Characterization of Aquimarina hainanensis isolated from diseased mud crab Scylla serrata larvae in a hatchery

Mass mortality due to necrosis signs occurred in hatchery-reared zoea stage larvae of the mud crab Scylla serrata in Okinawa, Japan, and a causative bacterium was isolated. In this study, we identified and characterized the bacterium by genome analysis, biochemical properties and pathogenicity. The bacterium was a Gram-negative, non-motile, long rod, forming yellow colonies on a marine agar plate. It grew at 20–33°C (not at 37°C) and degraded chitin and gelatin. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Aquimarina hainanensis. Genome sequence data obtained from Illumina MiSeq generated 29 contigs with 3.56 Mbp in total length and a G + C content of 32.5%. The predicted 16 chitinase genes, as putative virulence factors, had certain homologies with those of genus Aquimarina. Experimental infection with the bacterium conducted on larvae of four crustacean species, brine shrimp Artemia franciscana, freshwater shrimp Caridina multidentata, swimming crab Portunus trituberculatus and mud crab S. serrata, revealed that this bacterium was highly virulent to these species. The present study suggests that the bacterium caused mass mortality in mud crab seed production was A. hainanensis and can be widely pathogenic to crustaceans.     

Effects of date palm leaf fiber on the thermal and tensile properties of recycled ternary polyolefin blend composites

This work investigated the effects of date palm leaf fiber (DPLF) content on the thermal and tensile properties; and morphology of compatibilized polyolefin ternary blend. Recycled polyolefin ternary blend consisting of low density polyethylene (RLDPE), high density polyethylene (RHDPE) and polypropylene (RPP) were fabricated at different parts per hundred resin (phr) of DPLF. Maleic anhydride grafted polyethylene (MAPE) was used as compatibilizer to enhance the adhesion between filler and polymer matrix. The composites were prepared using melt extrusion and tests samples were produced via injection molding process. Thermal conductivity results showed that as much as 11 % reduction in thermal conductivity was achieved with the incorporation of 30 phr DPLF. Highest tensile strength was observed with the incorporation of 10 phr DPLF. The elongation at break was reduced with the addition of DPLF due to impediment of chain mobility by the fillers. Initial degradation temperature increased with the addition of DPLF. Hence, it is concluded that DPLF can be used to develop green and thermally insulating composites. It is hoped that the present results will stimulate further studies on the thermally insulative materials based on natural fibers reinforced polymer composites for applications in the building industries.     

Antiparasitic activity of the medicinal plant Dillenia suffruticosa against the marine leech Zeylanicobdella arugamensis (Hirudinea) and its phytochemical composition

Zeylanicobdella arugamensis (Annelida: Hirudinea), a marine parasitic leech, is currently affecting different species of cultured groupers, hybrid groupers, snappers and sea bass in Malaysia. Dillenia suffruticosa (Dilleniaceae), a medicinal plant found in Sabah, has been selected in our experiment to kill the leeches as a natural control method. The leech‐infested hybrid groupers were collected from aquaculture facilities, and the isolated leeches were challenged against methanol extract of D. suffruticosa leaves. The experiment was carried out using various concentrations of the extracts such as 25, 50 and 100 mg/ml. The methanol extract showed significant antiparasitic activity against Z. arugamensis with 100% mortality at a concentration of 100 mg/ml in 14.39 ± 3.75 min., followed by 50 and 25 mg/ml in 32.97 ± 9.29 and 41.77 ± 5.40 min., respectively. The phytochemical composition of the extract was determined using GC‐MS analysis to understand the nature of the principal compounds responsible for its antiparasitic properties. The leaves of D. suffruticosa demonstrated the presence of different bioactive compounds of various natures with varying percentages. Thus, it could be revealed that the methanol extract of D. suffruticosa mainly contains vital phytochemical compounds and showed an effective antiparasitic activity against the harmful leeches of hybrid groupers.     

Assessment of gut microbiota in different developmental stages of Malaysian Mahseer (Tor tambroides)

Malaysian Mahseer (Tor tambroides) has a good prospect for aquaculture because of its high market demand. However, there is a scarce information on gut microbiota associated with Malaysian Mahseer unlike other fish species. Therefore, we constructed and compared gut microbiota in different developmental stages (larval, juvenile, fingerling, yearling, and adult) using culture dependent and PCR‐DGGE fingerprinting technique for better understanding of gut microbiota composition associated with T. tambroides. Culturable gut microbiota composition in all developmental stages were composed of β‐ and γ‐Proteobacteria, and Bacilli. Biodiversity analysis of culturable gut microbiota showed that larval, juvenile, and adult stages have higher diversity than fingerling and yearling stages. Ward's linkage cluster analysis showed that culturable gut microbiota composition in larval and juvenile stages were close to adult stages, whereas fingerling and yearling stage composed same cluster. PCR‐DGGE fingerprinting technique showed that unculturable gut microbiota were constituted by α‐and γ‐Proteobacteria, and Actinobacteria. Ward's linkage cluster analysis showed that unculturable gut microbiota composition in both larval and juvenile stages were distinct from other developmental stages. Our results revealed that gut microbiota composition were varied in different developmental stages of Malaysian Mahseer and continuous shifts of gut microbiota from larval to adult stages.     

Influence of Hydrophobicity of Acetylated Nanocellulose on the Mechanical Performance of Nitrile Butadiene Rubber (NBR) Composites

Novel acetylation process by substitution of acetic anhydride substitution with hydroxyl groups on nanocellulose (NCC) has been explored to increase its dispersion and interaction in nitrile butadiene (NBR) matrix. The crystallinity index was increased after modification when compared to unmodified NCC, but no significant different with increases of treatment time from 1 hour to 3 hours treatments proven by X-ray diffraction (XRD) results. The Fourier transform infra-red (FTIR) showed the existent of acetyl groups on surface of the NCC after treatment by existent of the peak 1736 cm^-1 that attributed to carbonyl groups some peaks were observed at 1430, 1361 and 1248 cm^-1 and confirmed on the acetylation process. The nuclear magnetic resonance (NMR) also show the present of acetyl groups by existent of the signal of proton methyl group at 1.90 ppm and new peaks at 5.42, 4.70 and 4.34 ppm, for all ACN samples. The thermal results by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the acetylated NCCs were 10 % more thermally stable. Transmission electron microscopic (TEM) results showed that no significant changes were observed due to the acetylation process. The results also showed well distributed of individual NCC after acetylation, this improvement was primarily attributed to uniform dispersion of the ACN-NCC and less aggregated occurred. Due to its hydrophobic characteristics, highly crystalline and nano size, ACN-NCC brought a significant improvement up to 25 % on the mechanical properties of nitrile butadiene (NBR) rubber composites.     

Nutritional Composition and Thermal Properties of Goldstripe Sardinella (Sardinella gibbosa) Fillets and By-Products

Fish is a nutritious food for the whole family and a good source of protein and n-3 fatty acids. The fish-processing industry produces tonnes of fish-processing waste and by-products annually. Disposal of untreated by-products of the fish-processing industry may cause environmental pollution. Sardinella gibbosa or goldstripe sardinella is commonly used in surimi and fish cracker productions in Malaysia. However, data on the nutritional composition of goldstripe sardinella fillets (GSF) and by-products (GSB) remain limited. The objectives of this study are to determine the nutritional composition and thermal properties of fillets and by-products of S. gibbosa. Results showed that the protein and moisture contents of GSF were higher than GSB. Conversely, the ash and fat levels of GSF were lower than GSB. Levels of saturated fatty acids (SFA) in GSF and GSB were higher than monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids. Palmitic acid and oleic acid were the major SFA and MUFA found in GSF and GSB. Both GSF and GSB contain higher percentages of DHA and EPA. Melting and crystallization profiles of the oil from S. gibbosa fillets were similar to by-product oil, which was related to their fatty acid content.     

Effect of thermal stress on Hsp70 gene expression and female reproductive performance of giant freshwater prawn,Macrobrachium rosenbergii

Using Hsp70 as a biomarker, thermal stress impinges on reproductive organs, ovary and hepatopancreas were being analyzed by determining the expression of Hsp70 mRNA inside the organs after the adult inter‐molt females were subjected to thermal treatment at 35, 30 and 28°C (Control). Results showed the expression of Hsp70 mRNA under thermal treatment of 35°C after 2 hr recovery in ovary were upregulated at 2, 4, 6, 12, 24 hr and 30 days compared to control whereas in hepatopancreas under similar treatment, the expression of Hsp70 mRNA were significantly higher than control at 6, 24 hr and 30 days. Frequency of reproductive molt at 35°C showed the ovary of females were failed to develop and only entered common molt along three consecutive molt cycles. For 30°C thermal treatment, the expression of Hsp70 mRNA was significantly higher than control after 2 hr recovery but returned to normal afterwards until 30 days’ thermal treatment. Maternal heat shock for 2 hr at 35°C were found to give significantly lower frequency of reproductive molt and longer duration of ovarian development and incubation period whereas maternal heat shock for 2 hr at 30°C gave lower frequency of reproductive molt, slower development of embryo and lower hatching success compared to untreated control. This study suggests that short and long‐term thermal stress at 30 and 35°C were found to affect the induction of Hsp70 mRNA in reproductive organs of Macrobrachium rosenbergii and also influence their reproductive performance.     

Effects of replacing fish meal by soybean meal along with supplementing phosphorus and magnesium in diet on growth performance of Persian sturgeon, Acipenser persicus

Looking for replacing fish meal by cheaper and more sustainable protein sources is essential for reducing the cost of fish feeds. Soybean meal is a suitable alternative protein sources for carnivorous fish such as Persian sturgeon, Acipenser persicus. However, it contains antinutritional factors that may affect bioavailability of minerals and lead in reduced growth. Achieving a cost-effective diet that does not have negative effects on growth is the goal of aquaculture programs. A 10-week experiment was conducted with Persian sturgeon (352.07 ± 5.51 g) to determine the combined effects of phosphorous (SP), magnesium and phosphorous (SPMg), phytase (SF), phytase and magnesium (SFMg), phosphorous and phytase (SPF), phosphorous, magnesium and phytase (SPMgF) on weight gain, feed efficiency, specific growth rate, and condition factor. A control diet was prepared with fish meal as a control group. Inclusion of P, Mg, and phytase contents within soybean diets did not improve feed efficiency, and still, the control diet containing fish meal showed better weight gain and feed efficiency. Among soybean meal groups, feed efficiency and specific growth rate were significantly improved for fish fed the diet containing just phytase (SF) and both phytase and phosphorus (P ≤ 0.05). It was true for specific growth rate and condition factor. Phytase significantly enhanced growth whether included with or without phosphorous. This study showed that fish meal is more sufficient for Persian sturgeon, and soybean meal could be partly an alternative protein source if phosphorous supplied for fish by incorporation with microbial phytase or phosphorous.     

Apparent metabolizable energy value of whole date palm (<Emphasis Type="Italic">Phoenix dactylifera</Emphasis> L.) and its possible use as a feedstuff for aged laying hens

This study was conducted to evaluate the feeding value of whole date palm (WDP) with and without enzyme supplementation on aged laying hen’s performance. Apparent metabolizable energy value of WDP was determined by the total collection method using ten adult leghorn cockerels. WDP was substituted with a corn-soybean meal basal diet at 40% level, and then the metabolizable energy of this experimental diet and basal diet was determined. After that, a total number of 256 Bovanz 95-week-old hens were randomly allocated into eight groups consisting of four replicates of eight birds each, based on a 4 × 2 factorial arrangement of the treatments. Eight iso-caloric and iso-nitrogenous experimental diets including one corn-soybean meal-based control diet and two, three, and four corn-soybean meal-based diets included 70, 140, and 210 g/kg ground WDP, respectively. Each of the diets supplemented with two levels of an enzyme (0.0 and 0.07 g/kg Natozim Plus). There was no significant difference in feed intake, feed conversion ratio, egg production, egg mass, eggshell thickness, and Haugh unit among the treatments (P > 0.05). However, yolk color score significantly decreased as dietary WDP level increased. The serum biochemical metabolites were not significantly affected by WDP and enzyme supplementation (P > 0.05). There were no significant differences in the relative weight of different organs except for abdominal fat. Our findings show that using WDP up to 21% of the diet was more economic and had no adverse effect on productive performance and serum metabolites of laying hens. However, WDP had an adverse effect on yolk color which can be ameliorated by carotenoid supplementation.