Use of Duckweed (Landoltia punctata) as a Fermentation Substrate for the Production of Higher Alcohols as Biofuels

Duckweed (Lemnaceae) is a family of aquatic plants with potential for use as the next generation of alternative energy feedstocks, yet little related information about producing higher alcohols from duckweed has been published. We investigated the process of producing higher alcohols from duckweed via fermentation. Results showed that these plants have a promising future as the basis for developing biofuels. This could be achieved through fermentation by yeasts, producing not only traditional forms of energy such as ethanol but also higher alcohols with high energy yields through bioconversion by Clostridium acetobutylicum, mutant yeast strains, and bioengineered strains of Escherichia coli. The concentrations of butanol and total solvent produced via fermentation by C. acetobutylicum CICC 8012 were 12.03 and 20.03 g/L using acid hydrolysate of duckweed versus 12.33 and 20.05 g/L using enzymatic hydrolysate. The yields obtained of 24.06 g/L ethanol and 680.36 mg/L of isopentanol from duckweed using acid hydrolysate are 15 times higher than what could be obtained through the fermentation of the mutation of yeast. In addition, we were able to obtain yields of 16.27 mg/L butanol, 24.68 mg/L isopentanol, and 195.85 mg/L pentanol from the acid hydrolysate of duckweed via fermentation by the bioengineered strains of E. coli. Our results illustrated that duckweed represent an ideal fermentation substrate: they require only simple pretreatment, without the need for supplementary nitrogen or strengthening with redox agents. This provides a foundation for further development of industrialized biofuel production using duckweed.