Enhancing Bioethanol Production from Azolla filiculoides through Optimization of Pretreatment and Culture Conditions with Saccharomyces cerevisiae

Purpose: Increasing human population and extreme consumption of fossil fuels create a potential to generate alternative energy sources. Bioethanol is a renewable energy resource for fossil fuels and it can be produced from low-cost raw material. This study was aimed to convert the low-value freshwater flora into high-value bioethanol using Saccharomyces cerevisiae and to optimize the conditions for yield enhancement with the Azolla filiculoides substrate.
Research Method: The freshwater flora was collected, cleaned, dried and then pre-treated with 1 M H₂SO₄ solution at 121 ⁰C for 15 min. The flora with significantly higher yields of reducing sugar and alcohol was chosen for further research. Three pre-treatment techniques, including acid (1 M H₂SO₄), enzymatic (1% α-amylase), and a combination of both (1 M H₂SO₄ and 1% α-amylase) were applied to the selected substrate. The technique that resulted in a significantly higher reducing sugar and alcohol yield was chosen.
Findings: The study revealed that Azolla filiculoides substrate produced significantly higher alcohol yield with Saccharomyces cerevisiae using combination of chemical and enzymatic pre-treatment technique. When fermentation was done at varying H₂SO₄ concentration (0.50-1.75 M), fermentation time (12-60 h), temperature (20-45⁰C), rotation speed (50- 250 rpm) and inoculum concentration (25-150 g/L), and significantly higher alcohol yield (19 times than the non-optimized) was obtained after 36 h, at 40 ⁰C and 0.75 M H₂SO₄ concentration with an inoculum concentration of 75 g/L at 200 rpm.
Originality/ Value: The study concluded that Azolla filiculoides can be used as an efficient raw material for alcohol production.