Published: 2023-06-01

Application of loop-mediated isothermal amplification to detect Salmonella spp. in egg samples

Kha T. Tran, & Trang T. P. Nguyen
Electronic version: 01 Jun 2023 | DOI: 10.52997/jad.1.03.2023
Abstract | pdf (3.5M)


The objective of the study was to evaluate the use of loop-mediated isothermal amplification (LAMP) technique for detection of Salmonella spp. in chicken eggs. Eight Salmonella strains and 26 non-Salmonella enteric strains were used to verify the specificity of the LAMP assay for detection of Salmonella. The Sal4 primer set was used to specifically amplify the target sequence on the invA gene of Salmonella and the hydroxyl naphthol blue was used as the indicator to read the reaction results. Blank egg samples were spiked with serial 10-fold diluted Salmonella suspensions to determine the limit of detection at 50% (LOD50) of the assay. Egg samples collected from multiple locations in Ho Chi Minh City were tested for the presence of Salmonella using both LAMP method and the traditional culture method to compare the effectiveness of these two methods. Among 34 bacterial strains tested by LAMP assay, false-positive or false-negative results were not observed. The assays of spiked egg samples showed that the LOD50 of the LAMP method was less than 2 CFU/25 g sample. These results indicated a high specificity and sensitivity of the LAMP assay in detection of Salmonella in egg samples, even with those of low levels of contamination. Upon testing collected egg samples (n = 42), the LAMP assay produced the same results of Salmonella detection as the culture method. Salmonella was detected in 4 out of 42 samples. This study showed that the LAMP method is highly effective and would be suitable for use in detection of Salmonella in egg samples. The assay has several advantages such as saving time and labor compared to traditional culture methods.

Efficiency of intensive tilapia culture in earthen ponds applied biofloc technology (BFT), probiotics and off-flavor control methods

Loan P. Phan, & Tu V. Nguyen
Electronic version: 01 Jun 2023 | DOI: 10.52997/jad.2.03.2023
Abstract | pdf (3.8M)


The aim of this study was to assess the efficiency of Nile and red tilapia cultured in intensive systems applied a combination of biofloc technology (BFT) and probiotics in earthen ponds with different methods to control the off-flavor problem. A growing-out experiment was conducted for 150 days in which both Nile tilapia (5.88 ± 0.59 g) and red tilapia (9.72 ± 0.72 g) fingerlings were randomly allotted into three replicates of earthen ponds which were subdivided into four treatment groups, including: off-flavor controlled by algae management in Nile tilapia ponds (NT - AM) and red tilapia ponds (RT - AM), and off-flavor controlled by active water exchange in Nile tilapia ponds (NT - WE) and red tilapia ponds (RT - WE). The results showed that water quality was maintained in suitable ranges for fish growth. There were no significant differences in growth performance (final weight, daily weight gain and specific growth rate) among all treatments (P < 0.05). Feed conversion ratio of Nile tilapia (1.28 - 1.31) was significantly lower than that of red tilapia (1.35 - 1.37) (P < 0.05). The survival ratio (about 80%) and extrapolated yield (21.50 tons/ha in 150 days) of fish was similar and high for both Nile and red tilapia. The quality of the harvested fish in term of condition factor, size even and off-flavor intensity was also excellent. The economic efficiency of red tilapia farming in this system was higher as compared to cage systems. This study clearly demonstrated that the technique of combined BFT and probiotic application in earthen ponds could contribute to the sustainable development of tilapia production in Vietnam by reducing production cost, saving water resource and avoiding environmental pollution.

Isolation and characteristics of Pseudomonas fluorescens to inhibit Phytophthora palmivora causing rot disease in durian

Van T. Tran, Ha T. Nguyen, Hang T. Nguyen, & Don D. Le
Electronic version: 01 Jun 2023 | DOI: 10.52997/jad.4.03.2023
Abstract | pdf (3.3M)


Plant growth promoting Rhizobacteria (PGPR) have long been selected as biocontrol agents for plants. The PGPR are beneficial bacteria that live in plant roots and enhance plant growth by various of mechanisms. The PGPR have many species of the bacterial genus Pseudomonas, in which the Pseudomonas fluorescens strains is suitable for application as a biocontrol agent due to its abundance in natural soil and plant root systems. Pseudomonas fluorescens strains have important characteristics such as the ability to adhere to soil particles and to rhizomes, the ability to synthesize antibiotics, and to produce hydrolytic enzymes. Furthermore, P. fluorescens strains also possess plant growth promoting characteristics such as proteolysis, phosphate solubilization, iron chelation, and phytohormone production. Durian is a crop that has been expanded in Southeast Asian countries but the rate of durians infected with root, stem and fruit rot caused by P. palmivora is quite large. In this study, five native P. fluorescens isolates were isolated from 70 soil and rhizome samples collected from 10 durian growing provinces and evaluated for their ability to antagonize P. palmivora in petri plates. These isolates were gram negative, small, single isolated rods without sporulation when observed under microscope. All of them tested positive for catalase test, oxidase test, starch hydorolysis, gelatine liquefaction, H2S, citrate utilization and negative with indole, Voges-proskauers, methyl red. All of 5 native P. fluorescens isolates were capable of phosphate solubilizing activity, N2 fixation, siderophore and IAA production. The study showed that P. fluorescens P. fDN strain was able to inhibit P. palmivora causing rot disease in durian with 51.85% inhibition of radial growth.

Optimization of enzymatic hydrolysis condition of edible bird’s nest crumbs by response surface methodology and determination of biochemical characteristics of the hydrolysate

Hoang P. T. Truong, Thang T. Q. Vo, Ha T. T. Tran, Toan S. Vo, Ha T. Luong, & Tho P. Le
Electronic version: 01 Jun 2023 | DOI: 10.52997/jad.3.03.2023
Abstract | pdf (4.4M)


Edible bird's nest (EBN) crumbs are the by-product of the bird's nest industry. Despite having lower economic value compared to the original material, EBN crumbs still maintain high protein and carbohydrate content. Therefore, this study aimed to determine the optimal hydrolysis condition for EBN crumbs using protease to achieve the maximum degree of hydrolysis (DH). Plackett Burman design was employed to identify the important factors. The results showed that enzyme loading, temperature and hydrolysis time had the strongest effect on the DH. These factors were subsequently subjected to the optimization study using central composite design (CCD) of response surface methodology (RSM). The optimized conditions for the enzymatic hydrolysis of EBN crumbs were at an enzyme loading of 4%, temperature of 51ºC, and hydrolysis time of 90 min. The experimental DH obtained at the optimized condition (63.5%) was close to the predicted DH (64.1%). The enzymatic hydrolysate prepared at the optimal condition showed relatively high amino acid concentration (151.6 ± 1.29 µg/mL) and radical scavenging activity (64.97 ± 0.79%) compared to the boiled sample with values of only 50.1 ± 2.43 µg/mL and 18.36 ± 0.17%, respectively. The resultant hydrolysate had no effect on some of the microorganisms employed in this study. The EBN crumbs hydrolysate inhibited tyrosinase activity with an IC50 of 70.22 µg/mL, greater than that of boiled EBN (IC50= 108.9 µg/mL). The results indicated that the EBN crumbs hydrolysate could be further applied in the cosmetic industry as a rich source of nutrients and bioactive compounds for the formulation of beauty products.

Improving the database on land use planning in Vung Tau city, Ba Ria - Vung Tau province

Linh D. T. Truong
Electronic version: 01 Jun 2023 | DOI: 10.52997/jad.6.03.2023
Abstract | pdf (4.2M)


Vung Tau city is an area where management of land use planning (LUP) and urban planning is quite complicated and has been successful in building LUP database. However, this database still has limitations that must be addressed, including (1) lack of data layer on current land use for building LUP database, (2) incompleted LUP attribute database, (3) lack of metadata, (4) no connection between LUP database and digital legal materials and (5) no overlay cadastral database to data layer of current land use and LUP database. To solve these problems, this research used many methods such as documents and data collection, inheritance, expert interview, data processing and analysis, mapping, GIS application, and IT applications. The results of this study showed that the structure of cadastral database of 8 wards was succesfully converted from existing structure (according to Circular 17/2010/TT-BTNMT) to the standard structure (according to Circular 75/2015/TT-BTNMT). The 2019 land inventory data was standardized and data layer of current land use for whole city was built. In addition, the LUP database (period 2010 - 2020) for Vung Tau was improved, including: supplementing attribute information, completing metadata, connecting LUP database with relevant digital legal records, overlaying cadastral database with LUP database and data layer of current land use. Briefly, our results could be a foundation to help Vung Tau manage land sustainably, contribute to successfully building national land database and meet the exploitation requirements of LUP information in accordance with the orientation of Ministry of Natural Resources and Environment for study area.

Water desalination of Chlorella vulgaris

Hau T. T. Nguyen, Giang T. K. Ho, Huong T. Nguyen, Sang M. Nguyen, Suong T. Nguyen, Duy N. Dao, & Viet B. Nguyen
Electronic version: 01 Jun 2023 | DOI: 10.52997/jad.5.03.2023
Abstract | pdf (2.8M)


Saltwater intrusion is a common phenomenon in Southern Vietnam, but salinization is becoming more serious due to the rising sea level related to climate change. Among potential methods for water desalination, the application of halophytic microalgae is gaining high interest. This study investigated the effect of Chlorella vulgaris (C. vulgaris) microalgae on reducing water salinity at different media (Bold Basal Medium and Sea Salt Medium) and in different salt concentrations (1 - 30 g/L). The results indicated that C. vulgaris microalgae had good growth in all mediums used and contributed to lowering the salt content from 20% to 40% after 15 days of cultivation.