Effect of oxygenation and temperature on glucose-xylose fermentation in Kluyveromyces marxianus CBS712 strain

Microbial Cell Factories

Research

Paola Branduardi¹  Lorenzo Signori¹  Danilo Porro¹  Simone Passolunghi²  Laura Ruohonen³ 

[1] University of Milano Bicocca, Piazza della Scienza 2, 20126, Milan, Italy;University of Milano Bicocca, Piazza della Scienza 2, 20126, Milan, Italy;Sacco srl, Via Manzoni, 29/A, Cadorago Co, 22071, Italy;VTT Technical Research Centre of Finland, VTT, FI-02044, Espoo, Finland;

关键词: Kluyveromyces marxianus;    Glucose fermentation;    Xylose fermentation;    Ethanol production;    Oxygen requirement;    Xylose reductase;    Xylitol dehydrogenase;   

DOI  :  10.1186/1475-2859-13-51

 received in 2014-01-10, accepted in 2014-04-04,  发布年份 2014

来源: Springer

【 摘 要 】

BackgroundThe yeast Kluyveromyces marxianus features specific traits that render it attractive for industrial applications. These include production of ethanol which, together with thermotolerance and the ability to grow with a high specific growth rate on a wide range of substrates, could make it an alternative to Saccharomyces cerevisiae as an ethanol producer. However, its ability to co-ferment C5 and C6 sugars under oxygen-limited conditions is far from being fully characterized.ResultsIn the present study, K. marxianus CBS712 strain was cultivated in defined medium with glucose and xylose as carbon source. Ethanol fermentation and sugar consumption of CBS712 were investigated under different oxygen supplies (1.75%, 11.00% and 20.95% of O2) and different temperatures (30°C and 41°C). By decreasing oxygen supply, independently from the temperature, both biomass production as well as sugar utilization rate were progressively reduced. In all the tested conditions xylose consumption followed glucose exhaustion. Therefore, xylose metabolism was mainly affected by oxygen depletion. Loss in cell viability cannot explain the decrease in sugar consumption rates, as demonstrated by single cell analyses, while cofactor imbalance is commonly considered as the main cause of impairment of the xylose reductase (Km XR) - xylitol dehydrogenase (Km XDH) pathway. Remarkably, when these enzyme activities were assayed in vitro, a significant decrease was observed together with oxygen depletion, not ascribed to reduced transcription of the corresponding genes.ConclusionsIn the present study both oxygen supply and temperature were shown to be key parameters affecting the fermentation capability of sugars in the K. marxianus CBS712 strain. In particular, a direct correlation was observed between the decreased efficiency to consume xylose with the reduced specific activity of the two main enzymes (Km XR and Km XDH) involved in its catabolism. These data suggest that, in addition to the impairment of the oxidoreductive pathway being determined by the cofactor imbalance, post-transcriptional and/or post-translational regulation of the pathway enzymes contributes to the efficiency of xylose catabolism in micro-aerobic conditions. Overall, the presented work provides novel information on the fermentation capability of the CBS712 strain that is currently considered as the reference strain of the genus K. marxianus.

【 授权许可】

Unknown   
© Signori et al.; licensee BioMed Central Ltd. 2014. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.