Enriching Duckweed As an Energy Crop for Producing Biobutanol Using Enzyme Hydrolysis Pretreatments and Strengthening Fermentation Process Using pH-stat

Large scale production of biobutanol from a lignocellulosic feedstock for alternative fossil fuels consumption has garnered much interest by researchers in renewable energy. However, making biobutanol from lignocellulose requires the development of novel, renewable, nonfood sources for biofuel production and sustainable biorefining technology that maximizes the utilization of feedstock is indispensable. Duckweed (<i>Lemnaceae</i>) is a family of aquatic plants that in early trials has demonstrated great potential as an alternative nonfood energy feedstock for ethanol production. However, research on methods to obtain higher biobutanol yield from this plant is thus far insufficient. In this study, we tested several hydrolysis procedures with different enzyme combinations for duckweed pretreatment in detail. We then assessed the efficiency of these treatments for biobutanol production via fermentation with <i>Clostridium acetobutylicum</i>, using separate hydrolysis and fermentation (SHF) and simultaneous saccharification fermentation (SSF) and modulation of pH with pH-stat. The highest concentration of butanol and total solvent produced via SHF were 11.63 g/L and 24.06 g/L, respectively, using an enzyme hydrolysis method 4 (EHM4) with pH control. With SSF and controlled pH, butanol and total solvent concentrations achieved by EHM4 were 13.56 and 26.78 g/L, respectively, which was 14% and 10% higher than with SHF. Our results also show that duckweed is a promising feedstock for biobutanol production via comparison experiments. This study shows an additional advantage of using duckweed as a fermentation substrate is the potential to use simple enzyme hydrolysis instead of complex pretreatment. Having demonstrated the greatest butanol yield thus far, this study indicates that duckweed is a very promising bioenergy crop for industrial biobutanol development