Résumé
The purpose of this study was to analyze the response of different initial contamination levels of Alicydobadllus acidoterrestris ATCC 49025 spores in apple juice as affected by pulsed light treatment (PL, batch mode, xenon lamp, 3pulses/s, 0-71.6 J/cm²). Biphasic and Weibull frequency distribution models were used to characterize the relationship between inoculum size and treatment time with the reductions achieved after PL exposure. Additionally, a second order polynomial model was computed to relate required PL processing time to inoculum size and requested log reductions. PL treatment caused up to 3.0-3.5 log reductions, depending on the initial inoculum size. Inactivation curves corresponding to PL-treated samples were adequately characterized by both Weibull and biphasic models (R²d j 94-96%), and revealed that lower initial inoculum sizes were associated with higher inactivation rates. According to the polynomial model, the predicted time for PL treatment increased exponentially with inoculum size.
El objetivo del presente trabajo fue evaluar la influencia de la concentración de esporas de Alicyclobacillus acidoterrestris ATCC 49025 en la respuesta de inactivación por acción de la luz pulsada (modo estanco, lámpara de xenón, 3 pulsos/s, 0-71,6 J/cm²) en jugo de manzana comercial. Para caracterizar la relación existente entre la concentración de esporas y el tiempo de tratamiento con las reducciones logarítmicas alcanzadas luego de la exposición a la luz pulsada (LP), se aplicaron 2 modelos: el de Weibull y el bifásico. Adicionalmente, se estimó la relación entre el tiempo de tratamiento con LP y la concentración inicial de inoculo en el jugo con las reducciones logarítmicas logradas mediante regresión múltiple y la metodología de superficie de respuesta (MSR). La inactivación por LP provocó entre 3 y 3,5 reducciones logarítmicas, según la concentración inicial de esporas. Las curvas de inactivación fueron adecuadamente caracterizadas por los modelos matemáticos propuestos (Restado = 94-96%). El análisis por MSR permitió predecir un aumento exponencial del tiempo de tratamiento requerido conforme se incrementa el nivel de contaminación inicial.
Sujets)
Spores bactériens , Boissons , Malus , Alicyclobacillus , Contamination des aliments , Microbiologie alimentaireRésumé
Purpose: For antibiotic susceptibility results, conventional culture and sensitivity methods takes 48 hours after a blood culture is fl agged positive by automated systems. Early initiation of targeted antibiotic therapy is essential for effective management of sepsis to reduce morbidity, mortality, cost of treatment and prevent antibiotic resistance. Objective of this study was to evaluate Direct Sensitivity Test (DST) as a potential tool to get reliable antibiotic susceptibility results 24 hours earlier. Materials and Methods: Blood cultures fl agged positive between May 2011 to December 2012 by BacT/ALERT were Gram stained. All uni-microbial gram-negative blood cultures were simultaneously cultured and processed for DST from broth using disk diffusion method using British Society of Antimicrobial Chemotherapy (BSAC) guidelines. DST results available next day were compared with conventional antibiotic susceptibility test (AST) performed by Vitek-2 on isolated colonies. Results of DST (test method) and AST (reference method) were compared for agreements or errors. Results: Of the 840 antibiotic gram-negative organism combinations tested, Categorical and essential agreements were 83.7% and 96.2% respectively. Minor, major and very major errors were 12.5%, 3.33% and 0.47%, respectively. Conclusions: DST using disk diffusion from positive blood culture broths helps to initiate early targeted antibiotic therapy. There is high concordance between DST and AST.
Résumé
Aims: To produce Rhodobacter sphaeroides strain UMSPSB3 biomass with the reduction of chemical oxygen demand (COD) from palm oil mill effluent. Study Design: Locally isolated phototrophic bacterium with different inoculum levels were used in Palm Oil Mill effluent (POME). Collected POME was characterized before used as substrate. Inoculum of bacterium was grown in synthetic media and 48 hours inoculum was used to utilize the substrate. Place and Duration of Study: Biotechnological laboratory, Borneo Marine Research Institute, University Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia, between February 2014 to April 2014. Methodology: Growth characteristics of bacterium Rhodobacter sphaeroides strain UMSPSB3 was monitored at different light intensities. Later phototrophic bacterium Rhodobacter sphaeroides strain UMSPSB3 was grown in settled non-sterilized Palm Oil Mill effluent (POME). The growth characteristics of bacterium in term of dry cell weight and total carotenoids production, and reduction of COD were compared using 10%, 20% and 30% (v/v) levels of inoculum developed in synthetic 112 media. Results: The optimum light intensity for the growth of Rhodobacter sphaeroides strain UMSPSB3 was 2.5 klux. The highest bacterial biomass (Xmax) of 6.5 g/L (dry weight) and 72% reduction of COD were obtained after 96-h culture with 20% (v/v) inoculum level. The reduction of COD (%) and cell yield (Yx/y, g cell/g COD) in POME were 82% and 0.98 respectively, after 96-h culture with 30% (v/v) inoculum. Production of carotenoids was comparatively low in bacterium using POME as substrate. Inoculum levels of 20-30% (v/v) developed in synthetic 112 media supported the growth of phototrophic bacterium in settled POME, but higher level of inoculum was required for faster removal COD from effluent. A 10% (v/v) level of inoculum in POME did not support the isolate to grow. Conclusion: Production of bacterial biomass with bioremediation of effluent could be achieved using POME as substrate with locally isolated Rhodobacter sphaeroides strain.
Résumé
The aim of this study was to optimize cultural conditions for optimum growth and bioactive metabolite production by Aspergillus strain TSF 146, isolated from the subsurface soils of Brahmaputra plains, Assam, India. Agar disc diffusion assay was used to examine the antagonistic activity of the strain. The effect of different culture media, temperature, pH, incubation period, shaking, inoculum size and various carbon and nitrogen sources on the mycelial growth and bioactive metabolite production in a fixed volume of culture broth were studied. Aspergillus strain TSF 146 grew well and produced optimum bioactive metabolites in Potato dextrose broth medium at 25 °C on the 14th day of the incubation. The optimal mycelial growth, however, was obtained at pH 5.5. Sucrose (2.0 g/l) and asparagine (1.0 g/l) were the best carbon and nitrogen sources respectively for optimum growth and production of active metabolites by the isolate. Inoculum size of 2x1010 spores/ml with periodic shaking at 150 rpm optimized production of bioactive molecules. The results of the present investigation indicated that cultural conditions like carbon, nitrogen and mineral sources as well as physical factors such as temperature, pH, incubation period, inoculum size and shaking greatly affected the growth and production of bioactive metabolites by Aspergillus strain TSF 146.