Antimicrobial Activity of Selected Essential Oils on Pseudomonas Species Associated with Spoilage of Fish with Emphasis on Cinnamon Essential Oil

ABSTRACT

Eight plant essential oils (cardamom, cinnamon, clove, eucalyptus, lemongrass, lime, nutmeg and rosemary) were evaluated for their antimicrobial activity against three Pseudomonas species associated with microbial spoilage of refrigerated tilapia. In vitro test of the essential oils, using disc-diffusion method, showed various degrees of antimicrobial activity against the Pseudomonas species. Cinnamon essential oil (CEO) had the highest antimicrobial activity, followed by clove essential oil. The remaining essential oils showed consistently weak activity. The antimicrobial efficiency of CEO against the Pseudomonas species was confirmed by potential minimum inhibitory concentration and minimum bactericidal concentration values, ranging between 0.125 and 0.375 µL/mL and 0.250–0.500 µL/mL, respectively. The anti-Pseudomonas activity of CEO was also tested in fish extract model at refrigeration temperature. The essential oil reduced the Pseudomonas viable count in fish extract but to a lesser extent than when it was applied at the same concentrations in culture medium. The chemical composition of CEO showed that the oil contained 79.1% cinnamaldehyde, which was suggested to be responsible for its antimicrobial activity. These results revealed the potential of CEO as a promising natural antimicrobial agent that could efficiently contribute to the control of spoilage bacteria and retard microbial spoilage of fresh fish.     

In vitro oocyte maturation and blood‐circulating steroid hormones in Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri)

The oocyte of Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri) was evaluated after incubation with 17α, 20β‐Dihydroxyprogesterone (DHP) in artificial media. Concentration of testosterone (T), progesterone (P4) and 17‐β estradiol (E2) in blood and their relation to fertilization rate were measured during experimental period. The oocytes at the same developmental stages were incubated in SIS (based on sturgeon blood ionic composition), RM2 (Ringer solution modified for sturgeons) and L‐15 (Leibovitz medium) artificial mediums in the presence of 1 μg/ml of 17α, 20β‐Dihydroxyprogesterone for 12, 18 and 24 hr. The result of this study demonstrated that fertilization rate decreased with the increasing duration of incubation in all mediums. In the Siberian and Sterlet sturgeon, the highest fertilization rate was observed in the oocytes incubated in RM2 (0.81 ± 0.4) and SIS (0.44 ± 0.8) mediums for 12 hr respectively. In the Siberian sturgeon, fertilization rate decreased significantly (p < .05) with incubation time in all three mediums. In Starlet, fertilization rate decreased significantly (p < .05) with time and reached a minimum after 24 hr (0.16 ± 0.1) in L‐15 medium. No significant (p > .05) differences were observed between blood plasma hormones and fertilization rate. The results of this study indicated that 17α, 20β‐Dihydroxyprogesterone is essential for induction of in vitro oocyte maturation in these species.     

Anaesthetic efficacy of eugenol on various size classes of angelfish (Pterophyllum scalare Schultze, 1823)

Anaesthetic efficacy of eugenol was investigated on Pterophyllum scalare. A total of 130 fish with average weights of 1.0 ± 0.5, 5.0 ± 1.0 and 10.0 ± 1.0 g were subjected to 1.25, 2.5, 4.0, 5.5 and 7.0 mg/L eugenol, and behavioural responses were observed. Induction and recovery times were significantly affected by the interactive effect of eugenol concentration and fish weight (p < .05). Generally, 49.9–128 s after exposure to 1.25–7 mg/L eugenol, fish reached stage 3. Fish entered stage 4 over 55–135 s post exposure to such concentrations. Recovery time was 393.5–597.7 s in all sizes. Any increase in eugenol concentration led to a significant decrease in the induction time with a subsequent increment of the recovery time. Concentrations of eugenol and fish size along with their interactive effects have significantly contributed to the regression models, with concentration recording the highest beta values for stages 1, 2, 3 and 4 (?0.903, ?0.898, ?0.976 and ?0.864 respectively) and the product of size and anaesthetic concentration for full recovery in smaller fish (0.647) and eugenol concentration in larger ones (0.967). Recovery time was fitted to induction time to stage 4 via quadratic and linear regression models in smaller and larger fish respectively. Results revealed the minimal eugenol concentration to induce anaesthesia in various size classes of angelfish in less than 3 min was 1.25 mg/L. Our results showed eugenol as an effective and safe anaesthetic; however, it is not advisable for live fish transportation.     

A review of sex determination and searches for sex‐specific markers in sturgeon

The availability of monosex populations of caviar‐producing female sturgeon would considerably enhance the economic viability of domestic caviar production systems. However, it is not possible to distinguish males from females by morphological characters at larval, juvenile and even adult stages. The mechanism of sex determination in sturgeons is poorly understood, and to date no sex‐specific markers in sturgeon have been reported. This review concentrates on the methodologies used to elucidate the mode of sex determination in sturgeon species and provides information on the molecular tools used to determine genetic sex markers.     

Effects of protein and lipid concentrations in broodstock diets on growth, spawning performance and egg quality of yellowfin sea bream (Acanthopagrus latus)

A study was conducted to determine the effects of dietary protein and lipid concentrations on growth, spawning performance and egg quality of yellowfin sea bream, Acanthopagrus latus. Nine diets representing a combination of three protein concentrations (40, 50 and 60%) and three lipid concentrations (15, 20 and 25%) were tested with three replicates. Each replicate was stocked with 10 fish with a sex ratio of 1:1 and the average weights were 415 g and 236 g for females and males, respectively. Fish were fed to satiation twice daily. The weight gain of A. latus broodstock was not significantly (P > 0.05) different among fish fed diets with the various protein and lipid concentrations. Except for relative fecundity and survival rate of 3-day-post-hatch (3DPH) larvae, spawning performance of A. latus was not significantly affected by different concentrations of dietary protein or lipid. Relative fecundity was found to be significantly elevated by dietary lipid at 20% concentration. However, survival rate of 3DPH larvae was highest from broodstock fed diets with 40% protein and 25% lipid, 50% protein and 15% lipid and 60% protein and 15% lipid concentrations. Egg diameter generally increased with increasing dietary protein from 40 to 60% at each lipid concentration. Total length of hatchlings followed an inverse relationship with dietary protein regardless of the lipid concentration. The oil globule diameter (OGD) of hatchlings significantly increased with decreasing dietary protein from 60 to 40%. Yolk sac length (YSL) and OGD of hatchlings was generally greatest at 15% dietary lipid concentration irrespective of protein concentrations. Total length of 3DPH larvae was greatest from broodstock fed diets with 50% protein and 20% lipid, respectively. Body protein content of broodstock was not significantly affected by dietary protein and lipid concentrations. However, increasing dietary lipid generally resulted in increasing body lipid content regardless of the dietary protein concentration. Protein and lipid contents of eggs, hatchlings and 3DPH larvae were significantly affected by dietary protein and lipid concentrations of the broodstock diets. The present study revealed that the best reproductive performance of A. latus broodstock was achieved at 40% dietary protein and 20% dietary lipid concentrations based on relative fecundity, fertilization rate, hatchability and survival of 3DPH larvae.     

Live Spirulina (Arthrospira platensis) as a growth and immunity promoter for Nile tilapia, Oreochromis niloticus (L.), challenged with pathogenic Aeromonas hydrophila

The use of antibiotics to control fish disease is one of the constraints in tilapia farming. Hence, the use of probiotic and live organisms as alternative strategies has received much more attention. This study was undertaken to evaluate the use of Spirulina (Arthrospir platensis) as a growth and immunity promoter for Nile tilapia, Oreochromis niloticus (L.). Fish (1.88 g) were randomly distributed at 20 fish per 100 L aquarium and fed a diet containing either 0.0, 1.25, 2.5, 5.0, 7.5 or 10.0 g Spirulina kg^?1 diet for 12 weeks. After the feeding trial, fish of each treatment were challenged by pathogenic Aeromonas hydrophila, which was given by an interperitoneal injection, and they were kept under observation for 10 days to record any abnormal clinical signs and the daily mortality rate. The growth‐promoting influence of Spirulina was observed with fish, and the optimum growth and feed utilization were obtained at 5.0 g Spirulina kg^?1 diet. No significant changes were observed in fish survival among the different treatments. Spirulina supplementation improved the protein and lipid contents in fish bodies without significant differences among them, especially when fed 2.5–10.0 g kg^?1 diet, but no significant differences in the moisture and ash contents were observed among different treatments. The physiological parameters were improved when fish were fed a Spirulina‐enriched diet. However, the highest red blood cells, white blood cells and nitro blue tetrazolium values were obtained at 5.0–10.0 g Spirulina kg^?1 diet; meanwhile, the lowest value was obtained in the control. Total fish mortality due to A. hydrophila infection decreased with an increase in the Spirulina level in fish diets. These results indicate that Spirulina supplement is promising as an alternative method to antibiotics for disease prevention in tilapia aquaculture, and the optimum level of Spirulina in the fish diet should be 5.0–10.0 g kg^?1 diet.     

Effect of dietary protein regime during the growing period on growth performance, feed utilization and whole-body chemical composition of Nile Tilapia, Oreochromis niloticus (L.)

This study was conducted to evaluate the effect of various dietary protein regimes on growth performance, feed utilization and whole-body chemical composition of Nile tilapia, Oreochromis niloticus (L.). Twenty cages (1 m³ each) were randomly allocated to a four-replicate experiment to represent five treatments (T1–T5) where fish were randomly stocked at a rate of 50 fish (1.5–2.2 g) per cage. Fish in T1–T5 fed on a 45% crude protein (CP) diet for the first 4 weeks. In T1, T2 or T3 fish fed on 45%, 35% or 25% CP diets for the last 8 weeks respectively. In T4 fish fed 35% CP diet for the second 4 weeks followed by 25% CP diet for the last 4 weeks and in T5 fish fed 25% CP diet for the second 4 weeks followed by 35% CP diet for the last 4 weeks. Diets were offered to satiation and provided manually twice a day in the morning and in the afternoon, 6 days a week. The optimum fish growth and feed utilization were obtained at T1, T2 and T4. Protein efficient ratio and apparent protein utilization were lower at T1 and T2 than those of T3–T5. On the other hand, no significant changes in energy utilization were observed among the different treatments. There were no major changes in the carcass composition except in ash content, which was higher in T3 and T5 only. This study recommended that the dietary protein regime is an important management in tilapia culture, and the protein level could be reduced from 45% to 35% then to 25% on increasing the fish size.     

Anti-Inflammatory Activity of Fucoidan Extracts In Vitro

Fucoidans are sulfated, complex, fucose-rich polymers found in brown seaweeds. Fucoidans have been shown to have multiple bioactivities, including anti-inflammatory effects, and are known to inhibit inflammatory processes via a number of pathways such as selectin blockade and enzyme inhibition, and have demonstrated inhibition of inflammatory pathologies in vivo. In this current investigation, fucoidan extracts from Undaria pinnatifida, Fucus vesiculosus, Macrocystis pyrifera, Ascophyllum nodosum, and Laminaria japonica were assessed for modulation of pro-inflammatory cytokine production (TNF-α, IL-1β, and IL-6) by human peripheral blood mononuclear cells (PBMCs) and in a human macrophage line (THP-1). Fucoidan extracts exhibited no signs of cytotoxicity in THP-1 cells after incubation of 48 h. Additionally, all fucoidan extracts reduced cytokine production in LPS stimulated PBMCs and human THP-1 cells in a dose-dependent fashion. Notably, the 5–30 kDa subfraction from Macrocystis pyrifera was a highly effective inhibitor at lower concentrations. Fucoidan extracts from all species had significant anti-inflammatory effects, but the lowest molecular weight subfractions had maximal effects at low concentrations. These observations on various fucoidan extracts offer insight into strategies that improve their efficacy against inflammation-related pathology. Further studies should be conducted to elucidate the mechanism of action of these extracts.     

Molecular Investigation of Human Cytomegalovirus and Epstein-Barr virus in Glioblastoma Brain Tumor: A Case-Control Study in Iran

Background:Glioblastoma multiforme is the most invasive and lethal form of brain cancer with unclear etiology. Our study aimed to investigate the molecular prevalence of HCMV and EBV infections in patients with GBM. Methods:This case-control study was conducted on 42 FFPE brain tumor samples from GBM patients and 42 brain autopsies from subjects without neurological disorders. The presence of EBV and HCMV DNA was determined, using PCR and nested-PCR assays, respectively. Results:HCMV DNA was detected in 3 out of 42 (7.1%) of GBM samples and was absent from the control group (p = 0.07). Importantly, EBV DNA was detected in 9 out of 42 (21.4%) brain tissue specimens of GBM subjects, but again in none of the control group (p = 0.001). Conclusion:Our findings indicate that infection with EBV is associated with GBM. Key Words: Brain tumor, Epstein-Barr virus, Glioblastoma, Human cytomegalovirus     

Functional Properties of Rice Bran Protein Isolate at Different pH Levels

The functional properties of proteins from Tarom and Shiroodi cultivars were determined and compared with technological aspects of food and nutraceutical applications. Shiroodi has higher protein content than Tarom, and the yields of protein obtained were 72.88 and 66.36%, respectively. Nitrogen solubilities of rice bran protein of Tarom were more than Shiroodi at all pH levels. In addition, higher solubility was found in acidic or alkaline conditions. Although the rice bran proteins had lower emulsifying properties than bovine serum albumin, they had similar foaming properties in comparison with egg white. Tarom isolates had a significantly higher solubility, emulsifying property, and foaming stability and greater surface properties than Shiroodi isolates. The results showed the surface hydrophobicities of rice bran protein were greater than casein and ovalbumin and lower than other proteins such as bovine serum albumin. Water and oil absorption capacities were 1.03 and 1.66 for Tarom and 87.3 and 75.3 for Shiroodi, respectively. The bulk densities of Tarom and Shiroodi were also 0.55 and 0.53 g/mL, which make them suitable for weaning food and other industrial applications. As a result, these rice bran proteins showed higher hydrophobicity than that of other rice bran protein varieties as well as more functionality. Thus, they have good potential in the food and pharmaceutical industries.