Optimization of Bioethanol Production from Sweet Sorghum Stalk (Sorghum bicolor (l.) Moench) Juice Using Response Surface Method

Abstract

The use of fossil fuel as a source of energy has been unsustainable and has adverse effects to the environment. Bioethanol is a suitable alternative due to its exceptional properties. Bioethanol production can be done through fermentation of sucrose in presence of a catalyst and as is customary for every production processes, the fermentation parameters such as the pH, duration of reaction, the catalyst concentration and the temperature need to be optimized. Thus, this study sought to optimize bioethanol production parameters from the sweet sorghum stalk juice. Sweet sorghum is potential multipurpose crop since it can be used as human food, animal feed, animal fodder and processed for syrup and bio-fuel. For this work, Sweet sorghum stalks were harvested 15 weeks after planting, crushed to extract the juice and the juice fermented in presence of biocatalyst (Saccharymyes ceresiae). A 44 Factorial design in Minitab 17 software was used to design the experimental runs. Thereafter, response surface method (SRM) and contour plots were used to determine the best operating conditions among the applied factorial combination of parameters. It was concluded that the optimal catalyst concentration was 1.5±0.5 g/l, duration of reaction was 55.25±3.25 hrs., pH was 5.0±0.25 and the temperature was 40±1.0 degrees Celsius. The chemical composition of the produced bioethanol indicated that it is a good substitute for combustion engine fuel. Thus, the bioethanol has the potential to replace the fossil gasoline as a fuel hence being friendlier to the environment.