Abstract
The bioethanol production from the sweet potato variety BRS Cuia using three different strains of Saccharomyces cerevisiae (LPB1-93, ATCC-26602, and CA-11) was carried out in this research. Comparative analyses of consumed sugar, ethanol yield, and productivity (in tons per hectare) increased along with the concentration of cells in the inoculum. Additionally, to verify the aromatic quality of a potential sweet potato distilled spirit, volatile organic compounds were analyzed. The results showed a yield of over 90% ethanol. It was observed that the sugar consumption and ethanol production rates can be increased with a higher initial concentration of cells. This resulted in higher concentrations of ethanol in shorter times. From 100 g of the sweet potato variety BRS Cuia, the highest concentration of ethanol obtained was 25.74 g L−1 using the LPB1-93 strain. The estimated bioethanol production is about 10,000 L ha−1, with two sweet potatoes crops in a year. The ethanol production from the sweet potato variety BRS Cuia is viable, representing a sustainable alternative to fuel bioethanol, as well as an alcoholic beverage due to the volatile organic compounds present in the distilled fraction.
Highlights
Despite the low interest in sweet potatoes, Ipomoea potatoes (L.), because it is a subsistence crop, it presents a high potential for ethanol production due to the production cost and good productivity [1]
After the distillation and recovery of the ethanol-rich fraction, volatile organic compounds (VOC) present in the distillate were analyzed in a gas chromatograph (Shimadzu, model GC17A) equipped with a HP-DB 5 column (30 m × 0.32 mm) and flame ionization detector (FID)
In the experiments using a lower inoculum size of 107 cells mL−1, the sugar consumption was slower, showing that glucose was depleted between 18 and 24 h of fermentation, as well as fructose, when consumed (Fig. 2A, C, and F). It is important for the fermentation processes to be completed with minimum of sugar content or to a point where there would not be more raw material to be consumed, especially because the sugar content in the effluent can result in environmental problems, causing losses to the industry [15]
Summary
Despite the low interest in sweet potatoes, Ipomoea potatoes (L.), because it is a subsistence crop, it presents a high potential for ethanol production due to the production cost and good productivity [1]. The offer is still very centered, about 64% of global production in China, such as shown in Fig. 1 [1]. In these regions, besides being used for human food due to its good nutritional content, sweet potatoes are of great importance for the industrial production of flour, starch, and ethanol [4] and as raw material to obtain industrialized products with higher added value as dehydrated chips, cereals, jams, jellies, flour, and pasta [5]. There is a growing interest in finding other alternative sources of ethanol production, such sweet potato, promoting possibilities where corn and sugarcane are not viable, bringing economic benefits to the fuel market [10]
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