Antimicrobial activity of microencapsulated lemongrass essential oil and the effect of experimental parameters on microcapsules size and morphology

Lemongrass (Cymbopogom citratus) essential oil, known due to its broad-spectrum antimicrobial activity, was microencapsulated by simple coacervation. Poly(vinyl alcohol) (PVA, 78,000 Da and 88 mol% degree of hydrolysis) crosslinked with glutaraldehyde was used as wall-forming polymer. The influence of stirring rate and oil volume fraction on the microcapsule size distribution were evaluated. Sodium dodecil sulphate (SDS) and Poly(vinyl pirrolidone) were tested in order to avoid microcapsules agglomeration during the process. Depending on the experimental conditions, microcapsules in the range of 10 μm to 250 μm were obtained. Microcapsules presenting no agglomeration were obtained when SDS at 0.03 wt.% was used. The composition and the antimicrobial properties of the encapsulated oil were determined, demonstrating that the process of microencapsulation did not deteriorate the encapsulated essential oil.     

Flow boiling in horizontal flattened tubes: Part II – Flow boiling heat transfer results and model

Experiments of flow boiling heat transfer were conducted in four horizontal flattened smooth copper tubes of two different heights of 2 and 3 mm. The equivalent diameters of the flattened tubes are 8.6, 7.17, 6.25, and 5.3 mm. The working fluids were R22 and R410A. The test conditions were: mass velocities from 150 to 500 kg/m² s, heat fluxes from 6 to 40 kW/m² and saturation temperature of 5 °C. The experimental heat transfer results are presented and the effects of mass flux, heat flux, and tube diameter on heat transfer are analyzed. Furthermore, the flow pattern based flow boiling heat transfer model of Wojtan et al. [L. Wojtan, T. Ursenbacher, J.R. Thome, Investigation of flow boiling in horizontal tubes: Part I – A new diabatic two-phase flow pattern map, Int. J. Heat Mass Transfer 48 (2005) 2955–2969; L. Wojtan, T. Ursenbacker, J.R. Thome, Investigation of flow boiling in horizontal tubes: Part II – Development of a new heat transfer model for stratified-wavy, dryout and mist flow regimes, Int. J. Heat Mass Transfer 48 (2005) 2970–2985], using the equivalent diameters, were compared to the experimental data. The model predicts 71% of the entire database of R22 and R410A ±30% overall. The model predicts well the flattened tube heat transfer coefficients for R22 while it does not predicts well those for R410A. Based on several physical considerations, a modified flow boiling heat transfer model was proposed for the flattened tubes on the basis of the Wojtan et al. model and it predicts the flattened tube heat transfer database of R22 and R410A by 85.8% within ±30%. The modified model is applied to the reduced pressures up to 0.19.     

Flow boiling in horizontal smooth tubes: New heat transfer results for R-134a at three saturation temperatures

The present study presents new flow boiling heat transfer results of R-134a flowing inside a 13.84 mm internal diameter, smooth horizontal copper tube. The heat transfer measurements were made over a wide range of test conditions: saturation temperatures of 5, 15 and 20 °C, (corresponding to reduced pressures of 0.08, 0.12 and 0.14), vapor qualities ranged from 0.01 to 0.99, mass velocities of 300 and 500 kg/m² s, and heat fluxes of 7.5 and 17.5 kW/m². The experimental results clearly show that a local minimum heat transfer coefficient systematically occurs within slug flow pattern or near the slug-to-intermittent flow pattern transition. The vapor quality x_min at which the local minimum occurs seems to be primarily sensitive to mass velocity and heat flux. Thus, it is influenced by the competition between nucleate and convective boiling mechanisms that control macroscale flow boiling. The experimental results were compared to four types of predictive methods: (a) strictly convective, (b) superposition, (c) strictly empirical and (d) flow pattern based. Generally, all the methods tend to underpredict the experimental data and the higher errors occur in two particular regions: low and high vapor qualities. These vapor qualities correspond to slug and annular patterns, respectively. For slug flow, methods that require the identification of nucleate boiling related regions tend to predict the heat transfer coefficient accurately. This emphasizes that for slug flows, heat transfer is not a simple juxtaposition of nucleate and convective boiling contributions, but that the integration of these two heat transfer mechanisms is also a function of flow parameters. The comparisons between experimental and predicted data show that the best overall results are obtained with superposition and flow pattern based methods.     

Growth and acidification performance of probiotics in pure culture and co-culture with Streptococcus thermophilus: The effect of inulin

Inulin was used as a prebiotic to improve the quality and consistency of skim milk fermented by co-cultures and pure cultures of Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus and Bifidobacterium lactis with Streptococcus thermophilus. We compared, either in the presence or absence of 4 g inulin/100 g, the results of the main kinetic parameters, specifically the generation time (t_g), the maximum acidification rate (V_max), and the times to reach V_max (t_max), to attain pH 5.0 (t_pH5.0) and to complete the fermentation (t_pH4.5). Post-acidification, lactic acid formation and cell counts were also determined and compared, either 1 day after the fermentation was complete or after 7 day storage at 4 °C. In general, inulin addition to the milk increased in co-cultures V_max, decreased t_max, t_g and t_pH4.5, favored post-acidification, exerted a bifidogenic effect, and preserved almost intact cell viability during storage. In addition, S. thermophilus was shown to stimulate the metabolism of the other lactic bacteria. Contrary to co-cultures, most of the effects in pure cultures were not statistically significant. The most important aspect of this paper is the use of the generation time as a tool to investigate the microbial response to inulin addition.     

Relationship between occurrence of mastitis pathogens in dairy cattle herds and raw-milk indicators of hygienic-sanitary quality

Mastitis is an inflammation of the mammary glands and in most cases it is caused by the presence of microorganisms. High mastitis rates in dairy cattle herds can cause an increase in total microorganism counts of bulk tank milk. The present paper was aimed at verifying whether the occurrence of mastitis in dairy cattle herds is reflected in raw-milk indicators of hygienic-sanitary quality. To observe the correlation among the analysed variables, we performed a logarithmical transformation (log10) of different indicator counts of raw milk and compared them with the occurrence of mastitis in dairy cattle herds. Few correlations were observed among mastitis cases in dairy cattle herds and the raw-milk indicators of hygienic-sanitary quality. We observed a negative correlation between the log10 of mesophilic aerobic plate counts and psychotropic aerobic plate counts when compared with the occurrence of no bacterial growth. The log10 of thermophilic aerobic plate counts and yeasts and mould aerobic plate counts presented a positive correlation with the cases of infectious mastitis and mastitis caused by Staphylococcus spp.     

Ceramic membranes applied to membrane distillation: A comprehensive review

Membrane distillation (MD) has been increasingly studied in the past decade for its potential as a separation process of nonvolatile components. The present study demonstrates a comprehensive overview of the current progress and challenges in the application of ceramic membranes to MD based on the available state of the art. There are already published review papers about MD, but the present study focuses on ceramic membranes, which are still the few used in MD when compared to polymeric membranes. Significant issues such as membrane material, module, characteristics, and hydrophobic modification are discussed. The main operating conditions and their effects on the separation process are given. Current applications of ceramic membranes in MD are also presented. Likewise, challenges and future perspectives associated with MD performance using ceramic membranes are highlighted. A review focused on ceramic membranes applied specifically to MD will contribute for future research in order that this process achieves successful implementation in industry.     

Inhibitors of Xanthine Oxidase: Scaffold Diversity and Structure-Based Drug Design

Xanthine oxidase (XO) is the enzyme responsible for the catabolism of purines and their conversion into uric acid. XO is thus the target for the treatment of hyperuricemia and gout. For more than 50 years the only XO inhibitor drug available on the market was the purine analogue allopurinol. In the last decade there has been a resurgence in the search for new inhibitors of XO, as the activity of XO and hyperuricemia have also been associated with a variety of conditions such as diabetes, hypertension, and other cardiovascular diseases. In recent years the non-purine inhibitor febuxostat was approved in Europe and the USA for the treatment of hyperuricemia. This drug was followed by another XO inhibitor called topiroxostat. This review discusses the molecular structures and activities of the multiple classes of inhibitors that have been developed since the discovery of allopurinol, with a brief review of the molecular interactions between inhibitors and XO active site residues for the most important molecules. The challenges ahead for the discovery of new inhibitors of XO with novel chemical structures are discussed.     

Genomic merit for reproductive traits. II: Physiological responses of Holstein heifers

Fertility traits were recently added to the evaluation of genetic merit, allowing for the selection of Holstein cattle with improved reproductive performance. In the current study, we investigated the associations among genomic merit for daughter pregnancy rate (GDPR) and heifer conception rate (GHCR) and physiological responses during proestrus and diestrus. Holstein heifers (n = 99) were classified based on GDPR [high = 3.26 ± 0.76 (1.6 to 5.3), n = 48; low = ?0.17 ± 0.75 (?1.8 to 1.0), n = 51] and GHCR [high = 2.75 ± 0.77 (1.5 to 5.5), n = 49; low = 0.06 ± 0.67 (?2.1 to 1.2), n = 50]. Heifers were fitted with an automated estrous detection device, were treated with PGF_2α for synchronization of estrus, and received either artificial insemination or embryo transfer at detected estrus. Blood was sampled at the time of PGF_2α treatment, within 24 h of the onset of estrus (d 0), and on d 7, 14, 19 ± 2, 28, and 35. Blood samples from all heifers were analyzed for concentrations of estradiol (d 0) and progesterone (on the day of PGF_2α treatment and d 0, 7, and 14). Blood samples from heifers pregnant on d 38 ± 3 were analyzed for concentrations of progesterone (d 0, 7, 14, 19 ± 2, 28, and 35), pregnancy-specific protein B (d 19 ± 2, 28, and 35), and insulin-like growth factor 1 (d 0, 7, 14, 19 ± 2, 28, and 35). Expression of mRNA for interferon-stimulated gene 15 in peripheral leukocytes isolated from blood collected on d 19 ± 2 was determined. Ovaries were scanned by ultrasound daily from d 0 to 4 or until ovulation was detected. Heifers with low GHCR tended to be less likely to be detected in estrus (78.0 vs. 91.8%). Estradiol concentration on d 0 was greater for heifers with high GDPR (4.53 ± 0.23 vs. 3.79 ± 0.23 pg/mL). The ovulatory follicle was larger for heifers with high GDPR (16.28 ± 0.33 vs. 14.55 ± 0.35 mm), whereas heifers with high GHCR tended to have smaller ovulatory follicles (15.00 ± 0.31 vs. 15.83 ± 0.37 mm). Heifers with high GDPR tended to be more likely to ovulate within 96 h of the onset of estrus (90.7 vs. 75.0%). Among heifers pregnant on d 38 ± 3, GDPR and GHCR were not associated with mRNA expression for interferon-stimulated gene 15. Heifers with high GDPR had greater concentration of pregnancy-specific protein B from d 28 to 35 (3.03 ± 0.15 vs. 2.48 ± 0.1 ng/mL). Heifers with high GHCR tended to have greater insulin-like growth factor 1 concentration from d 7 to 35 (108.0 ± 3.2 vs. 97.7 ± 4.2 ng/mL). Our results suggest that selection for Holstein cattle for GDPR may have positive effects on reproductive performance through changes in ovarian follicle development and steroidogenesis. Although selection of Holstein cattle for GHCR may negatively affect estrous expression by affecting ovarian follicle growth, selection for GHCR may improve reproductive performance by altering the somatotropic axis.     

Genetic parameters and morpho‐agronomic characterization of barley in the Brazilian Savannah

There is a growing demand for malting barley in the world and the supply relies on introducing the crop into new agricultural regions, such as the Brazilian Savannah. This requires selection for high yield and seed quality, critical factors for the success of commercial production. This study aimed at estimating genetic parameters associated with morpho‐agronomic characterization of 433 preliminarily selected accessions from a worldwide barley collection. The accessions were grown on a limed and fertilized Haplustox soil, using interpolated control experimental design, in the Savannah highlands, in Brazil. High‐magnitude heritability and genetic variation coefficients were found for agronomic traits, allowing the identification of genotypes for crossing schemes to generate high‐yield recombinants. Strong negative correlation between yield and number of days to heading and protein content indicated that selection should be directed at early‐maturity cultivars with desirable malting quality. The method proved efficient and revealed interesting indicators to be considered in barley breeding programmes directed at high‐quality malting production in the tropics. Copyright © 2018 The Institute of Brewing & Distilling