Production of bioethanol from guinea grass (Panicummaximum) and ragi tempeh as Fermentation starter using bioreactor and shaker

Nowadays, the depletion of fossil fuels as prime source of energy is a serious issue that trigger the research and development of biofuel. Biofuel as renewable fuel source is sustainable and less carbon emission to environment compare to fossil fuels. Currently, the first- and second-generation biofuel has high potential to be commercialise, especially second-generation biofuel that using lignocellulosic feedstock as material that would not compete with edible food crops. This study was investigating the production of bioethanol from the mixture of guinea grass (Panicum maximum) and using ragi tempeh through fermentation. The acid pretreatment process was carried out using 15% v/v sulphuric acid, it is considered as concentrated acid pretreatment and the reason for selecting this method is because it release higher amount of glucose compare with diluted acid pretreatment process, with concentration of 0.6%, 0.9%, 1.2%, 1.5%, and 5.0% at most. The fermentation was carried out in anaerobic condition using bioreactor and shaker at 37°C and different pH of 5,6,7, and 8. Freezing test and Tollens’ test result showed very ethanol concentration in the sample product is very low, and aldehyde compounds, which is the inhibitory substance for microorganisms’ activity during ethanoic fermentation is present in product sample. The aldehyde is releases due to degradation of lignocellulosic feedstock by acid hydrolysis. FTIR and HPLC is carried out for getting more accurate result. FTIR result showed the major component of recovered sample is water, beside water the major component for the sample wasn’t ethanol, it is suspected to be lactic acid, glucose, or aldehyde. The best result that showed higher ethanol yield is 7.89%, obtained by fermentation using shaker at pH 8 for 48 hours.