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Higher thermostability of l-lactate dehydrogenases is a key factor in decreasing the optical purity of d-lactic acid produced from Lactobacillus coryniformis

Paper ID Volume ID Publish Year Pages File Format Full-Text
17202 42651 2014 7 PDF Available
Title
Higher thermostability of l-lactate dehydrogenases is a key factor in decreasing the optical purity of d-lactic acid produced from Lactobacillus coryniformis
Abstract

•Lactobacillus coryniformis subsp. torquens KCTC 3535 was selected as the d-lactic acid producer.•The optical purity of d-lactic acid was decreased at culture temperatures above 40 °C.•d-LDH1 is the key responsible enzyme for the production of d-lactic acid.•Thermostable l-LDH2 and l-LDH3 are candidates for deteriorating the optical purity of d-lactic acid.

Lactobacillus coryniformis is known to produce d-lactic acid as a dominant fermentation product at a cultivation temperature of approximately 30 °C. However, the considerable production of l-lactic acid is observed when the fermentation temperature is greater than 40 °C. Because optically pure lactates are synthesized from pyruvate by the catalysis of chiral-specific d- or l-lactate dehydrogenase, the higher thermostability of l-LDHs is assumed to be one of the key factors decreasing the optical purity of d-lactic acid produced from L. coryniformis at high temperature. To verify this hypothesis, two types of d-ldh genes and six types of l-ldh genes based on the genomic information of L. coryniformis were synthesized and expressed in Escherichia coli. Among the LDHs tested, five LDHs showed activity and were used to construct polyclonal antibodies. d-LDH1, l-LDH2, and l-LDH3 were found to be expressed in L. coryniformis by Western blotting analysis. The half-life values (t1/2) of the LDHs at 40 °C were estimated to be 10.50, 41.76, and 2311 min, and the T5010 values were 39.50, 39.90, and 58.60 °C, respectively. In addition, the Tm values were 36.0, 41.0, and 62.4 °C, respectively, which indicates that l-LDH has greater thermostability than d-LDH. The higher thermostability of l-LDHs compared with that of d-LDH1 may be a major reason why the enantiopurity of d-lactic acid is decreased at high fermentation temperatures. The key enzymes characterized will suggest a direction for the design of genetically modified lactic acid bacteria to produce optically pure d-lactic acid.

Keywords
Lactic acid bacteria; Lactate dehydrogenase; Lactic acid; Enantiopurity
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Higher thermostability of l-lactate dehydrogenases is a key factor in decreasing the optical purity of d-lactic acid produced from Lactobacillus coryniformis
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volumes 58–59, 10 May 2014, Pages 29–35
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us