Evaluation of Sugar Content and Bioethanol Production of Ethiopian Local Varieties “Nech Tinkish” and “Hawaye”Sweet Sorghum (Sorghum Bicolor (L.)

Abstract

Diversifying the use of climate-smart crops such as Sweet sorghum has the potential to solve integrated food, bioenergy, feed, and land management problems. The study purposed to quantify the sugar content of Nech Tinkish (v1) and Hawaye (v2) indigenous sweet sorghum varieties and investigate the interaction effect of fermentation parameters to determine their capacity for ethanol production. Sweet sorghum varieties were analyzed to determine their difference in oBrix content by extracting their juices. The juice was clarified using milk lime. Its total soluble sugars, total carbohydrates, and reducing sugars were determined using a digital Refractometer, phenol sulfuric acid, and 3, 5-Dinitro salicylic acid, respectively. A completely Randomized Factorial was employed to evaluate ethanol production capacity, and the ethanol content was estimated using a potassium dichromate solution. The oBrix results revealed that v2 had a higher sugar concentration than v1. Additionally, the estimated carbohydrate content of the juice ranged from 37.402 g/L to 157.641 g/L. The estimated reducing sugar also varied from 4.644 g/L to 33.412 g/L. Therefore, the estimated reducing sugar showed the hydrolysis of Sweet sorghum juice by invertase and sulfuric acid produced more fermentable sugars. Fermentation at 30 oC with pH 4.5 incubated for four days yields the highest ethanol, and v2 yields higher (15.31%) ethanol, compared to v1 produced 15.31%. This study showed a basis for the existence of two sugar-rich climate smart sweet sorghum varieties with an extraordinary amount of sugar used as a source of biofuel and food simultaneously in a single plot of land.