Effect of furfural on carbon metabolism key enzymes of lactose-assimilating yeasts

Hristozova, Tsonka; Angelov, Angel; Tzvetkova, B.; Paskaleva, D.; Gotcheva, Velitchka; Gargova, S.; Pavlova, K.

doi:10.1016/j.enzmictec.2006.02.015

Cited by 24 publications

(12 citation statements)

References 23 publications

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“…Furfural has been suggested to interfere with electron transport and inhibit glycolytic enzymes (Palmqvist et al 1999a;Taherzadeh et al 1999;Hristozova et al 2006). Addition of 4 g l À1 HMF was reported to cause a decrease of about approximately 32% in the carbon dioxide evolution rate.…”

Section: Introductionmentioning

confidence: 98%

Degradation of 5-hydroxymethylfurfural during yeast fermentation

Akıllıoğlu

Mogol

Gökmen

2011

Food Additives & Contaminants: Part A

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5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693 × 10(-2) and 1.397 × 10(-2)min(-1) for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79-84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p<0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.

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Section: Introductionmentioning

confidence: 98%

Degradation of 5-hydroxymethylfurfural during yeast fermentation

Akıllıoğlu

Mogol

Gökmen

2011

Food Additives & Contaminants: Part A

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“…Furfural has also been shown to potentiate the toxicity of other compounds known to be present in acid hydrolysates of hemicellulose (47)(48)(49). Furfural has been reported to alter DNA structure and sequence (3,17), inhibit glycolytic enzymes (6), and slow sugar metabolism (11).…”

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confidence: 99%

Silencing of NADPH-Dependent Oxidoreductase Genes (yqhDanddkgA) in Furfural-Resistant EthanologenicEscherichia coli

Miller

Jarboe

Yomano

et al. 2009

Appl Environ Microbiol

166

232

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Low concentrations of furfural are formed as a side product during the dilute acid hydrolysis of hemicellulose. Growth is inhibited by exposure to furfural but resumes after the complete reduction of furfural to the less toxic furfuryl alcohol. Growth-based selection was used to isolate a furfural-resistant mutant of ethanologenic Escherichia coli LY180, designated strain EMFR9. Based on mRNA expression levels in the parent and mutant in response to furfural challenge, genes encoding 12 oxidoreductases were found to vary by more than twofold (eight were higher in EMFR9; four were higher in the parent). All 12 genes were cloned. When expressed from plasmids, none of the eight genes in the first group increased furfural tolerance in the parent (LY180). Expression of three of the silenced genes (yqhD, dkgA, and yqfA) in EMFR9 was found to decrease furfural tolerance compared to that in the parent. Purified enzymes encoded by yqhD and dkgA were shown to have NADPH-dependent furfural reductase activity. Both exhibited low K m values for NADPH (8 M and 23 M, respectively), similar to those of biosynthetic reactions. Furfural reductase activity was not associated with yqfA. Deleting yqhD and dkgA in the parent (LY180) increased furfural tolerance, but not to the same extent observed in the mutant EMFR9. Together, these results suggest that the process of reducing furfural by using an enzyme with a low K m for NADPH rather than a direct inhibitory action is the primary cause for growth inhibition by low concentrations of furfural.

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“…Furfural and 5-hydroxymethyl furfural (dehydration product from hexose sugars) have been previously proposed to inhibit growth by damaging DNA (3,16,36), inhibiting glycolysis and glycolytic enzymes (5,11,25), and chemically reacting with cellular constituents (10,30). An Escherichia coli enzyme has been partially purified and characterized that catalyzes the NADPH-dependent reduction of furfural to the less toxic alcohol furfuryl alcohol (7,45,46).…”

mentioning

confidence: 99%

Furfural Inhibits Growth by Limiting Sulfur Assimilation in EthanologenicEscherichia coliStrain LY180

Miller

Jarboe

Turner

et al. 2009

Appl Environ Microbiol

142

190

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A wide variety of commercial products can be potentially made from monomeric sugars produced by the dilute acid hydrolysis of lignocellulosic biomass. However, this process is accompanied by side products such as furfural that hinder microbial growth and fermentation. To investigate the mechanism of furfural inhibition, mRNA microarrays of an ethanologenic strain of Escherichia coli (LY180) were compared immediately prior to and 15 min after a moderate furfural challenge. Expression of genes and regulators associated with the biosynthesis of cysteine and methionine was increased by furfural, consistent with a limitation of these critical metabolites. This was in contrast to a general stringent response and decreased expression of many other biosynthetic genes. Of the 20 amino acids individually tested as supplements (100 M each), cysteine and methionine were the most effective in increasing furfural tolerance with serine (precursor of cysteine), histidine, and arginine of lesser benefit. Supplementation with other reduced sulfur sources such as D-cysteine and thiosulfate also increased furfural tolerance. In contrast, supplementation with taurine, a sulfur source that requires 3 molecules of NADPH for sulfur assimilation, was of no benefit. Furfural tolerance was also increased by inserting a plasmid encoding pntAB, a cytoplasmic NADH/NADPH transhydrogenase. Based on these results, a model is proposed for the inhibition of growth in which the reduction of furfural by YqhD, an enzyme with a low K m for NADPH, depletes NADPH sufficiently to limit the assimilation of sulfur into amino acids (cysteine and methionine) by CysIJ (sulfite reductase).Lignocellulose contains up to 70% carbohydrate by weight (35 to 45% cellulose and 20 to 35% hemicellulose) and represents an excellent potential source of sugars for microbial conversion into renewable fuels, plastics, and other chemicals (9,13,15,38). Prior to fermentation, these carbohydrate polymers must be converted to soluble sugars. Hemicellulose can be conveniently hydrolyzed to sugar monomers using dilute mineral acids. However, this process is accompanied by side products that inhibit microbial growth (20,21,29,30,(44)(45)(46). Furfural, the dehydration product of pentose sugars, is one of the most important such inhibitors (1). Previous studies have shown that furfural levels directly correlate with toxicity (20, 21). Overliming treatments that render hemicellulose hydrolysates fermentable also reduce the levels of furfural. Full toxicity in overlimed hydrolysates is restored by the addition of furfural. Of the many components of hydrolysates that have been tested for toxicity, only furfural was found to potentiate the toxicity of other agents in binary combinations (45).A number of approaches have been used to investigate the mechanism of furfural action. Furfural and 5-hydroxymethyl furfural (dehydration product from hexose sugars) have been previously proposed to inhibit growth by damaging DNA (3,16,36), inhibiting glycolysis and glycolytic enzymes (5,11,25), an...

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Effect of furfural on carbon metabolism key enzymes of lactose-assimilating yeasts

Cited by 24 publications

References 23 publications

Degradation of 5-hydroxymethylfurfural during yeast fermentation

Degradation of 5-hydroxymethylfurfural during yeast fermentation

Silencing of NADPH-Dependent Oxidoreductase Genes (yqhDanddkgA) in Furfural-Resistant EthanologenicEscherichia coli

Furfural Inhibits Growth by Limiting Sulfur Assimilation in EthanologenicEscherichia coliStrain LY180

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