Published: 2021-11-30

Applications of bacteriophages in controlling rice bacterial grain rot caused by Burkholderia glumae

Doan Thi Kieu Tien, Ngo Ngoc Tai, Kaeko Kamei, Tran Thi Thu Thuy, Nguyen Thi Thu Nga
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The study on the procedure of applicating bacteriophage (or phage) to prevent rice bacterial grain rot caused by Burkholderia glumae was conducted in the greenhouse conditions. The first experiment investigated the effect of different phage titers (i.e. 105 PFU/mL, 106 PFU/mL, 107 PFU/mL, 108 PFU/mL) in controlling bacterial grain rot of rice. The results showed that all four titers gave disease reduction with different levels, among these were the titer of 108PFU/mL expressed highest efficacy in disease reduction with the lowest percentage of infected grains compared to the rest treatments. The second experiment examined the effect of phage application times (i.e. spraying phage at 2 hours before pathogen inoculation, 2 hours before and 5 days after pathogen inoculation, and 5 days after pathogen inoculation) in suppressing bacterial grain rot disease. The results found that two treatments (i.e. one time spraying at 2 hours before pathogen inoculation, and two times spraying at 2 hours before and 5 days after pathogen inoculation) expressed high efficacy in reduction of grain rot disease through percentage of infected grains and improved yield parameter regarding rate of filled grains.

Effects of β-glucan and vitamin products supplementation into diets on growth performance of growing-finishing pigs in Ben Tre province

Tran Ngoc Bich, Quang Trung Le, Dang Thi Ngoc Truc, Truong Van Hieu, Nguyen Thi Kim Quyen, Ngo Hoang Khanh
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The aim of this study was to evaluate the influence of vitamin and β-glucan supplementations on growth performance of growing-finishing pigs in Ben Tre province. A total of 36 post-weaned piglets (Duroc x Yorkshire-Landrace) with the initial live weight of 17.42 kg±0.26, was allotted into 3 treatments and 4 replications in a completely randomized design. There were three diets, including basal diet (BD) without any addition of β-glucan or vitamin (diet CT), the BD supplemented with vitamin (diet Vit) and the BD supplemented with β-glucan (diet Glu). The results on growth parameters indicated that final live weight (kg), weight gain (kg), and average daily gain (g/head/day) of pigs in the experimental diets were significantly higher (P

Synthesis of lignin-based phenol-formaldehyde adhesive - A sustainable alternative to petrochemical

Nguyen Thi Nhu Y, Nguyen Thi Yen Nhi, Tran Thi Minh Thu, Nguyen Thi Ven, Tran Nguyen Phuong Lan, Luong Huynh Vu Thanh
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This study is to investigate the capability of producing lignin-based phenol-formaldehyde adhesive (LBPFA) with lignin derived from coir pith collected in the Mekong Delta, Viet Nam. The LBPFA synthetic process underwent non chemical modifications to minimize petrochemicals and energy. Effective factors as reaction time, reaction temperature and various lignin contents of phenol substitution were examined. Physical, chemical and thermal properties containing formaldehyde content, viscosity, solid content, Fourier transformed infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), tensile strength, tensile modulus and tensile strain were conducted. LBPFA was successfully synthesized at various levels of lignin contents substituting for phenol. The LBPFA’s parameters were in accordance with GB/T14372-2006 standard. The optimum reaction time, reaction temperature and lignin replacement content for LBPFA synthesis process were identified at 180 minutes, 900C and 40% wt/wt, respectively. The LBPFA showed the highest dry and wet tensile strengths of 14.42 MPa and 7.66 MPa on wooden boards compared to corresponding figures of commercial resin with 2.98 MPa and 0 MPa, respectively. For plywood, bending strength shown in LBPFA and commercial adhesive were 15.97 MPa and 20.16 MPa, respectively.

Effects of Voki-supported self-practice on high school students’ English speaking performance

Nguyen Thi Kieu Diem, Nguyen Van Loi
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Web 2.0 applications with multimedia affordances provide a creative way to expose students to a non-threatening environment for practising English. Motivated by the potentials of this type of application for English speaking instruction, this study aimed to examine the effects of high school learners’ self-practice using an app called Voki on their speaking performance. A quasi-experimental control group design was employed, in which the effect was measured by means of two speaking tests before and after the treatment, and further explored with a semi-structured interview. The results showed the increase in the students’speaking skills and the satisfaction with this Web 2.0 tool for its effectiveness and engagement. Their shyness and nervousness about uttering the target language diminished as their confidence increased. Accordingly, more evidence of the efficacy of Voki on EFL learners’ speaking performance was offered in the study. Future research can investigate learners’ improvement in language proficiency in different skills and contexts and involve larger sample sizes.

Vietnamese EFL pre-service teachers’ perceptions of the quality of a training course on English Language Teacher Education

Nguyen Anh Thi, Nguyen Thi Ngoc Lien
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The present study aims to investigate perceptions of pre-service teachers of English on the quality of a training course on English Language Teacher Education. Thirty-nine pre-service teachers who had just completed their training program at a university participated in the study. Data were collected through semi-structured interviews. The results show that the pre-service teachers on the whole showed a high level of satisfaction with the quality of the training course. However, the results indicate certain variances in the way the pre-service teachers responded to the issue of quality. The study also indicates suggestions proposed by pre-service teachers regarding how to help the university improve the quality of education and training as well as the services it offers. Accordingly, this study brings significant insights for related stakeholders in achieving a better quality for education.

Effects of different temperatures on the growth and survival of mud crab (Scylla paramamosain) larvae

Nguyen Thanh Phuong, Nguyen Tinh Em, Nguyen Thi Kim Ha, Le Quoc Viet, Do Thi Thanh Huong
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This study aimed to evaluate the effects of temperature on the growth and survival of mud crab (Scylla paramamosain) larvae in two stages including zoea-1 to megalopa (the first experiment) and megalopa to crablet-1 (the second experiment). Each experiment was conducted in a completely randomized design with four temperature levels (27, 30, 33, and 36℃) in triplicate. Stocking density of 200 ind./L for the first experiment and 4 ind./L for the second experiment. Fiberglass tanks of 500-L (containing 300-L and 250-L of 25‰ water for the first and second experiment, respectively) were used in the experiments. The results showed that S. paramamosain larvae at zoea-3 and zoea-4 died at 33℃ or above, while the highest survival rate of this stage was found at 27℃ (11.5%). The growth and larval stage index during the zoea to megalopa stage were significantly higher in 30℃ (p

Growth and survival performance of G2 crossbreeds from two strains of bighead catfish (Clarias macrocephalus)

Dedan Karanja Njihia, Duong Thuy Yen
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The development of bighead catfish (Clarias macrocephalus) aquaculture in Viet Nam has been constrained by the slow growth performance in the domesticated strain. Crossbreeding can be a solution to improve fish production. This study was aimed to evaluate the growth and survival performance of the second generation (G2) fingerlings crossbreeds (CMCT and CTCM) from two bighead catfish strains (wild Ca Mau, CM, and domesticated Can Tho, CT) compared to offspring from their original strains (G0-CT and G0-CM) and G1 crossbreeds (♀CM × ♂CT and ♀CT × ♂CM). The larvae were reared in 50-L tanks (3 to 5 replications) with the density of 1,000 individuals/tank and fed with Moina and artificial feed (40% protein). After 40 days of rearing, the fish grew differently among crosses (P0.05). The performance of these crossbreeds should be investigated further at the grow-out stage to see whether crossbreeding between wild and cultured strains of bighead catfish may be used in practice to increase bighead catfish production.

Optimization of the encapsulation of the mixture made from flesh and peel pitaya extract by spray drying

Duong Thi Ngoc Diep, Hoang Quang Binh, Do Le Hanh Trang
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In this study, the optimal conditions for spray drying of the extract made from flesh and peel of red pitaya were tested using the central composite design (CCD). The response surface methodology was used to evaluate the effect of inlet air drying temperature (145 – 155°C) and concentration of maltodextrin (13-17% w/w) on the physicochemical properties of the powder. The regression models accurately predicted the retention of betacyanin (R2=0.94) and total phenolic (R2=0.95). The optimal conditions for spray drying were determined as inlet air drying temperature at 148  and 14.62% maltodextrin. Under these conditions, the spray-dried powder achieved retention of betacyanin of 68.04% and retention of total phenolic of 84.17%. The optimized sample achieved a moisture content of 4.41%, the water activity of 0.39, and the water solubility index of 97.41%.

Primary investigating chemical constituents of bioactive extract from Centrostachys aquatica (R.Br.) Wall. ex Moq.-Tand.

Quoc Luan Ngo, Ta Thao Cuong, Tran Thi Manh Huynh, Le Minh Dan, Ngo Khac Khong Minh, Ngo Trong Nghia, Nguyen Diep Xuan Ky, Phan Nhat Minh, Nguyen Tan Phat
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This study is aimed to screen the biological activities and chemical composition to find evidences for potential medicinal applications of Centrostachys aquatica in the Mekong Delta. Crude methanol extract and subextracts in n-hexane, ethyl acetate, and acetone from Centrostachys aquatica were tested bioactivities. The methanol extract, n-hexane and ethyl acetate subextracts exhibited antimicrobial activity with corresponding MIC values of 200, 100 and 200 µg/mL, respectively. The ethyl acetate subextract was inhibited cytotoxicity against cancer cell line LU-1 with IC50 of 27.66 µg/mL. None of the  extracts showed antioxidant ability. Three known secondary metabolites including oleanolic acid (1), 20(E)-hydroxy-b-ecdysone (2), and b-spinasterol (3) were isolated for the first time from the bioactive (ethyl acetate) subextract of Centrostachys aquatica. Their structures were elucidated by modern spectra as MS, NMR and comparison with published data.

Chemical composition and antioxidant activity of Psidium guajava L. leaves

Thi Bach Le, Le Tien Dung, Nguyen Trong Tuan, Do Xuan Canh, Lam Chan Du, Bui Ngoc Anh, Nguyen Hoang Thien Long, Tran Nguyen Gia Huy, Bui Thi Buu Hue
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Guava, Psidium guajava L., is well-known tropic tree which is abundantly grown for fruit. It belongs to phylum Magnoliophyta, class Magnoliopsida and Myrtaceae family and has been found a lot in the Mekong Delta of Viet Nam. Antioxidant activity of different extracts from Psidium guajava L. leaves revealed that ethyl acetate and n-butanol extracts have the good activities. Processing of these fractions using repeated column and thin layer chromatographic techniques resulted in the isolation of four compounds, which have identified their chemical structures by spectroscopic techniques including avicularin (1), kaempferol (2), gallic acid (3), and protocatechuic acid (4). All the isolated compounds showed antioxidant activity using DPPH and ABTS scavenging assays. These results suggest that the leaves of guava  would be useful natural sources of antioxidants.

Estimating economic value of household municipal solid waste reduction program: A willingness-to-accept (WTA) approach

Huynh Thi Dan Xuan, Khong Tien Dung, Huynh Viet Khai
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This study is aimed at estimating economic value of municipal solid waste (MSW) reduction program in the Mekong Delta by employing the willingness-to-accept (WTA) approach. This research will address two important issues in current growing literature about MSW management. First, this is the first research to evaluate economic value of the MSW reduction program in Mekong Delta. The second major contribution is the approach employed - supply curve through the WTA. This program requires community participation and provision incentives to them, therefore the requirement of public acceptance through WTA is estimated. Findings reveal that people are willing to accept an average of 30,000 VND/month for the MSW reduction program. Assume that household's MSW management fee subsidy policy is canceled, and the household is facing a full fee for the MSW collection (about 150,000 VND/month), they are willing to classify MSW at source to get a reduction of 30,000 VND or they are willing to accept a fee of 120,000 VND/month. In addition, it is interesting that more than 70 percent of people are willing to participate in this program. The determinants of WTA identified include the type of MSW at the source, education level, type of urban areas. This research then proposes that MSW management implementation policy should be focused on motivating households and improving people's perception of MSW. In case of government budget deficit, community participation would be more appropriate to manage MSW.

Value chain and competitiveness of OCOP standardized clown knife fish products in Hau Giang province

Nguyen Thuy Trang, Vo Hong Tu
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The study was conducted to analyze the competitiveness of OCOP standardized clown knife fish products in Hau Giang province. The data were collected from 73 observations involved in the clown knife fish value chain. The research results show that most farmers culture knife fish intensively and the feed cost shares the highest proportion of the total production cost. Processed products from knife fish are mainly boneless fish and fish balls. The OCOP knife fish value chain operated through four main distribution channels and included actors: fish farmers, traders, processors, and retailers. The farmers normally sell fresh knife fish to middleman, accounting for 80.15%. The processing factories create and share the highest proportion of added value. The distribution channel that farmers are linked directly with processors create higher added value than others. The study also analyzed the Porter’s five forces of the knife industry. The study found that there are many potential risks in the farming process, high competitive pressures from substitute products, and limited negotiation ability of both farmers and processors.