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

Abstract

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. ■ INTRODUCTIONGiven the widely recognized unsustainability of depending solely on petroleum for development and environmental problems, increasing efforts have been directed at synthesizing biofuels from renewable resources. 1−3 To date, several such renewable sources of energy have been developed, including ethanol from sugar cane, corn, and cassava and biodiesel from various plant oils such as coconut, palm, and rapeseed, which are also the sources of food for people and livestock. The increasing demand for ethanol and other biofuels could contribute to a global food shortage. Given this concern about the competing uses of resources for "food versus fuel", the rising scarcity and price of fossil fuels, and the need to protect global environmental resources and food security, there is an even greater need to find new, renewable, nonfood sources for biofuel production.The use of agricultural waste or byproducts and nonfood crop sources as cheap fermentation substrates to produce biofuels has high economic appeal. 4 Among nonfood crops, duckweed, a family of fast-growing, floating species that represent the world's smallest and simplest flowering plants, has been proposed as an inexpensive, sustainable source of plant biomass for producing biofuels. 5 There are many advantages to using duckweed in this regard, compared to other starch feedstocks such as corn and cassava. 6 First, duckweed h...

Succinic acid production from duckweed (Landoltia punctata) hydrolysate by batch fermentation of Actinobacillus succinogenes GXAS137

“…6%), total solids (92.5% ± 0.5%), starch (39.8% ± 0.2%), protein (12.4% ± 0.2%), cellulose (14.5% ± 0.2%), lignin (3.4% ± 0.1%) and reducing sugar (0.2% ± 0.1%) based on the dried weight (w/w). The cellulose content was in agreement with the data for L. minor in previous reports (Su et al, 2014). Starch was the main polysaccharide in the raw material.…”

“…Furfural and 5-hydroxymethyl-2-furaldehyde (HMF) in liquid fractions were also detected by HPLC. Starch, crude protein, cellulose and lignin content were determined as described by Su et al (2014). Viscosity was determined with a CNSHP NDJ-5S viscometer (Shanghai, China) at room temperature (25°C), with a paddle speed of 100 rpm.…”

Taxonomy of duckweeds (Lemnaceae), potential new crop plants

“…Apart from their use as food and feed, duckweed biomass with high starch content produced under suitable cultivation conditions (Sree and Appenroth, 2014;Sree et al, 2015a, b) can be used as a raw material for biofuel and biogas plants (Jain et al, 1992;Su et al, 2014;Cui and Cheng, 2015). This would substantially replace the use of food crops that are grown in arable lands as raw materials for biofuel production.…”

Utility of Duckweeds as Source of Biomass Energy: a Review

“…However, concentration of lipid and starch seems comparatively lower in duckweed as compared to other plant biomasses that can be further enhanced considerably through plant growth conditions manipulations (like pH, temperature and nutrient concentration in culture substrates) [24,40,[42][43][44][45]. The major constituents of carbohydrate in duckweed biomass are 20.3 % pectin (including galacturonan, xylogalacturonan, rhamnogalacturonan), 3.5 % hemicellulose (comprising xyloglucan and xylan) and 0.03 % phenolic compounds [46]. Lipid mainly comprises of long chain alcohol and acids and abundant in nitrogen contains compounds like pyrrole and indole [47].…”