African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12496

Full Length Research Paper

Prediction of significant factors in the production of ethanol by ragi tapai co-culture using Taguchi methodology

Azlin S. Azmi1,2*, Cheng G. Ngoh1 and Maizirwan Mel2
1Department of Chemical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia. 2Department of Biotechnology Engineering, Faculty of Engineering, International Islamic University Malaysia, P.O. Box 10, 50728 Kuala Lumpur, Malaysia
Email: [email protected]

  •  Accepted: 07 November 2011
  •  Published: 16 December 2011

Abstract

Ethanol production by co-culture of ragi tapai and Saccharomyces cerevisiae from unhydrolyzed cassava starch without addition of enzymes was conducted in a 2 L batch fermentor. Taguchi’s method with orthogonal array of L8 was applied in design of experiment (DOE) and the results were analyzed using MINITAB v14 software. Seven factors: Nitrogen-phosphorus-potassium (NPK), urea, fermentation temperature, ragi tapai concentration, S. cerevisiae concentration, agitation and co-culturing time were varied at two levels for each factor. The significant factors for the production of ethanol were determined by setting S/N ratio to “larger-is-better” for high yield ethanol and “smaller-is-better” for low yield of ethanol byproducts. The optimum values obtained for each factor were similar to each other. Both have optimum factors of: Urea at 0.8 w/w%, dry ragi tapai and S. cerevisiaeconcentrations each at 10 w/w%, co-culturing time at 3 h gap, NPK at 0.09 w/w% and agitation speed at 100 rpm. The fermentation temperature for high ethanol yield was 35°C, whereas for the byproducts was 30°C. From the validation experiment conducted at 30°C in 10 L fermentor, the ethanol concentration obtained was 68.00 g/L, while all byproducts concentrations were below 9.00 g/L at the end of the fermentation.

 

Key words: Co-culture fermentation, ethanol, Taguchi’s experimental design, ragi tapai, Saccharomyces cerevisiae