Analysis of rice microbial communities under different storage conditions using culture-dependent and -independent techniques

Abstract

Rice is a staple food for over half of the world’s population, and fungal spoilage in stored rice may occur when the moisture content and temperature are conducive. Aspergillus sp. and Penicillium sp. are the most harmful toxigenic species that produce harmful mycotoxins. Molds pose a potential threat to public health and cause a huge economic loss. Therefore, it is of great importance to find out how molds multiply in rice. This study focused on the isolation and identification of fungi presented in rice and their evolution in rice with different moisture contents stored for varying periods of time and under different temperatures. Mold community was detected every month using the culture-dependent and -independent method of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Significant differences were detected by the traditional culture method under different storage conditions. For potato dextrose agar (PDA) media, high temperature and moisture were suitable for the dominant strains including Penicillium aurantiogriseum and Penicillium oxalicum. In particular, P. oxalicum competitively inhibited the other fungi. For Rose Bengal medium, no difference was observed under different storage conditions, and only typical strains such as Aspergillus candidus and Alternaria were detected. PCR-DGGE identified some uncultured strains such as Trichoderma sp. and Cladosporium sp., the dominant strains and the flora diversity such as Aspergillus restrictus and Eurotium athecium. These results indicated that storage conditions greatly shape fungal growth. This study provides a foundation for the evolution of fungal flora in rice during storage in China and may help in developing biological control methods to prevent mold contamination in rice.