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Research Article
ScienceAsia 31 (2005): 415-424|doi: 10.2306/scienceasia1513-1874.2005.31.415
Molecular hydrogen production by
a thermotolerant Rubrivivax gelatinosus using
raw cassava starch as an electron donor
Polson Mahakhan,a Chintana Chobvijuk,a Mongkol Ngmjarearnwong,a Savitr Trakulnalermsai,a
Christopher Bucke,b Jisnuson Svasti,c Weerasit Kanlayakritd and Lerluck Chitradona*
ABSTRACT: Thirteen strains of phototrophic purple non-sulfur bacteria selected from 226 isolates showed the
ability to digest raw cassava starch at elevated temperature, 40 ํC, under illuminated anaerobic conditions.
A selected strain, designated as SB24, produced more amylolytic enzyme activities toward raw and cooked
cassava starch, when grown in cooked starch than when grown in raw starch. SB24 showed photoproduction
of molecular hydrogen using raw cassava starch as an electron donor, when incubated with illumination
under anaerobic conditions at 40 ํC. In small scale (23 mL) culture, SB24 produced hydrogen from raw
cassava starch after 20-24 h of cultivation, with a 3-fold higher rate of H2 production and a 3-fold higher total
accumulation of hydrogen at 72 h, as compared to when it used malate as an electron donor. In the larger
scale reactor containing a 5.5 liter culture of SB24, hydrogen was produced at an earlier time using raw
cassava starch than using malate. In addition, the highest rate of H2 production (38.79 mL H2 liter culture-1 h-1) by SB24 with raw cassava starch was 7 times higher than that with malate, while the total volume of H2
accumulated with raw cassava starch (4.61 liters of H2 at 90 h) was almost two-fold higher than with malate.
Raw starch from rice, sticky rice, corn and mungbean, could also be used as electron donors for H2 production
by SB24 at 40 ํC. From morphological and biochemical characteristics, comparison of 16S rDNA sequence,
and comparative studies of the bacterial characteristics, SB24 was found to be a thermotolerant anoxygenic
phototrophic purple non-sulfur bacterium, Rubrivivax gelatinosus.
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a Department of Microbiology, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.
b School of Biosciences, University of Westminster, 115 New Cavendish St. W1W 6UW, London, UK.
c Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.
d Department of Biotechnology, Faculty of Agro-industry, Kasetsart University, Bangkok 10900, Thailand.
* Corresponding author, E-mail: fscillc@ku.ac.th
Received 16 Aug 2004,
Accepted 13 Jun 2005
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