Adaptation of Clostridiumtyrobutyricum for Enhanced Tolerance to Butyric Acid in a Fibrous‐Bed Bioreactor

Biotechnology Progress - Tập 19 Số 2 - Trang 365-372 - 2003
Ying Zhu1, Shang‐Tian Yang1
1Department of Chemical Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, Ohio, 43210

Tóm tắt

AbstractBy immobilization in a fibrous‐bed bioreactor (FBB), we succeeded in adapting and selecting an acid‐tolerant strain of Clostridium tyrobutyricumthat can produce high concentrations of butyrate from glucose and xylose. This mutant grew well under high butyrate concentrations (>30 g/L) and had better fermentative ability as compared to the wild‐type strain used to seed the bioreactor. Kinetic analysis of butyrate inhibition on cell growth, acid‐forming enzymes, and ATPase activity showed that the adapted cells from the FBB are physiologically different from the original wild type. Compared to the wild type, the adapted cultureapos;s maximum specific growth rate increased by 2.3‐fold and its growth tolerance to butyrate inhibition increased by 29‐fold. The key enzymes in the butyrate‐forming pathway, phosphotransbutyrylase (PTB) and butyrate kinase (BK), were also more active in the mutant, with 175% higher PTB and 146% higher BK activities. Also, the mutantapos;s ATPase was less sensitive to inhibition by butyric acid, as indicated by a 4‐fold increase in the inhibition rate constant, and was more resistant to the enzyme inhibitor N, N′‐dicyclohexylcarbodiimide (DCCD). The lower ATPase sensitivity to butyrate inhibition might have contributed to the increased growth tolerance to butyrate inhibition, which also might be attributed to the higher percentage of saturated fatty acids in the membrane phospholipids (74% in the mutant vs 69% in the wild type). This study shows that cell immobilization in the FBB provides an effective means for in‐process adaptation and selection of mutant with higher tolerance to inhibitory fermentation product.

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Biotechnology Progress

Tập 19 Số 2

365-372

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