Linglin Fu

Immune responses of Fenneropenaeus chinensis against white spot syndrome virus after oral delivery of VP28 using Bacillus subtilis as vehicles

The protective efficacy of oral administration of VP28 using Bacillus subtilis as vehicles (rVP28-bs) in shrimp, Fenneropenaeus chinensis, upon challenge with white spot syndrome virus (WSSV) was investigated. The calculated relative percent survival (RPS) value of rVP28-bs fed shrimp was 83.3% when challenged on the 14th day post-administration, which is significantly higher (p < 0.001) than that of the group administered recombinant Escherichia coli over-expressing rVP28 (rVP28-e21). After immunization, activities of phenoloxidase (PO), superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) in hemolymph were analyzed. It was found that the supplementation of rVP28-bs into shrimp food pellets resulted in the most pronounced increase of iNOS activity (p < 0.001), but had the least influence on activities of PO and SOD. Besides, in the shrimp orally administered with rVP28-bs, the caspase-3 activity was one-fifth that of the control, though the signs of apoptosis (chromatin margination, nuclear fragmentation and apoptotic bodies) could not be observed by transmission electron microscope (TEM). These results suggest that by oral delivery of rVP28-bs, shrimp showed significant resistance to WSSV and an effect on the innate immune system of shrimp. The remarkably enhanced level of iNOS after rVP28-bs administration might be responsible for antiviral defense in shrimp.

Aquaculture Industry in China: Current State, Challenges, and Outlook

Aquaculture in China accounts for nearly 70% of world aquaculture production. Aquaculture, including a wide variety of freshwater and marine fishes, shellfish, crustaceans, and aquatic plants, has become one of the most vital primary industries and a center of economic activity within the local and global economies. Along with the development of aquaculture, concerns come about such problems in the industry such as aquatic pollution, disease, genetic degradation of aquaculture species, decline of comparative profitability, lack of knowledge on market risks, and financial crises. Thus, there is a need to acquire further knowledge on this industry and provide sound suggestions for its sustainable development. This review aims to identify the current state of and challenges facing the aquaculture industry in China and to provide some suggestions for its sustainable development.

Identification and characterization of extracellular cyclic dipeptides as quorum-sensing signal molecules from Shewanella baltica, the specific spoilage organism of Pseudosciaena crocea during 4 °C storage.

Quorum-sensing (QS) signaling molecules are able to mediate specific gene expression inside spoilage bacteria in response to population density and thus are implicated in food spoilage. In the present work, a total of 102 strains of spoilage bacteria were isolated from Pseudosciaena crocea at 4 °C storage, and of these, 60 strains were identified as Shewanella spp., and 48 strains (47.1%) were identified as S. baltica. In addition, the spoilage capabilities of three different S. baltica strains (00A, 00B, and 00C) were compared by total volatile base nitrogen (TVB-N) and sensory analysis (off-odors). Furthermore, four cyclic dipeptides (diketopiperazines, DKPs) that function as QS signal molecules were isolated and characterized from the extracellular metabolites of S. baltica 00C which had the strongest spoilage activity based on gas chromatography mass spectrometry (GC-MS). By supplementation of four synthesized DKPs, the spoilage capability of S. baltica could be significantly enhanced. So far, this was the first attempt to characterize DKPs as the signaling molecules in QS of S. baltica. Our study may provide some evidence of the role of DKPs involved in microbial spoilage.

Effect of tea polyphenols on microbiological and biochemical quality of Collichthys fish ball

BACKGROUND Tea polyphenols (TP), as the most active constituents of tea, are considered natural food additives. This study examined the preservative properties of TP for Collichthys fish ball in well storage. Vacuum-packed Collichthys fish balls were treated with 0, 0.1, 0.15, 0.20, 0.25, and 0.30 g kg(-1) TP and stored at 0 °C for 17 days. RESULTS Microbiological results were obtained using a biochemical test, API system kit, and 16S rDNA sequence analysis. Results confirmed that the dominant bacteria in Collichthys fish balls are the genera Serratia and Pseudomonas. Total viable counts dropped two orders of magnitude in Collichthys fish balls with 0.25 g kg(-1) TP compared with the control. The advantages of total volatile basic nitrogen value, 2-thiobarbituric acid value and texture value were clearly observed, whereas pH and whiteness value exhibited no significant decrease for the group treated with 0.25 g kg(-1) TP. More than 0.25 g kg(-1) TP added could retain excellent fish ball characteristics in terms of sensory assessment after 17 days. CONCLUSION The shelf life of Collichthys fish balls supplemented with tea polyphenols can be prolonged for an additional 6 days in good condition at 0 °C storage.

Characterization and toxicology evaluation of chitosan nanoparticles on the embryonic development of zebrafish, Danio rerio

In the present study, chitosan nanoparticles were prepared, characterized and used to evaluate the embryonic toxicology on zebrafish (Danio rerio). The average particle size of chitosan nanoparticles was 84.86nm. The increased mortality and decreased hatching rate was found in the zebrafish embryo exposure to normal chitosan particles and chitosan nanoparticles with the increased addition concentration. At 120h post-fertilization (hpf), the rate of mortality were 25.0 and 44.4% in the groups treated with chitosan nanoparticles and normal chitosan particles at 250mg/L, respectively. At 72hpf, the hatching rate in the groups treated with normal chitosan particles were lower (P<0.01) at 300 and 400mg/L than those of the corresponding control groups, respectively. However, there were no significant differences between the groups treated with chitosan nanoparticles and the control groups across all the addition concentrations. More abundant typical malformation of embryos was observed in the groups treated with normal chitosan particles compared with those treated with chitosan nanoparticles. The LC50 (medium lethal concentration) of chitosan nanoparticles was 280mg/L at 96hpf and 270mg/L at 120hpf. As for normal chitosan particles, the LC50 was 257mg/L at both 96hpf and 120hpf. The TC50 (medium teratogenic concentration) of the zebrafish treated with chitosan nanoparticles and normal chitosan particles were 257mg/L and 137mg/L, respectively. It indicated that the chitosan nanoparticles were relatively more secure compared with normal chitosan particles.

Temporal genetic variability and host sources of Escherichia coli associated with fecal pollution from domesticated animals in the shellfish culture environment of Xiangshan Bay, East China Sea

This study was conducted to analyze the genetic variability of Escherichia coli from domesticated animal wastes for microbial source tracking (MST) application in fecal contaminated shellfish growing waters of Xiangshan Bay, East China Sea. (GTG)(5) primer was used to generate 1363 fingerprints from E. coli isolated from feces of known 9 domesticated animal sources around this shellfish culture area. Jackknife analysis of the complete (GTG)(5)-PCR DNA fingerprint library indicated that isolates were assigned to the correct source groups with an 84.28% average rate of correct classification. Based on one-year source tracking data, the dominant sources of E. coli were swine, chickens, ducks and cows in this water area. Moreover, annual and spatial changes of E. coli concentrations and host sources may affect the level and distribution of zoonotic pathogen species in waters. Our findings will further contribute to preventing fecal pollution in aquatic environments and quality control of shellfish.

Quality evaluation of farmed whiteleg shrimp, Litopenaeus vannamei, treated with different slaughter processing by infrared spectroscopy.

The present study was to evaluate two slaughter processing methods (ice water immersion (T-1) and individual beheaded (T-2)) on whiteleg shrimp quality farmed in freshwater culture systems using attenuated total reflection infrared (ATR-IR) technology. In addition, the corresponding physical, chemical and microbial properties of shrimp samples were also determined. No significant differences were observed in pH, total volatile basic nitrogen (TVB-N), thiobarbutiric acid (TBA) and K value as well as the contents of moisture, crude protein, crude fat and ash between groups of T-1 and T-2. However, significantly higher springiness and chewiness (P<0.05) were observed in T-1 as compared to those of T-2. As for the result of total viable counts (TVC), significantly lower value (P<0.05) was shown in T-1 than that of T-2, indicating that the quality and shelf life of whiteleg shrimp killed by ice water immersion could be improved and prolonged. Furthermore, all the samples were successfully divided into two categories regarding the two slaughter methods by principal component analysis (PCA) according to the infrared spectra. By analysis of the regression coefficients of PLS-DA, it can be supposed that the quality differences of whiteleg shrimp with different slaughter processing are largely caused by structural changes of their protein and fat. All together, our results indicated that the springiness and chewiness of whiteleg shrimp with different processing could be correctly distinguished using infrared spectroscopy.

Probiotic (Bacillus coagulans) Cells in the Diet Benefit the White Shrimp Litopenaeus vannamei

ABSTRACT We evaluated the effects of the dead probiotic Bacillus coagulons as a diet additive on growth performance, survival rate, digestive enzymes, and meat quality of the white shrimp Litopenaeus vannamei. Two treatment groups (T-1 and T-2) and a control group, each with 3 replicates, were established. The shrimp in the control were fed a basal diet, and those in T-1 and T-2 were fed with a basal diet containing viable and dead probiotic cells, respectively. After 50 days of culture, the addition of the probiotic resulted in greater (P < 0.05) final weight and daily weight gain, and survival rate. As for growth performance, the highest values (P < 0.05) were observed in T-1. Higher activities (P < 0.05) of protease, amylase, and lipase were also found in T-1 compared with T-2 and the control. No significant differences appeared in the muscle compositions of moisture, crude protein, and ash. However, the group that received viable probiotic showed greater (P < 0.05) muscle crude fat composition than that seen in the control group. In addition, greater (P < 0.05) inosinic acid content was observed in T-1. Our results showed that the dietary supplementation of both viable and dead probiotic, especially viable, can improve growth and survival rates of white shrimp.

Kinetic study of the bioaccumulation of heavy metals (Cu, Pb, and Cd) in Chinese domestic oyster Ostrea plicatula.

Much attention has been given to heavy metal contamination in coastal waters and on seafood safety induced by bioaccumulation of aquatic organisms in China. To obtain the kinetic characteristics of heavy metal bioaccumulation in Chinese native organisms, the accumulation and elimination of three heavy metals (Cu, Pb, and Cd) in domestic oyster Ostrea plicatula were investigated in both laboratory and field conditions. The kinetic parameters of bioaccumulation, including the uptake rate constant (K 1), elimination rate constant (K 2), bioconcentration factors (BCFs), and biological half-life (t 1/2), were estimated through nonlinear curve fitting using a two-compartment model. The results showed that the Pb and Cd metal concentration data perfectly fitted the two-compartment model, and good agreement was obtained between the predicted data and those obtained by the goodness-of-fit test. However, the Cu data did not fit the model. The modeling results indicated that the Pb and Cd concentrations in O. plicatula could reflect the contamination status of seawater and that O. plicatula is a potentially dependable indicator for monitoring heavy metal (Pb and Cd) contamination and seafood safety in the coastal areas of China.

Alterations of Protein Expression in the Muscle of Pacific White Shrimp (Litopenaeus vannamei) Contribute to Postmortem Changes

ABSTRACT The freshness of Pacific white shrimp (Litopenaeus vannamei) stored for 0, 2, 4, 6, 8, and 10 days under vacuumpacking at 4°C was assessed by physicochemical, sensory, and microbiological methods. Thiobarbituric acid, total volatile basic nitrogen, pH, total viable counts, and K values increased significantly (P < 0.05) with the storage time, whereas the texture profile indexes decreased significantly (P < 0.05). Furthermore, a proteomic approach of 2-dimensional gel electrophoresis coupled with MALDI-TOF/TOF identification was used to analyze the differentially expressed muscle proteins at the different storage times. All of the 3 identified proteins (arginine kinase, phosphopyruvate hydratase, and actin T2, which were involved in muscle energy metabolism, glycolytic pathway in adenosine triphosphate generation, and organization of myofibril, respectively) were downregulated with the increase of storage time. Quantitative reverse transcription—polymerase chain reaction showed that messenger RNA levels of these proteins also decreased during storage time. Downregulation of the identified proteins may contribute to changes of flesh texture and color. This study has important implications for understanding the molecular mechanism of postmortem changes and for developing predictive models suitable for determining the freshness and shelf life of shrimp.