The synergistic preservative effects of the essential oils of sweet basil (Ocimum basilicum L.) against acid-tolerant food microflora

Essential oils extracted by hydrodistillation from five different varieties of Ocimum basilicum L. plants (Anise, Bush, Cinnamon, Dark Opal and a commercial sample of dried basil) were examined for antimicrobial activity against a wide range of foodborne Gram-positive and -negative bacteria, yeasts and moulds by an agar well diffusion method. All five essential oils of basil showed antimicrobial activity against most of the organisms tested with the exception of Flavimonas oryzihabitans and Pseudomonas species. The inhibitory effect of Anise oil, in comparison with mixtures of the predominant components of pure linalool and methyl chavicol, against the acid-tolerant organisms, Lactobacillus curvatus and Saccharomyces cerevisiae, was examined in broth by an indirect impedance method. Synergistic effects between Anise oil, low pH (pH 4.2) and salt (5% NaCl) were determined. The antimicrobial effect of Anise oil was also assessed in a tomato juice medium by direct viable count, showing that the growth of Lact. curvatus and S. cerevisiae was completely inhibited by 0.1% and 1% Anise oil, respectively. The results of the current study indicate the need for further investigations to understand the antimicrobial effects of basil oils in the presence of other food ingredients and preservation parameters.

The effect of essential oils of basil on the growth of Aeromonas hydrophila and Pseudomonas fluorescens

Basil essential oils, including basil sweet linalool (BSL) and basil methyl chavicol (BMC), were screened for antimicrobial activity against a range of Gram-positive and Gram-negative bacteria, yeasts and moulds using an agar well diffusion method. Both essential oils showed antimicrobial activity against most of the micro-organisms examined except Clostridium sporogenes, Flavimonas oryzihabitans, and three species of Pseudomonas. The minimum inhibitory concentration (MIC) of BMC against Aeromonas hydrophila and Pseudomonas fluorescens in TSYE broth (as determined using an indirect impedance method) was 0.125 and 2% (v/v), respectively; the former was not greatly affected by the increase of challenge inoculum from 10(3) to 10(6) cfu ml-1. Results with resting cells demonstrated that BMC was bactericidal to both Aer. hydrophila and Ps. fluorescens. The growth of Aer. hydrophila in filter-sterilized lettuce extract was completely inhibited by 0.1% (v/v) BMC whereas that of Ps. fluorescens was not significantly affected by 1% (v/v) BMC. In addition, the effectiveness of washing fresh lettuce with 0.1 or 1% (v/v) BMC on survival of natural microbial flora was comparable with that effected by 125 ppm chlorine.

Oxidized cholesterol in oxidized low density lipoprotein may be responsible for the inhibition of LPS-induced nitric oxide production in macrophages

Previous work has shown that oxidized low density lipoprotein (Ox-LDL) inhibited lipopolysacchride (LPS)-induced nitric oxide (NO) production in macrophages. In this paper, the role of different components of Ox-LDL in the inhibitory effect was studied by measuring nitrite in media. Ox-LDL inhibited LPS-induced NO production in macrophage cell line J774.A1. When compared with Ox-LDL, native and acetylated LDL had a lesser effect on NO production. Pre-clearance of lipid hydroperoxides (LOOH) in Ox-LDL and removal of soluble thiobarbituric acid reactive substances (TBARS) in Ox-LDL solution by dialysis had no influence on the inhibitory effect of Ox-LDL. The protein moiety of Ox-LDL had no effect on NO production, but the lipid moiety inhibited NO production to about the same extent as intact Ox-LDL. Linoleic acid and phosphatidylcholine, the main components of LDL lipid, whether oxidized separately or together, had no effect on NO production. However, if linoleic acid and cholesterol oxidized together, there was very strong inhibition of NO production. Cholesterol oxidized alone also had some inhibitory effect. These results suggest that oxidized cholesterol in Ox-LDL might be responsible for the inhibition of NO production in macrophages.

Expression of four rat CYP2D isoforms in Saccharomyces cerevisiae and their catalytic specificity

We cloned four cDNAs belonging to the CYP2D subfamily to express these enzymes in yeast cells and to compare their catalytic activities simultaneously. Three are believed to be alleles of CYP2D1, 2D2, and 2D3, respectively, based on high nucleotide sequence similarity, while CYP2D4 had both sequences of CYP2D4 and CYP2D18. Expression plasmids carrying CYP2D cDNAs were transformed into Saccharomyces cerevisiae. Typical P450 CO-difference spectra with absorbance maximum at 448 nm were recorded with microsomal preparations from the yeast cells expressing the four CYP2D forms. A catalytic study of these CYP2D forms was done with debrisoquine, bufuralol, and lidocaine. CYP2D2 had the highest debrisoquine 4-hydroxylation (2.2 nmol/min/nmol P450) activity, similar to that (2.2 nmol/min/nmol) of human CYP2D6 expressed in yeast cells. CYP2D3 had high lidocaine N-deethylation (43 nmol/min/nmol P450) activity, and both CYP2D3 and 2D2 exhibited high lidocaine 3-hydroxylation (2.4 and 1.6 nmol/min/nmol P450, respectively) activity. Bufuralol 1'-hydroxylation catalytic capabilities were comparable among the four isoforms. The activity of CYP2D1 was relatively low toward the three substrates (debrisoquine, 0.091; bufuralol, 1.5; lidocaine 3-hydroxylation, 0.019; lidocaine N-deethylation, 2.8 nmol/min/nmol P450). These findings indicate that debrisoquine, a typical substrate for CYP2D forms, was mainly metabolized by CYP2D2 but not CYP2D1 in rat liver and that the CYP2D forms have different substrate specificity.

Enuresis and common voiding abnormalities

Voiding problems, and in particular nocturnal enuresis, can usually be evaluated and managed without resorting to complex procedures or invasive tests. A good history with attention to toilet habits and the possible presence of infection can help distinguish patients who may have significant organic pathologic conditions who require further investigation. Wetting alarms are effective with a low recidivism rate but are noisy. DDAVP is effective, works rapidly, and is discrete but has a higher recidivism rate. Treatment is aimed at correcting any poor toilet habits and using the appropriate alarm device or medication.

Oxidative and malondialdehyde modification of low-density lipoprotein: a comparative study

Low-density lipoprotein (LDL) was modified with copper ions (Cu2+) and malondialdehyde (MDA), and the differences were compared. The results show that both oxidative and MDA modification produce a decrease in free amino groups in LDL and enhance its electrophoretic mobility on agarose gel, and that these observations are linked. However, differences produced by the two forms of modification were observed. Oxidative modification of LDL involves free radical-mediated lipid peroxidation which produces large amounts of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes. In addition, vitamin E was reduced considerably and cholesterol lowered, and apolipoprotein B (apo B) fragmentation and aggregation were seen. Similar changes were not seen with MDA modification which does not involve lipid peroxidation. Fluorescence emission spectra of both forms of modified LDL show that emission intensity increases gradually as the modification progresses, but maximum emission wavelength and spectrum patterns are not the same. These findings may be of some significance in the study of the antigenicity, scavenger receptor multiplicity and toxic effects of modified LDL.

Experience with vesicoureteral reflux in children: clinical characteristics

PURPOSE

We reviewed our 9-year experience with a large population of children with vesicoureteral reflux who were evaluated and treated according to contemporary concepts.

MATERIALS AND METHODS

From 1985 to 1993 we followed 288 boys and 752 girls with vesicoureteral reflux. If surgery was not performed, patients were on antibiotic prophylaxis and evaluation was done every 18 months with contrast voiding cystography and radionuclide renal imaging. Urine cultures were obtained every 4 months. Two negative voiding cystourethrograms 1 year apart were required to discontinue prophylaxis.

RESULTS

The major reasons for initial evaluation were urinary tract infection in 560 children (54%), voiding dysfunction without urinary tract infection in 156 (15%), sibling surveys in 122 (12%) and prenatal hydronephrosis in 23 (2%). In 150 kidneys (10%) in 132 children scarring at presentation was grade 0 in 10 (7%), I in 18 (12%), II in 27 (18%), III in 30 (20%), IV in 48 (32%) and V in 17 (11%). Of these 132 patients 17 presented at ages less than 1 year (13%), 29 at ages 1 to 3 (22%), 50 at ages 4 to 6 (38%), 24 at ages 7 to 9 (18%) and 12 at ages greater than 10 (9%). No new scars were seen in children on prophylaxis without breakthrough infection. After 1 negative voiding cystourethrogram reflux was noted again in 27% of the cases. Breakthrough infections developed in 62 children of whom a third were older than 7 years. Reimplantation in 205 children (20%) was performed for grade IV to V reflux (101), breakthrough infection (62), advanced age (18), large periureteral diverticulum (12) and noncompliance (3). Five boys and 57 girls (30% of all children) had urinary tract infections after successful reimplantation.

CONCLUSIONS

Almost half of the children with vesicoureteral reflux have no history of culture proved urinary tract infection. Scarring may be associated with any reflux grade and it may be initially diagnosed at any age. Only half of the scars are noted with higher grades of reflux (IV and V). Continuous prophylaxis prevents new scarring. Breakthrough infections are rare but they can occur at ages greater than 7 years. Two consecutive negative cystograms are necessary before discontinuing prophylaxis. Children should be monitored after reimplantation for recurrent urinary tract infection.

Detection of bacteriocins of lactic acid bacteria isolated from foods and comparison with pediocin and nisin

A total of 663,533 colonies from 72 dairy and meat sources showed a detection rate of 0.2% for bacteriocin producers using direct plating techniques. A further 83,000 colonies from 40 fish and vegetable sources showed a detection rate of 3.4% for bacteriocin producers using selective enrichment procedures. A collection of seven purified isolates showing a different host spectrum of bacteriocin activity and with the ability to produce bacteriocins in broth culture were compared with nisin and pediocin (with respect to their inhibitory activity, determined by the critical dilution method), against various indicator bacteria in agar and broth. The sensitivity of Listeria species to various bacteriocins was influenced by the agar and broth test systems used. A Lactobacillus curvatus strain was found to be the most suitable indicator for quantitating antimicrobial effects of all the bacteriocins investigated in both agar and broth test systems. The bacteriocin-producing isolates were characterized by biochemical reactions and DNA restriction enzyme profiles and taxonomic identification revealed species of Lactobacillus, Carnobacterium and Lactococcus assigned on the basis of 16S rDNA sequences.

Resolution rates of low grade vesicoureteral reflux stratified by patient age at presentation

PURPOSE

Most children with grades I to III primary vesicoureteral reflux are monitored for years on antibiotic prophylaxis until reflux resolves. While the overall resolution rate of these grades is known, the rates for various patient ages at presentation are unknown. Therefore, we examined resolution rates of these grades for different ages at presentation.

MATERIALS AND METHODS

From 1985 through 1990, 168 boys (245 ureters) and 433 girls (590 ureters) with all grades of reflux were enrolled in the study and monitored through the end of 1993. Urine cultures were obtained every 4 months and contrast voiding cystourethrography was repeated every 18 months. Age at presentation was stratified into groups younger than 1, 1 to 3, 4 to 6, 7 to 9, and 10 years and older. Resolution rates were then calculated for grades I to III reflux for each age at presentation. Time to resolution was also evaluated for each age and grade.

RESULTS

There were no significant differences between rates of resolution at different ages for each grade. Children less than 10 years old had as high a likelihood of resolution as infants. Neither sex nor bilaterality versus unilaterality was a helpful predictor of resolution. Time to resolution varied widely and it was also not helpful for identifying the cases of reflux that resolved.

CONCLUSIONS

Low grade vesicoureteral reflux may not resolve until adolescence and age at presentation is not a reliable predictive factor. Children should remain on prophylaxis for many years unless definitive correction is undertaken.

Age might influence the frequency distribution of metoprolol hydroxylation polymorphism in a Chinese population

The frequency distribution of the 8-hour urinary ratio of metoprolol/alpha-hydroxymetoprolol (MR) was investigated in 206 healthy rural Chinese volunteers. The frequency of the poor metabolizer phenotype of metoprolol alpha-hydroxylation was 0% in this Chinese population. When the 206 subjects were subgrouped into four groups by age, the excretion of alpha-hydroxymetoprolol was significantly lower in the subjects with age older than 41 years compared to two younger groups (16-30 years), and the metoprolol hydroxylation metabolic ratio(metoprolol/a-hydroxymetoprolol, MR) was higher in these middle-aged subjects, indicating that age may affect the frequency distribution of the 8-hour urinary MR or log MR, although multiple regression analysis did not show a significant correlation between age, urine volume and MR. Also, a significant correlation was found between age and the excretion (percentage of dose) of alpha-hydroxymetoprolol in 8-hour urine (r = 0.259, P < 0.001). On the other hand, both multiple regression analysis and nonparametric tests showed that the larger the amount of urine excreted, the more metoprolol was recovered, demonstrating that the urinary excretion of unchanged metoprolol is renal flow-limited.

Inhibition of Listeria monocytogenes by piscicolin 126 in milk and Camembert cheese manufactured with a thermophilic starter

The effect of bacteriocin, piscicolin 126, on the growth of Listeria monocytogenes and cheese starter bacteria was investigated in milk and in Camembert cheese manufactured from milk challenged with 10(2) cfu ml(-1) L. monocytogenes. In milk incubated at 30 degrees C, piscicolin 126 added in the range of 512-2,048 AU ml(-1) effectively inhibited growth of L. monocytogenes for more than 20 d when challenged with approximately 10(2) cfu ml(-1) L. monocytogenes. At higher challenge levels (10(4) and 10(6) cfu ml(-1)), piscicolin 126 reduced the viable count of L. monocytogenes by 4-5 log units immediately after addition of the bacteriocin; however, growth of Listeria occurred within 24 h. The minimum inhibitory concentration (MIC) of piscicolin 126 against lactic acid cheese starter bacteria was generally greater than 204,800 AU ml(-1) , and the viable count and acid production of these starter cultures in milk were not affected by the addition of 2,048 AU ml(-1) piscicolin 126. Camembert cheeses made from milk challenged with L. monocytogenes and with added piscicolin 126 showed a viable count of L. monocytogenes 3-4 log units lower than those without piscicolin 126. Inactivation of piscicolin 126 by proteolytic enzymes from cheese starter bacteria and mould together with the emergence of piscicolin 126-resistant isolates was responsible for the recovery of L. monocytogenes in the cheeses during ripening.

Incorporation of nisin in micro-particles of calcium alginate

Nisin was successfully incorporated into a matrix of calcium alginate and ground into micro-particles smaller than 150 microns. Formation of micro-particles and incorporation of nisin was verified by scanning electron microscopy and by the reduction in the inactivation of nisin activity with proteolytic enzymes. Incorporation efficiency was 87-93% and the nisin in the alginate-incorporated form was 100% active against an indicator culture of Lactobacillus curvatus both in MRS broth and reconstituted skim milk.

Transit peptides play a major role in the preferential import of proteins into leucoplasts and chloroplasts

The in vitro import characteristics of six different precursors of plastid proteins were assessed to determine differences in the protein import pathways of leucoplasts and chloroplasts. Five of these precursor proteins are destined to different subchloroplast sites, and one is a leucoplast stromal precursor protein. The results indicate that some of these precursors can be imported equally into both plastid types and others preferentially into one type of plastid versus the other. The ability of plastids to import different proteins correlates with the in vivo steady state levels of these proteins. Additional differences were also observed in the intraorganellar portion of the translocation pathway for two thylakoidal proteins. The differences in import characteristics were found to be predominantly governed by information in the transit peptides, since attachment of the various transit peptides to different plastid and foreign proteins demonstrated that the import behavior of the proteins is transferable with the transit sequence. These results indicate that the import mechanisms of leucoplasts and chloroplasts are sufficiently different such that the plastids respond differently to the information present in the transit peptides.

Vesicoureteral reflux: practical aspects of evaluation and management

The efficacy of both medical and surgical therapy for vesicoureteral reflux (VUR) has been well established. Controversy remains, however, regarding who should be evaluated for the presence of VUR, who should undergo corrective surgery, who should be treated medically and for how long. Medical treatment requires many years of continuous antibiotic prophylaxis, so compliance with therapy is essential. Many children are lost to followup, however, and remain untreated after a medical regimen is started. This large number of untreated children raises issues of the appropriateness of blanket therapeutic recommendations for all children with VUR and challenges the clinician to devise more effective treatment strategies.

[A clinical study of polytetrafluoroethylene (polytef) as a substitute for conjunctiva]

Burn, tumor or congenital reasons may cause coloboma of conjunctiva. We were seeking for a thin membrane to cover the coloboma that would make the survival peripheral conjunctiva to grow and self-repair so that mucosa transplantation could be avoided. A polytetrafluoroethylene membrane of 0.1 mm thickness, 2-3 mm larger in diameter than the coloboma was sutured in place. After 2-3 weeks the membrane was removed. A total of 16 patients underwent the operation. Of them there were 2 of plasmacytoma, 5 of symblepharon, 6 of contracture of socket of eyeball and 3 of complex pterygium. In two to three weeks, the region of coloboma of conjunctiva was found being repaired. On an average 12 months' follow-up study, the eyeball movements in all cases were normal and the eyes looked symmetric. No symblepharon was found. We conclude that the polytetrafluoroethylene is a non-toxic, smooth, non-adhesive and non-distort substance resistant to high and low temperatures. When used as a substitute for conjunctiva at the region of coloboma of conjunctiva, it makes the peripheral normal conjunctiva tissues to grow and repair the coloboma.

The elimination of diazepam in Chinese subjects is dependent on the mephenytoin oxidation phenotype

1. The disposition of diazepam and desmethyldiazepam was studied in 21 healthy male Chinese subjects who were phenotyped with mephenytoin. Four poor metabolizers (PM) were identified by phenotyping with mephenytoin and by genotyping for CYP2C19. 2. Serum diazepam and desmethyldiazepam concentrations were measured by high performance liquid chromatography in samples drawn up to 24 days after administration. 3. The plasma elimination half-lives of diazepam (100.8 +/- 32.3 h) and desmethyldiazepam (219.9 +/- 62.7 h) in PMs were significantly longer than those (34.7 +/- 23.0 h for diazepam, 103.1 +/- 25.9 h for desmethyldiazepam) of the 17 phenotyped extensive metabolizers (EM), and those (30.8 +/- 24.9 h for diazepam, 103.1 +/- 27.5 h for desmethyldiazepam) of the five genotyped EMs. 4. The mephenytoin S/R ratios were significantly correlated with the plasma half-lives of diazepam (r = 0.543, P < 0.05) and desmethyldiazepam (r = 0.522, P < 0.05), and with the clearance (r = -0.524, P < 0.05) of diazepam in 21 subjects. 5. These results are compatible with the conclusion that both diazepam and desmethyldiazepam are metabolized by cytochrome P450 CYP2C19 in the Chinese population. 6. The mephenytoin S/R ratios in nine EMs who drank alcohol frequently were significantly higher than those of seven EMs who were non-drinkers, but the plasma kinetics of diazepam and desmethyldiazepam were not significantly different between the two groups. The explanation for these finding is not clear.

Expanded followup of intravesical oxybutynin chloride use in children with neurogenic bladder

PURPOSE

We evaluated the long-term results of intravesical oxybutynin chloride use in children with neurogenic bladders who could not tolerate or whose conditions were refractory to oral therapy.

MATERIALS AND METHODS

We reviewed our experience with 28 children (myelomeningocele in 27 and imperforate anus in 1) who presented with urinary incontinence and/or elevated bladder pressures refractory to intermittent catheterization and oral anticholinergic medication. Intravesical oxybutynin was administered to each child by instillation of 5 mg. crushed oxybutynin chloride in 10 cc sterile saline 2 times daily during catheterization.

RESULTS

Seven patients (25%) could not tolerate intravesical oxybutynin secondary to anticholinergic side effects. The remaining 21 children have been followed on intravesical oxybutynin for a mean of 35 months (range 3 to 67). Of these 21 children 12 (57%) became completely dry day and night, 5 (24%) achieved daytime continence between catheterizations and 4 (19%) remained clinically unchanged with 2 in diapers. On urodynamics these 21 patients had increased bladder capacity of up to 1,150% (mean 237%, p < 0.0001) and decreased mean maximum filling pressures of -31% (p = 0.002).

CONCLUSIONS

Although a number of patients continued to have anticholinergic side effects, a majority had significant improvement in urodynamic parameters and continence. The response appears to be durable, and it spares many of these children from undergoing bladder augmentation.

Sibling reflux: a dual center retrospective study

PURPOSE

Siblings of index patients with vesicoureteral reflux are known to have an increased incidence of reflux. Previous reports may be biased due to significantly more female siblings undergoing screening. In addition, it has been suggested that screening is unnecessary in older children.

MATERIALS AND METHODS

We retrospectively reviewed the records of probands with vesicoureteral reflux. A total of 422 families comprising 622 siblings was identified at our centers from 1985 to 1994. Of the 255 boys and 277 girls newborn to 16 years old (mean age 6.2 years) 85% were evaluated. Almost 43% of the probands (225) were older than 7 years.

RESULTS

Vesicoureteral reflux was noted in 144 siblings (52 boys and 92 girls, 27%). The majority had low grade reflux but in 111 (77%) maximum reflux grade was II or III. Reflux nephropathy was demonstrated on a nuclear renal scan in 18 of the 132 tested siblings (13.6%). In all of these children reflux was grades II to IV and 27% were older than 10 years.

CONCLUSIONS

When vesicoureteral reflux is discovered, all siblings should be considered for screening. The evaluation of older siblings remains controversial, since they comprise only a small fraction of all siblings with reflux but may have a significant portion of reflux nephropathy. There was a 27% overall incidence with a 33% rate in girls. The incidence of reflux in siblings decreased after age 7 years but reflux nephropathy was identified even in the older children.

Adsorption of bacteriocins by ingestible silica compounds

Bacteriocins including nisin, pediocin PO2, brevicin 286 and piscicolin 126 were adsorbed from culture supernates by various food-grade porous silica anti-caking agents and the food colourant, titanium dioxide. All the porous silica (calcium silicate or silicon dioxide) materials showed substantial capacity in adsorbing bacteriocin activities from the culture supernate and biological activity was recovered in the adsorbents. In contrast, the food colourant titanium dioxide adsorbed most of the bacteriocin activity from the supernate, with minimal biological activity retained in the adsorbent. Experiments with piscicolin 126 showed that optimum adsorption could be achieved with Micro-Cel E within 30 min, independent of the supernate pH (2.0-10.0). Piscicolin activity of up to 5 x 10(7) AU g(-1) of Micro-Cel E was obtained after adsorption from culture supernates and the adsorbed piscicolin demonstrated substantial biological activity against Listeria monocytogenes in both broth and a milk growth medium.

An analysis of social and economic factors associated with followup of patients with vesicoureteral reflux

PURPOSE

Nonsurgical treatment of vesicoureteral reflux requires antibiotic prophylaxis and long-term surveillance. We examined factors that affect followup compliance and influence quality of care in these children.

MATERIALS AND METHODS

We retrospectively reviewed the records of 288 boys and 742 girls with vesicoureteral reflux.

RESULTS

Of the children treated nonsurgically for vesicoureteral reflux 34% were lost to followup and the majority (80%) were not monitored beyond the 1-year followup appointment. Older maternal age (36 years or older) was significantly associated with improved followup compliance. Paternal age, primary physician type, medical insurance type, income, education level and environment (urban, suburban or rural) were not significant.

CONCLUSIONS

Approximately a third of children treated nonsurgically for vesicoureteral reflux will be lost to followup. Only older maternal age predicts for good compliance. Preconceptions about compliance on the basis of other factors, such as socioeconomic status and primary physician type, may be incorrect. Furthermore, the notion that certain forms of medical insurance plans may help to promote followup may also be unsupported. These children would benefit from efforts to improve compliance with a medical regimen or early correction of reflux.

Characterization of the chemical and antimicrobial properties of piscicolin 126, a bacteriocin produced by Carnobacterium piscicola JG126

A novel peptide bacteriocin produced by the lactic acid bacterium Carnobacterium piscicola JG126 isolated from spoiled ham was purified and characterized. This bacteriocin, designated piscicolin 126, inhibited the growth of several gram-positive bacteria, especially the food-borne pathogen Listeria monocytogenes, but had no effect on the growth of a number of yeasts and gram-negative bacteria. Bactericidal activity was not destroyed by exposure to elevated temperatures at low pH values; however, bactericidal activity was lost at high pH values, especially when high pH values were combined with an elevated temperature. Piscicolin 126 activity was not affected by catalase, lipase, or lysozyme but was destroyed by exposure to a range of proteolytic enzymes. Piscicolin 126 was purified to homogeneity and was found to be a peptide having a molecular weight of 4,416.6 +/- 1.9. A sequence analysis revealed that this compound is a cystibiotic (class IIa) bacteriocin containing 44 amino acid residues and one intrapeptide disulfide ring. Piscicolin 126 has regions of homology with some other bacteriocins obtained from lactic acid bacteria and is most closely related to sakacin P and pediocin PA-1 (levels of identity, 75 and 55%, respectively). Addition of piscicolin 126 to a devilled ham paste test food system inhibited the growth of L. monocytogenes for at least 14 days. Piscicolin 126 was more effective than two commercially available bacteriocin preparations tested in the same system.

A food-grade process for isolation and partial purification of bacteriocins of lactic acid bacteria that uses diatomite calcium silicate

Bacteriocins, including nisin, pediocin PO2, brevicin 286, and piscicolin 126, were extracted from fermentation media by adsorption onto Micro-Cel (a food-grade diatomite calcium silicate anticaking agent) and subsequent desorption. The optimal conditions for desorption of piscicolin 126 were determined and applied to other bacteriocins, and the relative purities of the desorbed preparations were compared. Piscicolin was not successfully desorbed from Micro-Cel at pH 1.0 to 12.0, with organic solvents, or by increase of ionic strength up to 1 M NaCl. However, 25 and 75% of the bacteriocin activity was desorbed by using 1% sodium deoxycholate and 1% sodium dodecyl sulfate (SDS), respectively. Higher levels (up to 100%) of desorption were achieved by repeated elution or by an increase in surfactant concentration. Desorption of piscicolin with 1/10 volume of SDS solution resulted in a preparation with 10 times concentration in activity, equivalent to that of ammonium sulfate preparations (409,600 to 819,200 activity units/ml). Determination of organic nitrogen (N) content revealed that the desorbed piscicolin preparations were substantially free of proteinaceous substances (approximately 92 to 99%) compared with original culture supernatants and ammonium sulfate preparations. Nisin, pediocin, and brevicin were also desorbed with 1% SDS with a similar level of purification.