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Electronic Journal of Biotechnology ISSN: 0717-3458 Vol. 9 No. 5, Issue of October 15, 2006
© 2006 by Pontificia Universidad Católica de Valparaíso -- Chile Received June 6, 2005 / Accepted November 21, 2005
DOI: 10.2225/vol9-issue5-fulltext-18  

Continuous gluconic acid production by Aureobasidium pullulans with and without biomass retention

Savas Anastassiadis*
Pythia Institute of Biotechnology of Research in Biotechnology
Co., Vat. #: 108851559
Avgi/Sohos, 57002
Thessaloniki, Greece
Tel. 30 2395 051324
Fax. 30 2395 051470

Hans-Jürgen Rehm
Institute of Molecular Microbiology and Biotechnology
University of Münster
Corrensstr. 3, 48149 Münster, Germany
(retired Professor)


*Corresponding author

Financial support: The work has been carried out at the Institute of Biotechnology 2 of Research Center Jülich (formerly known as Nuclear Research Center Jülich, Germany) and was financed by Haarmann and Reimer, a daughter company of the company Bayer, Leverkusen, Germany.

Keywords: biomass immobilization, continuous fermentation, cross over filtration, gluconic acid fermentation, reaction technique, residence time.


Rj: Formation rate of the generic product (volumetric productivity), g gluconic acid/(l x h), gluconic acid concentration (g/l)/RT (h), g/(l x h)
mp: Specific gluconic acid productivity, [g gluconic acid/(g biomass x h)], Rj [g/(l x h)]/biomass concentration (g/l), g/(g x h)
RT: Residence time - hours, [Bioreactor volume (ml)/(medium feeding rate (ml/h) + NaOH feeding rate (ml/h))], h
Rs: Glucose consumption rate, g/(l x h), [(g feeding glucose-g consumed glucose)/RT (h)], g/(l x h)
Conversion (%): [(g consumed glucose/g feeding glucose) x 100], dilution of medium glucose by NaOH feeding was considered in the calculations
Yield (%): [(g gluconic acid/g feeding glucose) x 100]
Selectivity (%): [(g gluconic acid/g consumed glucose) x 100]

Full Text

New alternative processes for the continuous production of gluconic acid by Aureobasidium pullulans, using biomass retention by cell immobilization or cross over filtration, are described in the present work. 315 g/l gluconic acid was continuously produced in chemostat cultures at 21 hrs residence time without any biomass retention. 260 g/l gluconic acid was produced in fluidized bed reactor at 21 hrs residence time. The support carrier was overgrown resulting in limitations of oxygen transfer towards the inner layers of immobilized biomass. 375 g/l gluconic acid was produced under continuous cultivation at 22 hrs of residence time with a formation rate for the generic product of 17 g/(l x h) and a specific gluconic acid productivity of only 0.74 g/(g x h), using biomass retention by cross over filtration. 370 g/l were obtained at 19 hrs RT and 100% conversion with 25 g/l biomass and a formation rate of 19 g/(l x h). At 100% conversion, a selectivity of only 78% was determined at 22 hrs and of 77% at 19 hrs RT, because of the very high biomass concentration. Biomass retention makes it possible to break the existing link between growth and residence time.

Supported by UNESCO / MIRCEN network
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