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A microfiltration bioreactor to achieve high cell density in Sulfolobus solfataricus fermentation
C Schiraldi1, F Marulli, I Di Lernia
1Istituto di Farmacologia e Tossicologia-CRIB, Seconda Università degli Studi di Napoli Facoltà di Medicina, Naples, Italy.
Extremophiles : Life Under Extreme Conditions
|September 14, 1999
Summary
A new bioreactor design enhances extremophile fermentation by removing toxic compounds, achieving significantly higher cell yields. This method overcomes limitations in traditional batch fermentation for organisms like Sulfolobus solfataricus theta.
Area of Science:
- Biotechnology
- Microbial Physiology
- Extremophile Research
Background:
- Low biomass yields in extremophile fermentation are often attributed to the accumulation of toxic byproducts.
- Traditional fermentation methods struggle to mitigate the effects of these inhibitory compounds, limiting cell density.
Purpose of the Study:
- To develop and validate a novel bioreactor system for enhanced cell yield in extremophile fermentation.
- To investigate the efficacy of in-situ product removal using microfiltration to manage toxic compound accumulation.
Main Methods:
- A microfiltration hollow-fiber module was integrated into a conventional fermentation vessel.
- Cultivation of the thermoacidophilic archeon Sulfolobus solfataricus theta was used as a model system.
- Membrane stability was assessed under harsh sterilization, high temperature, and acidic pH conditions.
Main Results:
- A maximum biomass yield of 35 g/L dry weight was achieved, significantly outperforming the 2 g/L yield from batch fermentation.
- The integrated membrane module demonstrated high stability during prolonged operation under extreme conditions.
- Ultrafiltration and ion-exchange successfully regenerated the exhaust medium, indicating toxic compounds are ionic species <1 kDa.
Conclusions:
- The proposed bioreactor design effectively removes toxic compounds, enabling prolonged growth phases and high cell densities in extremophile fermentation.
- The system's robustness and the identification of toxic compound characteristics provide a foundation for optimizing industrial-scale extremophile cultivation.