Isolation, diversity, and biotechnological potential of maize (Zea mays) grains bacteria
Brazil is the third world largest maize producing country, and Paraná state is the second largest producer state of this essential crop in this country. The bacterial microbiota of cereal grains depends on the environment where they were grown, handled, and processed – and it can influence plant growth and food safety. The industrial enzymes market is rapidly increasing around the globe, and new producer microorganisms are in demand. Hydrolases correspond to 75% of all industrial enzymes. Considering the dearth of information about maize bacterial microbiota in Brazil and that this microbiota might produce hydrolases for degrading maize grains biomolecules, we examined the bacteria of maize grains within a region of Paraná state and looked for hydrolytic enzymes producers. Harvest leftover dried maize ears presenting rotting symptoms were collected from three different farms in two towns of the North Central region of Paraná state. The ears were threshed, and a grain portion of each ear was incubated in peptone water. Aliquots of this suspension were diluted and inoculated in nutrient agar. Individualized and morphologically diverse colonies were transferred to selective media containing starch, microcrystalline cellulose, skimmed milk, or triolein. Halo development around the bacterial colonies was representative of hydrolase production. Isolates (n = 137) presenting hydrolytic activity were stored, and their biochemical profile was analyzed. Fifty-five isolates that had unique biochemical characteristics were chosen to be molecularly identified by DNA barcoding. A phylogenetic tree showed that most of the bacterial strains belonged to the phylum Proteobacteria, but some also were from the phyla Actinobacteria and Firmicutes. Some of the isolated species had already well-characterized enzymes. However, new producers were also found, including amylase producing isolate of Massilia timonae and a lipase producing isolate of Pantoea dispersa.