The inoculation of Bacillus paralicheniformis and Streptomyces thermoviolaceus enhances the lignocellulose degradation and microbial communities during spent mushroom substrate composting

The burgeoning global mushroom industry has precipitated challenges related to the efficient and sustainable utilization of spent mushroom substrate (SMS). Composting is regarded as an efficient way for the ecological utilization of SMS. The addition of microbial inoculants can promote the composting process and improve the quality of compost products. This study introduced two bacterial inoculants, Bacillus paralicheniformis HL-05 (BP) and Streptomyces thermoviolaceus LC-10 (ST), into the composting process of SMS. The impact of these inoculants was evaluated through analyses of physicochemical properties, lignocellulose degradation, and high-throughput sequencing to elucidate their ecological roles and optimize the composting process. The results suggest that inoculation with BP and ST significantly prolonged the thermophilic stage by 2-3 days, representing an increase of 22.22-33.33%. Moreover, it boosted the degradation rates of cellulose, hemicellulose, and lignin by 18.37-29.77%, 35.74-50.43%, and 40.32-40.83%, respectively, compared to the control. Furthermore, inoculation rapidly altered the microbial community structure during the rapid temperature-rising stage and strengthened interconnections among composting microorganisms. The microbial inoculation substantially enhanced the proliferation of thermophilic lignocellulose-degrading microorganisms during the thermophilic stage, thereby facilitating the utilization of lignocellulose. This study proposes a novel and effective strategy for SMS composting using microbial inoculants.