ABSTRACT
Natamycin is a polyene macrolide antibiotics with strong and broad spectrum antifungal activity. It not only effectively inhibits the growth and reproduction of fungi, but also prevents the formation of some mycotoxins. Consequently, it has been approved for use as an antifungal food preservative in most countries, and is also widely used in agriculture and healthcare. Streptomyces natalensis and Streptomyces chatanoogensis are the main producers of natamycin. This review summarizes the biosynthesis and regulatory mechanism of natamycin, as well as the strategies for improving natamycin production. Moreover, the future perspectives on natamycin research are discussed.
Subject(s)
Antifungal Agents/pharmacology , Fungi , Natamycin , StreptomycesABSTRACT
In2O3nanoparticles-modified multiwalled carbon nanotubes (In2O3-MWCNTs) were successfully prepared as solid phase extraciton (SPE) adsorbent for the determination of three food preservatives(benzoic acid,sorbic acid,and methylparaben) in beverage samples coupled with high performance liquid chromatography (HPLC).Because of the large surface area and amount of hydroxyl groups on the surface of In2O3nanoparticles,In2O3nanoparticles could interact with specific functional groups.In2O3-MWCNTs adsorbent was prepared based on the large surface area of In2O3and superior thermal and chemical stability of MWCNTs.The obtained adsorbent was characterized via transmission electron microscope (TEM),thermogravimetric analysis (TGA),and Fourier transform-infrared (FT-IR) spectroscopy.Several experimental parameters affecting the extraction efficiency were investigated by single-factor experiments,such as adsorbents amount,sample volume,eluent volume,sample pH,and eluent type.The first four factors were then further evaluated by means of a Taguchi's L16(44) orthogonal array experimental design.According to the results of orthogonal array experiment,the optimal conditions were chosen as follows: 0.15 g of adsorbent amount,5.0 mL of sample volume,0.6 mL of ACN-H2O (60:40,0.1% formic acid,V/V) as eluent,and sample pH 4.0.Under the optimum conditions,the LODs (S/N=3) and LOQs (S/N=10) for three preservatives were in the range of 0.004-0.012 μg/mL and 0.012-0.038 μg/mL,respectively.The recoveries ranged from 70.2% to 109.4%.The method is rapid,sensitive,and suitable for the determination of preservatives in food samples.
ABSTRACT
Nisina é um peptídeo antimicrobiano natural produzido por Lactococcus lactis subsp. lactis ATCC 11454 durante a fase exponencial de crescimento. A bacteriocina é usada como conservante natural de alimentos, uma vez que mostra atividade antimicrobiana contra bactérias Gram-positivas e esporos. Tem potencial aplicação em inúmeros campos (farmacêutico, veterinário e cosméticos). O objetivo deste trabalho foi estudar a cinética de crescimento bacteriano e a produção de nisina em biorreator, utilizando leite desnatado diluído, como um meio de cultura a baixo custo. Também foram avaliados os consumos de açúcar e proteína, formação de ácido lático e adsorção de nisina nas células produtoras durante os processos de produção de nisina. Pré-cultivos com 107 UFC.mL-1 de Lactococcus lactis foram cultivados em biorreator de 2 L contendo 25 por cento de leite desnatado diluído em água (1,5 L, pH 6,7). Os ensaios foram esenvolvidos a 30°C por 52 horas, variando a agitação e aeração: (i) 200 rpm (0,0, 0,5, 1,0 e 2,0 L.min-1) e (ii) 100 rpm (0,0 e 0,5 L.min-1). A atividade de nisina foi avaliada pelo método de difusão em ágar, utilizando Lactobacillus sakei ATCC 15521 como microrganismo sensível à ação de nisina. A melhor concentração de nisina (62,68 mg.L-1 ou 2511,89 AU.mL-1), foi obtida em 16 horas, 200 rpm e sem aeração (kLa = 5,29 x 10-3 h-1). A adsorção de nisina nas células produtoras foram baixas (6,8 - 15,1 por cento), quando comparadas com a atividade do sobrenadante. Estes resultados mostraram que o meio de cultivo composto por leite desnatado diluído favoreceu o crescimento celular e produção associada ao crescimento da nisina. Foram realizados estudos preliminares de liofilização (bioconservação) e purificação por cromatografia da nisina produzida em biorreator. A liofilização apresentou perda da atividade de nisina (24,8 por cento), enquanto a purificação por cromatografia de interação hidrofóbica com resina Butyl-Sepharose,...
Nisin is a natural antimicrobial peptide produced by Lactococcus lactis subsp. lactis ATCC 11454 during its exponential growth phase. The bacteriocin is used as natural food preservative due to its antimicrobial activity against Gram-positive bacteria and outgrowth of spores. This property allows its application in numerous fields (pharmaceutical, veterinary and cosmetic). The aim of this work was to study the bacterial growth kinetics of L. lactis and respective nisin production in bioreactor, using diluted skimmed milk as an inexpensive medium. During the production, the consumption of sugar and protein, lactic acid formation and nisin adsorption on the producer strain cells were evaluated. Pre-cultivation with 107 UFC.mL-1 of L. lactis were expanded in a 2 L bioreactor containing 25 percent diluted skimmed milk in water (1.5 L, pH 6.7). The assays were performed at 30°C for 52 hours, varying agitation and airflow rate: (i) 200 rpm (0.0, 0.5, 1.0 and 2.0 L.min-1) and (ii) 100 rpm (0.0, 0.5 L.min-1). Nisin activity was evaluated through diffusion assays using Lactobacillus sakei ATCC 15521 as sensitive strain. The best nisin concentration (62.68 mg.L-1 or 2511.89 AU.mL-1), was achieved at 16 hours, 200 rpm and with no airflow rate (kLa = 5.29 x 10-3 h-1). The quantity of nisin adsorbed by the producer cells were low (6.8 -15.1 percent) when compared to the quantity released in the supernatant. These results showed that diluted skimmed milk supported cell growth and growth-associated nisin. Preliminary assays of lyophilization (biopreservation) and purification by chromatography of nisin produced in bioreactor were performed. Lyophilization presented a loss of nisin activity (24.8 percent) while purification by hydrophobic interaction chromatography with Butyl-Sepharose column recovered 40 percent of the activity, showing that both processes can be applied to the bacteriocin.