Biochemical Engineering

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Browsing Biochemical Engineering by Subject "bacillus subtilus"

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    Production of Bioethanol from Brewery Spent Grain Using Cellulase Enzyme Hydrolysis
    (Addis Ababa University, 2018-07) Emru, Yidnekew; Eduardo, Ojito (Prof.)
    Bioethanol is a clear, colorless and mobile flammable liquid chemical compound with acceptable odour, and produced from biomass feed stocks through fermentation. The objective of this study was production of bioethanol from Barley spent grain by using cellulase enzyme hydrolysis. Decreasing of world petroleum reserves, fluctuation of petroleum price and environmental concerns, low yield cellulose acid hydrolysis and formation of inhibitory were the problem statement. Enzymatic hydrolysis method was used for cellulose hydrolysis, producing monomeric C6 sugars (glucose); enzymatic hydrolysis is more specific and high conversion rates can be achieved in long reaction times obtaining very high yields. Raw material characterization of BSG were, hemicelluloses content 28.4 %, cellulose content 27 %, and dry matter content 98.2 %. The aim of pretreatment is to disrupt recalcitrant structures of cellulosic biomass to make cellulose more accessible to the enzymes that convert carbohydrate polymers into fermentable sugars. The pretreated feedstock was mixed with 1.25 % (v/v) sulfuric acid solutions with a liquid-to-solid ratio of 20 %( w/w) and it was occurred on the temperature 121 ºC and time of 17 min, the severity factor coefficient was 0.198. Cellulase enzyme was produced from BSG using bacillus subtilus, under liquid state fermentation for 5 days at temperature of 37 ºC with pH of 5.0, in controlled incubator. For the enzyme hydrolysis, 26 full factorial central composite design (CCD) was applied to investigate the effect of temperature (40-50 ºC), pH (4.0-5.0), reaction time (24-72 hr.) and enzyme loading (1-2 %) using Design expert® 6 software. RSM was applied to investigate the interaction effect of hydrolysis process variables on the yield of ethanol from BSG. After hydrolysis process sugar content of the hydrolysate was quantified using spectrophotometer measuring its absorbance. Fermentation of the hydrolysate were performed 2.5 % Saccharomyces cerevisiae and 2.5 % fusarium oxysporum at 30 ºC temperature, pH 5.0 and 72 hr. fermentation time for all samples. Significance of the process variables were analyzed using analysis of variance. As the result of RSM optimization, the best yield of TRS was found at 40 ºC hydrolysis temperature, 4.5 PH, 48 hr. reaction time and 1.5 % v/v enzyme loading. Under these condition 96.55 %w/w and 53.68 % per 6.58 g dry barley spent grain of TRS and bio-ethanol respectively obtained.