Sweet sorghum is a promising energy crop for biofuel production due to its low input requirements, wide environmental adaptability, and high productivity (Mathur et al., 2017, Cheng et al., 2020). Sugars stored in sorghum stems are readily available for bioethanol conversion after harvest. Sucrose, fructose, and glucose are the three major sugars in sorghum juice (Kawahigashi et al., 2013). However, a wide range of Brix content is observed among different sorghum varieties. Genetic engineering and breeding technologies have been commonly applied to increase sugar content in sorghum stems (Bandara et al., 2020, Liu et al., 2021). In this study, the sugar concentration of sorghum juices collected from six sorghum inbreds and two seed set treatments were investigated. The sugar concentration ranging from one to 15 g/100ml was observed. The sorghum treated with bagging to prevent seed set resulted in a threefold higher sugar concentration than the sorghum allowed to set seed. Additionally, the high sugar tolerant ethanol red yeast was used to ferment sorghum sugar into ethanol. The rate of fermentation was fast, and all the sugars were completely depleted within 12 h, and the ethanol titers ranging from 59 to 65 ml/L were observed. The maximum theoretical ethanol yield of 95.87% was obtained for selected inbred. From the results, seed set treatments and sorghum genotype affected the juice sugar concentration. However, the theoretical ethanol yields were observed over 85%, regardless of various sugar concentrations derived from different sorghum inbreds and seed set treatments.
Reference:
Mathur, S., Umakanth, A.V., Tonapi, V.A., Sharma, R., Sharma, M.K., 2017. Sweet sorghum as biofuel feedstock: recent advances and available resources. Biotechnol. Biofuels. 10, 146.
Cheng, M.-H., Kadhum, H.J., Murthy, G.S., Dien, B.S., Singh, V., 2020. High solids loading biorefinery for the production of cellulosic sugars from bioenergy sorghum. Bioresour. Technol. 318, 124051.
Bandara, A.Y., Weerasooriya, D.K., Gobena, D.D., Hopper, D.J., Tesso, T.T., Little, C.R., 2020. Improving sweet sorghum for enhancing juice traits and biomass. Plant Breed. 139, 131-140.
Liu, G., Zhang Y., Gong, H., Li, S., Pan, Y., Davis, C., Jin, H-C., Wu, L., Godwin, I.D., 2021. Stem vacuole-targetted sucrose isomerase enhances sugar content in sorghum. Biotechnol. Biofuels. 14, 53
