Sorghum Stalk Juice Pre-treatment Method for Bioethanol Fermentation Process

Sorghum stalk juice preparation method is not yet fully explored and mainly still adopting those of cane juice. The suitability of pre-treatment to remove impurities and total phenolic compound to the growth rate of yeast in sorghum stalk juice, in aerobic and anaerobic fermentation needs to be evaluated. Process adopted for this research was liming method at 80 oC followed by addition of phosphoric acid. Liming method reduces juice turbidity to 82.43% ± 0.50% and gives specific growth rate (μ) of inoculated yeast of 0.38 h–1 (aerobic) and 0.17 h–1 (anaerobic). Other method evaluated was by addition of Poly-aluminium chloride (PAC), which gives higher juice clarity but negative impact to cell growth. The effect of total phenolic compound to the microbial growth was also studied. Phenolic compound was reduced through activated carbon absorption column. Reduction of 75% total phenolic compound in sorghum stalk juice promotes yeast cell growth rate up to 10.5% in aerobic condition compared to growth in clarified juice without phenolic compound reduction.