Enhancement of nisin, lysozyme, and monolaurin antimicrobial activities by ethylenediaminetetraacetic acid and lactoferrin

A microtiter plate assay was employed to systematically assess the interaction between ethylenediaminetetraacetic acid (EDTA) or lactoferrin and nisin, lysozyme, or monolaurin against strains of Listeria monocytogenes, Escherichia coli, Salmonella enteritidis, and Pseudomonas fluorescens. Low levels of EDTA acted synergistically with nisin and lysozyme against L. monocytogenes but EDTA and monolaurin interacted additively against this microorganism. EDTA synergistically enhanced the activity of nisin, monolaurin, and lysozyme in tryptic soy broth (TSB) against two enterohemorrhagic E. coli strains. In addition, various combinations of nisin, lysozyme, and monolaurin with EDTA were bactericidal to some gram-negative bacteria whereas none of the antimicrobials alone were bactericidal. Lactoferrin alone (2000 microg ml(-1)) did not inhibit any of the bacterial strains, but did enhance nisin activity against both L. monocytogenes strains. Lactoferrin in combination with monolaurin inhibited growth of E. coli O157:H7 but not E. coli O104:H21. While lactoferrin combined with nisin or monolaurin did not completely inhibit growth of the gram-negative bacteria, there was some growth inhibition. All combinations of EDTA or lactoferrin with antimicrobials were less effective in 2% fat UHT milk than in TSB. S. enteritidis and P. fluorescens strains were consistently more resistant to antimicrobial combinations. Resistance may be due to differences in the outer membrane and/or LPS structure.     

蛋清溶菌酶与渗透剂对大肠杆菌的协同抑菌作用

为了提高溶菌酶对革兰氏阴性菌的抑菌性能,研究蛋清溶菌酶和渗透剂甘氨酸、EDTA-Na2复配对大肠杆菌ATCC25922、DH5α的抑菌效果,及细胞外膜渗透性和细胞表面形态的变化。结果表明：大肠杆菌ATCC25922对溶菌酶的敏感性明显强于DH5α,其外膜渗透性也高于大肠杆菌DH5α。当溶菌酶分别和渗透剂甘氨酸或EDTA-Na2复配后,对大肠杆菌ATCC25922和DH5α的抑菌性能都显著提高;三者共同作用时,对大肠杆菌ATCC25922的抑菌能力从101.0提高到103.45,对大肠杆菌DH5α则从100.35提高到103.15,表现出协同抑菌作用。细胞外膜渗透性的N-苯基-1-萘胺(NPN)测定结果表明：溶菌酶与甘氨酸、EDTA-Na2复配后,两种大肠杆菌的外膜渗透性相应提高,TEM电镜结果也证实溶菌酶与渗透剂对大肠杆菌细胞表面有协同破坏作用。因此改善大肠杆菌的外膜渗透性有助于增强溶菌酶对其抑菌效果。     

玫瑰红景天挥发性成分分析及其抗氧化和抗菌活性

目的:提取玫瑰红景天根茎中的挥发性物质,测试抗氧化和抗菌活性,为玫瑰红景天的综合利用提供科学依据。方法:采用水蒸气蒸馏法提取玫瑰红景天根茎中的挥发性物质,经GC-MS分离和鉴定,借助GC用系列正构烷烃对各组分进行定性,面积归一化法确定各组分的相对含量;通过H₂O₂/Fe2+体系考察对羟基自由基的清除作用;用微量肉汤稀释法测定最小抑菌浓度(MIC)和平板转种法测定最小杀菌浓度(MBC)确定抗菌活性。结果:从玫瑰红景天挥发性物质中鉴定出53种化合物,主要组分有1-辛醇(42.72%)、香叶醇(29.85%)、苯乙醇(9.67%)、桃金娘烯醇(2.69%)、芳樟醇(1.89%)等,玫瑰红景天挥发性物质对羟基自由基有清除作用,其半抑制浓度IC₅₀为0.0073 mg/mL,对抗菌试验所选的7个菌株均有抑制作用,对金黄色葡萄球菌ATTCC25925的MIC值是0.12 mg/mL、MBC值是0.36 mg/mL,对大肠杆菌ATCC25922的MIC值是0.58 mg/mL、MBC值是1.90 mg/mL。结论:通过水蒸气蒸馏法提取得到的玫瑰红景天根茎挥发性物质的组分丰富多样,是一种天然的抗氧化、抗菌活性物质。     

常用防腐剂对牛乳铁蛋白抗菌活性的影响

乳铁蛋白的抗菌活性常受到其他共存成分的影响。本文研究了常用防腐剂对乳铁蛋白抗菌活性的影响。在研究过程中,以大肠杆菌为实验菌株,进行了实验研究。研究表明,在牛肉膏蛋白胨培养基中,pH6.0,菌浓为106CFU/ml的条件下,乳铁蛋白对大肠杆菌的最小抑菌质量浓度为3mg/ml;苯甲酸钠、山梨酸钾、乳酸链球菌素、对羟基苯甲酸等分别与乳铁蛋白共同作用时,对乳铁蛋白的抗菌活性都有明显的影响。其中,山梨酸钾和苯甲酸钠减弱了乳铁蛋白的抗菌活性,乳酸链球菌素和对羟基苯甲酸丁酯加强了乳铁蛋白的抗菌活性。     

Inhibition of mastitic bacteria by bovine milk apo-lactoferrin evaluated by in vitro microassay of bacterial growth

An in vitro microassay was developed to evaluate antimicrobial properties of bovine apo-lactoferrin. The growth of coliform, staphylococcal, and streptococcal bacterial strains in a defined synthetic medium was inhibited by bovine apo-lactoferrin (.5 to 30.0 mg/ml). Addition of iron-saturated lactoferrin to the synthetic medium did not inhibit growth of test strains. Inhibition by apo-lactoferrin was greater for coliform than Gram-positive strains for all concentrations of apo-lactoferrin evaluated. No concentration of apo-lactoferrin proved bactericidal for either coliform or Gram-positive strains. Inhibition of two coliform strains by apo-lactoferrin (10 mg/ml) was abolished by addition of ferric iron to the assay system, indicating an iron-dependent nature of apo-lactoferrin induced inhibition of bacteria. Bicarbonate supplementation of the growth system containing apo-lactoferrin (1 mg/ml) increased inhibition of three coliform strains by apo-lactoferrin. Addition of increasing concentrations of citrate (2.0 mg/ml) to an assay system containing apo-lactoferrin (5 mg/ml) resulted in a concomitant reduction of growth inhibition of three coliform strains. These data indicate a potential relationship between the molar ratio of citrate to lactoferrin of the lacteal secretion and its capacity to inhibit coliform strains associated with mastitis.     

三甲胺柱[5]芳烃的合成及其抑菌性能

本研究合成基于三甲胺的柱[5]芳烃,并以金黄色葡萄球菌（Staphylococcus aureus ATCC 6538）和大肠杆菌（Escherichia coli DH5α）为供试菌对三甲胺柱[5]芳烃的抑菌性能和抑菌机制进行分析。通过抑菌实验确定三甲胺柱[5]芳烃最小抑菌浓度（minimal inhibit concentration,MIC）和最小杀菌浓度（minimal bactericidal concentration,MBC）,并探讨其对细菌生物被膜形成的影响;利用透射电子显微镜（transmission electron microscopy,TEM）观察三甲胺柱[5]芳烃对细菌细胞膜的损伤情况,并通过噻唑蓝（3-(4,5-dimethyl-2-thiazyl)-2,5-diphenyl-2H-tetrazolium bromide,MTT）法测定其细胞毒性。结果显示,三甲胺柱[5]芳烃对S. aureus ATCC 6538的MIC和MBC分别为0.125 mg/mL和1.000 mg/mL,对E. coli DH5α的MIC和MBC分别为0.250 mg/mL和＞1.000 mg/mL;三甲胺柱[5]芳烃对S. aureus ATCC 6538生物被膜形成的抑制效果优于对E. coli DH5α。TEM观察结果表明三甲胺柱[5]芳烃对不同菌株细胞膜的损伤不同;MTT实验结果表明MIC范围内三甲胺柱[5]芳烃无毒。本研究结果明确了三甲胺柱[5]芳烃的具体抑菌性能,可为其在食品领域的进一步开发利用提供一定的理论依据。     

合成甜味剂对牛乳铁素抗菌活性的影响

乳铁素B是牛乳铁蛋白经胃蛋白酶酶解后得到的最重要的抗菌肽,具有很强的抗菌活性。选取大肠杆菌为实验菌株,进行了合成甜味剂对乳铁素抑菌活性影响的研究。研究表明,在牛肉膏蛋白胨培养基中,pH7.0,菌浓为107CFU/ml的条件下,纯化乳铁素B对大肠杆菌的最小抑菌质量浓度为20μg/ml;阿斯巴甜、甜蜜素、糖精钠在0～5mg/ml的质量浓度范围内,对乳铁素B的抗菌活性都有削弱的作用;而安塞蜜在0～5mg/ml的质量浓度范围内,对乳铁素B的抗菌活性没有太大的影响。     

产胞外多糖乳杆菌的筛选及多糖功能的研究

本论文从大连地区海产品消化腺中筛选产胞外多糖(EPS)的乳杆菌属菌株,并研究其所产EPS的功能特性,选出一株目标菌,对其EPS分离纯化,测定纯化后各多糖组分的相对分子量。获得EPS产量相对较高的菌株经16S r RNA序列测定鉴定为Lactobacillus plantarum subsp.plantarum-4,Lactobacillus plantarum-12,Lactobacillus plantarumsubsp.plantarum-49;对3株植物乳杆菌及其EPS进行清除DPPH自由基的测定,Lactobacillus plantarum-12的EPS浓度为0.5 mg/mL时,清除率为48.82±3.88%,显著高于另外2株菌(p0.05);测定植物乳杆菌的EPS抑制E.coli ATCC25922在HT-29细胞上的粘附效果,Lactobacillus plantarum-12的EPS浓度为0.2mg/mL时,抑制率为78.23%±2.46%,显著高于另外两株菌(p0.05);Lactobacillus plantarum-12的EPS可显著抑制E·coli ATCC25922刺激HT-29细胞产生IL-8(p0.05)。Lactobacillus plantarum-12的EPS经DEAE-Sepharose Fast Flow离子交换柱、Sepharose CL-6B凝胶柱和Sephacryl HR S200凝胶柱层析分离得到两组分,测定两组分的相对分子质量分别为8.5×10~4 u和7.4×10~4 u。     

SURVIVAL AND GROWTH OF ACID ADAPTED ESCHERICHIA COLI STRAINS IN BROTH AT DIFFERENT PH LEVELS

Acid resistance of Escherichia coli O157:H7 strain UT 10 and Escherichia coli ATCC 25922 was determined in brain heart infusion broth at pH 7.4, 4.5 and 2.5. Variations due to acid stress in the counts of both strains were also determined. Acid adaptation enhanced the survival of both strains at pH 4.5, but neither strain could survive after 4 h at pH 2.5. At optimum growth conditions (pH 7.4), E. coli ATCC 25922 exhibited increased viability over E. coli UT 10. At pH 4.5, E. coli UT 10 was more tolerant to low pH than E. coli ATCC 25922. An increase in saturated fatty acids of both AA strains was observed, indicating the importance of lipid modification in enhancing survival at low pH. The results of this study indicated that the food industry should therefore adapt their processing/preservation procedures by taking the most acid tolerant pathogenic E. coli strains into consideration in order to ensure the safety of their products.

PRACTICAL APPLICATIONS

The study will enlighten the industry on the survival of acid adapted pathogens such as E. coli O157:H7 at low pH. It also indicates that current measures used in the preservation of low pH foods can trigger acid adaptation. For this reason, the effectiveness of current preservation measures in controlling foodborne pathogens should be reassessed. The importance of using cells adapted to different pH values in food challenge studies is also highlighted. Since fermented foods, which are generally regarded as safe, have been implicated in foodborne disease outbreaks, more attention should be given to the prevention of contamination of foods with pathogens such as E. coli O157:H7 since they may survive in low pH foods and cause disease.     

High pressure increases bactericidal activity and spectrum of lactoferrin, lactoferricin and nisin

We have studied the inactivation of a panel of eight test bacteria (two Escherichia coli strains, Salmonella enteritidis, Salmonella typhimurium, Shigella sonnei, Shigella flexneri, Pseudomonas fluorescens and Staphylococcus aureus) by high pressure in the presence of bovine lactoferrin (500 microg/ml), pepsin hydrolysate of lactoferrin (500 microg/ml), lactoferricin (20 microg/ml) and nisin (100 IU/ml). None of these compounds, at the indicated dosage, were bactericidal when applied at atmospheric pressure, except nisin, which caused a low level of inactivation of the bacteria. Under high pressure, lactoferrin, lactoferrin hydrolysate and lactoferricin displayed bactericidal activity against some of the test bacteria, however, the former had a narrower bactericidal spectrum than the two latter compounds. The bactericidal efficiency and spectrum of nisin were also enhanced under high pressure. The sensitisation of the test bacteria to these antimicrobials under pressure was transient, since no bactericidal activity was observed when bacteria were pressure treated before exposure to the compounds. We propose a mechanism of pressure-promoted uptake of these antimicrobial proteins and peptides in gram-negative bacteria to explain this sensitisation.     

含硫杯[4]芳烃银系配合物在织物上的抗菌性能

为提高银系抗菌剂的稳定性,用银的络合离子替代银离子,将杯芳烃应用在纺织品抗菌整理中。利用含硫杯[4]芳烃具有可修饰性和对银离子有很好的络合作用等特点,制备了一系列新型杯芳烃银系配合物,并证明其对大肠埃希菌ATCC25922、铜绿假单胞菌ATCC27853、金黄色葡萄球菌ATCC29213和白色念珠菌ATCC10231有良好的抗菌性能。将杯芳烃含银配合物作为抗菌剂整理到棉织物上,整理后的棉织物经10次水洗后,对大肠埃希菌ATCC25922、金黄色葡萄球菌ATCC29213和白色念珠菌ATCC10231仍有良好的抗菌效果。     

Medicinal plant extracts as anti-Escherichia coli O157:H7 agents and their effects on bacterial cell aggregation

Ethanolic extracts of eight Thai medicinal plants (representing five families) that are used as traditional remedies for treating diarrhea were examined with a salt aggregation test for their ability to modulate cell surface hydrophobicity of enterohemorrhagic Escherichia coli strains, including E. coli O157:H7. Four of these medicinal plants, Acacia catechu, Peltophorum pterocarpum, Punica granatum, and Quercus infectoria, have high bacteriostatic and bactericidal activities. The ethanolic extract of Q. infectoria was the most effective against all strains of E. coli, with MICs of 0.12 to 0.98 mg/ml and MBCs of 0.98 to 3.91 mg/ml. The ethanolic extract of P. granatum had MICs of 0.49 to 1.95 mg/ml and MBCs of 1.95 to 3.91 mg/ml. Ethanolic extracts of Q. infectoria, P. pterocarpum, and P. granatum were among the most effective extracts against the two strains of E. coli O157:H7. The other four plants, Andrographis paniculata, Pluchia indica, Tamarindus indica, and Walsura robusta, did not have high bacteriostatic and bactericidal activities but were able to affect hydrophobicity characteristics on their outermost surface. All plants except Q. infectoria had some ability to increase cell surface hydrophobicity. There appears to be no correlation between antibacterial activity and cell aggregative properties.     

Antimicrobial performance of alkaline ionic fluid (GC-100X) and its ability to remove Escherichia coli O157:H7 from the surface of tomatoes

An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens-Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637-at three different temperatures (4, 25, and 36 degrees C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 x 10(4) CFU/ml reduction) against all pathogens reacted at 37 degrees C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.     

Activity against Listeria monocytogenes of human milk during lactation. A preliminary study

Human milk samples from three healthy donors were investigated in order to evaluate the antibacterial activity during lactation against Escherichia coli ATCC 25922 and Listeria monocytogenes. The concentration of the main human-milk antimicrobial proteins (lactoferrin (LF), lysozyme (LZ) and secretory immunoglobulin A (sIgA)) was determined by ELISA. Results showed that human milk exhibited antibacterial activity against List. monocytogenes, although it was weakly active against Esch. coli ATCC 25922. The observed antilisterial activity was positively correlated with LZ concentration. In addition, the effect of gastrointestinal proteases, at different pH conditions, that prevail in the stomach of infants (pH 2.0-6.5), on antilisterial activity and protein degradation was evaluated. Hydrolysis with pepsin at pH 4.0-6.5, followed by treatment with pancreatic enzymes, resulted in a decreased hydrolysis of LZ, LF and sIgA and an enhanced antibacterial activity against List. monocytogenes. It is suggested that partial degradation of certain milk proteins at the gastrointestinal level may produce peptides that could act synergistically with the remnant intact proteins.     

Antimicrobial activity of lactoferrin against foodborne pathogenic bacteria incorporated into edible chitosan film

The objectives of this research were to develop and characterize edible chitosan film containing lactoferrin as a natural antimicrobial agent, and to investigate the combination effects of lactoferrin with lysozyme in chitosan film against the growth of Escherichia coli O157:H7 and Listeria monocytogenes. Chitosan films containing lactoferrin, lysozyme, or nisin were fabricated, and the antimicrobial concentrations were 0.5, 1, or 2 mg in a circular disc of chitosan film. Three concentrations of lactoferrin or EDTA (0.28, 0.56, or 1.12 mg per disc) were also incorporated into the chitosan film containing lysozyme to investigate the combination effects of lactoferrin. The water barrier properties of the chitosan films containing lactoferrin were characterized. The antimicrobial activities against E. coli O157:H7 and L. monocytogenes were determined using the agar diffusion assay and cell count assay. The chitosan films containing lactoferrin less than 1 mg per disc did not alter the water vapor permeability of the chitosan film. Although the film containing lysozyme exhibited significant antimicrobial activity, the incorporation of lactoferrin alone into chitosan film did not exhibit significant antimicrobial activity against both E. coli O157:H7 and L. monocytogenes. However, the combination of lactoferrin with lysozyme-containing chitosan film significantly decreased the growth of E. coli O157:H7, exhibiting a comparable effect to that of the combination of EDTA with lysozyme (P < 0.05). Furthermore, the combination of lactoferrin with lysozyme in chitosan film exhibited greater reduction in the growth of L. monocytogenes than did the combination EDTA with lysozyme, resulting in an approximate 3-log reduction.     

The use of Fourier transform infrared spectroscopy to differentiate Escherichia coli O157:H7 from other bacteria inoculated into apple juice

Fourier transform infrared spectroscopy (FT-IR) can discriminate Escherichia coli O157:H7 ATCC 35150 from other bacteria: E. coli ATCC 25522, Bacillus cereus ATCC 10876, and Listeria innocua ATCC 51742 inoculated in to apple juice. Spectra of bacterial suspensions (ca. 10(9) cfu/ml in 0.9% NaCl) on Anodisc (aluminum oxide) filters were tested. Unique FT-IR vibrational combination bands from mid-IR active components of bacterial cells are present in the "fingerprint region" at wavenumbers between 1500 and 800 cm(-1). Principal component analysis (PCA) revealed clear segregations between different bacterial strains. Also, soft independent modeling of class analogy (SIMCA) correctly classified E. coli O157:H7 ATCC 35150 from E. coli ATCC 25522 at an 82% confidence level; whereas a 77% confidence level was obtained when using SIMCA to classify E. coli O157:H7 from three other bacterial strains.     

迎春花叶抑菌活性物研究

采用硅胶柱层析(CC)、薄层层析(TLC)和重结晶等技术,从迎春花叶乙酸乙酯萃取物中分离到一强抑菌活性单体。经理化检测和波谱分析数据鉴定属裂环烯醚萜葡糖苷类(secoiridoid glucosides)的迎春花素(jasminin)。该单体在强酸性环境中不稳定,高温、紫外光处理后抑菌活性稳定,对金黄色葡萄球菌的最小抑菌浓度(MIC)为均为1mg/ml,对痢疾杆菌、大肠杆菌的最小抑菌浓度为0.5mg/ml,对三个受试菌的最小杀菌浓度(MBC)为2mg/ml。     

Pharmacokinetics of marbofloxacin in lactating cows after repeated intramuscular administrations and pharmacodynamics against mastitis isolated strains

The plasma and milk pharmacokinetics of marbofloxacin, a fluoroquinolone antibacterial compound, were evaluated in dairy cows, as well as its pharmacodynamic characteristics against mastitis-isolated pathogens. Marbofloxacin was given intramuscularly as a 10% aqueous solution to dairy cows either at a single dose or at repeated doses of 2 mg/kg once daily for 3 d. Blood and milk samples were collected for the determination of the concentration of marbofloxacin and of its putative metabolites: N-desmethyl-marbofloxacin and N-oxide-marbofloxacin. Bacterial field isolates were from milk samples collected from dairy cows suspected of having an intramammary infection. After identification, the minimal inhibitory concentration (MIC) was determined against the isolated strains. The maximal marbofloxacin concentration (Cmax) observed in milk after the first administration was 1.024 microg/mL, and the area under the curve during the first dosing interval was 6.513 microg/h per milliliter. After the third administration, these parameters were slightly increased (about 20% at most). Both metabolites were detected in the milk, but their concentrations were below the limit of quantification. The MIC against 90% of the population (MIC90) of Escherichia coli was 0.016 microg/mL, and it was 0.229 microg/mL against Staphylococcus aureus. The following surrogate clinical outcome markers were obtained against E. coli strains: a Cmax/MIC ratio of 67 and an area under the curve/MIC ratio of 407 h. Hence, a possible efficacy of marbofloxacin in the treatment of E. coli-induced mastitis could be expected as the endpoints of 10 and 250 h, respectively, are reached.     

1株抑制乳房炎病原菌乳杆菌的筛选、鉴定及其抑菌机理研究

为了研究乳酸菌对牛乳房炎病原菌的抑制作用,降低牛乳房炎所造成的经济损失。本实验以大肠杆菌ATCC25922、金黄色葡萄球菌ATCC25923、无乳链球菌ATCC14556作为指示菌,综合抑菌试验和黏附试验从8株乳杆菌中筛选抑菌效果较好的菌株。结果表明,乳杆菌KLDS1.0344对指示菌的抑制作用比其他乳杆菌的作用更明显,最大抑菌直径为15.4 mm,经过对16S rDNA鉴定,发现KLDS1.0344为植物乳杆菌,同时,对抑菌机理的初步研究表明,其代谢过程中产生的乳酸和细菌素类物质对抑制三种指示菌发挥主要作用,而且这些抑菌活性物质在酸性条件下才具有更强的抑菌活力。     

Antimicrobial efficacy of UV radiation on Escherichia coli O157:H7 (EDL 933) in fruit juices of different absorptivities

The efficacy of UV light for inactivating E. coli (ATCC 25922) and E. coli O157:H7 (EDL 933) was examined in fruit juices (orange, apple, and multifruit) with different absorptivities under several operating conditions (liquid film thickness and agitation rate). The juices were inoculated with two bacterial concentrations (10(5) and 10(7) CFU/ml) and were treated using a UV desinfection unit at 254 nm; UV doses ranged from 0 to 6 J/cm2. The effect of the culture medium, tryptone soy agar (TSA) and sorbitol MacConkey agar (SMAC), on the recovery of E. coli strains exposed to UV radiation was also analyzed. The most suitable culture medium for recovery of E. coli strains in juices exposed to UV radiation was TSA. Values of D (radiation dose [joules per square centimeter] necessary to decrease the microbial population by 90%) obtained in all juices assessed were higher in TSA than in SMAC. In the juices analyzed, stirring of the medium exposed to UV radiation and reducing liquid film thickness (to 0.7 mm) produced the highest bactericidal effect. A linear relationship was found between the D-values obtained and the absorptivity coefficients for all the juices. The higher the absorbance of the medium, the greater the values of D required to inactivate E. coli strains by UV radiation. An equation was developed to describe the relationship of the fraction of energy absorbed by the system (absorbed energy factor [AEF]), the thickness of the film exposed to UV radiation, and the absorptivity coefficient of the juices. A linear relationship was found between D and AEF in the different juices tested.