of high temperatures, lower pH, and lower electrical conductivity (EC). Firmicutes (e.g. Bacillus, Paenibacillus) and Ascomycota (e.g. Aspergillus) along with Bacteroidota, Actinobacteriota, and Basidiomycota (e.g. Peniophora) dominated the microbial community in compost; carbohydrate metabolism dominated microbial metabolic pathways at the thermophilic phase, highlighting an active microbial community. As compost processed, highly mature and non-toxic compost products were finally obtained for the co-inoculation, with a pH of 7.87, C/N ratio of 13.5, NH4+-N/NO3‾-N ratio of 0.21-0.41, EC of 0.90 mS cm-1, and germination index of 149 %. The co-inoculation of P. crassitunicata with the commercial microbial inoculant effectively accelerated lignocellulose degradation and compost maturation, producing a friendly and non-toxic organic fertilizer for agricultural applications and thereby providing a new strategy for orchard wastes management and agricultural applications.

Enhancing aerobic composting of cow dung and wheat straw with nanobubble water: Improved lignocellulose degradation and nutrient enrichment for increased crop biomass

Cow dung and wheat straw are rich in lignocellulose, which has a complex structure, making it difficult to biodegrade. This study investigated the promotion of composting effectiveness and product fertility by adding nanobubble water (Air, CO2, He, and N2) during aerobic composting of cow dung and wheat straw. Nanobubble water prolonged the high-temperature period by 1-2 days, increased the activity of soil urease and soil ligninase, reduced the lignocellulose content by 1.4 %-6.1 %, and increased the total potassium/total phosphorus ratio of the final compost products by 1.8 %-3.5 %/31.6 %-43.0 %. Nanobubble water of N2 significantly increased the total nitrogen of final compost products by 8.3 %. The lignocellulose content was significantly positively correlated with the moisture content, but significantly negatively correlated with the relative abundances of Georgenia and Marinimicrobium. The final compost products of the nanobubble water groups significantly increased the total biomass of cabbage by 37.1 %-195.3 %. The results showed that adding nanobubble water to aerobic compost of cow dung and wheat straw improved the biodegradation of lignocellulose and enriched the nutrient elements (total nitrogen, total phosphorus, and total potassium) of the final compost products. Among the four types of nanobubble water, N2-containing nanobubble water is the most promising.

Two-stage inoculation with lignocellulose-degrading microorganisms in composting: Enhanced humification efficiency and underlying mechanisms

In this study, lignocellulose-degrading microbes were added to cattle manure and bagasse co-compost through initial- and two-stage inoculations. A comparison was made between the effects of the two inoculations on compost humification parameters, and an investigation was conducted into the dynamic succession of the microbial community, microbial interactions, and amino acid metabolism to uncover the underlying mechanisms. The results showed that two-stage inoculation increased the humus (HS) and humic acid (HA) contents to 86.59 mg/g and 25.80 mg/g, respectively, and achieved a germination index (GI) of 128.77%. At the genus level, it stimulated the growth of Corynebacterium, Thermobifida, and Aspergillus during the high-temperature period, and Luteimonas, Pseudomonas, Actinomadura, and Rhizopus during the maturity period. Two-stage inoculation increased the stability of the bacterial network and microbial cooperation within the fungal network. Additionally, from the cooling to the maturity period, it boosted ten amino acid synthesis pathways. In conclusion, two-stage inoculation is an effective method to promote the maturation and stabilization of co-compost.

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.

Small molecule carbon sources drivers increase in heavy metal passivation during chicken manure composting by regulating microbial functional and metabolic pattern

The application of compost products to the soil impacts the soil microenvironment. Optimize the composting process is essential to minimize potential harm to the soil. This research aims to explore the effects of small molecular carbon source (SMCS) additives on the transformation of heavy metal (HM) fractions, bacterial community structure and metabolism functions to better comprehend the degradation of organic compounds and HM passivation during composting. The results indicate that the addition of SMCS accelerates the degradation of organic matter and total organic carbon. The exchangeable fraction (F1) of HM was effectively reduced. After adding SMCS, a significant change was observed at family and species levels in the 17th days, accounting for 20.0 %, 17.2 % and 32.3 %, 7.8 % respectively. Additionally, the incorporation of SMCS enhances the abundance of carbohydrate metabolism and amino acid metabolism pathways, while also modulating the microbial community composition essential for the effective transformation of HM fractions during the composting process. Finally, Variance partitioning analysis (VPA) results reveal that both environmental indicators and microbial communities play a role in metabolic function, with microbial community composition more significantly (explanation 22.8 %). These findings are of great significance for regulating HM passivation through metabolic pathways and achieving the green recycling of organic wastes.

Response surface methodology to optimize the Bacillus subtilis var. sojae semen praeparatum liquid fermentation process for the production of fibrinolytic enzyme

Previously, during the Sojae Semen Praeparatum (SSP, Dandouchi in China) concoction process, three types of fibrinolytic enzyme-producing bacteria were screened and identified: Bacillus subtilis, Stenotrophomonas maltophilia and Micrococcus. The fibrin plate approach was used to measure the fibrinolytic enzyme activity of pure fermentation broth, it was found that fibrinolytic enzyme produced by Stenotrophomonas maltophilia has the highest enzyme activity, followed by Bacillus subtilis and Micrococcus is the lowest. In this study, in order to improve enzyme activity and yield, the response surface method was used to optimize the fermentation conditions, including 6 factors such as nitrogen source, carbon source, initial pH, inoculum amount, loading volume and fermentation temperature. Then, the results showed that: the optional fermentation temperature was determined as 28 ℃, 6% inoculum amount, 30.42 h fermentation time and 20 mL of loading volume in 100 mL erlenmeyer flask. Ultimately, under optimal fermentation conditions, enzyme activity produced by Bacillus subtilis var. SSP was 360.82 IU/mL, which was an increase of 109.68% (1.10 folds) compared to before optimization.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-06051-8.

Harnessing the potential of exogenous microbial agents: a comprehensive review on enhancing lignocellulose degradation in agricultural waste composting

Composting converts organic agricultural wastes into value-added products, yet the presence of significant non-biodegradable lignocelluloses hinders its efficiency. The introduction of various exogenous microbial agents has been shown to effectively addresses this challenge. In this context, basing on the microbial enzymatic mechanism for lignocellulose degradation, this paper synthesizes the latest research advancements and practical applications of exogenous microbial agents in agricultural waste composting. Given that the effectiveness of lignocellulose degradation is highly dependent on the waste's inherent characteristics, it is crucial to carefully consider the composition of fungi and bacteria, the dosage of microbial agents, and the composting process operation, tailored to the specific type of agricultural waste. Moreover, the combination of additives with exogenous microbial agents can further enhance the degradation of lignocelluloses and the humification of organic matters. Furthermore, insights into the future research and application trends of exogenous microbial agents in agricultural waste composting was prospected.

Optimizing green waste composting with iron-based Fenton-like process

The presence of refractory lignocellulose presents a significant challenge in green waste (GW) composting. This research applied both a conventional iron-based Fenton-like process (with a Fenton-like reagent composed of 1.0 % Fe3O4 nanoparticles and 1.0 % H2O2) and three modified iron-based Fenton-like processes (with a Fenton-like reagent composed of 1.0 % Fe3O4 nanoparticles and 1.0 % oxalic acid/1.0 % sodium percarbonate/0.5 % Phanerochaete chrysosporium) in GW composting to systematically assess their impacts on lignocellulose degradation during GW composting. The results revealed that iron-based Fenton-like process modified sodium percarbonate exhibited the most significant effects on lignocellulose degradation. Compared with control, degradation rates for lignin, cellulose, and hemicellulose increased by 49.8 %, 39.3 %, and 26.2 % (p < 0.05), respectively. Furthermore, this process enhanced the relative abundance of bacterial communities linked to lignocellulose degradation, particularly Firmicutes and Bacteroidota. These findings offer valuable insights into optimizing GW composting, understanding reactive oxygen species dynamics, and the application of iron-based Fenton-like process.

Performance evaluation and microbial community succession analysis of co-composting treatment of refinery waste activated sludge

Refinery waste activated sludge (RWAS) is riched in organic matter with energy recovery value, while unique petroleum components in RWAS may pose challenges to the recycling process. Aerobic composting technology is an effective means of organic solid waste resource treatment, which can convert organic solid waste into fertilizer for agriculture. This study explores the effect of petroleum components on the performance of RWAS composting by co-composting it with chicken manure. The results showed that more than 65% of petroleum was removed by aerobic composting. After composting, germination index (GI) exceeded 80%, and a humic acid to fulvic acid ratio (HA/FA) was greater than 1. These results signified that the petroleum components slightly affect the harmless and recycling of RWAS. The microbial community succession found that Firmicutes (54.11-91.96%) and Ascomycota (82.35-97.21%) emerged as the dominant phyla during the thermophilic phase of composting. Thermobifida, norank_f__Limnochordaceae and Kernia were the key microorganism in the degradation of petroleum and the humification of composting, and reduced the phytotoxicity of composting products. Redundancy analysis found that the degradation of petroleum was conducive to the formation of humic acid. These findings indicate that aerobic composting technology can remove petroleum components in RWAS and convert them into composted fertilizers, providing key technical support for managing RWAS in a sustainable and environmentally friendly manner.

Combining citrus waste-derived function microbes with biochar promotes humus formation by enhancing lignocellulose degradation in citrus waste compost

The low degradation rate of lignocellulose limits the humification process of citrus organic waste composting. This study explored the roles of general microbial inoculation (GM), citrus waste-derived function microbial inoculation (CM), and CM combined with biochar (CMB) in citrus waste compost. Results showed microbial inoculations all promoted lignocellulose degradation and humus formation, but the roles of CM and CMB were better than GM, especially CMB. Compared to the control, CMB raised the temperature and duration of thermophilic phase by 2.8 °C and 4 days, and improved lignin degradation rate and humus content by 21.5% and 7.6%. Furthermore, CMB promoted bacterial community succession and cooperation, and decreased network complexity. Moreover, CMB strengthened the correlation between mainly bacterial communities and polysaccharides, reducing sugars as well as carbohydrates metabolic, enhancing the contribution of bacteria such as Bacillus, Flavobacterium and Staphylococcus to humus and its precursors. It concludes that the naturally derived microbes in compost had better effects on promoting humus synthesis than exogenous microbes, which provides a new route for rapid humification of high-lignin organic waste in composting.

Response of humification process to fungal inoculant in corn straw composting with two different kinds of nitrogen sources

Inoculation is widely used in composting to improve the mineralization process, however, the link of fungal inoculant to humification is rarely proposed. The objective of this study was to investigate the effect of compound fungal inoculation on humification process and fungal community dynamics in corn straw composting with two different kinds of nitrogen sources [pig manure (PM) and urea (UR)]. Structural equation modeling and random forest analysis were conducted to identify key fungi and explore the fungi-mediated humification mechanism. Results showed that fungal inoculation increased the content of humic acids in PM and UR by 71.76 % and 53.01 % compared to control, respectively. High-throughput sequencing indicated that there were more key fungal genera for lignin degradation in PM especially in the later stage of composting, but a more complex fungal (genera) connections with lower humification degree was found in UR. Network analysis and random forest suggested that inoculation promoted dominant genus such as Coprinus, affecting lignocellulose degradation. Structural equation modeling indicated that fungal inoculation could promote humification by direct pathway based on lignin degradation and indirect pathway based on stimulating the indigenous microbes such as Scedosporiu and Coprinus for the accumulation of carboxyl and polyphenol hydroxyl groups. In summary, fungal inoculation is suitable to be used combining with complex nitrogen source such as pig manure in straw composting.

Inoculation of Saccharomyces cerevisiae for facilitating aerobic composting of acidified food waste

In aerobic composting of food waste, acidification of the material (acidified food waste, AFW) often occurs and consequently leads to failure of fermentation initiation. In this study, we solved this problem by adding Saccharomyces cerevisiae inoculants. The results showed that the inoculation with S. cerevisiae effectively promoted the composting process. In 2 kg composting, inoculation with S. cerevisiae significantly elevated the pile temperatures by 4 ~ 14 °C, accompanied by a rapid increase in pH from 4.5 to 6.0. In 15 kg composting, total acid decreased faster and the thermophilic stage above 50 °C was prolonged by 3 days longer than in the control. The residual oxygen content in the reactor indicated that S. cerevisiae, which proliferated during composting, increased microbial activity and reduced ammonia emission during the thermophilic phase. Cell density analysis showed that compost inoculated with S. cerevisiae promoted thermophilic bacterial propagation. Metagenomic analysis showed that the dominant bacteria in the AFW compost were Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria, and the relative abundance of Bacillus, Thermobacillus, and Thermobifida increased when inoculated with S. cerevisiae. These results indicate that the inoculation of S. cerevisiae is an effective strategy to improve the aerobic composting process of AFW by accelerating the initial phase and altering microbial community structure in the thermophilic phase. Our findings suggest that S. cerevisiae can be applied to aerobic composting of organic wastes to effectively address the problem of acidification.

Effective microorganism combinations improve the quality of compost-bedded pack products in heifer barns: exploring pack bacteria-fungi interaction mechanisms

BACKGROUND

Compost-bedded pack barns (CBP) are getting huge attention as an alternative housing system for dairy cows due to their beneficial impact on animal welfare. Effective microorganisms (EM) inoculums are believed to enhance compost quality, improve soil structure and benefit the environment. However, little information is available on the impact of incubation with external EM combinations on the barn environment, compost quality and microbial diversity in CBP. This experiment was carried out to investigate the effect of inoculating different combinations of EM [Lactobacillus plantarum (L), Compound Bacillus (B) and Saccharomyces cerevisiae (S)] on compost quality and microbial communities of CBP products, as well as the relationship with the heifers' barn environment. CBP barns were subjected to the following four treatments: CON with no EM inoculum, LB/LS/LBS were Incubated with weight ratios of 1:2 (L: B), 1:2 (L: S), 1:1:1 (L: B: S), respectively.

RESULTS

The EM inoculation (LB, LS, LBS) reduced the concentration of respirable particulate matter (PM10 and PM2.5) in the CBP, and decreased the serum total protein and total cholesterol levels in heifers. Notably, LBS achieved the highest content of high-density lipoprotein compared to other treatments. Microbiome results revealed that EM inoculation reduced the bacterial abundance (Chao1 index) and fungal diversity (Shannon & Simpson indexes), while increasing the relative abundance of various bacterial genera (Pseudomonas, Paracoccus, Aequorivita) and fungi (Pestalotiopsis), which are associated with cellulose decomposition that ultimately resulted in accelerating organic matter degradation and humification. Furthermore, high nutrient elements (TK&TP) and low mycotoxin content were obtained with EM inoculation, with LBS showing a particularly pronounced effect. Meanwhile, LBS contributed to a decline in the proportion of fungal pathogen categories but also led to an increase in fungal saprotroph categories.

CONCLUSION

Generally, EM inoculation positively impacted compost product quality as organic fertilizer and barn environment by modifying the abundance of cellulolytic bacteria and fungi, while inhibiting the reproduction of pathogenic microbes, especially co-supplementing with L, B and S achieved an amplifying effect.

Enhancing C and N turnover, functional bacteria abundance, and the efficiency of biowaste conversion using Streptomyces-Bacillus inoculation

Microbial inoculation plays a significant role in promoting the efficiency of biowaste conversion. This study investigates the function of Streptomyces-Bacillus Inoculants (SBI) on carbon (C) and nitrogen (N) conversion, and microbial dynamics, during cow manure (10% and 20% addition) and corn straw co-composting. Compared to inoculant-free controls, inoculant application accelerated the compost's thermophilic stage (8 vs 15 days), and significantly increased compost total N contents (+47%) and N-reductase activities (nitrate reductase: +60%; nitrite reductase: +219%). Both bacterial and fungal community succession were significantly affected by DOC, urease, and NH4+-N, while the fungal community was also significantly affected by cellulase. The contribution rate of Cupriavidus to the physicochemical factors of compost was as high as 83.40%, but by contrast there were no significantly different contributions (∼60%) among the top 20 fungal genera. Application of SBI induced significant correlations between bacteria, compost C/N ratio, and catalase enzymes, indicative of compost maturation. We recommend SBI as a promising bio-composting additive to accelerate C and N turnover and high-quality biowaste maturation. SBI boosts organic cycling by transforming biowastes into bio-fertilizers efficiently. This highlights the potential for SBI application to improve plant growth and soil quality in multiple contexts.