Use of digital images to count colonies of biodiesel deteriogenic microorganisms

Camila Correa; Pedro Henrique A Konzen; Ânderson R Carvalho; Patrícia Giovanella; Fátima Menezes Bento; Marco Flores Ferrão

doi:10.1016/j.mimet.2020.106063

Use of digital images to count colonies of biodiesel deteriogenic microorganisms

J Microbiol Methods. 2020 Sep 18:178:106063. doi: 10.1016/j.mimet.2020.106063. Online ahead of print.

Authors

Camila Correa¹, Pedro Henrique A Konzen², Ânderson R Carvalho³, Patrícia Giovanella⁴, Fátima Menezes Bento⁴, Marco Flores Ferrão⁵

Affiliations

¹ Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS CEP 91501-970, Brazil. Electronic address: camilacorrea@outlook.com.br.
² Universidade Federal do Rio Grande do Sul, Instituto de Matemática e Estatística, Porto Alegre, RS CEP 91501-970, Brazil.
³ Universidade Federal do Rio Grande do Sul, Programa de Pós-Graduação em Ciências Farmacêuticas, Porto Alegre, RS CEP 90610-000, Brazil.
⁴ Universidade Federal do Rio Grande do Sul, Laboratório de Biodeterioração de Combustíveis e Biocombustíveis, Porto Alegre, RS CEP 90040-060, Brazil.
⁵ Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS CEP 91501-970, Brazil; Instituto Nacional de Ciência e Tecnologia-Bioanalítca (INCT Bioanalítica), Cidade Universitária, Zeferino Vaz s/n, Campinas, SP CEP: 13083-970, Brazil.

PMID: 32956723
DOI: 10.1016/j.mimet.2020.106063

Abstract

This work presents a novel, robust procedure for the semi-automated counting of colony-forming units of Bacillus pumilus (a bacterium) and Meyerozyma guilliermondii (a yeast) both isolated from diesel oil. 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.

Keywords: Automated counting; Biodiesel; Diesel; Image processing; Microorganisms.