The assessment of the antibacterial and antifungal activities of aspirin, EDTA and aspirin–EDTA combination and their effectiveness as antibiofilm agents

Aims:  To evaluate the antimicrobial activities of aspirin, EDTA and an aspirin-EDTA (A-EDTA) combination against Pseudomonas aeruginosa , Escherichia coli and Candida albicans in planktonic and biofilm cultures.
Methods and Results:  Minimal inhibitory concentrations (MIC) and minimal biocidal concentrations (MBC) were determined using twofold broth microdilution and viable counting methods, respectively. Aspirin's recorded MIC values ranged from 1·2 to 2·7 mg ml⁻¹. Checkerboard assay demonstrated a synergism in antimicrobial activity upon combination. Aspirin's minimal biofilm eradication concentration values (MBEC) against the established biofilms ranged between 1·35 and 3·83 mg ml⁻¹. A complete eradication of bacterial biofilms was achieved after a 4-h treatment with the A-EDTA combination.
Conclusion:  Both aspirin and EDTA possess broad-spectrum antimicrobial activity for both planktonic and biofilm cultures. Aspirin used at the MBEC for 24 h was successful in eradicating P. aeruginosa , E. coli and C. albicans biofilms established on abiotic surfaces. Moreover, the exposure to the A-EDTA combination (4 h) effected complete bacterial biofilm eradication.
Significance and Impact of the Study:  There is a continuous need for the discovery of new antimicrobial agents. Aspirin and EDTA are 'nonantibiotic drugs', the combination of which can be used successfully to treat and eradicate biofilms established on abiotic surfaces.     

Comparison of antimicrobial resistance patterns between clinical and sewage isolates in a regional hospital in Taiwan

Aims:  To compare bacterial populations and antimicrobial resistance patterns between clinical and sewage isolates from a regional hospital in northern Taiwan. The dissemination of antibiotic-resistant bacteria from hospital compartments to the hospital sewage treatment plant was examined.
Methods and Results:  A total of 1020 clinical isolates and 435 sewage isolates were collected between July and September 2005. The percentages of Gram-negative bacteria from the clinical and sewage isolates were 87·2% and 91·0%, respectively ( P  =   0·033). Escherichia coli were the leading bacterial isolates in both groups. Antimicrobial susceptibility testing showed a significant difference ( P  <   0·001) in resistance to ampicillin (85·6% vs 94·1%), ampicillin/sulbactam (31·7% vs 55·4%), cefazolin (29·2% vs 71·5%) and cefuroxime (20·7% vs 61·9%) between clinical and sewage coliform isolates, respectively.
Conclusions:  The sewage isolates had higher antimicrobial resistance rates than the clinical isolates from the same hospital.
Significance and Impact of the Study:  The low efficacy of the hospital sewage treatment may contribute to the dissemination of multidrug resistant bacteria from this hospital compartments to the environment. Practices which limit the disposal of antimicrobial agents into the wastewater system may be the possible measure to prevent the selection of multidrug-resistant bacteria from sewage treatment plants.     

Influence of lyophilization, fluidized bed drying, addition of protectants, and storage on the viability of lactic acid bacteria

Aims:  The present study focuses on the impact of two different drying technologies and the influence of protectants on process survival and storage stability of the two lactic acid bacterial strains Enterococcus faecium and Lactobacillus plantarum .
Methods and Results:  After incubation with the protectants glucose, sucrose, trehalose, and maltodextrin the concentrated bacterial suspensions were subjected to fluidized bed drying and lyophilization and subsequently stored at 4, 22, and 35°C for half a year. Lactobacillus plantarum turned out to be more sensitive to both drying methods than Ent. faecium . Without the addition of a protectant cells of both strains suffered higher losses during fluidized bed drying. Elevated storage temperatures correlate with a higher decline of viable bacterial cells.
Conclusions:  Although survival rates varied between the strains, the nonreducing disaccharides revealed overall best protection for both investigated lactic acid bacteria during processing and storage. The addition of protective carbohydrates can prevent the decline in viability during fluidized bed drying.
Significance and Impact of the Study:  The influence of protectants proved to be species specific and therefore needs to be determined on a case-to-case basis. Survival rates, duration, and energy consumption appear to be the crucial parameters to evaluate the economy of production processes for industrial starter cultures.     

The effect of surface charge, negative and bipolar ionization on the deposition of airborne bacteria

Aims:  A series of experiments were conducted to evaluate the effect of surface charge and air ionization on the deposition of airborne bacteria.
Methods and Results:  The interaction between surface electrostatic potential and the deposition of airborne bacteria in an indoor environment was investigated using settle plates charged with electric potentials of 0, ±2·5kV and ±5kV. Results showed that bacterial deposition on the plates increased proportionally with increased potential to over twice the gravitational sedimentation rate at +5kV. Experiments were repeated under similar conditions in the presence of either negative or bipolar air ionization. Bipolar air ionization resulted in reduction of bacterial deposition onto the charged surfaces to levels nearly equal to gravitational sedimentation. In contrast, diffusion charging appears to have occurred during negative air ionization, resulting in an even greater deposition onto the oppositely charged surface than observed without ionization.
Conclusions:  Static charges on fomitic surfaces may attract bacteria resulting in deposition in excess of that expected by gravitational sedimentation or simple diffusion. Implementation of bipolar ionization may result in reduction of bacterial deposition.
Significance and Impact of Study:  Fomitic surfaces are important vehicles for the transmission of infectious organisms. This study has demonstrated a simple strategy for minimizing charge related deposition of bacteria on surfaces.     

Presence and environmental circulation of enteric viruses in three different wastewater treatment plants

Aims:  The aim of the work was to evaluate the circulation of the viruses and to determine a correlation between faecal indicators and viruses.
Methods and Results:  Raw wastewater and effluent samples were collected from three wastewater treatment plants, during three sampling periods, and analysed, using cultural and molecular methods, to determine bacteria and virus presence. The results show a removal of bacterial indicators, but a limited reduction of the phages. The viral analysis displays the circulation of cultivable enteroviruses and differences in the seasonal-geographical distribution. Hepatitis A virus was found with only two genotypes: IA-IB. Rotavirus was present in 11·11%, 24·14%, 2·78% of the samples in the 1st, 2nd and 3rd sampling periods; Astrovirus in 33·33%, 6·9%, 25%; Adenovirus in 7·41%, 3·45%, 2·78%; Norovirus in 7·41%, 10·34%, 5·56% respectively. Adenovirus was never identified in plants B and C as Rotavirus in plant C.
Conclusions:  The presence of faecal indicators was not predictive of the enteric virus presence, whereas a different circulation of Enteroviruses was found in the wastewater treatment plants.
Significance and Impact of the Study:  The study shows the importance and the usefulness of molecular methods to evaluate the virus circulation and the genetic variability of Enteroviruses.     

Survival and growth of Cronobacter species (Enterobacter sakazakii) in wheat-based infant follow-on formulas

Aims:  To determine the survival and growth characteristics of Cronobacter species ( Enterobacter sakazakii ) in infant wheat-based formulas reconstituted with water, milk, grape juice or apple juice during storage.
Methods and Results:  Infant wheat-based formulas were reconstituted with water, ultra high temperature milk, pasteurized grape or apple juices. The reconstituted formulas were inoculated with Cronobacter sakazakii and Cronobacter muytjensii and stored at 4, 25 or 37°C for up to 24 h. At 25 and 37°C, Cronobacter grew more (>5 log₁₀) in formulas reconstituted with water or milk than those prepared with grape or apple juices ( c. 2–3 log₁₀). The organism persisted, but did not grow in any formulas stored at 4°C. Formulas reconstituted with water and milk decreased from pH 6·0 to 4·8–5·0 after 24 h, whereas the pH of the formulas reconstituted with fruit juices remained at their initial pH values, c. pH 4·8–5·0.
Conclusions:  Cronobacter sakazakii and C. muytjensii can grow in reconstituted wheat-based formulas. If not immediately consumed, these formulas should be stored at refrigeration temperatures to reduce the risk of infant infection.
Significance and Impact of the Study:  The results of this study will be of use to regulatory agencies and infant formula producers to recommend storage conditions that reduce the growth of Cronobacter in infant wheat-based formulas.     

Comparison of in vitro models to study bacterial adhesion to the intestinal epithelium

Aims:  To evaluate the adhesion ability of intestinal bacteria to different in vitro models of intestinal epithelia, and to estimate the suitability of these models and the type of interactions involved.
Methods and results:  The adhesion of probiotic ( Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp . lactis Bb12), commensal ( B. animalis IATA-A2 and B. bifidum IATA-ES2) and potentially pathogenic bacteria ( E. coli and L. monocytogenes ) was determined. The adhesion models used were polycarbonate-well plates, with or without mucin, and different configurations of Caco-2 and/or HT29-MTX cell cultures. All bacteria adhered to wells without mucin (2·6–27·3%), the values being highly variable depending on the bacterial strain. Adhesion percentages of potentially probiotic bacteria to Caco-2 cultures were remarkably lower ( P  <   0·05) than those to mucin, and more similar to those of pathogenic strains. The lowest adhesion of different bacterial strains was detected on HT29-MTX (0·5–2·3%) cultures and Caco-2/HT29-MTX (0·6–3·2%) cocultures, while these values were increased in Caco-2 cultures plus mucin.
Conclusions:  The results suggested that bacterial strains exhibit different capacities to adhere to cellular components and several types of mucin present in different models, showing preferences for intestinal MUC2.
Significance and impact of the study:  The use of Caco-2 cells monolayer plus mucin (type II) better approaches the physiological characteristics of in vivo situation, providing a reliable and suitable in vitro model to evaluate bacterial adhesion.     

The application of ionizers in domestic refrigerators for reduction in airborne and surface bacteria

Aim: To investigate the antimicrobial effect of ionization on bacteria in household refrigerators. Methods and Results: Ionizer prototypes were tested with respect to their technical requirements and their ability to reduce surface and airborne contamination in household refrigerators. Ion and ozone production of the tested prototypes were measured online by an ion meter and an ozone analyser. The produced negative air ion (NAI) and ozone amounts were between 1·2 and 3·7 × 10⁶ NAI cm^?3 and 11 and 19 ppb O₃, respectively. To test the influence of ionization on surface contamination, different materials like plastic, glass and nutrient agar for simulation of food were inoculated with bacterial suspensions. The reduction rate was dependent on surface properties. The effect on airborne bacteria was tested by nebulization of Bacillus subtilis– suspension (containing spores) aerosols in refrigerators with and without an ionizer. A clear reduction in air contamination because of ionization was measured. The antimicrobial effect is dependent on several factors, such as surface construction and airflow patterns within the refrigerator. Conclusions: Ionization seems to be an effective method for reduction in surface and airborne bacteria. Significance and Impact of the Study: This study is an initiation for a new consumer tool to decontaminate domestic refrigerators.     

Effects of temperature and humidity on the efficacy of methicillin-resistant Staphylococcus aureus challenged antimicrobial materials containing silver and copper

Aims:  To compare silver and copper, metals with known antimicrobial properties, by evaluating the effects of temperature and humidity on efficacy by challenging with methicillin resistant Staphylococcus aureus (MRSA) .
Methods and Results:  Using standard methodology described in a globally used Japanese Industrial Standard, JIS Z 2801, a silver ion-containing material exhibited >5 log reduction in MRSA viability after 24 h at >90% relative humidity (RH) at 20°C and 35°C but only a <0·3 log at ∼22% RH and 20°C and no reduction at ∼22% RH and 35°C. Copper alloys demonstrated >5 log reductions under all test conditions.
Conclusions:  While the high humidity (>90% RH) and high temperature (35°C) utilized in JIS Z 2801 produce measurable efficacy in a silver ion-containing material, it showed no significant response at lower temperature and humidity levels typical of indoor environments.
Significance and Impact of the Study:  The high efficacy levels displayed by the copper alloys, at temperature and humidity levels typical of indoor environments, compared to the low efficacy of the silver ion-containing material under the same conditions, favours the use of copper alloys as antimicrobial materials in indoor environments such as hospitals.     

Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beef

Aims:  In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces.
Methods and Results:  Ground beef samples inoculated with Salmonella Typhi (10⁶ CFU g⁻¹ ) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a ⁶⁰Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D ₁₀ value in the absence/presence of antimicrobial compound.
Conclusions:  Depending on the compound tested, the addition of antimicrobial compound decreased the D ₁₀ value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef.
Significance and Impact of the Study:  These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi.     

Corynebacterium pseudodiphtheriticum isolated from relevant clinical sites of infection: a human pathogen overlooked in emerging countries

Aims:  To examine the occurrence of and to determine the antimicrobial susceptibility of Corynebacterium pseudodiphtheriticum among patients with bacterial infections at a teaching hospital.
Methods and Results:  A total of 113 Coryne. pseudodiphtheriticum strains identified by conventional biochemical methods and API-Coryne System were recovered from patients from different age groups: 65·48% adults (18 to ≤59 years old), 9·73% aged (≥60 years old); 14·15% infants (<18 years old); 4·42% newborns (0–7 days). Micro-organisms were mostly related to infections in the urinary (29·2%) and respiratory tracts (27·45%) and intravenous sites (18·6%). Clinical samples were obtained only from 32·7% patients (26 adults, four aged, four infants and three newborns) presenting at least one of the predisposing conditions: end-stage renal disease; renal transplant; AIDS and Mycobacterium tuberculosis infection; cancer, hepatic cirrhosis; haemodialysis and catheter use. Antimicrobial susceptibility tests identified multiresistant phenotypes. Most strains (>50%) were resistant to oxacillin, erythromycin and clindamycin.
Conclusions:  Despite significant differences in age and functional status of patients Coryne. pseudodiphtheriticum may be implicated as a cause of respiratory and nonrespiratory human infections.
Significance and Impact of the Study:  Data are valuable for practitioners indicating the occurrence of multiresistant phenotypes and the possibility of severe infections due to Coryne. pseudodiphtheriticum , a pathogen usually overlooked in emerging countries.     

Effect of production conditions on the stability of a human bifidobacterial species Bifidobacterium longum in yogurt

Aims:  Human bifidobacteria are more sensitive to external environmental factors than animal bifidobacteria, and it is difficult to ensure their stable survival in yogurt. The purpose of this investigation was to observe the survival of human bifidobacteria in yogurts produced under various production conditions.
Methods:  Frozen or lyophilized bifidobacteria starters containing Bifidobacterium longum BB536 originally isolated from an infant, and commercial lyophilized yogurt starters were used for yogurt preparation. After producing yogurts under various conditions, the survival of bifidobacteria in these yogurts over various storage periods was observed.
Results:  Although there were some differences in bifidobacterial survival in yogurt between various production conditions, more than 1·0 × 10⁷ CFU g⁻¹ of Bif. longum survived in yogurt after 35 days' storage at 5°C. Lower fermentation temperature (37°C) and inclusion of Lactococcus lactis in the starter significantly ( P  < 0·05) improved survival of Bif. longum in the yogurt.
Conclusion:  In this investigation, the human bifidobacterial strain Bif. longum survived adequately in yogurt, although the fermentation temperature and starter composition affect bifidobacterial survival.
Significance and Impact of the Study:  This investigation indicates that stable probiotic yogurt using human bifidobacteria can be produced by choosing optimal production conditions.     

Antimicrobial activity of two peptides casecidin 15 and 17, found naturally in bovine colostrum

Aims:  To isolate and characterize peptides from bovine colostrum with antimicrobial activity.
Methods and Results:  Three peptides were purified from fresh colostrum by a range of chromatographic methods using antimicrobial activity against Escherichia coli DH5α to screen for the most active fractions. Two peptides, with antimicrobial activity, casecidin 17 and casecidin 15, were identical to sequences in the C-terminal of bovine β-casein (YQEPVLGPVRGPFPIIV and YQEPVLGPVRGPFPI) and had corresponding molecular masses of 1881·00 and 1669·06 Da, respectively. The third peptide was the known peptide isracidin which has a mass of 2763·80 Da and sequence of RPKHPIKHQGLPQEVLNENLLRF. Casecidin 17 and casecidin 15 had identical minimal inhibition concentrations (MICs) against E. coli DPC6053 of 0·4 mg ml⁻¹. Structural modelling suggested amphiphilic structures having identical inhibitory and structural properties. The MIC value of isracidin against E. coli DPC6053 was 0·2 mg ml⁻¹.
Conclusions:  This study shows the presence of three antimicrobial peptides in colostrum which may contribute to a bioprotective role to limit pathogen contamination. Furthermore, the discovery of casecidin 17 and 15 may provide the basis for novel antimicrobial peptide design.
Significance and Impact of the Study:  This is the first study to characterize peptides with antimicrobial activity present in fresh bovine colostrum.     

Factors influencing the presence and concentration of E. coli O157 and E. coli in farm waste on six cattle farms in North-West England

Aims:  To investigate the factors influencing the presence and burden of Escherichia coli O157 in farm wastes.
Methods and Results:  Wastes from six cattle farms were screened for the presence and concentration of E. coli O157 and E. coli on three occasions over a year and waste management data were collected. Sixty-three of 878 (7·1%) samples were positive for verocytotoxigenic Escherichia coli O157 and 664/875 (75·9%) for E. coli with detectable levels greater in fresh waste than in stored waste, pasture or dirty water.
Conclusions:  The turning/stirring of stored waste and the use of more than one store (allowing longer storage times) reduced the proportion of E. coli O157 positive samples. The presence of E. coli O157 significantly reduced from a high prevalence found in fresh faeces and stored waste to lower proportions in dirty water and pasture samples. Escherichia coli O157 was only detected on pasture when waste was spread from contaminated stores the day before sampling. A high prevalence of positive E. coli O157 samples were detected when cattle were re-housed.
Significance and Impact of the Study:  These findings help to support the importance of treating and storing farm waste, as well as providing evidence for the level of dilution of E. coli O157 from fresh waste to recently spread pastures.     

Antimicrobial activity of essential oils and structurally related synthetic food additives towards Clostridium perfringens

Aims:  To assess the potential of essential oils and structurally related synthetic food additives in inhibiting the growth of Clostridium perfringens for the control of necrotic enteritis in chickens.
Methods and Results:  The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Thirty-three of 66 oils/compounds exhibited ≥80% inhibition. Seven with the highest potency were further studied. The oils/compounds had MIC₉₅ values between 167 and 425  μ g ml⁻¹. Most of them were tolerant to low pH (2·0) and exhibited minor or no inhibition of Lactobacillus isolates from the chicken intestine. When mixed with chicken ileal digesta, the oils/compounds retained their efficacy against C . perfringens , but had little effect on the total number of lactobacilli and anaerobic bacteria in the digesta.
Conclusions:  Some essential oils/compounds demonstrated good potential in controlling C . perfringens .
Significance and Impact of the Study:  This study has identified candidates of essential oils/compounds for in vivo studies for the control of necrotic enteritis in chickens.     

Modelling the photosensitization-based inactivation of Bacillus cereus

Aims:  To study and to develop a model for the photo-destruction of the foodborne pathogen Bacillus cereus , initially treated with a precursor of endogenous photosensitizers (5-aminolevulinic acid, ALA).
Materials and methods:  The cells were incubated in the presence of ALA (3 or 7·5 mmol l⁻¹) for incubation times ranging from 2 to 60 min, inoculated onto the surface of LB Agar plates and submitted to light irradiation. The Weibull model was used to describe the survival curves of B. cereus . Quadratic equations were used to describe the effects of ALA concentration and incubation time on the Weibull model parameters.
Results:  ALA-based photosensitization proved to be an effective tool for inactivation of B. cereus . The decrease in viable counts observed after 20 min of irradiation, ranged from 4 to 6 log CFU g⁻¹.
Conclusions:  The developed model proved to be a parsimonious and robust solution to describe the observed data.
Significance and Impact of the Study:  The study demonstrates the effectiveness of photosensitization on B. cereus on agar plates. The model developed may be useful to optimize inactivation treatments by photosensitization.     

Surfactin reduces the adhesion of food-borne pathogenic bacteria to solid surfaces

Aims:  To investigate the effect of the biosurfactants surfactin and rhamnolipids on the adhesion of the food pathogens Listeria monocytogenes , Enterobacter sakazakii and Salmonella Enteritidis to stainless steel and polypropylene surfaces.
Methods and Results:  Quantification of bacterial adhesion was performed using the crystal violet staining technique. Preconditioning of surfaces with surfactin caused a reduction on the number of adhered cells of Ent. sakazakii and L. monocytogenes on stainless steel. The most significant result was obtained with L. monocytogenes where number of adhered cells was reduced by 10² CFU cm⁻². On polypropylene, surfactin showed a significant decrease on the adhesion of all strains. The adsorption of surfactin on polystyrene also reduces the adhesion of L. monocytogenes and Salm. Enteritidis growing cells. For short contact periods using nongrowing cells or longer contact periods with growing cells, surfactin was able to delay bacterial adhesion.
Conclusions:  The prior adsorption of surfactin to solid surfaces contributes on reducing colonization of the pathogenic bacteria.
Significance and Impact of the Study:  This is the first work investigating the effect of surfactin on the adhesion of the food pathogens L. monocytogenes , Ent. sakazakii and Salm. Enteritidis to polypropylene and stainless steel surfaces.     

Characterization and purification of a new bacteriocin with a broad inhibitory spectrum produced by Lactobacillus plantarum lp 31 strain isolated from dry-fermented sausage

Aims:  Characterization and purification of a new bacteriocin produced by Lactobacillus plantarum LP 31 strain, isolated from Argentinian dry-fermented sausage.
Methods and Results:  Lactobacillus plantarum LP 31 strain produces an antimicrobial compound that inhibits the growth of food-borne pathogenic bacteria. It was inactivated by proteolytic enzymes, was stable to heat and catalase and exhibited maximum activity in the pH range from 5·0 to 6·0. Consequently, it was characterized as a bacteriocin. It was purified by RP (reverse-phase) solid-phase extraction, gel filtration chromatography and RP-HPLC. Plantaricin produced by Lact. plantarum LP 31 is a peptide with a molecular weight of 1558·85 Da as determined by Maldi-Tof mass spectrometry and contains 14 amino acid residues. It was shown to have a bactericidal effect against Pseudomonas sp., Staphylococcus aureus , Bacillus cereus and Listeria monocytogenes.
Conclusions:  The bacteriocin produced by Lact. plantarum LP 31 may be considered as a new plantaricin according to its low molecular weight and particular amino acid composition.
Significance and Impact of the Study:  In view of the interesting inhibitory spectrum of this bacteriocin and because of its good technological properties (resistance to heat and activity at acidic pH), this bacteriocin has potential applications as a biopreservative to prevent the growth of food-borne pathogens and food spoilage bacteria in certain food products.     

Detection of bioterror agents in air samples using real-time PCR

Aims:  To use real-time PCR for the detection of bacterial bioterror agents in a liquid air sample containing potential airborne interferences, including bacteria, without the need for DNA extraction.
Methods and Results:  Bacteria in air were isolated after passive sedimentation onto R2A agar plates and characterized by 16S rRNA sequencing. Real-time PCR was used to identify different bacterial bioterror agents in an artificial air sample consisting of a liquid air sample and a mixture of miscellaneous airborne bacteria showing different colony morphology on R2A agar plates. No time-consuming DNA extraction was performed. Specifically designed fluorescent hybridization probes were used for identification.
Conclusions:  Fourteen different bacterial genera were classified by 16S rRNA gene sequencing of selected bacterial colonies showing growth on R2A agar plates. Real-time PCR amplification of all the bacterial bioterror agents was successfully obtained in the artificial air sample containing commonly found airborne bacteria and other potential airborne PCR interferences.
Significance and Impact of the Study:  Bacterial bioterror agents can be detected within 1 h in a liquid air sample containing a variety of commonly found airborne bacteria using real-time PCR. Airborne viable bacteria at Kjeller (Norway) were classified to the genera level using 16S rRNA gene sequencing.     

Synbiotics growth optimization of Bifidobacterium pseudocatenulatum G4 with prebiotics using a statistical methodology

Aims:  This study demonstrated the optimum growth of Bifidobacterium pseudocatenulatum G4 with prebiotics via statistical model.
Methods and Results:  Commercial prebiotics [inulin and fructooligosaccharide (FOS)], together with sorbitol, arabinan and inoculum rate, were tested by fractional factorial design to determine their impact on growth of Bif. pseudocatenulatum G4 in skim milk. At 48 h incubation, bacterial growth was mainly influenced by FOS and inoculum rate. Growth reduction was observed in all samples incubated for 72 h. Central composite design (CCD) was adopted using FOS and inoculum rate at 48 h incubation to develop the statistical model for optimization. The model predicted that 2·461 log CFU ml⁻¹ produced the optimum growth increase of Bif. pseudocatenulatum G4. The combination that produced the optimum point was 2·86% FOS (g/v) and 0·67% inoculum rate (v/v).
Conclusion:  At optimum combination of inoculum rate and FOS, validation experiments recorded 2·40 ± 10·02 log CFU ml⁻¹. The application in 1-l bioreactor for 24 h showed higher growth increase of 2·95 log CFU ml⁻¹.
Significant and Impact of the Study:  Response surface methodology approach is useful to develop optimum synbiotics combination for strain G4 with FOS.