RESUMEN
Presence of bacterial contaminants at levels > 107 colony forming units per milliliter (CFU/mL) during ethanol production processes reduces the alcoholic fermentation yield by 30%. Antibiotics are currently used to control contamination, but their residues may be detected in yeast extract, restricting this by-product trade to several countries. Thus, the objective of this study was to assess antimicrobial activity of the natural compounds hops extract, 4-hydroxybenzoic acid, nisin Z, and lysozyme against Lactobacillus fermentum, Leuconostoc mesenteroides, and Saccharomyces cerevisiae, aiming development of a formula. Minimum Inhibitory Concentration of each antimicrobial was determined for bacteria and subsequently, nisin (30 mg/L) and hops extract (5 mg/L) were tested together, showing inhibitory effects combining doses of each antimicrobial that were equivalent to an eightfold reduction of their original Minimum Inhibitory Concentrations (3.75 and 0.625 mg/L, respectively), resulting in a FICIndex of 0.25. Thereon, a formula containing both compounds was developed and tested in fermentation assays, promoting reductions on bacterial population and no severe interferences in yeast viability or population even at extreme doses. Therefore, these compounds have great potential to successfully substitute conventional antibiotics in the ethanol industry.
Asunto(s)
Antiinfecciosos/farmacología , Etanol/metabolismo , Fermentación/fisiología , Humulus/química , Extractos Vegetales/farmacología , Antibacterianos/farmacología , Microbiología Industrial , Lactobacillales/efectos de los fármacos , Limosilactobacillus fermentum/efectos de los fármacos , Leuconostoc mesenteroides/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Muramidasa/farmacología , Nisina/análogos & derivados , Nisina/farmacología , Parabenos/farmacología , Saccharomyces cerevisiae/efectos de los fármacos , Saccharum/químicaRESUMEN
The effects of natural antimicrobial compounds (garlic essential oil [GO], allyl isothiocyanate [AITC], and nisin Z [NI]) on microbiological, physicochemical and sensory characteristics of fresh sausage were assessed. The minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) towards Escherichia coli O157:H7 and Lactobacillus plantarum were determined in vitro. Sausages inoculated with E. coli O157:H7, were treated with different combinations of antimicrobials and assessed for microbiological and physicochemical parameters during storage (6C for 20 d). Treatments that presented the greatest antimicrobial effects were subjected to sensory evaluation. Combinations of 20â¯mg/kg NIâ¯+â¯125⯵L/kg GOâ¯+â¯62.5⯵L/kg AITC or 20â¯mg/kg NIâ¯+â¯62.5⯵L/kg GOâ¯+â¯125⯵L/kg AITC were effective in reducing E. coli O157H7 and spoilage lactic acid bacteria, and maintained the physicochemical characteristics of fresh sausage. Combinations of NI, GO and AITC were effective to improve the safety and the shelf life of fresh sausage, with no impact on its sensory acceptance.
Asunto(s)
Antibacterianos , Conservantes de Alimentos , Ajo/química , Isotiocianatos , Productos de la Carne/análisis , Nisina/análogos & derivados , Aceites Volátiles , Animales , Antibacterianos/efectos adversos , Brasil , Bovinos , Fenómenos Químicos , Escherichia coli O157/crecimiento & desarrollo , Escherichia coli O157/aislamiento & purificación , Conservantes de Alimentos/efectos adversos , Inocuidad de los Alimentos , Almacenamiento de Alimentos , Humanos , Isotiocianatos/efectos adversos , Lactobacillus plantarum/crecimiento & desarrollo , Lactobacillus plantarum/aislamiento & purificación , Productos de la Carne/efectos adversos , Productos de la Carne/microbiología , Pruebas de Sensibilidad Microbiana , Viabilidad Microbiana , Nisina/efectos adversos , Aceites Volátiles/efectos adversos , Refrigeración , Sensación , Sus scrofa , GustoRESUMEN
Cronobacter sakazakii and Escherichia coli O157:H7 are well known food-borne pathogens that can cause severe disease. The identification of new alternatives to heating to control these pathogens in foods, while reducing the impact on organoleptic properties and nutritional value, is highly desirable. In this study, nisin and its bioengineered variants, nisin V and nisin S29A, are used alone, or in combination with plant essential oils (thymol, carvacrol and trans-cinnamaldehyde) or citric acid, with a view to controlling C. sakazakii and E. coli O157:H7 in laboratory-based assays and model food systems. The use of nisin variants (30 µM) with low concentrations of thymol (0.015%), carvacrol (0.03%) and trans-cinnamaldehyde (0.035%) resulted in extended lag phases of growth compared to those for corresponding nisin A-essential oil combinations. Furthermore, nisin variants (60 µM) used in combination with carvacrol (0.03%) significantly reduced viable counts of E. coli O157:H7 (3-log) and C. sakazakii (4-log) compared to nisin A-carvacrol treatment. Importantly, this increased effectiveness translated into food. More specifically, sub-inhibitory concentrations of nisin variants and carvacrol caused complete inactivation of E. coli O157:H7 in apple juice within 3 h at room temperature compared to that of the equivalent nisin A combination. Furthermore, combinations of commercial Nisaplin and the food additive citric acid reduced C. sakazakii numbers markedly in infant formula within the same 3 h period. These results highlight the potential benefits of combining nisin and variants thereof with carvacrol and/or citric acid for the inhibition of Gram negative food-borne pathogens.
Asunto(s)
Ácido Cítrico/farmacología , Cronobacter sakazakii/efectos de los fármacos , Escherichia coli O157/efectos de los fármacos , Conservación de Alimentos/métodos , Conservantes de Alimentos/farmacología , Nisina/análogos & derivados , Aceites de Plantas/farmacología , Acroleína/análogos & derivados , Acroleína/farmacología , Antibacterianos/farmacología , Bioingeniería , Recuento de Colonia Microbiana , Cronobacter sakazakii/crecimiento & desarrollo , Cimenos , Escherichia coli O157/crecimiento & desarrollo , Aromatizantes/farmacología , Microbiología de Alimentos , Jugos de Frutas y Vegetales/microbiología , Humanos , Lactante , Fórmulas Infantiles/microbiología , Malus , Monoterpenos/farmacología , Nisina/química , Nisina/farmacología , Timol/farmacologíaRESUMEN
Lactococcus lactis KTH0-1S isolated from Thai traditional fermented shrimp (Kung-som) is able to produce heat-stable bacteriocin and inhibits food spoilage bacteria and food-borne pathogens. The inhibitory effect of bacteriocin remained intact after treatment with different pHs and after heating, but was sensitive to some proteolytic enzymes. Addition of bacteriocin KTH0-1S to Staphylococcus aureus cultures decreased viable cell counts by 2.8 log CFU/ml, demonstrating a bactericidal mode of action. Furthermore, the growth of S. aureus decreased significantly after 12-h co-cultivation with bacteriocinogenic strain. The molecular mass of bacteriocin KTH0-1S was found to be 3.346 kDa after ammonium sulfate precipitation, reversed phase (C8 Sep-Pak), cation-exchange chromatography, RP-HPLC on C8 column and mass spectrometry (MS/MS) analysis. Bacteriocin KTH0-1S was identified as nisin Z using PCR amplification and sequencing. The majority of tested virulence factors were absent, confirming the safety. Evidenced inhibitory effect of this strain, the absence of virulence factors creates the possibility for its application as protective culture to inhibit pathogenic bacteria in the several fermented seafood products.
Asunto(s)
Antibacterianos/farmacología , Bacteriocinas/farmacología , Lactococcus lactis/fisiología , Nisina/análogos & derivados , Staphylococcus aureus/efectos de los fármacos , Animales , Antibacterianos/química , Antibacterianos/aislamiento & purificación , Bacteriocinas/química , Bacteriocinas/genética , Bacteriocinas/aislamiento & purificación , Fermentación , Lactococcus lactis/efectos de los fármacos , Lactococcus lactis/aislamiento & purificación , Lactococcus lactis/patogenicidad , Interacciones Microbianas , Nisina/genética , Nisina/aislamiento & purificación , Nisina/farmacología , Penaeidae/microbiología , Mariscos/microbiología , Tailandia , Factores de Virulencia/genéticaRESUMEN
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.