Use of digital images to count colonies of biodiesel deteriogenic microorganisms.

Abstract This work presents a novel, robust procedure for the semi-automated counting of colony-forming units of isolated Bacillus pumilus (a bacterium) found in biodiesel and Meyerozyma guilliermondii (a yeast) found in diesel. The counting is performed from digital images of Petri dishes containing the samples by a developed Python code, and the images are acquired from a low-cost scanning apparatus. The counting algorithm is based on the similar morphological characteristics of the bacterium and the yeast colonies. It was compared with classical counting methodology, and the results showed calibration and validation curves with a coefficient of determination (R2) of 0.99 and 0.98, respectively. The developed methodology is a valuable alternative to estimate the microbial contamination of biofuels.