Short communication: Algicide activity of antimicrobial peptides compounds against Prototheca bovis

This study evaluated the in vitro activity of antimicrobial peptides pexiganan (MSI-78), h-Lf1–11, LL-37, cecropin B, magainin-2, and fengycin B against the veterinary mastitis agent Prototheca bovis. The results showed that pexiganan, h-Lf1–11, LL-37, and cecropin B were able to inhibit the growth and had effect on algicide P. bovis isolates (n = 32). The minimum inhibitory concentration ranged from 5 to 10 µg/mL for pexiganan, and algicide effect was detected from 5 to 20 µg/mL. The minimum inhibitory concentration ranged from 10 to 80 µg/mL for h-Lf1–11, 20 to 80 µg/mL for LL-37, and 40 to 160 µg/mL for cecropin B. These findings present a promising and novel alternative for P. bovis treatment and growth control.     

Short communication: Postruminal infusion of conjugated linoleic acids negatively impacts milk synthesis in Holstein cows

In view of the potential of rumen-protected conjugated linoleic acid (CLA) as a means to increase the CLA content of bovine milk, a study was undertaken to evaluate the effect of synthetic CLA on milk production and composition. Four Holstein cows received abomasal infusion of: 1) control, no lipid infusion, 2) 150 g/d of synthetic CLA, 31.7% cis-9, trans-11; 30.4% trans-10, cis-12, 3) 150 g/d of safflower oil, and 4) 150 g/d of tallow. Infusion was carried out for 20 to 22 h/d for 11-d periods in a 4 x 4 Latin square design. The milk fat concentration of cis-9, trans-11 and trans-10, cis-12 isomers of CLA was significantly increased with infusion of CLA. However, CLA infusion had other unexpected effects on milk production and composition. Milk yield dropped significantly during the period of CLA infusion. Furthermore, as well as the typical depression in milk fat reported with trans-10 isomers of CLA, other negative effects specific to CLA infusion were observed including a drop in lactose concentration and yield, a drop in protein yield, and an elevated somatic cell count. The important difference between synthetically produced CLA and CLA produced naturally in the cow is the much higher proportion of trans-10 isomers of CLA in the former. The results of this study suggest that the extent of enrichment possible for trans-10 isomers of CLA, and hence the usefulness of synthetic CLA for this purpose, may be limited because of unacceptable effects on milk yield and composition.     

麝香草酚抑菌活性及其影响因素研究

采用滤纸片法和扩散法,研究不同浓度的麝香草酚对食品中常见10种污染菌的体外抑菌作用,并对其抑菌影响因素进行了研究。实验结果表明,麝香草酚对细菌、酵母和霉菌均有一定抑制作用。经测定,麝香草酚对金黄色葡萄球菌、枯草芽孢杆菌、大肠杆菌、变形杆菌、保加利亚乳杆菌、嗜热乳酸链球菌、异常汉逊氏酵母、酿酒酵母、黑曲霉、黄曲霉的最低抑菌浓度分别为10、20、20、40、40、40、80、40、80、160μg/mL。抑菌影响因素研究表明,吐温-80和有机氮（BSA）能明显消弱麝香草酚的抑菌能力;低pH则会明显增强麝香草酚的抑菌作用。      

Short communication: Urea hydrolysis in dairy cattle manure under different temperature,urea, and pH conditions

The objective of the study was to quantify the rate of urea hydrolysis in dairy cattle manure under different initial urea concentration, temperature, and pH conditions. In particular, by varying all 3 factors simultaneously, the interactions between them could also be determined. Fresh feces and artificial urine solutions were combined into a slurry to characterize the rate of urea hydrolysis under 2 temperatures (15°C and 35°C), 3 urea concentrations in urine solutions (500, 1,000, and 1,500 mg of urea-N/dL), and 3 pH levels (6, 7, and 8). Urea N concentration in slurry was analyzed at 0.0167, 1, 2, 4, 6, 8, 12, 16, 20, and 24 h after initial mixing. A nonlinear mixed effects model was used to determine the effects of urea concentration, pH, and temperature treatments on the exponential rate of urea hydrolysis and to predict the hydrolysis rate for each treatment combination. We detected a significant interaction between pH and initial urea level. Increasing urea concentration from 1,000 to 1,500 mg of urea-N/dL decreased the rate of urea hydrolysis across all pH levels. Across all pH and initial urea levels, the rate of urea hydrolysis increased with temperature, but the effect of pH was only observed for pH 6 versus pH 8 at the intermediate initial urea concentration. The fast rates of urea hydrolysis indicate that urea was almost completely hydrolyzed within a few hours of urine mixing with feces. The estimated urea hydrolysis rates from this study are likely maximum rates because of the thorough mixing before each sampling. Although considerable mixing of feces and urine occurs on the barn floor of commercial dairy operations from cattle walking through the manure, such mixing may be not as quick and thorough as in this study. Consequently, the urea hydrolysis rates from this study indicate the maximum loss of urea and should be accounted for in management aimed at mitigating ammonia emissions from dairy cattle manure under similar urea concentration, pH, and temperature conditions reported in this experiment.     

酸浓度和pH值对浓香型大曲酯化酶催化活力的影响

研究了己酸、乳酸、丁酸、乙酸的浓度以及pH值对浓香型大曲酯化酶催化合成四种酯（己酸乙酯、乳酸乙酯、丁酸乙酯、乙酸乙酯）的影响。结果表明,大曲酯化酶催化合成四种酯的最适酸质量浓度分别为己酸8 g/L,乳酸1 g/L,丁酸9 g/L,乙酸12 g/L;在同一酸浓度条件下,大曲酯化酶催化合成己酸乙酯、丁酸乙酯、乙酸乙酯最适pH值均为4.5,乳酸乙酯最适pH值为6.0;大曲酯化酶催化相同物质的量浓度混合酸的试验结果表明,己酸乙酯的合成以酯化酶催化反应为主,而乳酸乙酯和丁酸乙酯的合成以化学反应为主。     

Effect of pH on the antimicrobial activity and oxidative stability of oil-in-water emulsions containing caffeic acid

ABSTRACT:  Antioxidant properties in food are dependent on various parameters. These include the pH value and interactions with food components, including proteins or metal ions. Food components affect antioxidant stability and also influence the properties of microorganisms and their viability. This paper describes an investigation of the effect of pH on the antioxidant and antibacterial properties of caffeic acid in different media. The pH values studied, using an oil-in-water emulsion as model system, were 3, 5 (with and without phosphate buffer), and 9. Effects of mixtures of caffeic acid, bovine serum albumin (BSA), and Fe (III) on oxidative deterioration in the emulsion samples were studied. The results show that the antioxidant activity of caffeic acid was increased by the presence of BSA. This effect was pH dependent and was affected by the presence of iron ions. Antibacterial properties were also pH dependent. The minimum concentration of caffeic acid required to inhibit some microorganisms in the pH range of 5 to 7 was determined. A concentration of 0.4% (w/w) caffeic acid was enough to inhibit the growth of some of the studied microorganisms in the pH range of 5 to 7. However, near-neutral pH concentrations higher than 0.4% were needed to inhibit some microorganisms, including Listeria monocytogenes , E. coli, and Staphylococcus aureus , in the medium.     

Short communication: milk fat response to low doses of tran-10, cis-12 conjugated linoleic acid (CLA)

Trans-10, cis-12 conjugated linoleic acid (CLA) is a potent inhibitor of milk fat synthesis. We examined the effect of low doses of trans-10, cis-12 CLA using Holstein cows in a 4 x 4 Latin square design. Milk yield and milk protein were unaffected, but abomasal infusion of 1.25, 2.5, and 5.0 g/d of trans-10, cis-12 CLA reduced milk fat yield by 7, 16, and 29%, respectively. When combined with previous data, the reduction in milk fat yield was curvilinear, relating to both quantity infused and milk fat content of trans-10, cis-12 CLA (R2 = 0.99 and 0.96, respectively). Further, changes in milk fatty acid composition indicated the mechanism involved inhibition of de novo fatty acid synthesis and the utilization of circulating fatty acids.     

长裙竹荪子实体乙醚和乙酸乙酯提取物的化学组成分析及抑菌活性研究

依次用乙醚和乙酸乙酯为溶剂,对正己烷提取后的长竹荪子实体粉末进行索氏提取。乙醚和乙酸乙酯的提取率分别为1.57%和1.85%,然后采用GC-MS对乙醚和乙酸乙酯提取物的化学成分进行分析,图谱解析结果显示乙醚提取物中含有43种成分,占总含量的99.98%;乙酸乙酯提取物中含有73种成分,占总含量的99.56%。两种提取物对金黄色葡萄球菌、变形杆菌、枯草芽孢杆菌、伤寒杆菌等均有明显的抑制作用,而乙酸乙酯提取物的抑菌效果优于乙醚。      

Chemical composition and antimicrobial activity of essential oils of Thymus algeriensis,Eucalyptus globulus and Rosmarinus officinalis from Morocco

BACKGROUND: The present study reports on the antimicrobial activity and chemical composition of the essential oils (EOs) of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco. RESULTS: The composition of these species was analysed by GC‐MS, and 65 components were identified. Eucalyptus globulus EO showed a great similarity with EOs from other regions, with 1,8‐cineole (79.85%) the major component. Also rich in this constituent was Rosmarinus officinalis (43.99%). However, the chemical profile of Thymus algeriensis was rather different, and for the first time such a high content of borneol (23.48%) has been described in this EO. The antimicrobial activity of these species has also been studied against seven pathogenic and spoiling bacteria of significant importance. According to the results, Thymus algeriensis showed the best bacteriostatic and bactericidal effect, followed by Eucalyptus globulus and Rosmarinus officinalis. CONCLUSIONS: As far as we know this is the first time that minimum inhibitory and bactericidal concentration values have been reported for Eucalyptus globulus EO. Our data support the possible use of this EO as well as Thymus algeriensis EO, as potential natural agents in preservatives for food and pharmaceutical products. Copyright © 2011 Society of Chemical Industry     

Short communication: effects of supplementation with pomegranate seed pulp on concentrations of conjugated linoleic acid and punicic acid in goat milk

The effects of feeding pomegranate seed pulp (PSP) on milk yield, milk composition, fatty acid profiles of milk fat, and blood metabolites were examined in this study. During a pretrial period, 27 multiparous southern Khorasan (Iran) cross-bred goats were fed a similar diet and dry matter intake, milk yield, and milk composition were recorded. After adaptation and based on pretrial records, the goats were randomly assigned to 1 of 3 experimental diets and were housed in individual stalls. Experimental diets included 0, 6, or 12% of PSP (dry matter basis) and were fed as total mixed rations ad libitum for a 45-d period. Diets were formulated to be isonitrogenous and isocaloric. Supplementation of PSP did not affect dry matter intake or average daily gain of goats. Milk yield was not affected by inclusion of PSP in the diet. Milk fat concentration of goats fed diets with 6 and 12% PSP increased, but milk fat yield, milk protein concentration, and milk solids-not-fat concentration of goats were not affected by diets. Feeding PSP did not affect blood glucose, cholesterol, urea N, triglyceride, or lipoproteins. Feeding goats a diet containing 12% PSP modified the milk fatty acid profile, including conjugated linoleic, punicic, and vaccenic acids.     

食品级壳聚糖乳酸盐的制备、表征和抗菌活性

壳聚糖可完全溶解于乳酸水溶液中。按等摩尔比进行完全溶解后，经过滤和冷冻干燥得到壳聚糖乳酸盐白色固体。该盐热稳定性良好，可速溶于中性水中，水溶液pH值适中，且稳定性好，对金黄色葡萄球菌和大肠杆菌有一定抑制作用。鉴于组成的食品安全性，可作为防腐剂应用于食品品体系中。     

Effects of substrate, passage rate, and pH in continuous culture on flows of conjugated linoleic acid and trans C18:1

A dual-flow continuous culture system consisting of 4 fermenters was used in a 4 x4 Latin square design. The objective of the research was to evaluate the effects of solid dilution rate (SDR), pH, and concentration of linoleic acid (LA) in the feed mixture on the production of conjugated linoleic acid (CLA) and trans-C18:1. The 4 treatments were 1) control = pH 6.5, 1% LA, 4%/h SDR; 2) high solid dilution rate (HSDR) = pH 6.5, 1% LA, 8%/h SDR; 3) high linoleic acid (HLA) = pH 6.5, 3% LA, 4%/h SDR; and 4) low pH (LPH) = pH 5.8, 1% LA, 4%/h SDR. Inoculum was collected 6 h after feeding from a cow fed 40% alfalfa hay and 60% grain. Liquid dilution rate was held at 0.12/h. All treatments except HLA contained 2% tallow. The LA was dissolved in buffer and continuously infused into the fermenters. The CLA flows were 16.5, 20.4, 23.2, and 25.2 mg/d for control, HSDR, HLA, and LPH, respectively. Compared with control, LPH increased flows of CLA, cis-C18:1, and C18:2, and decreased flow of C18:0. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibilities were not affected by pH. The HSDR tended to increase CLA flow compared to control, possibly because a shorter solid retention time led to incomplete biohydrogenation (BH). The NDF and ADF digestibilities and bacterial numbers were reduced by HSDR. With more LA available as a substrate for CLA, HLA resulted in a higher flow of CLA than control. The HLA resulted in the highest acid detergent fiber and fatty acid digestibilities, bacterial numbers, and BH. Increasing solids passage rate, reducing pH, and increasing dietary LA appears to increase in vitro CLA production.     

Assessment of factors influencing antimicrobial activity of carvacrol and cymene against Vibrio cholerae in food

Carvacrol and cymene, phenolic compounds naturally present in the essential oil of oregano and thyme, were examined for their antimicrobial activity against Vibrio cholerae (ATCC 14033, VC1, and VC7) inoculated in carrot juice. Carvacrol exhibited a dose dependent inhibitory effect on the bacteria. Although cymene did not have antimicrobial activity against the bacteria, it enhanced the inhibitory ability of carvacrol. At 25 °C, the lowest concentrations of carvacrol and cymene required for zero detectable viable count varied depending on bacterial strains; 5 and 5 ppm, respectively, for VC7; 5 and 7.5 ppm, respectively, for VC1; and 7.5 and 7.5 ppm, respectively, for ATCC 14033. This study also examined several factors influencing the antimicrobial activity of carvacrol and cymene against V. cholerae ATCC 14033, including temperature, bacterial cell number, and food substrate. Carvacrol and cymene inhibited the bacterium in carrot juice at 25 °C more efficiently than at 15 and 4 °C. The doses of both compounds required for zero detectable viable count increased as the number of the bacterial cells in the carrot juice increased. The fat content and the complexity of foods were shown to decrease the antimicrobial activity of the compounds.     

Short communication: Improving the activity of bile salt hydrolases in Lactobacillus casei based on in silico molecular docking and heterologous expression

Bile salt hydrolase (BSH) plays an essential role in the cholesterol-removing effect of lactic acid bacteria, which hydrolyze conjugated bile salts to amino acid and deconjugated bile salts. However, Lactobacillus casei lacks the bsh gene, which may make it highly sensitive to bile salt stress. We wanted to improve the BSH activity of L. casei for various food-industry applications (e.g., milk fermentation). Plate assay testing indicated that Lactobacillus plantarum AR113 has the highest BSH activity. We cloned and sequenced 4 bsh genes from the genome of L. plantarum AR113. Structure modeling and molecular docking of BSH indicated that BSH1 and BSH3 could react efficiently with bile salts, so we selected BSH1 and BSH3 for heterologous expression in L. casei. Compared with single expression of BSH1 or BSH3, co-expression of both protein sequences showed the highest hydrolysis activity by HPLC analysis. Our results suggested that heterologous expression of BSH in L. casei can significantly improve host activity against bile salts, and in silico molecular docking could be an efficient method of rapid screening for BSH with high activity.     

Short communication: impact of pH and temperature on the acidifying activity of Carnobacterium maltaromaticum

The acidifying activity of Carnobacterium maltaromaticum LMA28, a strain isolated from French soft cheese, was studied in trypticase soy broth with yeast extract (TSB-YE) medium and in milk. In TSB-YE supplemented with lactose, glucose, or galactose, lactose and glucose were metabolized with a maximum growth rate of 0.32 h⁻¹ and galactose was not metabolized. During hydrolysis of lactose, the galactose moiety was not excreted. The major product was l(+) lactic acid, with no significant difference in the lactic acid yield. Glucose was not completely metabolized because cell growth stopped when pH values reached an average of 5.0. In sterilized UHT milk, the addition of 1 g/L of YE enhanced its coagulation. Compared with commercial starter lactic acid bacteria such as Lactococcus lactis DSMZ 20481 or Streptococcus thermophilus INRA 302, Carnobacterium maltaromaticum LMA 28 was shown to be a slow acidifying strain. However, in spite of this weak acidifying ability, C. maltaromaticum LMA 28 can sustain low pH values in coculture with Lc. lactis DSMZ 20481 or S. thermophilus INRA 302. The individual and interactive effects of initial pH values (5.2 to 8.0) and incubation temperatures (23 to 37°C) on acidifying activity were studied by response surface methodology. The 3 strains displayed different behaviors depending on pH and temperature. The psychrotrophic lactic acid strain C. maltaromaticum LMA 28 was able to grow at alkaline pH values and during storage conditions. It could be used as a potential ripening flora in soft cheese.     

甜橙精油的化学成分、抑菌和抗氧化活性研究

采用气相色谱-质谱法（GC-MS）对甜橙精油的挥发性成分进行分析,通过抑菌圈实验和试管二倍稀释法对其抑菌效果、最低抑菌浓度（MIC值）进行测定,采用3种方法（DPPH、ABTS和FRAP）对甜橙精油的抗氧化活性进行体外评价。结果表明:甜橙精油含有101种组分,鉴定出50种成分,主要为脂肪族（5.96%）和萜类化合物（78.39%）;甜橙精油对6种供试菌均有较明显的抑制作用,其中对枯草芽孢杆菌的抑制作用最强（MIC值7.5μL/m L）,绿色木霉最弱（MIC值15μL/m L）;甜橙精油对DPPH自由基和ABTS+自由基有明显的清除作用,样品量与清除率间呈量效关系。      

Short communication: Molecular characteristics,antimicrobial susceptibility,and pathogenicity of clinical Nocardia cyriacigeorgica isolates from an outbreak of bovine mastitis

The occurrence of nocardial mastitis, mostly in the context of outbreaks, has been reported in many countries. However, there is a paucity of reports regarding detailed characterization of Nocardia cyriacigeorgica from bovine mastitis. Thus, herein we report characteristics, antimicrobial susceptibility patterns, molecular identification, and pathogenicity of N. cyriacigeorgica isolated from an outbreak of clinical mastitis in a dairy herd in northern China. A total of 182 (80.2%) lactating cows had clinical mastitis with severe inflammation and firmness of the udder, reduced milk production, and anorexia, with no apparent clinical response to common antibiotics. Out of 22 mastitic milk samples submitted to our laboratory, 12 N. cyriacigeorgica were isolated and characterized using standard microbiological analysis, 16S rRNA gene sequencing, random amplified polymorphic DNA PCR analysis, biochemical assays, and antibiotic susceptibility testing. Additionally, in vivo experiments were done to determine pathogenicity of these clinical mastitis isolates. All isolates were resistant to ampicillin, amoxicillin-clavulanic acid, ciprofloxacin, minocycline, rifampicin, and aminoglycosides (type VI pattern). Additionally, intramammary inoculation of mice with N. cyriacigeorgica caused chronic inflammatory changes, including hyperemia, edema, and infiltration of lymphocytes and neutrophils, as well as hyperplasia of lymph nodules in mammary glands. Therefore, we concluded that N. cyriacigeorgica was involved in the current outbreak of mastitis. To our best knowledge, this is the first report to characterize N. cyriacigeorgica isolated from cases of bovine mastitis in China.     

Short communication: effect of production variables on the cis-9, trans-11 conjugated linoleic acid content of cows' milk

Although there have been numerous studies investigating effects of nutrition and individual variation on the concentration of cis-9, trans-11 conjugated linoleic acid (rumenic acid; RA) in milk, there is limited information on relationships among RA content of milk and production variables. The objective of the current analysis was to examine the effects of production variables on RA content and desaturase index of milk fat. A total of 430 samples were collected from cows fed a commercial total mixed ration in winter and grazing in summer. Across a >6-fold range in production variables, RA content of milk ranged from 1 to 32 mg/g of fatty acids and desaturase index ranged from 0.03 to 0.15. Days in milk, milk yield, milk fat content, and milk fat yield had minimal or no effect on RA content of milk fat or desaturase index (R² values all <0.08). Thus, whereas nutrition and individual variation are major factors affecting RA content and desaturase index of milk fat, these values are minimally affected by days in milk, milk yield, milk fat content, and milk fat yield. Differences in these parameters do not need to be considered, therefore, when designing management strategies to increase RA content of milk fat.     

Chemical composition,antioxidative capacity and interactive antimicrobial potency of Satureja khuzestanica Jamzad essential oil and antimicrobial agents against selected food‐related microorganisms

This study aimed to determine the chemical composition, antimicrobial and antioxidative activity of Satureja khuzestanica Jamzad essential oil. The oil was analysed by GC and GC/MS. Twenty‐eight constituents were identified. The oxygenated monoterpenes (78.22%) were the principal compound group. Among them, carvacrol (53.86%) and thymol (19.84%) were the most abundant constituents. The oil exhibited an acceptable antimicrobial activity against most of the tested microorganisms. The checkerboard method was applied to determine fractional inhibitory concentration indices (FICIs) to interpret the synergetic, additive, indifference or antagonistic interactions between essential oil and each of antimicrobials (lysozyme, ciprofloxacin, fluconazole and amphotericin B) against food‐related microorganisms. The synergetic phenomenon (FICI ≤ 0.5) was observed in majority of combinations with the exception of the essential oil and lysozyme. The oil exhibited good 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity (IC₅₀ = 28.71 μg mL^?1). Also, the oil had strong antioxidative activity in β‐carotene‐linoleic acid assay relative antioxidant activity (RAA% = 95.45). This study demonstrated that the essential oil has beneficial biological properties and its simultaneous application with standard antimicrobials against food‐related microorganisms result in reduction in inhibitory doses of the antimicrobials in vitro.