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Alcohol dehydrogenases from Kluyveromyces marxianus: heterologous expression in Escherichia coli and biochemical characterization.

ABSTRACT: BACKGROUND: Kluyveromyces marxianus has recently become a species of interest for ethanol production since it can produce ethanol at high temperature and on a wide variety of substrates. However, the reason why this yeast can produce ethanol at high temperature is largely unknown. RESULTS: The ethanol fermentation capability of K. marxianus GX-UN120 at 40°? was found to be the same as that of Saccharomyces cerevisiae at 34°?. Zymogram analysis showed that alcohol dehydrogenase 1 (KmAdh1) was largely induced during ethanol production, KmAdh4 was constitutively expressed at a lower level and KmAdh2 and KmAdh3 were almost undetectable. The genes encoding the four alcohol dehydrogenases (ADHs) were cloned from strain GX-UN120. Each KmADH was expressed in Escherichia coli and each recombinant protein was digested with enterokinase to remove the fusion protein. The optimum pH of the purified recombinant KmAdh1 was 8.0 and that of KmAdh2, KmAdh3 and KmAdh4 was 7.0. The optimum temperatures of KmAdh1, KmAdh2, KmAdh3 and KmAdh4 were 50, 45, 55 and 45°C, respectively. The K(m) values of the recombinant KmAdh1 and KmAdh2 were 4.0 and 1.2 mM for acetaldehyde and 39.7 and 49.5 mM for ethanol, respectively. The V(max) values of the recombinant KmAdh1 and KmAdh2 were 114.9 and 21.6 ?mol min?¹ mg?¹ for acetaldehyde and 57.5 and 1.8 ?mol min?¹ mg?¹ for ethanol, respectively. KmAdh3 and KmAdh4 catalyze the oxidation reaction of ethanol to acetaldehyde but not the reduction reaction of acetaldehyde to ethanol, and the K(m) values of the recombinant KmAdh3 and KmAdh4 were 26.0 and 17.0 mM for ethanol, respectively. The V(max) values of the recombinant KmAdh3 and KmAdh4 were 12.8 and 56.2 ?mol min?¹ mg?¹ for ethanol, respectively. CONCLUSION: These data in this study collectively indicate that KmAdh1 is the primary ADH responsible for the production of ethanol from the reduction of acetaldehyde in K. marxianus. The relatively high optimum temperature of KmAdh1 may partially explain the ability of K. marxianus to produce ethanol at high temperature. Understanding the biochemical characteristics of KmAdhs will enhance our fundamental knowledge of the metabolism of ethanol fermentation in K. marxianus.

SUBMITTER: Liang JJ

PROVIDER: S-EPMC4062290 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Alcohol dehydrogenases from Kluyveromyces marxianus: heterologous expression in Escherichia coli and biochemical characterization.

Liang Jing-juan JJ Zhang Mei-ling ML Ding Meng M Mai Zhi-mao ZM Wu San-xing SX Du Yue Y Feng Jia-xun JX

BMC biotechnology 20140521

<h4>Background</h4>Kluyveromyces marxianus has recently become a species of interest for ethanol production since it can produce ethanol at high temperature and on a wide variety of substrates. However, the reason why this yeast can produce ethanol at high temperature is largely unknown.<h4>Results</h4>The ethanol fermentation capability of K. marxianus GX-UN120 at 40°С was found to be the same as that of Saccharomyces cerevisiae at 34°С. Zymogram analysis showed that alcohol dehydrogenase 1 (Km ...[more]

PMID: 24885162

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Project description:BACKGROUND:The yeast Kluyveromyces marxianus is an emerging cell factory for heterologous protein biosynthesis and its use holds tremendous advantages for multiple applications. However, which genes influence the productivity of desired proteins in K. marxianus has so far been investigated by very few studies. RESULTS:In this study, we constructed a K. marxianus recombinant (FIM1/Est1E), which expressed the heterologous ruminal feruloyl esterase Est1E as reporter. UV-60Co-? irradiation mutagenesis was performed on this recombinant, and one mutant (be termed as T1) was screened and reported, in which the productivity of heterologous Est1E was increased by at least tenfold compared to the parental FIM1/Est1E recombinant. Transcriptional perturbance was profiled and presented that the intracellular vesicle trafficking was enhanced while autophagy be weakened in the T1 mutant. Moreover, whole-genome sequencing combined with CRISPR/Cas9 mediated gene-editing identified a novel functional protein Mtc6p, which was prematurely terminated at Tyr251 by deletion of a single cytosine at 755 loci of its ORF in the T1 mutant. We found that deleting C755 of MTC6 in FIM1 led to 4.86-fold increase in the production of Est1E compared to FIM1, while the autophagy level decreased by 47%; on the contrary, when reinstating C755 of MTC6 in the T1 mutant, the production of Est1E decreased by 66% compared to T1, while the autophagy level increased by 124%. Additionally, in the recombinant with attenuated autophagy (i.e., FIM1 mtc6C755? and T1) or interdicted autophagy (i.e., FIM1 atg1? and T1 atg1?), the productivity of three other heterologous proteins was also increased, specifically the heterologous mannase Man330, the ?-1,4-endoxylanase XynCDBFV or the conventional EGFP. CONCLUSIONS:Our results demonstrated that Mtc6p was involved in regulating autophagy; attenuating or interdicting autophagy would dramatically improve the yields of desired proteins in K. marxianus, and this modulation could be achieved by focusing on the premature mutation of Mtc6p target.

Project description:BACKGROUND:Kluyveromyces marxianus is a promising cell factory for producing bioethanol and that raised a demand for a high yield of heterologous proteins in this species. Expressions of heterologous proteins usually lead to the accumulation of misfolded or unfolded proteins in the lumen of the endoplasmic reticulum (ER) and then cause ER stress. To cope with this problem, a group of ER stress response target genes (ESRTs) are induced, mainly through a signaling network called unfolded protein response (UPR). Characterization and modulation of ESRTs direct the optimization of heterologous expressions. However, ESRTs in K. marxianus have not been identified so far. RESULTS:In this study, we characterized the ER stress response in K. marxianus for the first time, by using two ER stress-inducing reagents, dithiothreitol (DTT) and tunicamycin (TM). Results showed that the Kar2-Ire1-Hac1 pathway of UPR is well conserved in K. marxianus. About 15% and 6% of genes were upregulated during treatment of DTT and TM, respectively. A total of 115 upregulated genes were characterized as ESRTs, among which 97 genes were identified as UPR target genes and 37 UPR target genes contained UPR elements in their promoters. Genes related to carbohydrate metabolic process and actin filament organization were identified as new types of UPR target genes. A total of 102 ESRTs were overexpressed separately in plasmids and their effects on productions of two different lignocellulolytic enzymes were systematically evaluated. Overexpressing genes involved in carbohydrate metabolism, including PDC1, PGK and VID28, overexpressing a chaperone gene CAJ1 or overexpressing a reductase gene MET13 substantially improved secretion expressions of heterologous proteins. Meanwhile, overexpressing a novel gene, KLMA_50479 (named ESR1), as well as overexpressing genes involved in ER-associated protein degradation (ERAD), including HRD3, USA1 andYET3, reduced the secretory expressions. ESR1 and the aforementioned ERAD genes were deleted from the genome. Resultant mutants, except the yet3Δ mutant, substantially improved secretions of three different heterologous proteins. During the fed-batch fermentation, extracellular activities of an endoxylanase and a glucanase in hrd3Δ cells improved by 43% and 28%, respectively, compared to those in wild-type cells. CONCLUSIONS:Our results unveil the transcriptional scope of the ER stress response in K. marxianus and suggest efficient ways to improve productions of heterologous proteins by manipulating expressions of ESRTs.

Dataset Information

Alcohol dehydrogenases from Kluyveromyces marxianus: heterologous expression in Escherichia coli and biochemical characterization.

Publications

Alcohol dehydrogenases from Kluyveromyces marxianus: heterologous expression in Escherichia coli and biochemical characterization.

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