High doses of potassium metabisulphite are required to control the growth of native bacteria and yeasts from sugarcane juice

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 (SO2) 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 SO2, 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.