Abstract
A major concern of ethanol production plants is the control of native microorganisms mainly derived from the sugarcane juice that may reduce the fermentative yield. In the wine industry, the sulphur dioxide (SO 2 ) is commonly used to control the undesirable populations of yeast and bacteria, however, this substance has not been evaluated yet in the context of the ethanol industry. This study aimed to verify the effect of different concentrations and incubation times of potassium metabisulphite (PMB), as a source of SO 2 , with raw sugarcane juice in order to control the growth of native bacteria and yeasts. PMB was effective to control the growth of native yeasts and bacteria from the sugarcane juice at the concentration of 800 mg L -1 , reducing almost one log cycle for yeasts and 1.9-2.9 log cycles for bacteria, with incubation times of 3 and 6-9 hours, respectively. Although PMB is effective in the context of wine fermentation, it was not appropriate to the fuel ethanol production especially due to the peculiar characteristics of the substrate and also to the cost in terms of high doses of the antimicrobial and the volumes of sugarcane juice to be treated daily.
Highlights
Sugarcane juice, as the culture medium for alcoholic fermentation for fuel ethanol production, has a diverse composition that may affect several industrial operating parameters, especially the fermentative yield
Bacteria and yeasts are the main microorganisms that enter the industrial process through the equipments or because they live inside the sugarcane
The ethanol-producing plant commonly employs an acid treatment to control the microbial growth. This treatment is performed at the end of each fermentative cycle by adding sulphuric acid to decrease the flocculation caused by bacteria. It consists of the acid treatment of the yeast cells in an acid solution prepared with sulphuric acid at pH 1.8-2.5 for 2-3 hours
Summary
As the culture medium for alcoholic fermentation for fuel ethanol production, has a diverse composition that may affect several industrial operating parameters, especially the fermentative yield. The ethanol-producing plant commonly employs an acid treatment to control the microbial growth This treatment is performed at the end of each fermentative cycle by adding sulphuric acid to decrease the flocculation caused by bacteria. It consists of the acid treatment of the yeast cells in an acid solution prepared with sulphuric acid at pH 1.8-2.5 for 2-3 hours. The cell mass returns to the tank for a new round of fermentation (Amorim, Lopes, Oliveira, Buckeridge, & Goldman, 2011). This treatment is not always effective against native yeasts or when the bacterial contamination is high
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