Modulation of mycobiota associated with rice stored in bamboo reinforced concrete silo- molecular identification and phenotypic characterization

Abstract

The present study was undertaken to investigate the fungal load and community composition on milled rice stored in the form of paddy in bamboo reinforced concrete (BRC) silo for 12 months. The storage period was divided into Phase 1 and 2, corresponding to the first and last six months of storage, respectively. Ten strains of fungi with maximum frequencies were identified throughout the storage duration by molecular (Internal transcribed spacer sequences) and phenotypic (culture method and scanning electron microscopy) characterization. The fungal load remained unchanged during Phase 1 but increased progressively during Phase 2, which could be a direct effect of the changes in grain water activity (0.47–0.63) and storage temperature (25–35°C). Among the isolated fungal strains, Alternaria padwickii was the most predominant species in the rice samples during Phase 1 while Phase 2 was highlighted by the maximum frequency of Aspergillus flavus. Other species encountered and isolated from the rice grains include Curvularia spp., Rhizomucor spp., Pencillicum spp., Hypoxylon spp. and Aspergillus spp. Though undetectable in Phase 1, total aflatoxin content at the end of storage period was found to be 0.42 μg/kg grain, indicating the presence of the Aspergillus spp. in Phase 2. Rapid and accurate identification of fungal species is critical for formulating efficient strategies in management of fungal contamination in a storage system. Storage of rough rice in BRC silo has been shown to be highly effective in mitigating the growth and proliferation of fungi under tropical conditions.