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Research Journal of Microbiology
Year: 2006  |  Volume: 1  |  Issue: 3  |  Page No.: 234 - 242

Application of Factorial Design to Polyhydroxyalkanoate Production by Recombinant Escherichia coli

Gustavo Graciano Fonseca and Regina Vasconcellos Antonio    

Abstract: Polyhydroxyalkanoates (PHAs) are biodegradable, thermoplastic polyesters produced from renewable carbon sources by a number of bacteria. However, their application is limited by high production costs. One of the strategies aimed to reduce their costs is the development of recombinant strains able to utilize different carbon sources. The optimal conditions for 3-hydroxybutyrate (P[3HB]) production by the recombinant Escherichia coli strain JM101, harboring Ralstonia eutropha PHA biosynthesis genes, in a defined medium containing hydrolyzed corn starch and soybean oil as carbon sources and cheese whey as a supplement had been established earlier. In order to optimize PHA production, the present study investigated the influence of other variables, such as isopropyl-1-thio-β-D-galactopyranoside (IPTG) and acrylic acid addition, temperature, inoculum size and cultivation time, on dry cell weight (DCW) and PHA accumulation through a 25 factorial design. Statistical models suggested that quite good PHA production performances would be obtained in E. coli JM101 cultures grown in a medium lacking IPTG and acrylic acid with an inoculum size of 5% (v/v) and performed at 37°C for 96 h. Theoretically, about 3.5 g L-1 DCW and 75% PHA could be accumulated. Acrylic acid had a negative effect on DCW at its high level (1 mmol) and was unable to promote incorporation of medium-chain-length units into PHA polymers as expected. Remarkably, IPTG, a very expensive inducer of PHA synthesis gene expression had no influence on PHA production.

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