ABSTRACT

The production of bioethanol from corn waste was studied. The composition of the corn cob was determined using Association of Official and Analytical Chemists methods. Physicochemical analyses such as pH, temperature, total dissolved solids, total suspended solids, titratable acidity, specific gravity and reducing sugar were determined. One hundred grams (100g) of corn cob was pretreated and hydrolyzed using 1000ml of water and 20ml of 5% concentrated sulphuric acid. Ten grams (10g) of the ground corn waste was added as source of indigenous organisms. The fermentation was carried out for 7days using indigenous organisms and combination of indigenous organisms with starter culture. Ethanol yield was measured using a volumetric flask. The concentration of ethanol was done using spectrophotometric method. The indigenous bacteria and fungi were isolated using standard microbiological procedures as well as molecular identification techniques. The composition of corn cob was 6.02%, 2.21%, 0.54%, 2.28%, 0.30%, 44.02%, 32.72% and 11.30% for moisture, ash, starch, protein, fat, cellulose, hemicellulose and lignin, respectively. The physicochemical parameters tested varied with time. The pH decreased from 6.5-3.0 in both fermentation broths. Temperature was 300C in both fermentation broths. Total dissolved solids decreased from 889.00-0.80 in the fermentation broth that contained only indigenous organisms and 889.00-0.40 in fermentation broths that contained combination of indigenous organisms with starter culture. Total suspended solids increased from 104.50-314.50 and 104.50-365.50 in the fermentation broths that contained indigenous organisms and indigenous organisms with starter culture, respectively. Titratable acidity increased from 0.02-0.07 and 0.02-0.08 in fermentation broths that contained indigenous organisms and indigenous organisms with starter culture respectively. The specific gravity decreased from 1.0110-0.8281 and 1.0121-0.6120 for fermentation broths that contained indigenous organisms, and indigenous organisms with starter culture, respectively. Total reducing sugar was 38.30g and 40.98g for fermentation broths that contained indigenous organisms and indigenous organisms with starter culture, respectively. The ethanol yield using indigenous organisms were 0.0g/l, 3.0g/l, 7.0g/l, 10.0g/l, 9.0g/l, 8.5g/l and 7.5g/l while the yield using indigenous organisms with starter culture were 2.0g/l, 5.0g/l, 8.0g/l, 13.0g/l, 12.5g/l, 12.0g/l and 10.0g/l. The concentration of bioethanol produced using indigenous organisms were 0.7%, 3.2%, 11.3%, 10.3%, 9.0% and 8.4% while the concentration of bioethanol produced using indigenous organisms with starter culture were 0.3%, 1.7%, 6.5%, 13.2%, 12.0%, 10.3% and 9.0%. The indigenous bacteria were Lactobacillus casei, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Gluconobacter frateuri. The indigenous fungi were Mucor racemosus, Saccharomyces cerevisiae and Mucor circinelloides. There is variation in the genera and total number of bacteria and fungi with increase in time during ethanol production. Lactobacillus casei was able to survive in the medium even when the pH was low. This study shows that indigenous organisms in corn waste can be used in the production of bioethanol and the process is recommended as a means of generating wealth from waste.