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Simultaneous enumeration of yeast and bacterial cells in the context of industrial bioprocesses

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Author(s):
Martins, Carolina Teixeira ; Jacobus, Ana Paula ; Conceicao Jr, Renilson ; Barbin, Douglas Fernandes ; Bolini, Helena ; Gombert, Andreas Karoly
Total Authors: 6
Document type: Journal article
Source: Journal of Industrial Microbiology & Biotechnology; v. 51, p. 14-pg., 2024-09-11.
Abstract

In scenarios where yeast and bacterial cells coexist, it is of interest to simultaneously quantify the concentrations of both cell types, since traditional methods used to determine these concentrations individually take more time and resources. Here, we compared different methods for quantifying the fuel ethanol Saccharomyces cerevisiae PE-2 yeast strain and cells from the probiotic Lactiplantibacillus plantarum strain in microbial suspensions. Individual suspensions were prepared, mixed in 1:1 or 100:1 yeast-to-bacteria ratios, covering the range typically encountered in sugarcane biorefineries, and analyzed using bright field microscopy, manual and automatic Spread-plate and Drop-plate counting, flow cytometry (at 1:1 and 100:1 ratios), and a Coulter Counter (at 1:1 and 100:1 ratios). We observed that for yeast cell counts in the mixture (1:1 and 100:1 ratios), flow cytometry, the Coulter Counter, and both Spread-plate options (manual and automatic CFU counting) yielded statistically similar results, while the Drop-plate and microscopy-based methods gave statistically different results. For bacterial cell quantification, the microscopy-based method, Drop-plate, and both Spread-plate plating options and flow cytometry (1:1 ratio) produced no significantly different results (p > .05). In contrast, the Coulter Counter (1:1 ratio) and flow cytometry (100:1 ratio) presented results statistically different (p < .05). Additionally, quantifying bacterial cells in a mixed suspension at a 100:1 ratio wasn't possible due to an overlap between yeast cell debris and bacterial cells. We conclude that each method has limitations, advantages, and disadvantages. (AU)

FAPESP's process: 23/10728-3 - Microbial ecology in alcoholic fermentations: sample collection, DNA extraction, bioinformatics and statistical analyses
Grantee:Carolina Teixeira Martins
Support Opportunities: Scholarships in Brazil - Technical Training Program - Technical Training
FAPESP's process: 22/15256-0 - Towards understanding the microbial ecology of alcoholic fermentations in sugarcane biorefineries
Grantee:Andreas Karoly Gombert
Support Opportunities: Program for Research on Bioenergy (BIOEN) - Regular Program Grants