Evaluation of different genotypes of sweet sorghum juice for the production of ethanol, lactate and succinate using Saccharomyces cerevisiae and Escherichia coli

Sweet sorghum can be cultivated twice a year at diverse climates, having low requirement for fertilizer, high efficiency in water usage, and the potential to be drought resistant. Sweet sorghum juice is composed of fermentable sugars consisting of sucrose, glucose, and fructose which can be readily converted to biofuels or organic acids.  The aim of this study was evaluate the yields and composition of sweet sorghum juice from several genotypes and test the production ethanol, succinate, and lactate using those juices. Eleven different sorghum genotypes were evaluated, along with three additional commercial strains.  Ethanol yields using Saccharomyces cerevisiae (Turbo yeast) after 48 h ranged between 82% and 94% for all the juices tested, whereas with the ethanologenic Escherichia coli strain SL300 the ethanol yields varied from 89% to 98%. In the case of succinate production, E. coli strain SL200A had yields between 44% and 55%. On the other hand, lactate production was carried out using the E. coli strain SL400 with the sorghum juice and the yields varied between 70% and 95% after 96 h of fermentation. In addition to using the juice for fermentation, the fiber leftover has the potential of being used to generate lignocellulosic biochemicals. These results demonstrate the potential of using sweet sorghum for the productions of chemicals and fuels in an integrated biorefinery.