Ecytonucleospora hepatopenaei n. gen. et comb. (Microsporidia: Enterocytozoonidae): A redescription of the Enterocytozoon hepatopenaei (Tourtip et al., 2009), a microsporidian infecting the widely cultivated shrimp Penaeus vannamei.

The microsporidian Enterocytozoon hepatopenaei from Penaeus vannamei (EHPPv) was redescribed on the basis of spore morphology, life cycle, pathology, and molecular character. Compared with the Enterocytozoon hepatopenaei isolated from Penaeus monodon (EHPPm), described by Tourtip et al. in 2009, new features were found in EHPPv. Electron microscopy demonstrated that EHPPv was closely associated with the nucleus of host cell. The merogony and sporogony phages were in direct contact with the cytoplasm of host cells, whereas some of the sporoblasts and the spores were surrounded by the interfacial envelope. Mature spores of EHPPv were oval and monokaryotic, measuring 1.65 ± 0.15 µm × 0.92 ± 0.05 µm. Spores possessed many polyribosomes around a bipartite polaroplast and the polar filament with 4-5 coils in two rows. Phylogenetic analyses showed all Enterocytozoon hepatopenaei isolates shared a common ancestor. Based on the morphological and molecular analyses, we propose the establishment of a new genus Ecytonucleospora and transferring Enterocytozoon hepatopenaei to the genus Ecytonucleospora, retaining the specific epithet hepatopenaei that Tourtip et al. proposed in recognition of their first research, as the new combination Ecytonucleospora hepatopenaei n. comb. Furthermore, it was suggested Enterospora nucleophila, Enterocytozoon sp. isolate RA19015_21, and Enterocytozoon schreckii be assigned into this new genus.

Impacts of Nile Tilapia (Oreochromis niloticus) exposed to microplastics in bioflocs system.

Microplastics (MPs) are abundant in aquaculture water, including in bioflocs aquaculture systems. Compared with other aquaculture systems, biofloc technology systems have the richest microbes and are beneficial to cultivated organisms. Therefore, this study provides a comprehensive assessment of the potential effects of MPs on aquaculture organisms in bioflocs systems. Here, Nile Tilapia (Oreochromis niloticus) were exposed to MPs (polystyrene; 32-40 µm diameter) with 0, 80 items/L (30 µg/L), and 800 items/L (300 µg/L) for 28 days in a bioflocs aquaculture system. The results showed that the MPs generally had no apparent effect on water quality, tilapia growth, or digestive enzyme activity. However, MPs accumulated the most in the liver (5.65 ± 0.74 µg/mg) and significantly increased the hepato-somatic index of tilapia and reduced the crude protein and lipid of tilapia muscle (p < 0.05). The levels of the antioxidant enzymes catalase and glutathione S-transferase increased significantly in response to MPs (p < 0.05). In contrast, MPs did not affect the content of glutathione, glutathione peroxidase, oxidized glutathione, and malondialdehyde, or the enzyme activity of Na+/K+-ATPase. Moreover, using an improved integrated biomarker response index, growth performance was found to be less responsive to MPs than to oxidative stress and digestive activity. Exposure to MPs did not significantly influence the microbial communities of the bioflocs and tilapia guts (p < 0.05). These results suggest that MPs barely affected tilapia in the bioflocs system. This study contributes to the evaluation of the ecological risk of MPs in aquaculture systems and a better understanding of the integrated response of cultivated vertebrates to MPs in biofloc technology systems.

Enhancement of Anaerobic Digestion to Treat Saline Sludge from Recirculating Aquaculture Systems.

The effectiveness of carbohydrate addition and the use of ultrasonication as a pretreatment for the mesophilic anaerobic digestion of saline aquacultural sludge was assessed. Analyses were conducted using an anaerobic sequencing batch reactor (ASBR), which included stopped gas production attributed to the saline inhibition. After increasing the C : N ratio, gas production was observed, and the total chemical oxygen demand (TCOD) removal efficiency increased from 75% to 80%. The TCOD removal efficiency of the sonication period was approximately 85%, compared to 75% for the untreated waste. Ultrasonication of aquaculture sludge was also found to enhance the gas production rate and the TCOD removal efficiency. The average volatile fatty acid (VFA) to alkalinity ratios ranged from 0.1 to 0.05, confirming the stability of the digesters. Furthermore, soluble chemical oxygen demand (SCOD), VFA, and PO4 (3-) concentrations increased in the effluents. There was a 114% greater gas generation during the ultrasonication period, with an average production of 0.08 g COD/L · day(-1).

[Kinetic Characteristics of Degradation of Geosmin and 2-Methylisoborneol by Bacillus subtilis].

The earthy and musty odor problem in aquaculture systems has been a worldwide problem, especially in freshwater aquaculture systems. Geosmin (GSM) and 2-methylisoborneol (2-MIB), the most common causative agents of the off-flavor in fish, are lipophilic secondary metabolites of cyanobacteria, actinomycetes, and other microorganisms. The odor threshold concentrations for 2-MIB and GSM are approximately 9-42 ng x L(-1) and 4-10 ng x L(-1), and 600 ng x kg(-1) and 900 ng x kg(-1) in the aquaculture water and fish, respectively. With such a low odor threshold concentration, the off-flavor compounds greatly reduce the quality and economic value of aquatic products. This renders the fish, especially some valuable fish produced in recirculating aquaculture systems (RAS), unmarketable. The study reported the kinetic characteristics of degradation of GSM and 2-MIB by Bacillus subtilis and discussed the impacts of the initial concentration of GSM and 2-MIB (T1, T2) and inoculation amount (T1, T3 ) on the biodegradation rate. The result demonstrated that these two compounds could be degraded by B. subtilis effectively and the biodegradation rate reached more than 90% in T1, T2 and T3 treatments. The biodegradation of these two compounds behaved as a pseudo-first-order kinetics with rate constants (K) in the range of 0.14-0.41. K values indicated that the degradation rate was dependent on the inoculation amount but the start concentration of GSM and MIB. The degradation kinetics showed the maximum specific rate value (u(max)) and the Monod constant (K(s)) were 0.311 and 1.73, however, 2-MIB degradation process did not meet the Monod microbial growth equation (R2 = 0.781).

[Denitrification and kinetic characteristics using biodegradable polymers as carbon source and biofilm carrier].

The PBS material that in the form of insoluble biodegradable polymers pellets was investigated as the solid carbon source and the biofilm carrier for nitrate removal from wastewater. The denitrification of nitrate removal and kinetic process were carried out in a packed-bed reactor in order to remove nitrate in recirculation aquaculture system. The experimental results indicated that the optimal influent loading rate was in the range of 0.107-1.098 kg/(m3 x d), when the water temperature was (29 +/- 1) degrees C and the influent nitrate concentration was in the range of 25-334 mg/L. The maximum nitrate volumetric removal rate of 0.577 kg/(m3 x d) was achieved at the influent loading rate of 1.098 kg/(m3 x d). When the influent loading rate exceeded 1.098 kg/(m3 x d), the nitrate volumetric removal rate was declined. The kinetic experimental results show that the denitrification rate of PBS as the solid carbon source and the biofilm carrier corresponds to first-order kinetics. Based on the kinetics characteristics, constants n and K used in Eckenfelder model were deduced, which can be successfully applied for the prediction of effluent nitrate concentration. The two groups' predictive values and actual values were analyzed by using SPSS 16.0 software for Paired-Samples t test analysis. The Paired-Samples t test analysis indicates that the corresponding p > 0.05 values are 0.553 and 0.632, which proved that no significant differences exist between the predictive values and actual values of the model.

[Isolation, identification and denitrification characterization of Thiobacillus denitrificans].

A autotrophic denitrifying bacterial strain, TD, was isolated from soil and the strain was identified and characterized. The strain was gram negative, strictly chemolithoautotrophic, and short rod shaped bacterium. The 16S rDNA sequence analysis revealed that strain TD had a similarity of 99.85% with Thiobacillus denitrificans. According to the morphologic, physiobiochemical characteristics and the analysis of its 16S rDNA, the strain was identified as Thiobacillus denitrificans. Studies showed that the optimal conditions for denitrification were pH 6.85 and 32.8 degrees C, while the optimal growth conditions were pH 6.90 and 29.5 degrees C. The bacteria grew slowly with no apparent stable phase. The maximal denitrification rate reached 2.245 mg x (L x h)(-1) which was found in exponential phase. In the process of the culture, the medium pH decreased significantly. Relatively high salinity restrained the denitrification activity of Thiobacillus denitrificans. The acute toxicity test results showed that Thiobacillus denitrificans was non-toxic.

[Effects of external carbon source on nitrogen and phosphorus removal in subsurface flow and free water surface integrated constructed wetland].

By adding municipal wastewater in effluent of ANOXIC-OXIC (A/O) reactor as external carbon source, effects of external carbon source on nitrogen and phosphorus removal in subsurface flow and free water surface integrated constructed wetland were studied in pilot-scale. Results indicate that, COD/TN and (NO2(-) + NO3(-))/TN in influent of wetland are 1.00 and 0.48, respectively, and load removal rates of COD, TN and TP are 1.82, 1.59 and 0.14 g (m2 x d)(-1), respectively, as directly treating effluent of A/O reactor in wetland (working condition I). COD/TN and (NO2(-) + NO3(-))/TN in influent of wetland are 3.55 and 0.44, respectively, and load removal rates of COD, TN and TP are 19.03, 5.42 and 0.29 g (m2 x d)(-1), respectively, as adding municipal wastewater in effluent of A/O reactor as external carbon source in wetland (working condition II). Compared with working condition I, load removal rates of TN and TP for working condition II increase 3.4 times and 2.1 times, respectively. Impact factors of load removal rate of TN and TP are water temperature, HRT, COD/TN and (NO2(-) + NO3(-))/TN, respectively, when ranges of influent load rates are 3.8 - 38.7 g x (m2 x d)(-1) for COD, 5.07 - 13.08 g x (m2 x d)(-1) for TN and 0.57 - 1.92 g x (m2 x d)(-1) for TP, respectively, and range of HRT is 0.5 - 1.0 d. TN load removal rate decreases by exponent function along with increase of HRT, linearly increases along with increase of water temperature and (NO2(-) + NO3(-))/TN, and increases by power function along with increase of COD/TN. TP load removal rate also increases by power function along with increase of COD/TN.

[Studies on nitrogen and phosphorus enhancing removal in combined shale and steel slag subsurface constructed wetlands].

Effluent of municipal wastewater treatment plant operated under A/O process was treated by constructed wetlands for reclamation and reuse. These methods, such as phosphorus removal by adsorption of shale and steel slag, regulating C/N ratio and nitrogen oxidability in influent of wetland, were employed to study efficiency and impact factors of nitrogen and phosphorus removal in pilot-scale in combined shale and steel slag subsurface constructed wetlands. Results indicate that, When COD area load rate, TN area load rate, TP area load rate and hydraulic retention time (HRT) is 6.5-20.7 g x (m2 x d)(-1), 2.57-8.22 g x (m2 x d)(-1), 0.41 -1.32 g x (m2 x d)(-1) and 0.5- 1.6d, respectively. Removal efficiency of ammonium nitrogen, nitrite nitrogen and nitrate nitrogen is 85.8%, 56.3% and 18.6%, respectively. Removal efficiency, area load removal rate and removal kinetic constant of total nitrogen are 58.0%, 3.58 g x (m2 x d)(-1) and 0.31m x d(-1), respectively. TN area load removal rate is linearly increased with the increase of total nitrogen area load rate. Removal efficiency, area load removal rate and removal kinetic constant of total phosphorus are 90.4%, 0.89 g x (m2 x d)(-1) and 0.86 m x d(-1), respectively. TP area load removal rate is linearly increased with the increase of total phosphorus area load rate. Water temperature, HRT, COD/TN ratio and (NO2(-) -N + NO3(-) -N) /TN ratio are primary factors impacting nitrogen and phosphorus area load removal rate. Along with HRT and COD/TN ratio increase, TN area load removal rate increases according to power function. Along with water temperature and (NO2(-) -N + NO3(-) -N)/TN ratio increase, TN area load removal rate increases according to exponential function.