Potential Use of Native Yeasts to Produce Bioethanol and Other Byproducts from Black Sugarcane, an Alternative to Increment the Subsistence Farming in Northern Ecuador

The high consumption of energy, mainly in the automotive sector, is supplied by fossil fuels, which, when combusted, generate polluting gases leading to the great problem of climate change. This has led society to seek alternatives. Bioethanol is a biofuel that can be obtained from the fermentation of different raw materials rich in sucrose such as sugarcane, which can be mixed with gasoline and used to reduce polluting emissions. The following investigation focused on studying the efficiency of three selected native yeasts in the fermentation of black sugarcane POJ 27-14 variety juice to produce bioethanol and other byproducts of biotechnological interest. A comparison between the size of the inoculum of three selected native yeasts (Lev6, Lev9, and Lev30) and two reference commercial controls in the fermentation process was performed. The phylogenetic classification was carried out based on the analysis of the internal transcribed spacer 1 sequence, 5.8S ribosomal RNA, and internal transcribed spacer 2. Lev6 and Lev30 were classified as Saccharomyces cerevisiae, while Lev9 was Candida intermedia, with 99% nucleotide sequence identity. The results showed that the optimal growth temperature was 30 ffiC with constant agitation (200 rpm) for biomass production. The Lev30 strain presented the highest yield in the production of biomass from sugarcane juice fermentation, while the Lev6 strain presented the highest yield in ethanol production. Additionally, among native yeasts, Lev6 registered the highest ethanol concentration (Q) and volumetric productivity (Qp) values of 0.61 (g/L/h) and 43.92 g/L, respectively, which were comparable with the control yeasts. The gas chromatography coupled to mass spectrometry (GC-MS) indicated the presence of ethanol in all samples (98% to 99% relative percentages) along with some therapeutic substances such as (2-aziridinylethyl) amine and tetraacetyl-d-xylonic nitrile with greater efficiency than commercial controls from the alcoholic fermentation of black sugarcane juice.

Automated summary

The study focused on the production of bioethanol, specifically looking at the efficiency of native yeasts in fermenting black sugarcane juice. Results showed that the Lev6 and Lev30 strains were highly efficient in biomass and ethanol production, with Lev6 exhibiting the highest ethanol concentration and volumetric productivity. Gas chromatography coupled to mass spectrometry indicated the presence of ethanol and therapeutic substances in all samples, showing greater efficiency than commercial controls in alcoholic fermentation of black sugarcane juice.