Comparison of microbial communities and histological changes in Phase I rice straw-based Agaricus bisporus compost prepared using two composting methods

• Rice straw is an important raw material for Agaricus bisporus compost in China.
• Traditional composting was compared with an aerated tunnel-based composting system.
• Microbial communities associated with the two composts were significantly different.
• Aeration-assisted composting leads to improved degradation of rice straw.
• Aerated method resulted in faster mycelial growth and higher mushroom yields.

Rice straw is an important raw material for preparing Agaricus bisporus compost in China, and the size mushroom yield is largely determined by the quality of compost, which in turn is dependent on the microbial processes occurring during composting and the microbial populations inhabiting the mature compost. In this study, we compared the traditional composting method used in China with an aerated tunnel-based composting system through Phase I of the process. Phospholipid fatty acid (PLFA) analysis, used to monitor changes in the respective microbial populations, demonstrated a significant difference in the structure of the microbial communities and bacterial biomass associated with the two compost types. Chemical analysis of the degraded rice straw (RS) revealed that hemicellulose and silicate levels decreased more strongly in the aerated compared than in traditional non-aerated compost. Transmission electron microscopy (TEM), used to assess histological changes occurring in the stem tissue and cell walls of RS subjected to the two composting methods, showed that the aeration treatment resulted in more pronounced effects on stem structure. Composting using the aerated method also facilitated faster mycelial growth rates and higher yields of mushroom fruit bodies. Our data indicated that aeration-assisted composting of RS leads to improved degradation and assimilation of breakdown products by A. bisporus, and suggest that introduction of the process on a commercial scale in China has huge potential.