Ferment Maltose Research Articles

Improvement of production of lipopeptide antibiotic iturin A using fish protein

To enhance the production of lipopeptide antibiotic iturin A, nutrient contents of the culture mediums were investigated in both submerged and biofilm fermentations. As a carbon source maltose and as nitrogen source, fish protein was used. In submerged fermentation maltose uptake was found lower (12%) compared to biofilm fermentation (15%) that was associated with higher cellular growth in biofilm. However, requirement of nitrogen (fish protein) concentration was found similar in both submerged and biofilm fermentations. Production of iturin A in submerged fermentation with 12% maltose and 5% fish protein was 4450 mg/L, and in biofilm fermentation it was 5050 mg/L when 15% maltose and 5% fish protein was used.

Transcriptome Analysis of Acetyl-Homoserine Lactone-Based Quorum Sensing Regulation in Yersinia pestis

The etiologic agent of bubonic plague, Yersinia pestis, senses self-produced, secreted chemical signals in a process named quorum sensing. Though the closely related enteric pathogen Y. pseudotuberculosis uses quorum sensing system to regulate motility, the role of quorum sensing in Y. pestis has been unclear. In this study we performed transcriptional profiling experiments to identify Y. pestis quorum sensing regulated functions. Our analysis revealed that acyl-homoserine lactone-based quorum sensing controls the expression of several metabolic functions. Maltose fermentation and the glyoxylate bypass are induced by acyl-homoserine lactone signaling. This effect was observed at 30°C, indicating a potential role for quorum sensing regulation of metabolism at temperatures below the normal mammalian temperature. It is proposed that utilization of alternative carbon sources may enhance growth and/or survival during prolonged periods in natural habitats with limited nutrient sources, contributing to maintenance of plague in nature.

Modulation of the Structures and Properties of Bacterial Cellulose Film by Fermentation Carbon Sources

Bacterial cellulose (BC), a natural pure cellulose synthesized by some bacteria, shows great potentials for wound dressing applications. In order to obtain suitable properties, different fermentation carbon sources, i.e. glucose, maltose and sucrose were used to synthesize BC films by static culture. The crystallinity and pore analysis was performed by X-ray diffraction spectroscopy and nitrogen physisorption measurements, respectively. Some important properties of BC materials from different carbon sources were investigated, such as the mechanical strength, water holding capacity, water swelling ratio and water diffusion ability, which were key parameters for wound dressing applications. For comparison, the conventional cotton fiber was used as control. It was found that the carbon sources could change both the structures and properties of BC. The sucrose-derived BC exhibited lower crystallinity, but more suitable mechanical property, higher water holding capacity and water swelling ratio than other samples. All tested BC samples showed higher water holding capacity and water swelling ratio, but lower water diffusion property than the cotton fibers which were expected as good wound-healing biomedical materials.

Enhanced leavening properties of baker’s yeast overexpressingMAL62with deletion ofMIG1in lean dough

This study aimed to increase maltose fermentation in industrial baker's yeast to increase its leavening properties. To this end, we overexpressed MAL62 encoding alpha-glucosidase (maltase) and deleted MIG1 encoding a transcriptional repressor that regulates MAL gene expression. Strain overexpressing MAL62 showed 46.3% higher alpha-glucosidase activity and enhanced leaving activity than the parental strain when tested in glucose-maltose low sugar model liquid dough (LSMLD). Deleting MIG1 was much less effective, but it could further strengthen leavening properties in a strain overexpressing MAL62. The relationship between maltose permease and alpha-glucosidase was further dissected by transforming the two genes. The results indicated that without increasing the maltose permease activity, maltose metabolism could also be enhanced by the increased alpha-glucosidase activity. Previous strategies for strain improvement have targeted the enhancement of alpha-glucosidase and maltose permease activities in concert. Our results suggest that increasing alpha-glucosidase activity is sufficient to improve maltose fermentation in lean dough.

Evaluation of Brazilian ethanol production yeasts for maltose fermentation in media containing structurally complex nitrogen sources

Maltose and glucose fermentations are strongly affected by the structural complexity of the nitrogen source and by the presence of oxygen. In this study five industrial Saccharomyces cerevisiae strains were grown in synthetic medium, containing maltose or glucose, supplemented with different nitrogen sources, with or without agitation. All strains were able to grow and efficiently ferment glucose, but not all strains were able to grow and ferment maltose well. Peptone and ammonium sulfate induced improved fermentation for all strains and conditions. Under agitation, as expected, higher biomass accumulation was detected. Casamino acids supplementation induced efficient maltose fermentation for all of the strains under aerated conditions, but differing maltose utilization patterns were observed for the static cultures. Copyright © 2012 The Institute of Brewing & Distilling

Effects of chemical additives and ensiling time on whole plant wheat silage microbial profiles inferred by phenotypic and 16S ribosomal DNA analyses

The objectives of this study were to test the effects of various chemical additives, and ensiling time periods on microbial profiles of whole plant wheat silage (WPWS). WPWS was harvested at dough maturation stage, and ensiled with sodium chloride (T), sodium bicarbonate (N), sucrose (S), or urea (U) at 1% dry matter (DM) (w/w). Each WPWS treatment (i.e. T, N, S, and U) was ensiled in 1dm(3) duplicate anaerobic jars for 7, 14, 28, 35, 42, 49, and 56days. The highest lactic acid concentration was detected for U (5.9% DM) compared to the control (0.5% DM) at day 56. Similarly, the highest ammonia concentration was observed for U (9.3% DM) compared to the control; T, N, and S treatments averaged 2.4% DM. A higher lactic acid bacteria (LAB) count was observed between days 14 and 56 for all treatments relative to control WPWS, which averaged 6.7 and 5.6 c.f.u./g of fresh material, respectively. The highest quality silage was observed for N and U treated WPWS, with an absence of yeasts and molds from days 7 to 49. Identification of bacterial isolates at days 7 and 56 from each individual silage treatment was performed based on phenotypic (biochemical tests), and molecular (16S rDNA partial gene sequence) methods. 16S rDNA sequence results identified U7 and N56 isolates as Enterococcus faecium, and demonstrated positive galactose, ribose, lactose, maltose, mannitol, mannose, sucrose, and trehalose fermenting characteristics. In addition, most isolates exhibited growth potential in 6.5% NaCl. Overall sequence alignment results supported phenotypic identification, and indicated that U and N treated WPWS were LAB (Enterococcus) dominant compared to the control (non-LAB).

Evaluation of a simplified key for the identification of coagulase-positive Staphylococcus isolated from bovine mastitis

Evaluation of a simplified key for the identification of coagulase-positive Staphylococcus isolated from bovine mastitis. Three hundred fourty four strains of coagulase-positive Staphylococcus (CPS), isolated from mastitis cases, underwent phenotypic and genotypic tests to evaluate the efficiency of a simplified key, based on phenotypic tests for the discrimination of these microorganisms. The tests consisted of amplification of the femA gene and hemolysis in blood agar, production of acetoin and fermentation of maltose, mannitol and trehalose. Strains that showed negative results in the amplification test of the femA gene or that were not identified as Staphylococcus aureus (S. aureus) by phenotypic tests were tested with the APISTAPH kit (Biomériux-France), for precise identification of species. Phenotypic tests revealed 338 strains (98.25%) as S. aureus, three strains (0.86%) as Staphylococcus hyicus, and three microorganisms (0.86%) as Staphylococcus intermedius. PCR demonstrated that 338 (98.25%) strains belonged to the S. aureus species, confirming the results for 336 strains from 338 identified, through a simplified phenotypic key. A high rate of correlation (98.83%) was verifeid between the results of genotypic and phenotypic tests for the identification of S. aureus, demonstrating the applicability of the proposed key, for the discrimination of this microorganism in CPS isolated from bovine mastitis.

Comparison of phenotypic (Biolog System) and genotypic (random amplified polymorphic DNA-polymerase chain reaction, RAPD-PCR, and amplified fragment length polymorphism, AFLP) methods for typing Lactobacillus plantarum isolates from raw vegetables and fruits

The diversity of 72 isolates of Lactobacillus plantarum, previously identified from different raw vegetables and fruits, was studied based on phenotypic (Biolog System) and genotypic (randomly amplified polymorphic DNA-polymerase chain reaction, RAPD-PCR, and amplified fragment length polymorphism, AFLP) approaches. A marked phenotypic and genotypic variability was found. Eight clusters were formed at the similarity level of 92% based on Biolog System analysis. The most numerous clusters grouped isolates apart from the original habitat. Almost all isolates fermented maltose, d, l-lactic acid, N-acetyl- d-mannosamine and dextrin, and other typical carbon sources which are prevalent in raw vegetables and fruits. None of the isolates fermented lactose and free amino acids. At high values of linkage distance, two main clusters were obtained from both UPGMA (unweighted pair group with arithmetic average) dendrograms of RAPD-PCR and AFLP analyses. The two clusters mainly separated isolates from tomatoes and carrots from those isolated from pineapples. At 2.5 linkage distance, a high polymorphism was found and several sub-clusters were formed with both analyses. In particular, AFLP allowed the differentiation of 55 of the 72 isolates of L. plantarum. The discriminatory power of each technique used was calculated through the Simpson's index of diversity ( D). The values of the D index were 0.65, 0.92 and 0.99 for Biolog System, RAPD-PCR and AFLP analyses, respectively.

Microarray karyotyping of maltose‐fermenting Saccharomyces yeasts with differing maltotriose utilization profiles reveals copy number variation in genes involved in maltose and maltotriose utilization

We performed an analysis of maltotriose utilization by 52 Saccharomyces yeast strains able to ferment maltose efficiently and correlated the observed phenotypes with differences in the copy number of genes possibly involved in maltotriose utilization by yeast cells. The analysis of maltose and maltotriose utilization by laboratory and industrial strains of the species Saccharomyces cerevisiae and Saccharomyces pastorianus (a natural S. cerevisiae/Saccharomyces bayanus hybrid) was carried out using microscale liquid cultivation, as well as in aerobic batch cultures. All strains utilize maltose efficiently as a carbon source, but three different phenotypes were observed for maltotriose utilization: efficient growth, slow/delayed growth and no growth. Through microarray karyotyping and pulsed-field gel electrophoresis blots, we analysed the copy number and localization of several maltose-related genes in selected S. cerevisiae strains. While most strains lacked the MPH2 and MPH3 transporter genes, almost all strains analysed had the AGT1 gene and increased copy number of MALx1 permeases. Our results showed that S. pastorianus yeast strains utilized maltotriose more efficiently than S. cerevisiae strains and highlighted the importance of the AGT1 gene for efficient maltotriose utilization by S. cerevisiae yeasts. Our results revealed new maltotriose utilization phenotypes, contributing to a better understanding of the metabolism of this carbon source for improved fermentation by Saccharomyces yeasts.

Hsp90 Cochaperone Aha1 Is a Negative Regulator of the Saccharomyces MAL Activator and Acts Early in the Chaperone Activation Pathway

Aha1 is a ubiquitous cochaperone of the Hsp90/Hsp70 chaperone machine. It binds the middle domain of Hsp90 and stimulates ATPase activity, suggesting a function late in the chaperone pathway. Saccharomyces Mal63 MAL activator is a DNA-binding transcription factor and Hsp90 client protein. This study utilizes several MAL activator mutants to investigate Aha1 function in vivo. Deletion of AHA1 enhances induced Mal63-dependent maltase activity levels 2-fold, whereas overproduction of Aha1 represses expression. Maltase expression in strains carrying constitutive and super-inducible mutant activators with alterations near the C terminus (particularly residues 433-463) is unaffected by either aha1Delta or Aha1 overproduction. However, another constitutive activator with alterations outside of this C-terminal region is sensitive to Aha1 regulation. Previously, we showed that in the absence of inducer, Mal63 forms a stable intermediate complex with Hsp70, Hsp90, and Sti1, whereas noninducible mutant activators bind only with Hsp70 in an apparent early complex. Here, we find that triple Myc-tagged Aha1/Myc3 copurifies with all noninducible Mal63 mutant activators tested. Aha1/Myc3 association with inducible Mal63 is observed only in a sti1Delta strain, in which Hsp90 binding and intermediate complex formation are defective. Constitutive and super-inducible mutant activators with C-terminal alterations do not bind Aha1 even in a sti1Delta strain. Mal63 binding to Hsp90 and Hsp70 is enhanced 3-fold by loss of Aha1. These results suggest an interaction between Aha1 and residues near the C terminus of Mal63 thereby regulating Hsp90 association. A novel mechanism for the negative regulation of the MAL activator by Aha1 cochaperone is proposed.

Repeated batch fermentation from raw starch using a maltose transporter and amylase expressing diploid yeast strain

We successfully demonstrated batch ethanol fermentation repeated ten times from raw starch with high ethanol productivity. We constructed a yeast diploid strain coexpressing the maltose transporter AGT1, alpha-amylase, and glucoamylase. The introduction of AGT1 allows maltose and maltotriose fermentation as well as the improvement of amylase activities. We also found that alpha-amylase activity during fermentation was retained by the addition of 10 mM calcium ion and that the highest alpha-amylase activity was 9.26 U/ml during repeated fermentation. The highest ethanol productivity was 2.22 g/l/h at the fourth batch, and after ten cycles, ethanol productivity of more than 1.43 g/l/h was retained, as was alpha-amylase activity at 6.43 U/ml.

Hydrogen production characteristics from dark fermentation of maltose by an isolated strain F.P 01

A hydrogen producing strain F.P 01 was newly isolated from cow dung sludge in an anaerobic bioreactor. The strain F.P 01 was a mesophilic and facultative anaerobic bacterium, which exhibited gram-negative staining in both the exponential and stationary growth phases, and a regular long rod-shaped bacteria with the size of 0.6–0.9 μm × 1.2–2.5 μm, and also could biodegrade a variety of carbohydrates such as glucose, xylose, maltose, etc. The effects of important process parameters on hydrogen producing of F.P 01 were further investigated from hydrogen fermentation of maltose by strain F.P 01, including substrate concentration, medium pH, etc. And the results showed that hydrogen production potential and hydrogen production rate from maltose of this strain F.P 01 was180 mLH 2/g-maltose and 4.0 mLH 2/h, respectively. The corresponding hydrogen concentration of 58–73% was also be observed. Both butyric acid and acetic acid as main by-product was left in the reactor.

Histone modifying proteins Gcn5 and Hda1 affect flocculation in Saccharomyces cerevisiae during high-gravity fermentation

The performance of yeast is often limited by the constantly changing environmental conditions present during high-gravity fermentation. Poor yeast performance contributes to incomplete and slow utilization of the main fermentable sugars which can lead to flavour problems in beer production. The expression of the FLO and MAL genes, which are important for the performance of yeast during industrial fermentations, is affected by complex proteins associated with Set1 (COMPASS) resulting in the induction of flocculation and improved maltose fermentation capacity during the early stages of high-gravity fermentation. In this study, we investigated a possible role for other histone modifying proteins. To this end, we tested a number of histone deacetylases (HDACs) and histone acetyltransferases and we report that flocculation is induced in absence of the histone deacetylase Hda1 or the histone acetyltransferase Gcn5 during high-gravity fermentation. The absence of Gcn5 protein also improved utilization of high concentrations of maltose. Deletion of SIR2 encoding the HDA of the silent informator regulator complex, did not affect flocculation under high-gravity fermentation conditions. Despite the obvious roles for Hda1 and Gcn5 in flocculation, this work indicates that COMPASS mediated silencing is the most important amongst the histone modifying components to control the expression of the FLO genes during high-gravity fermentation.

Clostridium hydrogeniformans sp. nov. and Clostridium cavendishii sp. nov., hydrogen-producing bacteria from chlorinated solvent-contaminated groundwater

Four hydrogen-producing, aerotolerant, anaerobic bacterial strains isolated from chlorinated solvent-contaminated groundwater were characterized using a polyphasic approach. Three of the strains, designated BL-18, BL-19 and BL-20(T), were found to be identical in 16S rRNA gene sequences and in phenotypic properties. Cells of these strains are Gram-positive-staining, spore-forming, motile rods with peritrichous flagella. Growth occurred at 15-40 degrees C, pH 5.0-10.0 and at NaCl concentrations up to 5 % (w/v). Acid was produced in fermentation of cellobiose, fructose, galactose (weak), glucose, maltose and salicin. Products of fermentation in PYG medium were acetate, butyrate, ethanol, formate, carbon dioxide and hydrogen. Dominant cellular fatty acids when grown in PYG medium were C(13 : 0) iso, C(16 : 0), C(13 : 0) anteiso, C(15 : 0) iso and C(15 : 0) anteiso. The genomic DNA G+C content was 30.4 mol%. These isolates can be differentiated from their closest phylogenetic relative, the cluster I Clostridium species Clostridium frigidicarnis (97.2 % similar to the type strain in 16S rRNA gene sequence), on the basis of phenotypic and chemotaxonomic properties. The other strain characterized in this study, BL-28(T), was Gram-positive-staining with spore-forming, rod-shaped cells. Growth occurred at 15-46 degrees C, pH 6.0-8.5 and at NaCl concentrations up to 3 % (w/v). Acid was produced from cellobiose, dextran, fructose (weak), glucose, maltose, salicin and trehalose. End products of PYG fermentation included acetate, butyrate, pyruvate, carbon dioxide and hydrogen. Dominant cellular fatty acids from cells grown in PYG medium at 30 degrees C were C(14 : 0), C(14 : 0) dimethyl aldehyde, C(16 : 0) and C(12 : 0). The DNA G+C content was 28.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain BL-28(T) falls within cluster I of the genus Clostridium, but with <or=95.2 % identity with previously described species. On the basis of results presented here, strains BL-20(T) (=NRRL B-51348(T) =DSM 21757(T)) and BL-28(T) (=NRRL B-51352(T) =DSM 21758(T)) are proposed as the type strains of novel species of the genus Clostridium with the names Clostridium hydrogeniformans sp. nov. and Clostridium cavendishii sp. nov., respectively.

Amino Acids that Confer Transport of Raffinose and Maltose Sugars in the Raffinose Permease (RafB) of Escherichia coli as Implicated by Spontaneous Mutations at Val-35, Ser-138, Ser-139, Gly-389 and Ile-391

In order to identify amino acid residues in the Escherichia coli raffinose-H(+) permease (RafB) that play a role in sugar selection and transport, we first incubated E. coli HS4006 containing plasmid pRU600 (expresses inducible raffinose permease and alpha-galactosidase) on maltose MacConkey indicator plates overnight. Initially, all colonies were white, indicating no fermentation of maltose. Upon further incubation, 100 mutants appeared red. pRU600 DNA was prepared from 55 mutants. Five mutants transferred the phenotype for fermentation of maltose (red). Plasmid DNA from five maltose-positive phenotype transformants was prepared and sequenced, revealing three distinct types of mutations. Two mutants exhibited Val-35-->Ala (MT1); one mutant had Ile-391-->Ser (MT2); and two mutants had Ser-138-->Asp, Ser-139-->Leu and Gly-389-->Ala (MT3). Transport studies of [(3)H]-maltose showed that cells harboring MT1, MT2 and MT3 had greater uptake (P <or= 0.05) than cells harboring wild-type RafB. However, [(14)C]-raffinose uptake was reduced in all mutant cells (P <or= 0.05) with MT1, MT2 and MT3 mutants compared to cells harboring wild-type RafB. Kinetic analysis showed enhanced apparent K (m) values for maltose and reduced V (max)/ K (m) ratios for raffinose compared to wild-type values. The apparent K (i) value of maltose for RafB indicates a competitive relationship between maltose and raffinose. Maltose "uphill" accumulation was greater for mutants (P <or= 0.05) than for cells with wild-type RafB. Thus, we implicate residues in RafB that are responsible for raffinose transport and suggest that the substituted residues in RafB dictate structures that enhance transport of maltose.

Flour carbohydrate catabolism and metabolite production by sourdough lactic acid bacteria

The aim of this study was to assess the mode of carbohydrate catabolism by lactic acid bacteria isolated from traditional sourdoughs, as well as to study their effect on the metabolites produced. For this purpose, single cultures of the heterofermentative lactic acid bacteria Lactobacillus sanfranciscensis, Lactobacillus brevis, Weissella cibaria, and the homofermentative Lactobacillus paralimentarius and Pediococcus pentosaceus were grown in liquid media containing glucose, fructose, maltose and sucrose, either as a single carbon source or in combination with glucose. Carbon catabolism and the production of metabolites were determined by HPLC analysis. W. cibaria could ferment all carbon sources, L. sanfranciscensis, L. paralimentarius and P. pentosaceus could not ferment sucrose, while L. brevis could only ferment maltose. The presence of glucose did not influence the utilization of fructose and maltose by L. sanfranciscensis, while it repressed the fermentation of fructose, maltose and sucrose by W. cibaria, and fructose and maltose by L. paralimentarius and P. pentosaceus. Moreover, L. sanfranciscensis and L. brevis could obtain extra ATP through the reduction of fructose to mannitol, which favored the production of acetic acid against ethanol. The utilization of fructose as an electron acceptor has a decisive effect on the prevailing of L. sanfranciscensis and L. brevis in spontaneously fermented sourdough and in the scarce appearance of the other lactic acid bacteria studied.

Maltose and Maltotriose Active Transport and Fermentation by Saccharomyces Cerevisiaes

In the current study we analyzed the kinetics of growth, sugar consumption, and ethanol production by a Saccharomyces cerevisiae strain with the AGT1 permease as its unique α-glucoside transporter on synthetic or rich medium containing maltose or maltotriose. Our results show that to efficiently consume and ferment these sugars from the medium requires constitutive expression of the transporter gene, which can be achieved by the presence of a constitutive MAL (e.g., MAL63c) regulator. In addition to constitutive expression of the permease, growth on rich medium also increased the fermentation performance of the cells. Although a good correlation between the activity of the AGT1 transporter and the fermentation performance of the cells was observed, the same was not true for the activity of the intracellular α-glucosidase. The AGT1-containing S. cerevisiae strain fermented maltotriose more efficiently than maltose due to higher expression of the AGT1 permease during growth on maltotriose, leading to higher uptake rates of this sugar into the cells. Our results also indicate that during maltotriose fermentation by yeasts with constitutive expression of the AGT1 permease transport across the plasma membrane may no longer limit sugar utilization by S. cerevisiae cells.

Differences amongAGT1-encoded α-glucoside transporters and their ability to transport maltotriose inSaccharomyces yeasts

Improved fermentation of starch and its dextrin products would benefit the brewing and whiskey industries. Most strains ofSaccharomyces ferment glucose and maltose and partially ferment maltotriose, but are unable to utilise the larger dextrin products of starch. This utilisation pattern is partly attributed to the ability of yeast cells to transport the aforementioned mono-, di- and trisaccharides into the cytosol. The maltotriose transporting efficiency varies between differentSaccharomyces strains. In this study, severalSaccharomyces strains, including whiskey strains, were screened for growth on maltotriose. TheAGT1 genes, which encode a maltose transporter that show affinity for maltotriose uptake, were isolated from the strains that grew strongest in media with maltotriose as sole carbon source. The isolatedAGT1 alleles were sequenced and their chromosomal locations determined in the strains from which they were cloned. Nucleotide and deduced amino acid sequences of the isolated genes shared 95% and 98% identity, respectively. The efficiency of maltotriose transport was determined by expressing theAGT1 variants in an identical genetic background. TheK m values obtained for all the permeases were very similar (≈3), but the permease with improved performance for maltotriose transport showed an approximately 30% higherV max value than for the others. The data obtained suggest that the genetic variation among theAGT1-encoded transporters is reason for the variation in maltotriose transport efficiency among differentSaccharomyces strains. This study offers prospects for the development of yeast strains with improved maltose and maltotriose uptake capabilities that, in turn, could increase the overall fermentation efficiencies in the beer and whiskey industries.

Overlapping substrate specificity for sucrose and maltose of two binding protein-dependent sugar uptake systems inStreptococcus mutans

Sugar metabolism by Streptococcus mutans is associated with tooth decay. The most abundant sugars in the human diet are sucrose and maltose, a derivative of starch. Previously, we reported a binding protein-dependent transport system (msm) in S. mutans that transports sucrose and maltose, but its associated enzymes do not metabolize maltose. By searching the S. mutans genomic sequence for a maltose system (mal), we found a gene cluster encoding proteins with homology to those of msm and the Escherichia coli maltose system. Mutants were constructed by deleting msm or mal, or both, and tested for sugar utilization. Deletion of the mal system diminished the ability of S. mutans to ferment maltose, but deletion of only the mal transporter genes or msm showed reduced utilization of chromogenic maltosides. Maltose, sucrose, glucose, fructose, mannose, and N-acetyl glucosamine inhibited utilization of chromogenic maltosides by the wild-type strain and mutants. In conclusion, the two binding protein-dependent systems in S. mutans appear to transport collaboratively their common substrate sugars, notably sucrose and maltose.

Involvement of Pyruvate Oxidase Activity and Acetate Production in the Survival of Lactobacillus plantarum during the Stationary Phase of Aerobic Growth

In addition to the previously characterized pyruvate oxidase PoxB, the Lactobacillus plantarum genome encodes four predicted pyruvate oxidases (PoxC, PoxD, PoxE, and PoxF). Each pyruvate oxidase gene was individually inactivated, and only the knockout of poxF resulted in a decrease in pyruvate oxidase activity under the tested conditions. We show here that L. plantarum has two major pyruvate oxidases: PoxB and PoxF. Both are involved in lactate-to-acetate conversion in the early stationary phase of aerobic growth and are regulated by carbon catabolite repression. A strain devoid of pyruvate oxidase activity was constructed by knocking out the poxB and poxF genes. In this mutant, acetate production was strongly affected, with lactate remaining the major end product of either glucose or maltose fermentation. Notably, survival during the stationary phase appeared to be dramatically improved in the poxB poxF double mutant.