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BMC Biotechnol. 2017 Aug 1;17(1):63. doi: 10.1186/s12896-017-0385-y.

Effect of acetic acid on ethanol production by Zymomonas mobilis mutant strains through continuous adaptation.

Author information

1
Division of Allergy, Department of Pediatrics, Chung-Shan Medical University Hospital, Taichung, Taiwan.
2
Department of Biomedical Sciences, College of Medicine Sciences and Technology, Chung Shan Medical University, Taichung, Taiwan.
3
Department of Microbiology, Immunology and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan. cwhsieh@mail.ncyu.edu.tw.
4
Department of Microbiology, Immunology and Biopharmaceuticals, National Chiayi University, Chiayi, Taiwan.

Abstract

BACKGROUND:

Acetic acid is a predominant by-product of lignocellulosic biofuel process, which inhibits microbial biocatalysts. Development of bacterial strains that are tolerant to acetic acid is challenging due to poor understanding of the underlying molecular mechanisms.

RESULTS:

In this study, we generated and characterized two acetic acid-tolerant strains of Zymomonas mobilis using N-methyl-N'-nitro-N-nitrosoguanidine (NTG)-acetate adaptive breeding. Two mutants, ZMA-142 and ZMA-167, were obtained, showing a significant growth rate at a concentration of 244 mM sodium acetate, while the growth of Z. mobilis ATCC 31823 were completely inhibited in presence of 195 mM sodium acetate. Our data showed that acetate-tolerance of ZMA-167 was attributed to a co-transcription of nhaA from ZMO0117, whereas the co-transcription was absent in ATCC 31823 and ZMA-142. Moreover, ZMA-142 and ZMA-167 exhibited a converstion rate (practical ethanol yield to theorical ethanol yield) of 90.16% and 86% at 195 mM acetate-pH 5 stress condition, respectively. We showed that acid adaptation of ZMA-142 and ZMA-167 to 146 mM acetate increased ZMA-142 and ZMA-167 resulted in an increase in ethanol yield by 32.21% and 21.16% under 195 mM acetate-pH 5 stress condition, respectively.

CONCLUSION:

The results indicate the acetate-adaptive seed culture of acetate-tolerant strains, ZMA-142 and ZMA-167, could enhance the ethanol production during fermentation.

KEYWORDS:

Acetic acid; Acid adaptation; Bioethanol; Lignocellulosic hydrolysates; Zymomonas mobilis

PMID:
28764759
PMCID:
PMC5540488
DOI:
10.1186/s12896-017-0385-y
[Indexed for MEDLINE]
Free PMC Article

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