Jabasingh, S.Anuradha Asoc (Associate Professor)Fissha, Amare2018-07-112023-11-102018-07-112023-11-102016-06http://etd.aau.edu.et/handle/12345678/8084The objective of this study was production of bioethanol from Barley spent grain by using two-stage diluted acid hydrolysis. The production process was carried out in four main stage such as pretreatment, hydrolysis (first and second stage), fermentation and distillations. The first stage diluted acid hydrolysis was used as chemical pretreatment stage and the process variables were fixed at the best optimum condition (liquid/solid ratio of 8 g/g, 100 mg H2SO4/g of dry matter, 17 min reaction time and 121oC temperature). Before the first stage hydrolysis process was carried out, the wet Barley spent grain was dried using oven at 70oC temperature for 24 hours. For the second stage hydrolysis, 23 full factorial central composite design (CCD) was applied to investigate the effect of temperature (130-150oC), reaction time (20-30min) and acid concentration (1.5-2%) using Design expert® 6 software. RSM was applied to investigate the interaction effect of hydrolysis process variables and to find the optimum yield of ethanol from BSG. After hydrolysis process sugar content of the hydrolyzate was quantified using quantitative benedict reagent solution. Fermentation of the hydrolyzate was performed using 5g/L Saccharomyces cerevisiae at 30oC temperature, pH 5.0 and 72h fermentation time for all samples. After fermentation the specific gravity of the produced alcohol was measured by pycnometer (specific gravity bottle) and alcohol concentration was obtained from the relationship between the specific gravity and the proportion of ethanol in alcohol solution at 20oC (Perry Chemical Engineering Handbook). Significance of the process variables were analyzed using analysis of variance (ANOVA) and second order polynomial function was fitted to the experimental results. Thus, the influence of all experimental variables, factors and interaction effects on the response was investigated. Hydrolysis temperature, time and interaction between temperature and acid concentration have significance effect on the yield of ethanol. As the result of RSM optimization, the best yield of TRS and bioethanol were found at 144.29oC hydrolysis temperature, 26.26 min reaction time and 1.68% w/w acid concentration. Under these condition 47.60%w/w and 8.33mL per 50 g dry barley spent grain of TRS and bio-ethanol was obtained respectively. Keywords: Bioethanol, Barley spent grains, diluted-acid hydrolysis, and Saccharomyces cerevisiaeenBioethanol; Barley spent grains; diluted-acid hydrolysis; and Saccharomyces cerevisiaeThesis