Microflora for improving the Auricularia auricula spent mushroom substrate for Protaetia brevitarsis production

Regulation of antibiotic resistance gene rebound by degrees of microecological niche occupation by microbiota carried in additives during the later phases of swine manure composting

The occupation of microecological niches (MNs) by bacteria carrying lower antibiotic resistance genes (ARGs) has been demonstrated an effective strategy for reducing ARGs in compost, thereby mitigating the associated land use risks. In this study, humus soil (HS), matured compost (MC), and their respective isolated microbial agents (HSM and MCM), which exhibit varying abundances of ARGs, were introduced as additives after the thermophilic phase to investigate their influence on ARG removal and the mechanisms underlying effective MN occupation. The addition of HS resulted in the most favorable outcomes, including the highest carbon degradation, minimized nitrogen loss, and an 83.16 % reduction in ARG abundance during the later composting stages. In comparison, ARG rebound levels were 61.77 %-285.33 % across other treatments and 729.23 % in the control. Distinct dominant bacterial genera and potential ARG-host bacterial communities were observed, which varied with different additives and contributed to MN occupation dynamics. The addition of the HS additive intensified competition among non-host bacteria, and diversified the interactions both between genes and between bacteria. These changes suppressed horizontal gene transfer (HGT) mediated by mobile genetic elements (MGEs) and altered the abundance and composition of both dominant and non-dominant potential host species. Furthermore, it shifted the relative importance of key physicochemical parameters, collectively enhancing ARG removal during composting. These findings elucidate the mechanisms by which MN adjustments contribute to ARG reduction, providing actionable insights for designing composting strategies that mitigate environmental ARG dissemination risks more effectively.

Bioconversion efficiency and chemical composition of Hermetia illucens larvae fed spent mushroom substrates

Spent mushroom substrate (SMS) is a by-product remaining after harvesting mushrooms. We evaluated the effect of substituting chicken feed with 0-100% of Pleurotus eryngii and Lentinula edodes SMS at different stocking densities (200-1000 larvae/box) on development, composition, and substrate reduction of black soldier fly (Hermetia illucens) larvae. Although the survival rate was not significantly different, feeding pure SMS led to a low growth rate. The substitution level of SMS negatively correlated with individual larval weight, total harvested biomass, larval growth rate (LGR), feed conversion ratio (FCR), substrate reduction, and waste reduction index (WRI) except for the 20% substitution. Feeding 40% SMS resulted in the highest number of prepupae. In the density experiment, the heaviest larvae (220-239 mg fresh weight) were obtained at 200 larvae/box in the 0% SMS group. The frass residue and FCR decreased with increased density. Remarkably, when feeding 20% SMS at 250 larvae/box, the harvested biomass, LGR, and FCR did not differ significantly from the 0% SMS control, whereas some of the higher densities led to a deterioration. In fact, the frass residue, substrate reduction, and WRI were even improved at 250 larvae/box in the 20% SMS group. The chemical analyses of larvae reared on 20% SMS at 250 larvae/box showed comparable ash and fat contents and a higher protein content compared to the 0% SMS group. Accordingly, up to 20% of a standard diet such as chicken feed can be replaced by low-cost SMS without disadvantages for breeding.

Status and development of spent mushroom substrate recycling: A review

The edible mushroom industry is the sixth largest after grain, cotton, oil, vegetables and fruits, and the annual production of edible mushrooms in China exceeds 40 million tons. Edible mushroom cultivation produces a class of by-products consisting mainly of mycelium remnants and lignocellulosic waste, known as Spent Mushroom Substrate (SMS) or Spent Mushroom Compost (SMC). SMS/SMC is rich in nutrients and active ingredients and has an extremely high recycling potential. This review paper summarizes SMS recycling strategies from the perspectives of "environmental remediation" and "circular economy", and briefly discusses the legitimacy, possible challenges and future research of SMS recycling. It is hoped that this will assist researchers in related fields and promote the development of the SMS recycling industry, thereby contributing to sustainable environmental and economic development.Implications: The efficient management of SMS is important for many countries around the world, particularly major mushroom producing countries. Traditional disposal methods (incineration, burial, piling) can cause serious damage to the environment and waste resources. The correct disposal method can protect the natural environment and provide certain economic benefits. This study presents the main methods of SMS processing from both an "environmental remediation" and "circular economy" perspective. In general, this paper emphasizes the importance of SMS processing, introduces the current mainstream processing methods and briefly discusses the legality of their processing methods.

Effect of pyrolysis temperature on physicochemical characteristics and toxic elements for grub manure-derived biochar

While traditional solutions for disposing of animal manure are limited by their time-consuming nature and inefficiency, the pyrolysis of animal manure into biochar is considered a promising disposal option, offering high-value benefits. However, there are few research studies on the physicochemical properties and potential utilization pathway of grub manure-derived biochar (GB) prepared at different temperatures. In this study, grub manure (GM) was pyrolyzed at 450, 600 and 750 °C, and the effect of pyrolysis temperature on the characteristics and applications of GB was illustrated. The results showed that increasing pyrolysis temperature promoted the formation of an aromatic structure, enhanced the stability, and improved the surface pore structure of GB. The relationship between pyrolysis temperature and C/N-containing functional groups in GB was quantitatively analyzed. In the process of pyrolysis of GM to GB, carbonates first decomposed, and then, C[double bond, length as m-dash]O broke into C-O and finally condensed to form an aromatic ring structure at elevated pyrolysis temperature. Although GM was rich in organic matter and total N/P/K, the potentially toxic elements (PTEs) (Ni, Cu, Cd, Pb, Zn and As) in GM presented potential risk. The hazard of PTEs in GB was significantly decreased after GM was pyrolyzed. Overall, pyrolysis provided an opportunity for the sustainable management of GM, and GB is a multi-purpose and high-value product that could be applied in soil improvement, environmental remediation, and climate change mitigation for achieving sustainable development.

Characterization and evaluation of actinomycete from the Protaetia brevitarsis Larva Frass

Protaetia brevitarsis larvae (PBL) are soil insects important for the soil organic carbon cycle, and PBL frass not only contains a large amount of humic acid but also affects the diversity, novelty, and potential functions of actinomycetes. Here, we characterized and assessed the actinomycete. The operational taxonomic unit (OTU) data showed that 90% of the actinomycetes cannot be annotated to species, and pure culture and genome analysis showed that 35% of the strains had the potential to be new species, indicating the novelty of PBL frass actinomycetes. Additionally, genome annotation showed that many gene clusters related to antifungal, antibacterial and insecticidal compound synthesis were identified, and confrontation culture confirmed the antifungal activities of the actinomycetes against soil-borne plant pathogenic fungi. The incubation experiment results showed that all isolates were able to thrive on media composed of straw powder and alkaline lignin. These results indicated that PBL hindgut-enriched actinomycetes could survive in soil by using the residual lignocellulose organic matter from plant residues, and the antibiotics produced not only give them a competitive advantage among soil microflora but also have a certain inhibitory effect on plant diseases and pests. This study suggests that the application of PBL frass can not only supplement soil humic acid but also potentially affect the soil microbiota of cultivated land, which is beneficial for the healthy growth of crops.

A New Method for Discovering Plant Biostimulants

Structurally well-defined compounds have advantages for quality control in plant biostimulant production and application processes. Humic acid (HA) is a biostimulant that significantly affects plant growth, and soil-dwelling Protaetia brevitarsis larva (PBLs) can rapidly convert agricultural waste into HA. In this study, we use PBLs as a model to investigate HA formation and screen for structurally well-defined HA-related plant biostimulant compounds. Dephasing magic angle spinning nuclear magnetic resonance (13C DD-MAS NMR) analysis indicated HA structural changes during PBL digestion; metabolic profiling detected seven HA-related aromatic ring-containing compounds. A total of six compounds that significantly stimulate plant growth were identified through plant experiments, and all six compounds demonstrate the ability to enhance seed germination. It is noteworthy that piperic acid exhibits a remarkable promotion of root growth in plants, a finding reported for the first time in this study. Thus, this study not only provides insights into the insect-mediated transformation of HA but also illustrates a new method for discovering structurally well-defined plant biostimulant compounds.

Transformation Capability Optimization and Product Application Potential of Proteatia brevitarsis (Coleoptera: Cetoniidae) Larvae on Cotton Stalks

Cotton stalks (CS) are a potential agricultural biomass resource. We investigated the use of CS as a feed for Proteatia brevitarsis Lewis larvae and the resulting frass (larvae dung-sand) as a fertilizer. Based on a three-factor experiment (decomposition inoculant, fermentation duration, and cattle manure ratio), the optimal parameters for the transformation of CS using P. brevitarsis larvae were determined as 40-50% of cattle manure, the use of VT inoculant and a fermentation duration of 25-30 days. Regarding the products of the transformation, the protein content of the larval body was as high as 52.49%, and the fat content was 11.7%, which is a suitable-quality insect protein source. The organic matter content of larvae dung-sand was 54.8%, and the content of total nitrogen, phosphorus, and potassium (TNPK) was 9.04%, which is twice more than that of the organic fertilizer standard (NY525-2021, Beijing, China, TNPK ≥ 4.0%), and larvae dung-sand has the potential of fertilizer application. Therefore, CS as a feed and fertilizer based on the transformation of P. brevitarsis larvae is feasible, and it is a highly efficient way to promote the utilization of both CS and cattle manure.