Sour cassava starch is obtained from the natural fermentation of cassava in a spontaneous process conducted by microorganisms present in raw materials and fermentation tanks. The producer evaluates the end of the fermentation empirically, which leads to a process without standardization and to the achievement of inferior quality products. The objective of this work was to identify the predominant microbiota of cassava fermentation and select starter cultures for the production of sour cassava starch. The samples were collected in Formiga (MG, Brazil) during fermentation and plated on MRS and YM agar for isolation and enumeration of lactic acid bacteria and yeast, respectively. The bacteria were grouped by Restriction Fragment Length Polymorphism and yeasts by PCR-fingerprinting, a molecular profile of each isolated was identified by sequencing. The isolates were tested for total acid production and starch degradation. The BAL prevailed throughout the process, mainly representing the genus Lactobacillus and Lb. brevis was the most frequent. Yeasts appeared from the beginning until the middle of fermentation and Pichia scutulata was the predominant yeast. The acidity values were higher at 48 than at 24 hours for the majority of bacteria and these values were higher than yeasts ones, indicating their importance in the acidification of the medium during fermentation. P. scutulata had the largest number of isolates with amylolitic activity. According to the results, the bacteria Lb. brevis, Lb. plantarum and Lb. fermentum and the yeast P. scutulata showed potential as pure or mixed starter cultures for the production of sour cassava starch.