EFFECTS OF SELECTED FUNGAL SPECIES ON PRODUCTION OF BIOETHANOL USING THEOBROMACACAO POD

Abstract

The use of agricultural wastes as a bioenergy source has aroused increasing interest in the bioenergy sector and combustion of fossil fuel has been posing threat to the environment, therefore the search for an alternative means of fuel that will be environmental friendly was necessary. The aim was to produce bioethanol from cocoa pods (fresh and dry) following simultaneous sacharification and fermentation method using Sacharomyces cerevisiae and Aspergilus niger for 10 days. Isolation and identification of microorganisms, proximate and mineral composition, lignocellulosic content, fibre fractions, fermentation temperature, pH and bioethanol yield were determined using standard methods. Data were analysed and means were separated using ANOVA at p≤0.05. The results revealed total bacterial load of 4.5 x 105cfu/g and fungal load of 3.4 x 103 sfu/g before fermentation. Bacteria isolated include; Pseudomonas aeruginosa, Bacillus cereus, B. subtilis, Proteus vulgaris, Serratia marcescens, Klebsiella oxytoca and Staphylococcus aureus, while fungi isolated include; Rhizopus stolonifer, Aspergillus niger, Penicillium digitatum, Aspergillus flavus, and Saccaromyces cerevisiae. There was significant differences in proximate, mineral and lignocellulosic composition. Proximate composition of fresh cocoa pod showed high moisture content of 52.07±0.61 % and low ash content of 2.72±0.11 %, while those of dry cocoa pod recorded high crude fat of 24.83±0.03 % and low carbohydrate of 5.67±0.09 %. Mineral content of fresh cocoa pod revealed high Potassium (K) composition of 373.33±0.34 mg/kg and low Iron (Fe) composition of 3.31±0.13 mg/kg while dry cocoa pod also revealed high Potassium (K) composition of 311.00±0.00 mg/kg and low Iron (Fe) of 4.21±0.00 mg/kg. Other mineral compositions are Sodium (Na), Calcium (Ca) and Magnesium (Mg). Generally, it was observed that there was no production of ethanol on day 1, 2, 9 and 10 during fermentation period, but there was increase on day 4, 5, 6. and decrease in the ethanol yield after day 7 and 8. The highest ethanol yield was recorded at day 6 with fresh cocoa pod treated with neutral solution generated 24.88 v/v bioethanol yield, while for dry cocoa pod highest bioethanol was recorded at day 5 producing 15.68 v/v. The comparison of the bioethanol in this research revealed that the appearance and burning characteristics are the same, relative density, boiling point and flash point of bioethanol yield were lower than those of commercial ethanol however, melting point and viscosity of bioethanol yield were higher than those of commercial ethanol. Therefore, Saccharomyces cerevisiae and Aspergillus niger could be used for the fermentation of wet and dry cocoa pod for production of bioethanol.