Potential of Brachystegia nigerica Sawdust as Fermentation Medium for Biobutanol Production: A Preliminary Study

Abstract

The potential of Brachystegia nigerica sawdust as both fermentation medium and substrate for biobutanol production was investigated. Simultaneous saccharification and fermentation process using Clostridium acetobutylicum and Aspergillus niger as fermenting bacterium and hydrolyzing fungus respectively. Standard microbiological and biochemical methods were adopted. Fermentation of the sawdust was carried out for 120 hours. The substrate was prepared for fermentation was divided into three parts each. A part was subjected to acid pretreatment using 5% (v/v) sulphuric acid and the mixture was autoclaved at 121^oC for 15 minutes and then filtered using a sterile muslin cloth. The second part was done by alkaline pretreatment by adding 0.1 M of NaOH to the substrates and left to react for 48 hours while the third part was pretreated with 5% (v/v) H₂SO₄ for 48 hours and neutralize with 1M NaOH. The hydrolysates were inoculated with Aspergillus niger for saccharification, and left for 48 hours after which it was inoculated with Clostridium acetobutylicum for fermentation simultaneously. The hydrolysates were fermented for 120 hours and triplicate readings were taken every 24 hours to quantify the amount of biobutanol produced per day. Temperature and pH of the substrates were monitored daily for 120 hrs. Result showed that total bacterial and fungal count before fermentation was 3.6×10³ cfu/g and 2.83×10³ sfu/g respectively. Bacterial isolated were Pseudomonas aeruginosa, Bacillus cereus, Bacillus subtilis, Bacillus licheniformis, Proteus vulgaris, Bacillus badius, Bacillus lentus and Staphylococcus aureus and  fungal isolated were Saccharomyces cerevisiae, Rhizopus stolonifer, Aspergills niger, Aspergillus flavus, Penicillium notatum and Penicillium digitata. Biobutanol produced from biomass pretreated with NaOH, H₂SO₄ and Neutralized (H₂SO₄ neutralized with NaOH) as measured by Gas Chromatography Mass Spectrophotometer gives 1.75046 e^-1, 1.8367 e^-1, 1.31740 e^-1 respectively, while gravimetric analysis of biobutanol production shows no production at 24 hours, 0.52 ml, 0.75 ml, 0.44 ml at 48 hours, 1.76 ml, 1.86 ml, 0.86 ml at 72 hours, 1.32 ml, 0.62 ml, 0.51 ml at 96 hours and 0.22 ml, 0.61 ml, 0.20 ml at 120 hours respectively. This implies that biobutanol can be produced from the fermentation of Brachystegia nigerica sawdust with its highest yield at 72 hrs of fermentation thereby renewing wastes into useful products and reducing environmental pollution.

Keywords: Biobutanol; Fermentation; Sawdust; Production

DOI: 10.7176/JETP/10-7-02

Publication date: November 30^th 2020