Enhancing soybean straw composting through inoculation of a curated Bacillus-based synthetic microbial consortium

Microbial inoculation is crucial for enhancing the efficiency and quality of soybean straw composting. Herein, a Bacillus-based synthetic microbial consortium, YB1 (included Bacillus sonorensis , Bacillus licheniformis , and Bacillus subtilis ), was screened and constructed from compost samples for co-degradation function. The effects of inoculating YB1 on compost maturity indicators and microbial community succession were assessed. Compared with the control, the YB1 treatment increased the peak temperature by 4℃ and prolonged the high-temperature period by 5 days of the compost. The degradation rates of cellulose and hemicellulose increased by 13.77% and 21.53%, respectively. At the end of composting, nitrate and total nitrogen increased by 28% and 19%, respectively. YB1 significantly modified the microbial community structure and succession pattern, enabling Bacillus to stably occupy the dominant niche throughout the entire composting period. When YB1 was inoculated, Bacillus formed synergistic degradation functional groups with Saccharomonospora , Novibacillus , Ureibacillus , Thermoactinomyces and others. These functional groups, composed of thermotolerant and high-efficiency lignocellulose-degrading genera, enhanced the degradation of organic matter, accelerated the composting process and improved composting efficiency. SynCom inoculation significantly increased the predicted abundance of enzymes associated with carbon biodegradation and nitrogen transformation (e.g., EC 1.7.2.1, EC 1.7.2.4, EC 3.2.1.3, EC 3.2.1.91). Results offer practical guidance for constructing synthetic microbial communities and promoting the resource utilisation of agricultural waste.