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首页> 外文期刊>Applied Microbiology and Biotechnology >Two different pathways for D-xylose metabolism and the effect of xylose concentration on the yield coefficient of L-lactate in mixed-acid fermentation by the lactic acid bacterium Lactococcus lactis IO-1
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Two different pathways for D-xylose metabolism and the effect of xylose concentration on the yield coefficient of L-lactate in mixed-acid fermentation by the lactic acid bacterium Lactococcus lactis IO-1

机译：D-木糖代谢的两种不同途径以及木糖浓度对乳酸菌乳酸乳球菌IO-1混合酸发酵中L-乳酸产量系数的影响

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摘要

In lactic acid bacteria, pentoses are metabolized via the phosphoketolase pathway, which catalyzes the cleavage of D-xylulose-5-phosphate to equimolar amounts of glyceraldehyde 3-phosphate and acetylphosphate. Hence the yield coefficient of lactate from pentose does not exceed 1.0 mol/mol, while that of Lactococcus lactis IO-1(JCM7638) at high D-xylose concentrations often exceeds the theoretical value. This suggests that, in addition to the phosphoketolase pathway, L. lactis IO-1 may possess another metabolic pathway that produces only lactic acid from xylose. In the present study, the metabolism of xylose in L. lactis IO-1 was deduced from the product formation and enzyme activities of L. lactis IO-1 in batch culture and continuous culture. During cultivation with xylose concentrations above ca. 50 g/l, the yield coefficient of L-lactate exceeded 1.0 mol/mol while those of acetate, formate and ethanol were very low. At xylose concentrations less than 5 g/l, acetate, formate and ethanol were produced with yield coefficients of about 1.0 mol/mol, while L-lactate was scarcely produced. In cells grown at high xylose concentrations, a marked decrease in the specific activities of phosphoketolase and pyruvate formate lyase (PFL), and an increase in those of transketolase and transaldolase were observed. These results indicate that in L. lactis IO-1 xylose may be catabolized by two different pathways, the phosphoketolase pathway yielding acetate, formate and ethanol, and the pentose phosphate (PP)/glycolytic pathway which converts xylose to L-lactate only. Furthermore, it was deduced that the change in the xylose concentration in the culture medium shifts xylulose 5-phosphate metabolism between the phosphoketolase pathway and the PP/glycolytic pathway in L. lactis IO-1, and pyruvate metabolism between cleavage to acetyl-CoA and formic acid by PFL and the reduction to L-lactate by lactate dehydrogenase.
机译：在乳酸菌中，戊糖通过磷酸酮醇酶途径代谢，该酶催化D-木酮糖5-磷酸酶裂解为等摩尔量的3-磷酸甘油醛和乙酰磷酸酯。因此，戊糖中乳酸的产率系数不超过1.0mol / mol，而在高D-木糖浓度下乳酸乳球菌IO-1（JCM7638）的产率系数通常超过理论值。这表明，除了磷酸酮醇酶途径之外，乳酸乳球菌IO-1还可能具有另一种代谢途径，其仅从木糖产生乳酸。在本研究中，乳酸乳杆菌IO-1中木糖的代谢是由乳酸乳杆菌IO-1在分批培养和连续培养中的产物形成和酶活性推导的。在培养期间，木糖浓度高于约。 50 g / l，L-乳酸的产率系数超过1.0 mol / mol，而乙酸盐，甲酸和乙醇的产率非常低。在木糖浓度小于5 g / l时，产生乙酸盐，甲酸盐和乙醇，产率系数约为1.0 mol / mol，而几乎不产生L-乳酸盐。在高木糖浓度下生长的细胞中，观察到磷酸酮醇酶和丙酮酸甲酸裂解酶（PFL）的比活性显着下降，而转酮醇酶和反式醛缩酶的比活性显着增加。这些结果表明，在乳酸乳球菌中，IO-1木糖可能通过两种不同的途径被分解代谢，磷酸酮醇酶途径产生乙酸盐，甲酸盐和乙醇，而戊糖磷酸酯（PP）/糖酵解途径仅将木糖转化为L-乳酸盐。此外，据推断，培养基中木糖浓度的变化使乳酸乳球菌IO-1中的磷酸酮醇酶途径和PP /糖酵解途径之间的木酮糖5-磷酸代谢发生了转移，并且在裂解成乙酰辅酶A和PFL还原成甲酸，乳酸脱氢酶还原成L-乳酸。

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  • 来源
    《Applied Microbiology and Biotechnology》 |2002年第2期|160-167|共8页
  • 作者

    K. Tanaka; A. Komiyama; K. Sonomoto; A. Ishizaki; S. Hall; P. Stanbury;

  • 作者单位

    Department of Biological and Environmental Chemistry Kyushu School of Engineering Kinki University Kayanomori Iizuka-si Fukuoka 820–8555 Japan;

    Division of Bioscience and Biotechnology Graduate School of Bioresource and Bioenvironmental Science Kyushu University 6–10–1 Hakozaki Higashi-ku Fukuoka 812–8581 Japan;

    Division of Bioscience and Biotechnology Graduate School of Bioresource and Bioenvironmental Science Kyushu University 6–10–1 Hakozaki Higashi-ku Fukuoka 812–8581 Japan;

    Division of Bioscience and Biotechnology Graduate School of Bioresource and Bioenvironmental Science Kyushu University 6–10–1 Hakozaki Higashi-ku Fukuoka 812–8581 Japan;

    Division of Chemistry University of Hertfordshire Hatfield Herts. AL10 9AB UK;

    Department of Bioscience University of Hertfordshire Hatfield Herts. AL10 9AB UK;

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