Characterization of Starch from Duckweeds and Its Conversion Into Reducing Sugars Via Enzymatic Saccharification

Abstract

Background and Objective: Bioethanol derived from plants is a renewable energy source and promising alternative to fossil fuels. It can be produced from plant starch by fermentation, but the starch must first be broken down to sugars, a process known as saccharification. Duckweeds are small, fast-growing plants that are easy to cultivate and accumulate high levels of starch and hold promise as a bioethanol source. Here, the growth parameters and starch content of three species of duckweeds were examined and assessed the efficiency of enzymatic saccharification. Materials and Methods: The duckweeds used in this study were Landoltia punctata, Lemna aequinoctialis and Wolffia arrhiza. The saccharification process was performed at 50EC for 24 hrs. Three starch-degrading enzymes were assessed in the saccharification process, specifically, "-amylase, $-amylase and glucoamylase, in equal amounts (1 mL per mg starch) but four different combinations. Results: The measured doubling times were, respectively, 3.57±0.02, 3.77±0.07 and 3.94±0.04 days and the initial starch contents were 0.28±0.02, 0.26±0.01 and 0.24±0.02 g/g. The greatest percentage of starch conversion to sugar was observed when all three enzymes were used in saccharification. The conversion percentages were 82.0±1.3%, 80.8±1.9% and 81.4±1%, for L. punctata, L. aequinoctialis and W. arrhiza, respectively. Conclusion: Results concluded that duckweeds have the potential to serve as a substrate in the fermentation process to produce bioethanol and other products.

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