Enhanced organic degradation and microbial community cooperation by inoculating Bacillus licheniformis in low temperature composting

The activation of Parageobacillus toebii in hyperthermophilic composting was depended on the bioavailability of raw materials

Hyperthermophilic composting (HTC) with excellent disposal effect is a novel composting technology by inoculating exogenous thermophilic microorganisms. However, the role of exogenous thermophilic microorganisms in HTC remains debated, especially for the applicability of different compost feedstocks. In this study, the role of Parageobacillus toebii during HTC using chicken and pig manure was investigated. The addition of P. toebii could raise the maximum temperature to 78.2 °C and obviously enhanced maturation effect in chicken manure composting. However, the enhancement effect of P. toebii was weaker in pig manure compost, and the maximum temperature only reached 73 °C. Addition of P. toebii could stimulated functional microbial communities for C&N transformation, increased temperature, and promoted the growth of thermophilic microorganisms in chicken manure composting. Component analyses showed that chicken manure had higher bioavailability compared to pig manure. Correlation analysis indicated that P. toebii activated as a "leader", stimulating metabolic activity among functional microbial communities and enhancing organic matter degradation for heat release, while its activation depended on the bioavailability of the raw material. This study provides important insights into the role and application of exogenous microorganisms in promoting HTC.

Effect of black soldier fly larvae frass addition on humus content during low temperature co-composting

Initiating aerobic fermentation under low temperature is the main challenge for winter livestock manure composting. This study aims to address this issue by applying black soldier fly larvae (BSFL) frass as a co-composting additive to enhance the low-temperature composting process. Specifically, this work explored the effects of chicken manure and BSFL frass co-composting on the temperature, humus content, and microorganisms with fresh weight ratio of 2:1, 1:1, 1:2 (w/w) at 6 °C. The result showed frass could rapidly rise the temperature to 50 °C and significantly increased the humus content by 15.6 % ∼ 26.3 %. Moreover, microbial analysis revealed that Sphingobacteriaceae accelerated temperature rise via low-temperature reproduction, creating proper temperature for thermophilic bacteria (Truepera and Georgia). Additionally, Cellulomonas and other bacteria promoted organic matter degradation and participated in humus formation. This study presents a novel solution for low-temperature composting, providing practical insights for improving manure management in winter.

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.

Continuous thermophilic composting of distilled grain waste improved organic matter stability and succession of bacterial community

Continuous thermophilic composting (CTC) is potentially helpful in shortening the composting cycle. However, its universal effectiveness and the microbiological mechanisms involved are unclear. Here, the physicochemical properties and bacterial community dynamics during composting of distilled grain waste in conventional and CTC models were compared. CTC accelerated the organic matter degradation rate (0.2 vs. 0.1 d-1) and shortened the composting cycle (24 vs. 65 d), mainly driven by the synergism of bacterial genera. Microbial analysis revealed that the abundance of Firmicutes was remarkably improved compared to that in conventional composting, and Firmicutes became the primary bacterial phylum (relative abundance >70 %) during the entire CTC process. Moreover, correlation analysis demonstrated that bacterial composition had a remarkable effect on the seed germination index. Therefore, controlling the composting process under continuous thermophilic conditions is beneficial for enhancing composting efficiency and strengthening the cooperation between bacterial genera.