Fuel ethanol production from cassava (Manihot esculenta Crantz) in an oscillatory baffled reactor

ABSTRACT

Simultaneous saccharification and fermentation (SSF) of cassava in an oscillatory baffled reactor (OBR) and in a stirred tank reactor (STR) was studied at various agitation regimes. At power densities of 120 W m⁻³ (OBR: Re_o, 1400; STR: 250 rpm) and 200 W m⁻³ (OBR: Re_o, 1700; STR: 300 rpm), respectively, 20–24% more ethanol and 22–28% more biomass were produced in the OBR than in the STR, even at higher cassava loadings of 5 and 10%. Average shear rates in the STR were 2 and 3 times more than in the OBR, representing a 54 and 63% reduction in shear rate in the OBR at both power levels, respectively. Hence, the yeasts and especially the enzymes were more likely to experience mechanical shear and consequent deactivation in STR than in OBR. They would be exposed to fewer pockets of high shear in the more uniform shear field in OBR than in STR. These results in principle highlight the potential of the OBR as a reactor of choice in bioethanol production and for performing other bioprocesses.

KEYWORDS:

• Bioethanol
• saccharification
• fermentation
• oscillatory baffled reactor
• stirred tank reactor

Acknowledgements

The first author wishes to acknowledge the Petroleum Technology Development Fund (PTDF) for funding this research. Special thanks also to Novozymes, Bagsvaerd, Denmark, for graciously providing the enzymes and technical support.

Additional information

Funding

The Petroleum Technology Development Fund (PTDF) is acknowledged for funding this work under OSS/PhD/2008.