PRODUCTION OF BIOETHANOL FROM FOUR SPECIES OF DUCKWEEDS (Landoltia punctata, Lemna aequinoctialis, Spirodela Polyrrhiza, AND Wolffia arrhiza) THROUGH OPTIMIZATION OF SACCHARIFICATION PROCESS AND FERMENTATION WITH Saccharomyces cerevisiae

Bioethanol is a form of renewable energy produced from the fermentation of sugar by Saccharomyces cerevisiae. Among potential source of new raw materials for bioethanol production are duckweeds, known with high starch content and fast growth rates. In this study, four duckweeds species, Landoltia pu...

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Bibliographic Details
Main Author: Awal Sembada, Anca
Format: Theses
Language:Indonesia
Online Access:https://digilib.itb.ac.id/gdl/view/41075
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Institution: Institut Teknologi Bandung
Language: Indonesia
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Summary:Bioethanol is a form of renewable energy produced from the fermentation of sugar by Saccharomyces cerevisiae. Among potential source of new raw materials for bioethanol production are duckweeds, known with high starch content and fast growth rates. In this study, four duckweeds species, Landoltia punctata, Lemna aequinoctialis, Spirodela polyrrhiza, and Wolffia arrhiza were cultivated on 1/10 Hoagland medium for 12 days. Starch extraction was carried out by dissolving dry biomass in sodium acetate and water at 90 oC. In this research, an optimization of the saccharification process was carried out to convert starch into simple sugars using ?-amylase and amyloglucosidase enzymes. The combination of enzymes was varied at different ratios, 1:1, 1:2, and 2:1 (v/v) respectively. In addition, the incubation time was optimized for 6, 12, 18, 24, 30, and 36 h. Furthermore, the fermentation process was carried out in batches with a fermentation time of 48 h and 10% (v/v) yeast inoculum. The results showed that the initial starch content measured in L. punctata, L. aequinoctialis, S. polyrrhiza, and W. arrhiza were 0.28, 0.257, 0.304, and 0.238 (g/g d.b.) respectively. The growth rates of each species sequentially were 0.194, 0.184, 0.176, and 0.211 days-1. The optimum sugar conversion was obtained upon addition of ?-amylase and amyloglucosidase enzymes with a ratio of 2: 1 (v/v) and incubated for 24 h at 50 oC. Longer enzymatic reactions after 24 h didn’t show a significant increase in conversion. The final sugar contents after the saccharification process in each species sequentially were 0.25, 0.233, 0.269, and 0.22 (g/g d.b.). The results of the final bioethanol concentration obtained in each species sequentially were 0.186, 0.172, 0.192, and 0.156 (g/g d.b.). The statistical analysis test showed that the conversion value of bioethanol production was determined by enzyme ratio and incubation time during saccharification process. It can be concluded that the four species of duckweed plants have the potential to be developed as a source of bioethanol raw materials.