PubMed Health⌕ Search

Biomedical subjects

K Sonomoto

Publications and source records attributed to K Sonomoto.

At least 19 recordsLinked to original sources
PubMed2005

Identification and production of a bacteriocin from Enterococcus mundtii QU 2 isolated from soybean.

AIMS: Identification of the bacteriocin produced by Enterococcus mundtii QU 2 newly isolated from soybean and fermentative production of the bacteriocin. METHODS AND RESULTS: The bacteriocin produced by Ent. mundtii QU 2 inhibited the growth of various indicator strains, including Enterococcus, Lactobacillus, Leuconostoc, Pediococcus and Listeria. The bacteriocin activity was stable at wide pH range and against heat treatment, but completely abolished by proteolytic enzymes. The bacteriocin was purified from the culture supernatant by the three-step chromatographic procedure. Mass spectrometry, amino acid sequencing and DNA sequencing revealed that the bacteriocin was similar to class IIa bacteriocins produced by other Ent. mundtii strains. The bacteriocin production decreased in the absence of glucose, nitrogen sources, or Tween 80 in MRS medium. Additionally, it was strongly suppressed by addition of Ca(2+) (CaCO(3) or CaCl(2)). In pH-controlled fermentations, the highest bacteriocin production was achieved at pH 6.0, whereas the highest cell growth was obtained at pH 7.0. CONCLUSIONS: Ent. mundtii QU 2 produced a class IIa bacteriocin. Some growth factors (e.g. Ca(2+) and pH) influenced the bacteriocin production. SIGNIFICANCE AND IMPACT OF THE STUDY: A new soybean isolate, Ent. mundtii QU 2 was found to be a class IIa bacteriocin producer. Factors influencing the bacteriocin production described herein are valuable for applications of the bacteriocins from Ent. mundtii strains.

Amino Acid Sequence↗
PubMed2003

Isolation of nisin-producing Lactococcus lactis WNC 20 strain from nham, a traditional Thai fermented sausage.

A total of 14,020 lactic acid bacteria (LAB) were isolated from nham and screened for bacteriocin production. One Lactococcus lactis strain WNC 20 produced a bacteriocin that not only inhibited closely related LAB, but also some food-borne pathogens including Listeria monocytogenes, Clostridium perfringens, Bacillus cereus and Staphylococcus aureus. Biochemical studies revealed that the bacteriocin was heat-stable even at autoclaving temperature (121 degrees C for 15 min) and was active over a wide pH range (2-10). The bacteriocin was inactivated by alpha-chymotrypsin and proteinase K but not other proteases. The antimicrobial spectrum and some characteristics of this bacteriocin were nearly identical to that of nisin. The gene encoding this bacteriocin was amplified by polymerase chain reaction (PCR) with nisin gene-specific primer. Sequencing of this gene showed identical sequences to nisin Z as indicated by the substitution of asparagine residue instead of histidine at position 27. The ability of the bacteriocin produced by Lc. lactis WNC 20 may be useful in improving the food safety of the fermented product.

Amino Acid Sequence↗
PubMed2002

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.

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. lactisIO-1 may possess another metabolic pathway that produces only lactic acid from xylose. In the present study, the metabolism of xylose in L. lactisIO-1 was deduced from the product formation and enzyme activities of L. lactisIO-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. lactisIO-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. lactisIO-1, and pyruvate metabolism between cleavage to acetyl-CoA and formic acid by PFL and the reduction to L-lactate by lactate dehydrogenase.

Enzymes↗
PubMed2001

Biochemical and genetic evidence for production of enterocins A and B by Enterococcus faecium WHE 81.

Enterococcus faecium WHE 81, isolated from cheese, has been reported to produce a bacteriocin called "enterocin 81" [J. Appl. Microbiol. 85 (1998) 521.]. Purification of "enterocin 81" was carried out using ammonium sulfate precipitation, desalting on ODP-90 reverse-phase column, and purification through SP Sepharose HP cation exchange and C2/C18 reverse-phase chromatographies. The antimicrobial was eluted from the C2/C18 column as four individually active fractions, designated A81, B81, C81 and D81. The purification procedure used proved particularly efficient for the bacteriocin in fraction D81, with a yield of 46%, while only 3.8% the bacteriocin in fraction B81 could be collected. MALDI-TOF mass spectrometry of the bacteriocins in fractions B81 and D81 showed respective masses of 4,833.0 and 5,462.2 Da. Amino acid sequencing of the two peptides revealed two class-II bacteriocins whose sequences were similar to those of enterocin A and enterocin B, respectively. Using proper primers, chromosomal fragments of 212 and 216 bp enclosing bacteriocin structural genes were PCR-amplified. Cloning of the amplicons and their sequencing revealed two genes with sequences identical to the structural genes of enterocins A and B, respectively. It was therefore clearly established that E. faecium WHE 81 produces bacteriocins respectively identical to enterocins A and B. Our results, combined with data from previous reports, suggest that the two bacteriocins may be widespread among enterococcal strains and may play an important role in controlling the growth of pathogens and other undesirable bacteria in certain fermented food products.

Amino Acid Sequence↗
PubMed2001

The effect of osmotic stress on the production of nukacin ISK-1 from Staphylococcus warneri ISK-1.

The effects of several additives on the production of a lantibiotic, nukacin ISK-1, from Staphylococcus warneri ISK-1, in batch fermentation were studied. NaCl, KCl and sorbitol stimulated nukacin ISK-1 production. The addition of 1.4 M NaCl increased nukacin ISK-1 activity 1.5-fold over the control, while cell growth and glucose consumption were inhibited. Nukacin ISK-1 production increased with increasing osmolarity of the medium up to about 3 osmol/kg; however, further increases in osmolarity diminished productivity, irrespective of the kind of additive. Northern blot analysis showed that transcription of the nukacin ISK-1 structural gene (nukA) was activated in the presence of 1.4 M NaC1. These data indicate that the stimulation effect was due to osmotic stress, which acted, at least in part, at the transcriptional level on the nukA gene.

Bacterial Proteins↗
PubMed2000

Class IIa bacteriocins: biosynthesis, structure and activity.

In the last decade, a variety of ribosomally synthesized antimicrobial peptides or bacteriocins produced by lactic acid bacteria have been identified and characterized. As a result of these studies, insight has been gained into fundamental aspects of biology and biochemistry such as producer self protection, membrane-protein interactions, and protein modification and secretion. Moreover, it has become evident that these peptides may be developed into useful antimicrobial additives. Class IIa bacteriocins can be considered as the major subgroup of bacteriocins from lactic acid bacteria, not only because of their large number, but also because of their activities and potential applications. They have first attracted particular attention as listericidal compounds and are now believed to be the next in line if more bacteriocins are to be approved in the future. The present review attempts to provide an insight into general knowledge available for class IIa bacteriocins and discusses common features and recent findings concerning these substances.

Amino Acid Sequence↗
PubMed2000

Purification and identification of a growth-stimulating peptide for Bifidobacterium bifidum from natural rubber serum powder.

Natural rubber serum powder, which is a by-product obtained in the production of latex rubber, has a strong growth-stimulating activity for Bifidobacterium bifidum JCM 1254. The retained fraction obtained by ultrafiltration (molecular weight cutoff 1000) showed a growth-stimulating activity in a dose-dependent manner on B12 assay medium with ammonium sulfate. One of the growth stimulators was purified from the retained fraction by acetone precipitation, solid-phase extraction with a hydrophobic pretreatment column, and multistage reversed-phase HPLC. An increase of 53-fold in the specific activity, and a recovery of 1.3% were obtained. The amino acid composition and N-terminal sequence analysis of this growth stimulator provided the structure of Ala-Thr-Pro-Glu-Lys-Glu-Glu-Pro-Thr-Ala. The molecular mass was 1075 by MALDI-TOF MS analysis. These results showed that this growth stimulator was a decapeptide with the sequence shown above. This is the first report that clarified the structure of an active peptide for the growth of Bifidobacterium.

Amino Acid Sequence↗
PubMed2000

A novel lantibiotic, nukacin ISK-1, of Staphylococcus warneri ISK-1: cloning of the structural gene and identification of the structure.

Staphylococcus warneri ISK-1, which we had previously reported as Pediococcus sp. ISK-1, produces a novel bacteriocin, nukacin ISK-1. Edman degradation of the chemically reduced nukacin ISK-1 produced a sequence of 27 amino acids, 7 of which were unidentified. Using single-specific-primer-PCR product as a probe, a 3.6-kb HindIII fragment containing the nukacin ISK-1 structural gene (nukA) was cloned and sequenced. The deduced amino acid sequence of nukacin ISK-1 had 57 amino acids, including a 30-amino acid leader region. The propeptide sequence showed significant similarity to those of lacticin-481 type lantibiotics. In the region upstream of nukA, a part of a long open reading frame (ORF), designated as nukM, encoding a putative modification enzyme was oriented in the opposite direction. In the region downstream of nukA, ORF1 was found in which the sequence of the putative translational product was similar to various response regulatory proteins.

Amino Acid Sequence↗
PubMed1999

Extractive acetone-butanol-ethanol fermentation using methylated crude palm oil as extractant in batch culture of Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564).

The possibility of employing methylated crude palm oil (CPOE) as an extraction solvent to reduce end-product inhibition and to enhance solvent productivity in acetone-butanol-ethanol (ABE) fermentation was evaluated using oleyl alcohol as the standard butanol extractant. Fermentation was carried out at an initial glucose concentration of 90 g/l. CPOE did not inhibit the growth of the fermentative organism. Without solvent extraction, butanol production ceased after 30 h at a concentration of 15.4 g/l limiting cell growth to 3.98 g/l and glucose consumption to 62%. Applying CPOE as the extraction solvent, about 47% of the total butanol produced was extracted, glucose consumption was increased to 83% and relatively high glucose consumption rates and solvent productivities were obtained. Butanol production increased to 20.9 g/l; total ABE solvents and yield also increased from 21.2 g/l and 38% (in conventional fermentation) to 29.8 g/l and 40.4%, respectively.

Journal Article↗
PubMed1999

Class IIa bacteriocins from lactic acid bacteria: antibacterial activity and food preservation.

In the last decade, a variety of ribosomally synthesized antimicrobial peptides, or bacteriocins, produced by lactic acid bacteria have been identified and characterized. As a result of these studies, insight has been gained into various fundamental aspects of biology and biochemistry such as bacteriocin processing and secretion, mechanisms of cell immunity, and structure-function relationships. In parallel, there has been a growing awareness that bacteriocins may be developed into useful antimicrobial food additives. Class IIa bacteriocins can be considered as the major subgroup of bacteriocins from lactic acid bacteria, not only because of their large number, but also because of their significant biological activities and potential applications. The present review provides an overview of the knowledge available for class IIa bacteriocins and discusses common features and recent findings concerning these substances. The activity and potential food applications of class IIa bacteriocins are a major focus of this review.

Journal Article↗
PubMed1999

Complementary effects of bifidogenic growth stimulators and ammonium sulfate in natural rubber serum powder on Bifidobacterium bifidum.

Natural rubber serum powder, rich in crude protein and carbohydrates, had a strong growth-stimulating activity for Bifidobacterium bifidum JCM 1254, which was unable to grow in a fully synthetic medium, B12 assay medium. Natural rubber serum powder was fractionated by ultrafiltration (molecular weight cutoff 1000). The active ultrafiltrate was further concentrated and desalted with an adsorptive microconcentrator, which adsorbs virtually all amino acids and peptides. Through this purification step, it was found that the adsorbed fraction obtained did not stimulate growth independently but acted complementarily with a small amount of ammonium sulfate. The adsorbed fraction was subsequently analyzed on reversed-phase high pressure liquid chromatography, and the activities of the eluates were measured on B12 assay medium with ammonium sulfate. Consequently, it was proved that several peptidic ingredients in the adsorbed fraction increased the growth of B. bifidum.

Ammonium Sulfate↗
PubMed1997

A bacteriocin of strain Pediococcus sp. ISK-1 isolated from Nukadoko, bed of fermented rice bran.

Pediococcus sp. ISK-1 isolated in our laboratory from well-aged Nukadoko, produces a bacteriocin which has a unique antimicrobial spectrum among pediocins. The bacteriocin was stable at acidic pH, and more than 60% of antimicrobial activity still remained even after being autoclaved at 121 degrees C for 20 min in the pH range of 3 to 8. This is the first report dealing with a bacteriocin produced by lactic acid bacteria isolated from Nukadoko.

Bacteriocins↗
PubMed1996

Lantibiotic nisin Z fermentative production by Lactococcus lactis IO-1: relationship between production of the lantibiotic and lactate and cell growth.

The influence of several parameters on the fermentative production of nisin Z by Lactococcus lactis IO-1 was studied. Considerable attention has been focused on the relationship between the primary metabolite production of bacteriocin and lactate and cell growth, which has so far not been clarified in detail. Production of nisin Z was optimal at 30 degrees C and in the pH range 5.0-5.5. The addition of Ca2+ to the medium showed a stimulating effect on the production of nisin Z. A maximum activity of 3150 IU/ml was obtained during pH-controlled batch fermentation in the medium supplemented with 0.1 M CaCl2. It was about three times higher than that obtained under the optimal conditions for cell growth and lactic acid production.

Anti-Bacterial Agents↗
PubMed1995

A multifunctional flow-injection biosensor for the simultaneous determination of ammonia, creatinine, and urea.

A strategy for the multifunctionalization of the FIA biosensor was developed. The described multifunctional FIA system offers a fast and simple method for the simultaneous determination of ammonia, creatinine, and urea. The hydrolysis of creatinine by creatinine deiminase (CRDI) or of urea by urease forms ammonia, which is amperometrically detected by an oxygen electrode, based on an enzyme conversion system, glutamate dehydrogenase (GLDH)/glutamate oxidase (GLOD). The split of the stream into three after sample injection and confluence before the GLDH reactor resulted in a three-channel system, into which were set three parallel columns, respectively, filled with immobilized CRDI, urease, and CPG. A triple-peak recording was obtained by putting two delay coils at the channels involving CRDI and urease. Thus the interfering of the endogenous ammonia on the creatinine and urea assay is simultaneously compensated. Furthermore, the problem of great difference in concentration between urea and the other two components is resolved by taking advantage of the differentiated dilution effect for each channel caused from the split-stream, flow-injection system. Linear calibration ranges for ammonia, creatinine, and urea were 0.1-5, 0.2-10, and 2-40 mM, respectively. One run was finished within 5 minutes, and the system was reproducibility good (3 to 5%). The results of the urine assay obtained by the present method will be described in the near future.

Amino Acid Oxidoreductases↗