Production, Characterization and Optimization of Bioethanol from Microalgae Obtained from Waste Water in Maiduguri Metropolitan Council, Borno State- Nigeria

Abstract

Bioethanol is a renewable, colorless, less toxic, and readily biodegradable form of fuel from biological sources; that can be used for heat, electricity, and fuel. In this research study, an alternative feedstock known as microalgae was used. Bioethanol was produced from microalgae using enzymatic hydrolysis. The microalgae was pretreated with acid and alkaline. Hydrolysis was carried out by Aspergillus niger and Saccharomyces cerevisiae was used for fermentation. The concentration of the Bioethanol produced was determined using acid Potassium Dichromate. After hydrolysis, the reducing sugar concentration was determined using Dinitrosalicylic acid (DNS) colorimetric method. Results showed that there was significant difference at p<0.05 in the yields of the reducing sugar produced between acid and alkaline pretreated samples after microbial hydrolysis. Microbial hydrolysis of alkaline pretreated samples was higher in yield. Also, the results showed that the highest bioethanol yield of 0.142ml/l was obtained after alkaline pretreated hydrolysates were fermented with Saccharomyces cerevisiae at 40°C and pH of 6.0. The highest bioethanol yield of 0.116ml/l was obtained from the acid pretreated hydrolysates at 35°C and pH of 5.5. The volatile compounds produced by alkaline pre-treated samples using Gas Chromatography Mass Spectroscopy (GCMS) shows that Ethanol and Di-n-decylsulfone were the highest volatile compounds with peak areas of 30.70% and 41.87% respectively while 2-hydroxy-1-(hydroxymethyl) ethyl ester (linolenic acid) was found to be least volatile compound with peak area of 3.34%.Tthe volatile compounds produced by acid pre-treated samples shows that 2-ethyl-2-methyltridecanol was the highest volatile compound with peak area of 23.00% while Heptacosane was found to be the least volatile compound with peak area of 1.90%. Therefore bioethanol production using alkaline pretreated samples produced a large quantity of bioethanol and may be a preferred method. This study concluded that Microalgae is a suitable substrate for bioethanol production and hydrolyzing with Aspergillus niger and optimization of fermentation conditions at pH 6.0 and 40oC yielded higher bioethanol concentration.