Comparative analysis of Ethanol production from Sweet Sorghum and Maize stalks grown in different locations in Eastern Uganda.

Abstract

The study investigated the production of ethanol from the dilute acid Hydrolysate and their respective blends of 100%, 75%, 50%, 25% and 0% composition by sweet sorghum. The study also looked at the production of ethanol from juice extracts and their blends of 100%, 75%, 50%, 25% and 0% composition by sweet sorghum. Juice extracts and dilute acid 2% (98% H2SO4) Hydrolysate of sweet sorghum and maize stalks obtained from Serere and Kapchorwa respectively, were used as substrates for the production of ethanol using saccharomyces cerevisiae. Furthermore, the study compared the yields of ethanol from the juice extracts, blends of juice extracts, lignocellulosic Hydrolysate and blends of lignocellulosic Hydrolysate of both sweet sorghum and maize respectively. And finally, the study determined the optimal substrate blend ratios from the pure stalks and blended stalks for bio-digestion. The total sugars’ concentration in both the juice extracts of sweet sorghum and maize stalks were; 192±13.91gL-1 and 365.81±78.69gL-1 respectively, while the concentration of total sugars in the Hydrolysate of sweet sorghum and maize stalks were 172.30± 1.13gL-1 and164.52±18.37gL-1, respectively. The highest ethanol concentration was recorded from sweet sorghum stalk juice extracts; 53.360 ±3.070 gL-1 after 60h and the highest concentration of 49.11± 0.00 gL-1was obtained from maize juice extract after 72h of fermentation. The blends of juice extracts of sweet sorghum and maize stalk at the percentage composition of 75%, 50%, and 25% of sweet sorghum juice extract and the fermentation time of 12, 60, and 12 hours yielded 29.040±2.73, 48.650± 0.650, and 23.080± 2.47 gL-1 respectively. The dilute acid Hydrolysate at percentage composition of 100%, 75%, 50%, 25%, and 0%. Sweet sorghum stalk powder yielded (gL-1) 64.550±0.291, 10.390±0.080, 102.390±1.84, 14.70±0.140 and 87.280±2.450 of ethanol after fermentation time of (h) 84, 60, 60, 60 and 96 respectively. The yields from the juice extracts were highest at 100% Sweet sorghum (54.13%) and from the Hydrolysate, 100% maize stalk Hydrolysate (98.55%) followed by 100% Sweet sorghum Hydrolysate (76.76%). In all the fermentation of the substrates, each was supplemented with (gL-1); yeast 3, MgSO4.7H2O; 1, (NH4)2SO4; 1, KH2PO4; 2 and Peptone; 3.5 at the conditions of; temperature 30℃, pH 5.5, and without shaking. Therefore, the higher concentration of ethanol obtained from the juice extracts showed that ethanol can be obtained from juice extracts within a shorter period of fermentation than from the lignocellulosic. But on the other hand, the higher percentage yield of ethanol provides a support for lignocelluloses as the best feedstock for the ethanol production.