Impact and significance of microbial contamination during fermentation for bioethanol production

Ramon Peres Brexó, Anderson S. Sant’Ana

Department of Food Science, Faculty of Food Engineering, University of Campinas, Campinas, SP, Brazil.

Abstract

The bioethanol visibility in the global matrix of fuels, linked to ecological appeal and the possibility of using new raw materials justifies the increasing investments for the development of new processes. This fuel results from fermentation of sugars by yeasts, however the growth of exogenous microorganisms is sometimes unavoidable. The lactic acid bacteria and wild yeasts are the main contaminants, affecting yeasts’ performance and leading to negative impacts such as the formation of organic acids, polysaccharides and gummy biofilms. Further undesirable effects of the microbial contamination during bioethanol processing comprise flocculation, reduction of yeast cells viability and decrease in process yield. In extreme cases, the reduction in process yield can reach 20–30%, making the process impracticable. In this article, the impact and significance of microbial contaminants (lactic acid bacteria and wild yeasts) during fermentation of must for bioethanol production are reviewed.

Graphical abstract

Keywords: Ethanol; Bioenergy; Fuel; Feedstock; Wild yeasts; Saccharomyces; Lactic acid bacteria; Bioprocesses, microbial contamination; Sugarcane.