Date of Award

2014

Document Type

Thesis

First Advisor

Wang, Lijun

Abstract

In recent years, growing attention has been devoted to the conversion of biomass into biofuels and biochemicals. Biomass has several reasons to be considered as an attractive energy source. The main reason is that energy produced from biomass can contribute to sustainable development. Aquatic biomasses—microalgae, duckweed, and cattail—are considered as promising biomass sources due to their favorable characteristics such as high growth rate and low lignin content. The objective of this study was to produce biofuel- ethanol through Simultaneous Saccharification and Fermentation (SSF) of fresh algae, duckweed and cattail biomass by E. coli and to produce acetic acid by C. thermoaceticum fermentation of cattail, using ultrasonic pretreatment and 4% NaOH pretreatment, respectively. Effect of change in process parameters (Enzyme concentration, temperature, E. coli concentration) on ethanol yield and protein content was investigated for microalgae. For microalgae, highest ethanol yield at 77.7% of theoretical value was obtained at 37°C with 0.5g/L E. coli concentration, with 15 FPU cellulase/g glucan and with 0.5% (w/v) biomass concentration. The protein content of fresh algae after SSF was increased and the highest protein of the algal residue was 10%. For fresh duckweed fermentation, combined heat treatment and ultrasonic treatment resulted in the highest ethanol yield at 96% of theoretical value obtained at 37°C, 15FPU enzyme concentration and 1% (w/v) biomass concentration. For cattail, the ethanol yield at 8% of theoretical value was obtained. Although the ethanol yield from SSF of fresh cattail was very low, cattail juice was used successfully to grow microalgae Chlorella sp. Acetic acid of 0.212g/g of biomass was obtained by Clostridium fermentation of pretreated cattail. Production of acetic acid was hindered by the initial acetate concentration.

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