Development of a consortium-based microbial agent beneficial to composting of distilled grain waste for Pleurotus ostreatus cultivation

Abstract

Background Pleurotus ostreatus is an edible mushroom popularly cultivated worldwide. Distilled grain waste (DGW) is a potential substrate for P. ostreatus cultivation. However, components in DGW restrict P. ostreatus mycelial growth. Therefore, a cost-effective approach to facilitate rapid P. ostreatus colonization on DGW substrate will benefit P. ostreatus cultivation and DGW recycling. Results Five dominant indigenous bacteria, Sphingobacterium sp. X1, Ureibacillus sp. X2, Pseudoxanthomonas sp. X3, Geobacillus sp. X4, and Aeribacillus sp. X5, were isolated from DGW and selected to develop a consortium-based microbial agent to compost DGW for P. ostreatus cultivation. Microbial agent inoculation led to faster carbohydrate metabolism, a higher temperature (73.2 vs. 71.2 °C), a longer thermophilic phase (5 vs. 3 days), and significant dynamic changes in microbial community composition and diversity in composts than those of the controls. Metagenomic analysis showed the enhanced microbial metabolisms, such as xenobiotic biodegradation and metabolism and terpenoid and polyketide metabolism, during the mesophilic phase after microbial agent inoculation, which may facilitate the fungal colonization on the substrate. In accordance with the bioinformatic analysis, a faster colonization of P. ostreatus was observed in the composts with microbial inoculation than in control after composting for 48 h, as indicated from substantially higher fungal ergosterol content, faster lignocellulose degradation, and higher lignocellulase activities in the former than in the latter. The final mushroom yield shared no significant difference between composts with microbial inoculation and control, with 0.67 ± 0.05 and 0.60 ± 0.04 kg fresh mushroom/kg DGW, respectively (p > 0.05). Conclusion The consortium-based microbial agent comprised indigenous microorganisms showing application potential in composting DGW for providing substrate for P. ostreatus cultivation and will provide an alternative to facilitate DGW recycling.

From waste to protein: a new strategy of converting composted distilled grain wastes into animal feed

“…The raw DGW from the thermophilic phase (about 55-60°C) of DGW composting was diluted, spread on LB agar plates (LB, tryptone 10 g•L −1 , yeast extract 5 g•L −1 , NaCl 10 g•L −1 , Agar, 10 g•L −1 ), and then incubated at 55°C for strain isolation as previously described (Wu et al, 2021). The 16S rRNA gene of each strain was amplified using the primers Bact-27F (5 -AGAGTTTGATCMTGGCTCAG-3) and Bact-1492R (5 -GGTTACCTTGTTACGACTT-3) and sequenced.…”

“…Corncob was crushed to approximately 5 mm in length and mixed with DGW in the ratio of 3:7 to adjust the C/N ratio to 25-35. The pH was adjusted to 6-7 with an addition of 4% lime (based on raw DGW weight), and the moisture content was adjusted to 60-70% with tap water (Bari et al, 2020;Wu et al, 2021).…”

“…Composting was carried out in a ventilated room, following the method described by Wu et al (2021). Each pile was made of 200 kg of a mixture composed of DGW and corncob.…”

“…P. ostreatus can be used to convert lignin in DGW to prepare high-quality animal feed. However, high concentrations of toxic phenolics in DGW (about 3.5 mg/g phenolic compounds) limit the rapid colonization of fungal hypha (Wu et al, 2021).…”

“…X5 was developed. The compound microbial inoculum exhibited potential application in DGW composting, providing substrates for P. ostreatus cultivation (Wu et al, 2021). To simplify and optimize the composition of the compound inoculant, Sphingobacterium sp.…”