Phytochemical analysis and antibacterial activities of Eleutherine bulbosa(Mill.) Urb. extract against Vibrio parahaemolyticus

Objective: To analyze compounds in Eleutherine bulbosa(E. bulbosa)(Mill.) Urb. extract and to determine its antibacterial capability against Vibrio parahaemolyticus(V. parahaemolyticus).Methods: E. bulbosa bulb extract was preprared using 96% ethanol by the maceration method. Phytochemical investigation of E. bulbosa extract was analyzed using GC-MS, spectrophotometry and titrimetry methods. The zone of inhibition was identified by the diffusion agar method. The minimum inhibitory concentration and minimum bactericidal concentration were determined using the plate count method. The inhibitory rate against V. parahaemolyticus was determined by the microdilution method. Cellular leakage was evaluated by spectrophotometry and cellular damage was observed by scanning electron microscopy. Results: GC-MS analysis showed the high compound of the E. bulbosa extract was securixanthone E(7-hydroxy-1,2-dimethoxyxanthone). The compound groups also included fatty acid esters, isoquinolines, naphthalenes, and phenolics. The total phenolic content was(2.50 ± 0.00) mg/g, flavonoid(6.61 ± 0.00) mg/g, and tannin(0.03 ± 0.00)%. The greatest zone of inhibition and inhibitory rate were(11.83 ± 0.06) mm and(91.32 ± 2.76)%, respectively, at 10 mg/m L. The minimum inhibitory concentration was 0.156 mg/m L, while the minimum bactericidal concentration was 10 mg/m L. The E. bulbosa extract caused leakage and cellular damage to V. parahaemolyticus. Conclusions: The E. bulbosa extract possesses inhibitory activities against V. parahaemolyticus and causes cellular leakage and damage.

Biofloc system supplemented by Pseudoalteromonas piscicida 1Ub protects the Pacific white shrimp Penaeus vannamei from Vibrio parahaemolyticus infection

This study aimed to evaluate the supplementation of the probiotic Pseudoalteromonas piscicida 1Ub to the biofloc system as an ecofriendly strategy for protecting white shrimp(Penaeus vannamei)from Vibrio parahaemolyticus infection.Shrimp with an average body weight of(0.50±0.09)g were reared in 30 glass jars with a working volume of 2.5 L at a density of 20 ind/L.Shrimp were reared for 5 d for each treatment,which included the biofloc system without and with 106 colony forming unit(CFU)per mL probiotic.The regular clear water system was used as control.All treatment groups were challenged with 103,105,and 107 CFU/mL V.parahaemolyticus.For the negative control,shrimp were reared without V.parahaemolyticus.The results showed that the density of V.parahaemolyticus cocultured with P.piscicida 1Ub decreased and the density of V.parahaemolyticus in rearing water and shrimp body in the probiotic-treated group was lower than that in the control group(P<0.05).The survival and immune response(total hemocyte count,phagocytic activity,respiratory burst,phenoloxidase,and superoxide dismutase)of shrimp in the probiotic group was higher than that in the positive control(P<0.05).Moreover,supplementing the biofloc system with the probiotic could protect shrimp hepatopancreas from damage caused by V.parahaemolyticus,regardless of bacterial density.Thus,the supplementation of the probiotic P.piscicida 1Ub in the biofloc system could significantly protect and increase the resistance of shrimp to V.parahaemolyticus infection.

The age and quality of pond bottom soil affect water quality and production of Pangasius hypophthalmus in the tropical environment

Pangasius hypophthalmus is the most cultured freshwater fish by smallholder farmers in Indonesia.One of the main challenges in the production is the highly weathered and infertile soils on the bottom of a pond that influences aquaculture productivity.This work investigated the effects of pond age on soil quality,water quality,benthic algae population,and P.hypophthalmus production.We carried out a field experiment in a randomized design with pond age of 4 levels:Ponds aged 0-5 years(P1),6-10 years(P2),11-15 years(P3),and 16-20 years(P4).The soil is a Typic Palaeudult(Ultisol),and fish were grown for three months.The results showed that the chemical soil quality parameters and soil organic matter content increased linearly with pond age,resulting in the enhancement of water quality parameters.The increase in nitrate and phosphate directly affected benthic algae richness.These,in turn,in the highest fish production in P3,6.4 kg/m^(2),specific growth rate was 3.76%/d,survival rate of 66.7%,and feed conversion ratio of 1.8%.Linear correlation coefficients indicated that the contents of total N,total P,and organic carbon in the bottom soil of the pond were related to the increase in phosphate,nitrate,and organic matter content in pond water.Total N content,total P,carbon organic matter,C/N ratio,and CEC value in pond bottom soil significantly correlated to Pangus fish production.C/N ratio,CEC value in pond bottom soil,and CO_(2)concentration in pond water significantly correlated to fish survival rate.Multiple linear regression indicated that fish production was significantly related to the pond age,water NH3,total alkalinity,and soil total P and C/N ratio(R^(2)=0.99,P<0.001).Increased soil C/N ratio caused a negative effect on fish production.The results suggested that old-aged ponds,with proper management,act as a nutrient sink,resulting in increased aquaculture production.The implementation of the best practices will benefit the Pangus culture in the tropical environment.