Search

Search Results

##search.searchResults.foundPlural##

Isolation of Bacteria Caused Hemorrhagic Disease for Catfish (Ictalurus punctatus) in The Northern Parts of Vietnam

Trinh Thi Trang, Nguyen Thi Dung, Truong Dinh Hoai

Received: 28-02-2017 / Accepted: 24-04-2017
Cat fish, Ictalurus punctatusis increasingly cultured in the Northern part of Vietnam.However, the diseaseson the fish have not yet studied extensively with limited literature. The study was implemented to isolate pathogenic bacteria causing hemorrhagic disease in catfish and to find out highly effective antibiotics for disease treatment. The result showed that the external signs of the diseases are black skin with lossing mucus and haemorrhagic spots in the head part, fins, and abdomen. The internal signs showed damaged kidney and liquid accumulated abdomen. Thirteen rod shape, gram negative bacterial strains that grew in selected R-S medium were isolated from diseased fish. These strains were identified as Aeromonas hydrophila. Histopathological analysis of hemorrhagic diseased catfish revealed structural changes with slight necroses in muscle and gill filaments. There were many necrotic areas and granulomatous lesions on the liver, kidney and spleen, hydrophytic kidney and spleen tissues. After 2 day period of infection,bacterial strainsCL18, CL20, CL24 and CL26 at 108CFU/fish caused hemorrhagic septicemia in healthy catfish similarly to those in natural infection. Among 7 types of antibiotics, Doxycylin most sensitive with 13 tested isolates. Therefore, the use of Doxycylin on catfish haemorrhagic disease treatment is highly effective.
Effect of β-Glucan and Probiotics on the Survival rateandResistance of Tilapia (O. niloticus)to Streptococcusagalactiae

Kim Minh Anh, Nguyen Van Duy, Truong Dinh Hoai, Kim Van Van

Received: 09-08-2021 / Accepted: 10-01-2022
This study was conducted to investigate the effects of β-glucan and probiotics supplementation on the survival rate and disease resistance of tilapia (O. niloticus) juverniles. The experiment was set up with four treatments consisting of the control treatment (ĐC), the mixture of beneficial microorganisms (NT1), the mixture of β-glucan (NT2) and 50% NT1 + 50% NT2 in NT3 and was replicated thrice. Fish were randomly stocked in 12 units of 8.0 m3(2 × 4 ×1m) cement tank and fed the experimental diets for 30 days. Experimental fish were infected with bacteria S. agalactiae at109 CFU/kg of feed. Infectious bacteria were re-isolated, re-examined and the antibiogram tested after treatment to assess the disease resistance of experimental batches. The trial results showed that disease appeared later in fish fed the β-glucan supplemented diet with lower mortality rate, and higher recovery rate after medicinal treatment than those fed the probiotic and control diets.
Non-Vibrio ParahaemolyticusCausing Acute Hepatopancreatic Necrosis on Brackish Shrimps

Dang Thi Lua, Nguyen Viet Khue, Phan Thi Van

Received: 22-01-2016 / Accepted: 29-04-2016
Acute hepatopancreatic necrosis disease (AHPND), also known as Early Mortality Syndrome (EMS), has become one of the most harmful threats to the shrimp aquaculture industry in Southeast Asia, including Vietnam. It occurs on both tiger and white leg shrimps at 20 - 45 days of age with a mortality rate up to 100%. AHPND pathogens were identified as bacteria containing plasmid carrying toxin genes that cause acute hepatopancreatic necrosis. Observation of biochemical characteristics, the use of PCR technique using specific primers to detect the toxin genes and sequence analysis of 16S-rRNA gene confirmed that there were at least three strains of AHPND pathogenic bacteria on brackish shrimp cultured in Vietnam, of which two strains belong to Vibrio parahaemolyticus species, including V. parahaemolyticus KC13.14.2 and V. parahaemolyticus KC12.020; and the other strain of Vibrio sp. KC13.17.5. Vibrio sp. KC13.17.5 was confirmed as V. harveyi KC13.17.5, a non V. parahaemolyticus species. The detection of non - V. parahaemolyticus that caused AHPND is a new finding not only in Vietnam but also worldwide.
Assessing Soil Properties for Safe Vegetable CultivationinThanh Tri District, Ha Noi City

Phan Quoc Hung, Hoang Quoc Viet

Received: 17-05-2017 / Accepted: 09-08-2017
This study aimed to assess the properties of vegetable soil in three communes along the Red River in Thanh Tri district, Hanoi city to establish data base for safe and VietGAPvegetable cultivation. 72 soil samplesand15 vegetablesamples were collected to analyze the chemical, physical and biological properties of soil. Results showed that most of the samples weresandy soiland oflight bulk density. Almost samples haddensity less than 2.7. The data range hada low standard deviation with a confidence interval of ± 0.01 to ± 4.25 (= 0.05). The soilwasfrom lightly acidic to slightly alkaline, but most wasneutral.Total organic carbon and total nitrogen weremoderate,total phosphorus variedfrom medium to high, and total potassium from poor to high. Results of biological analysis indicated that the soil had a higher total number of aerobic bacteria than the total anaerobic bacteria.The earthworms distributed unevenly in the samples,ranging from 9 to 17 individuals. The heavy metal content (Cu, Pb, Zn) in the soil waslower than the allowable limits of heavy metals. Soil properties and content of heavy metals in the soil meet the conditions for safe vegetable cultivation in accordance with the current regulations of the Ministry of Agriculture and Rural Development as well as the standards of safe vegetables of the Ministry of Health.
Pig Slaughterhouse Hygiene in Lam Dong Province

Pham Thi Thanh Thao, Nguyen Xuan Trach, Pham Kim Dang

Received: 16-01-2018 / Accepted: 16-04-2018
This study aimed to evaluate the situation of hygiene conditions of pig slaughterhouses in Lam Dong province. A total of 24 slaughterhouses from 3 representative districts of the province were chosen for the survey. The awareness of abattoir workers was evaluated using a semi-structured questionnaire. The conditions of food hygiene and safety were assessed through analysis of microbial contamination in the samples collected from the investigated slaughterhouses including surfaces of pork, water, and equipment. Results showed that only a small number of the slaughterhouses were trained on the slaughtering procedure (11.11% and 50.0% of small and medium slaughterhouses, respectively). All the slaughterhouses carried out the slaughter operations on the floor. Most of the abattoir workers showed litte knowledge nor proper practices for hygiene of facilities, their individual hygiene, and the pork. Almost all equipment items were contaminated with the total aerobic bacteria and Enterobacteriaceae atunacceptable levels. Coliformswere found exceeding the specified standards in a relatively high proportion of the water samples from both types of slaughterhouses. 90.74% and 88.89% from the small and medium slaughterhouses were contaminated above the standards with the total aerobic bacteria, 66.67% and 72.22% with E. coli, 5.56% and 27.78% with Salmonella, respectively. It is therefore concluded that pig slaughterhouses in Lam Dong province are not yet satisfactory concerning food hygiene and safety and proper solutions should be warranted to improve the present status.
Evaluation of Quorum Sensing Communication between Pathogenic Bactria Causing Acute Hepatopancreatic Necrosis Disease and Vibrio Alginolyticus

Tran Thi Thuy Ha, Nguyen Thi Hanh, Pham The Viet, Phan Thi Van, Truong Thi My Hanh

Received: 01-08-2018 / Accepted: 26-08-2018
Bacterial cell-to-cell communication(quorum sensing - QS) is associated with the virulence of pathogenic bacteria. The study was conducted to evaluatethe QS communication between Vibrioparahaemolyticus - pathogenic agent causing acute hepatopancreatic necrosis disease (AHPND) and V. alginolyticus- non-AHPND and, concurrently, to determine the role of cinnamon essential oil for QS between two bacterial species mentioned above. The methods used included traditional bacterial culture and PCR technique. Results showed that V. alginolyticus received virulence gene AHPND from V. parahaemolyticusunder the culture condition with three times of heat shock at 400C (5 min) and 700C (2 min) via QS mechanism. In addition, cinnamon essential oil with a dose of 0.1μL/600μL disrupted the QS communication system of bacteria, causing V. alginolyticusimpossible to receive virulence gene causing AHPND from V. parahaemolyticus.
Biofilm Forming and Antibiotic Resistance of Biofilm Producing Staphylococcusspp.

Nguyen Van Giap, Cao Thi Bich Phuong

Received: 01-10-2018 / Accepted: 07-11-2018
This study was conducted to determine the biofilm formation and antibiotic resistance of the biofilm-forming Staphylococcusspp. By the application of microtiter plate test, a quantitative method, the biofilm formation of staphylococci was determined. It was found that 51.61% strains produced biofilms at strong, medium and weak levels. Study on the production of biofilm over time showed that the biofilm formation by staphylococci increased from 4 hours to 20 hours, and then decreased from 24 hours to 40 hours post innoculation in 96-wells plate. In terms of antibiotic resistance, the biofilm producing strains were able to survive under the concentrations of antibiotics of 10 to 100 times higher than the planktonic bacteria.
Isolation and Characterization ofBiofilm-FormingBacteriafor ApplicationPotential in Wastewater Treatment

Tran Thi Dao, Nguyen Thi Thanh Phuong, Nguyen Thanh Trung, Nguyen Huy Thuan, Do Thi Hanh, Nguyen Xuan Canh

Received: 23-06-2020 / Accepted: 24-02-2021
Biofilm is a complex structure that is formed by the adherence of living-organisms on their surfaces. The biofilm has been well studied and effectively applied in various-different fields, particularly in solving polluted environmental issues. This research aimed to find and identify the biofilm-forming bacteria which can be used in wastewater treatment in trade villages. Total 23 strains of formed biofilm bacterium were isolated from 15 wastewater samples collected from Khac Niem village (Bac Ninh province) where produced rice noodles by spreading on the agar LB medium. There were strains, viz.B22.5, B22.8, B22.9, B22.10, B22.11, B22.18, and B22.20, were not only composed of the highest ability to form biofilm but also resisted to four or five pathogenic bacterial strains. Additionally, 04strains (B22.5, B22.9, B22.10, and B22.18) had a high emulsifying activity of biosurfactants with an emulsification index above 60%. The complementary study of identifying the biological characteristics of representative strain B22.9 showed that this strain belongs to the Bacillus spp.,which is gram-positive and having the ability to form a biofilm at high temperatures. The optimum conditions for this strain to form biofilm are on LB medium adding glucose or fructose as a carbon source at 37C, pH 7, respectively.
Effect of Fermentation Time of Tofu Whey on Quality of Tofu

Nguyen Quang Duc, Tran Thi Thu Hang

Received: 11-09-2018 / Accepted: 27-03-2019
In traditional tofu (soybean curd) production, fermented tofu whey (acidic whey) - the watery part of soymilk remaining after the formation of tofu curd which is then naturally fermented -isutilized as protein coagulant. The aim ofthis studywas to investigate the changes of severalmajor chemical and microbiological components of the tofu whey during natural fermentation as well as the effect of fermentation time of tofu whey on the quality of tofu. The sugar and soluble protein content decreaseddue tomicroorganisms’ consumption as substrates. The increase of acid concentration was attributed tothe development of lactic acid bacteria. The whey after different fermentation times used as coagulants gavetofu with variablequality. Tofucoagulated with the whey after 24 h fermentation hadhigh protein and lipid content (14.8% and 5.2%, respectively)andgood water holding capacity(5 g water / g protein), and attainedhighest sensory evaluation scores (17.7). In addition,the whey after 24 h of fermentation used to coagulate tofu brought the highest yield(159%).
Effect of Probiotics Addition on Vibrioand Growth of Postlarval White-leg Shrimp (Litopenaeus vannamei) in Biofloc Nursery

Huynh Thanh Toi, Nguyen Thi Hong Van, Pham Thi Tuyet Ngan

Received: 10-10-2018 / Accepted: 15-03-2019
This study was carried out to assess probiotics addition on Vibrioin culture medium and the growth performanceof poslarval white-leg shrimp (Litopenaeus vannamei) usingbiofloc technology. The postlarvae (0.007g/ind.in weightand0.90 cmin length) were nursed at 2postlarvae/lin 100 L tank containing 50 lof 30 ‰ seawater. Probiotics were daily added at 0.01 g/l(recommended concentration) and ½, 2 times, 3 times and 4 times reccomnended concentration compared to the control (without probiotics added). Results showed that after 20-day of culturethe ratio of Vibrio/total bacteria was lower in the probiotics addition treatment than the control. The individual length and weight of shrimps increased in all treatments when probitic added, especially the shrimps with three-times higher recommended concentration of probiotics significantly (P< 0.05) increasedin length and weight than that in the control treatment. The results of this study indicated that the ratio of Vibrio/total bacteria was reduced and shrimp growth performace improved when probiotics was combined withbiofloctechnology.
Semen Quality and Bacterial Growth in Boar Semen Extender Preserved at Low Temperature

Bui Huy Doanh, Dinh Thi Yen, Dang Thai Hai, Pham Kim Dang

Received: 19-02-2021 / Accepted: 13-07-2021
This study was to evaluate the effect of hypothermic preservation strategy on semen quality as well as the bacterial growth in antibiotic-free extender at 5°C. Diluted boar semen containing antibiotic were stored in BTS and AndroStar Premium extenders at 17°C while antibiotic-free semen were stored at 5°C. Sperm motility, proportion of abnormal spermatozoa and bacterial growth after 24, 72 and 120 hours preservation were investigated. The results showed that the boar spermatozoa preserved in antibiotic-free AndroStar Premium extender at 5°C maintained high motility above 75% after 5 days of preservation and did not significantly differ from the control stored at 17°C in extender containing antibiotic (P <0.05). The proportion of abnormal spermatozoa in semen samples stored in AndPre extender at 5°C was similar to the samples stored in BTS and AndPre extenders at 17°C (P >0.05). The number of aerobic bacteria in semen samples stored at 5°C in antibiotic-free extenders was lower than 103CFU/ml after 24, 72 and 120 hours preservation and did not differ significantly with samples containing antibiotic extender stored at 17°C (P >0.05). Therefore, semen preservation in antibiotic-free AndPre extender at low temperatures might be applied to minimize the use of antibiotics in livestock.
Histopathological features of tilapias cultured in Nothern Vietnamese provinces naturally infected with Streptococcussp.

Truong Dinh Hoai, Nguyen Vu Son, Nguyen Thi Hoai, Nguyen Thi Mai Phuong, Nguyen Thi Hau

Received: 13-05-2014 / Accepted: 30-05-2014
This study was implemented to clarify some histopathological characteristics of tilapia naturally infected with Streptococcus sp. cultured in freshwater ponds in Northern Vietnamese provinces during summer of 2013. Infected tilapias (n=46) showing symptoms of dermal haemorrhage and exophthalmia were collected at 9 fish farms in Hai Duong, Ha Noi and Ha Nam provinces and examined for both gross lesion and histopathological signs. Internally, the most consistent gross findings were haemorrhage and swelling of liver, spleen, kidney, heart and intestine as well as pale coloured liver and splenomegaly. Fish occasionally exhibited the accumulation of fluid within the abdominal cavity, epicarditis, and peritonitis. Histopathological examination revealed systemic bacterial dissemination and infiltration of bacteria-laden macrophages. The cornea was damaged and invaded by bacteria. Haemorrhage, granuloma formation and necrosis were detected in the infected areas of the liver, spleen, kidney and gills. Microscopical examination confirmed the presence of severe congestion in these ograns, especially spleen and kidney. Brain lesions were present occasionally. The results indicated that infected fish exhibited obvious and systemic histopathology.Adverse environmental factors during the hot season played a certain role in the formation of lesions and outbreak of this disease.
Phân lập, nhận diện và đặc tính sinh học của xạ khuẩn sinh enzyme chitinase ở vườn quốc gia Yok Đôn

Dinh Minh Tran, To Uyen Huynh, Anh Dzung Nguyen

Received: 15-08-2020 / Accepted: 25-12-2023
Việc tạo ra phân bón sinh học mới là lĩnh vực rất được quan tâm trong nông nghiệp hiện đại. Nghiên cứu này tập trung vào xạ khuẩn có hoạt tính chitinase cao, tạo màng sinh học, thúc đẩy sinh trưởng và kháng nấm bệnh hại cây trồng. Trong nghiên cứu này, hai chủng xạ khuẩn YSS-3.3 và YWS-5.1 được phân lập từ các mẫu đất và giá thể chitin thu tại vườn quốc gia Yok Đôn ở Tây Nguyên. Các chủng này có hoạt tính chitinase cao và tạo màng sinh học. Phân tích trình tự gen 16S rRNA cho thấy chúng có quan hệ di truyền gần gũi nhất với loài Luteimicrobium album, với độ tương đồng trình tự 99,41% và độ phủ trình tự 100%. Phương pháp nuôi cấy trên đĩa thạch chỉ ra rằng các chủng xạ khuẩn sở hữu hoạt tính thủy phân cellulose và tinh bột; hòa tan kẽm, kali và phosphate khó tan; và tổng hợp siderophores. Phân tích bằng UV-HPLC cho thấy các chủng này cũng sản xuất hormone tăng trưởng cây trồng như IAA, GA3 và zeatin. Kỹ thuật nuôi cấy kép chỉ ra rằng các các chủng xạ khuẩn có hoạt tính đối kháng nấm Fusarium oxysporum. Từ những cơ sở trên, L. albumYSS-3.3 và L. albumYWS-5.1 là các ứng cử viên tốt cho các nghiên cứu tiếp theo liên quan đến ứng dụng trong nông nghiệp. Các chủng này cũng là nguồn nguyên liệu tiềm năng để thực hiện các nghiên cứu sâu về trình tự bộ gen, hệ thống chitinase, cellulase và amylase của chúng.
Study on Preparation of Chitosan Nanocapsules Transduced with Trans- cinnamaldehyde for Communication Inhibition in E. coli Top10

Dong Huy Gioi, Nguyen Thanh Hao, Nguyen Thi Bich Luu

Received: 27-02-2023 / Accepted: 05-01-2024
This study was conducted with the aim of preparing chitosan nanocapsules transduced with trans-cinnamaldehyde for communication inhibition in bacteria. We used emulsification method to synthesize nanocapsule and nanoemulsion complexes. The nanocapsule and nanoemulsion complexes were transduced with trans-cinnamaldehyde using an oil nucleus and chitosan as cover. The nanocomplex had a uniform particle structure, low dispersion, and the size ranges from 120 to 150nm. Both nanocapsule and nanoemulsion were stable in bacterial culture after 24h of incubation. The trans-cinnamaldehyde transduction efficiency for the nanocapsule and nanoemulsion complexes was 86 and 73%, respectively. Both complexes released the drug through two stages, slowly in the first 6 hours and followed by continuous drug release after 12 hours, reaching 35 and 45%, respectively, for the nanocapsule and nanoemulsion. Bioassays with the E. coli Top 10 biosensor showed that nanocapsule was superior to nanoemulsions in inhibiting bacterial communication, also known as quorum sensing. In the best formulation, nanocapsule inhibited the communication process in this bacterium up to 65%.
Effect of Biofertilizers Containing Strains of Phototrophic Purple Non-sulfur, Nitrogen-Fixing and Phosphorous-Solubilizing Bacteria on Growth and Yield of Black beans (Vigna cylindrica(L.) Skeels) Grown in Pots

Ly Ngoc Thanh Xuan, Le Vinh Thuc, Nguyen Thi Thuy Dung, Nguyen Tuan Anh, Nguyen Quoc Khuong

Received: 30-11-2022 / Accepted: 04-08-2023
The study was conducted to determine the efficacy of biofertilizers carrying strains of nitrogen-fixing and phosphorous-solubilizing purple non-sulfur bacteria (Rhodopseudomonas palustris) TLS06, VNW02, VNW64 and VNS89 (CPVS-NP) on black beans growth and yield. The experiment followed a completely randomized block design with 5 treatments and 4 replications, each of which corresponded to a pot. The treatments were (i) 100% N, P;(ii) CPVS-NP combined with 75% N, P;(iii) CPVS-NP combined with 50% N, P;(iv) CPVS-NP only;(v) not supplying CPVS-NP and no chemical fertilizers. The results showed that supplying CPVS-NP combined with75% N, P increased PNSB density and obtained the plant height, leaves number per plant, leaf length, leaf width and the branches per plant equivalent to or higher than those in the treatment fertilized with100% N, P. Supplying CPVS-NP plus 75% N, P enhanced yield by 22.0% compared to that in the treatment fertilized with 100% N, P.
Isolation and Selection of Antagonistic Bacteria Against AlternariaalternataCausing Leaf Spot Disease on Cucumber

Nguyen Thi Lien, Nguyen Nhut Hao, Nguyen Lam Minh, Nguyen Tang Phu

Received: 07-08-2023 / Accepted: 26-01-2024
Alternarialeaf spot on cucumber causes serious damage to marketable fruit yield and quality. The study was carried out to select bacterial strains from the cucumber rhizosphere soil with antagonistic activity against Alternariaalternata. The isolates were evaluated for their antifungal activity by dual culture method. The antagonistic isolates were investigated for their ability to produce hydrolytic enzymes and siderophore. The antifungal activity of volatile organic compounds was evaluated by the Petri dish inversion method. Twelve isolates exhibited antagonism against A. alternata. Growth inhibition of A. alternataby these isolates ranged from 9.7 to 47.8%. Eight isolates showed the ability to produce siderophore. All isolates were capable of producing hydrolytic enzymes (β-1,3-glucanase, chitinase, protease). Chitinase had a strong correlation with the ability to inhibit the growth of the pathogenic fungus (P <0.05). Volatile organic compounds of 12 antagonistic strains showed the ability to inhibit the growth of spores (61.8-95.2%) and mycelium (58.9-79.7%) of A. alternataThe results of this study indicated the potential of rhizobacteria in controlling A. alternatacausing leaf spot in cucumbers.
Composition, Quantity and Antibiotic Susceptibility of Some Bacteria Isolated from Vaginal Discharge of Dairy Cows

Nguyen Van Thanh, Nguyen Thi Lan, Nguyen Hoai Nam, Le Van Hung, Nguyen Ngoc Son

Received: 11-08-2016 / Accepted: 20-09-2016
The present study aimed to investigate the bacterial flora in the vaginal discharge of dairy cows and their susceptibility to various commonly used antibiotics. Overall, 54 samples from cows with or without post-partum metritis were used for bacterial isolation and identification usingstandard bacteriological criteria. Results showed that bacterial density in the vaginal discharge of cows with postpartum metritis was significantly higher (P<0,0001)than that of cows without postpartum metritis. Two bacteria genera were isolated from both uninfected and infected cows, i.e., Staphylococcus spp.and Streptococcus spp.Their prevalence in the vaginal discharge of uninfected cows was 20,00% and 13,13%, respectively. Meanwhile, these two bacterialgenera were detected from all the samples (100%) of infected cows. Antibiogram demonstrated that these two bacterialgenera were highly susceptible to four types of antibiotics including norfloxacin, amoxicillin, tetracycline and kanamycin. The results suggested that these four kinds of antibiotics could be used for the treatment of metritis in dairy cows.
Isolation and Antimicrobial Susceptibility of Streptococcus agalactiaeCausing Cloudy-eye Disease in Thai Frog (Rana tigerina) Cultured in Northern Vietnam Provinces

Dang Thi Hoa, Vu Duc Manh, To Thi Ngoc Anh, Tran Thi Trinh, Doan Thi Nhinh, Kim Van Van, Truong Dinh Hoai

Received: 16-12-2022 / Accepted: 27-03-2023
The study was conducted to determine the disease characteristics., isolation, identification, and evaluation of antibiotic resistance ofStreptococcus agalactiaecausing blindness in Thai frog(Rana tigerina)raised in Northern provinces ofVietnam. The infected frogs(n=83) were sampled from 26 frog-raising farms in Hanoi, Ha Nam, and Thai Binh provinces. Infected frogsexhibited opaque eyes, blindnessin one or both eyes (78.3%), skin darkening (53.0%), and swelling and hemorrhage liver (69.9%). The bacteria isolated from the eye, brain, kidney and liver of infected frogs were round, convex, cream-coloured, pinpoint (1mm), Gram (+), and of coccus type.Twenty sixstrains isolated from frogs were identified as S. agalactiaebased on morphological, biochemical, and PCR analysis. The LD50of three representative strains were between 1.2×104 to3.5 ×104CFU/frog. The isolated bacteria were highlyresistant to oxytetracycline and sulfamethoxazole/trimethoprim (61.5%), buthighly sensitive to amoxicillin, florfenicol, and erythromycin (65.4-80.8%).These results providesuseful information for effective prevention of the disease caused by S. agalactiaein cultured frogs.
An Initial Study on oil Pollution Removal Product using Biofilm Forming Bacteria Attached on Husk Biochar

Tran Thi Luong, Do Thi Lien, Cung Thi Ngoc Mai, Tran Thi Dao, Tran Phuong Minh, Le Thi Nhi Cong

Received: 01-02-2023 / Accepted: 07-03-2023
Oil contaminants create remarkably environmental pollution problems because they have high toxicity and are recalcitrant to the environment.Bioremediation is an attractive alternative of utilizing bacteria to remove oil contaminants. In the present study, bacterial strains producing biofilm capable of degrading oil contaminants/ components were screened and some fermentation conditions with rice husk biochar as carrierto produce biodegradation product to remove oil contaminants were tested. Several microbial traditional methods such as screening, biofilm formation, fermentation, microbe denstity and total oil removal by TCVN 4582-88 were conducted. As the results, four biofilm forming bacterial strains highly capable of degrading and metabolizing hydrocarbon compounds were selected, i.e. Acinetobacter baumanniiQN01, Rhizobium sp. DG2, Rhodococcussp. BN5 and Stenotophomonas maltophilia QNG02. Fermentation on husk biochar to produce oil degrader product showed that suitable fermentation temperature was 40C and the product moisture was 40%. The product exhibited high removal efficiency (99%) for diesel oil contaminants after 7 day-incubation at the initial concentration of 10g/kg oil polluted soil.
Isolation and Screening of Extracellular Phytase Producing Bacteria

Nguyen Van Giang, Tran Thi Dao, Dinh Quang Hieu, Dang Ngoc Bich, Tran Thi Cam Tu, Bui Thi Hang

Received: 15-05-2013 / Accepted: 16-08-2013
Phytases are enzymes hydrolyzing phytic acid to release inorganic phosphate and myo-inositol.Phytase produced by microorganisms have potential industrial applications. The supplementation of animal feed with phytases reduces the cost of diets by removing or reducing the need for supplemental inorganic phosphate and increases the bioavailability of phosphorous in monogastric animals. In this study, soil close to pig and chicken farms at Ha Noi university of agriculture was used as a source material for isolating phytase producing bacteria. On PSM medium, six bacterial isolates having potential phytase production were isolated. Among these, M4 isolate showed maximum phytase activity. M4 isolate was biochemically characterized as Bacillus spp.
Review: Bacteriocins - Classification, Antibacterial Activities and Applications

Ninh Thi Thao, Nong Thi Hue, Dinh Truong Son, Nguyen Xuan Canh

Received: 01-06-2022 / Accepted: 27-09-2022
Bacteriocins produced bybacteria are ribosomally synthesized peptides or proteins with antimicrobial activity that either kill or inhibit the growth of closely-related or non-related bacterial strains. Bacteriocins appear to be a weapon against microorganisms due to their specific properties of natural origin, high structural and functional diversity and heat stability. Recent studies have identified bacteriocins for application in food technology as natural bio-preservatives or in agriculture as biological control agents. Bacteriocins also present a potential approach for the treatment of pathogenic microbial infections and cancer diseases in humans and a promising alternative for replacing conventional antibiotics to treat multidrug-resistant bacteria. However, the majority of application-oriented studies were mainly conducted in laboratory conditions and focused on bacteriocins from Gram-positive bacteria. In this review, we summarized the classification and antibacterial activities of bacteriocins as well as discussed current achievements and potential applications of bacteriocins in the food preservationand inagricultural and pharmaceutical fields. Our paper provides an overview of bacteriocins, thus, orients the application of bacteriocins in Vietnam.
Isolation, Selection and Identification of Nitrogen Fixing Endophytic Bacteriafrom Ming aralia (Polyscias fruticosaL. Harms)

Le Thi My Thu, Tran Ngoc Huu, Nguyen Hong Hue, Le Vinh Thuc, Tran Chi Nhan, Ly Ngoc Thanh Xuan, Nguyen Khanh Linh, Nguyen Quoc Khuong

Received: 19-07-2021 / Accepted: 05-07-2022
The objective of study was to determine nitrogen fixing endophytic bacteriafrom Polyscias fruticosa(L.) Harms. Thirteen leaves and 11 root samples Ming aralia collected in Tri Ton district, An Giang province were used for isolating nitrogen fixing endophytic bacteria on NFB medium with free nitrogen. Results showed that the 51 isolates were isolated from leaf and root Ming aralia, in which 41 strains possessed the acidic resistance at pH 5.0. Strain LP5-L1showed highest nitrogen fixing activity, with the ammonium content of 35.3 ± 5.24 mg/l. However, strain LP1-R4 was selected for their functions to produce N, P and IAA with 31.6 ± 0.39, 18.8 ± 0.78, and 6.65 ± 0.26 mg/l, respectively. The selected strain was identified as Bacillus circulans LP1-R4 based on 16S rDNA nucleotide sequences. The efficacy of a selected strain should be evaluated for replacing N for Ming aralia in pot and field conditions.
Isolation, Selection and Identification of Strain of Enterococcus faeciumHN1 Capable of Producing Bacteriocin

Pham Hong Hien, Duong Van Hoan, Tran Thi Dao, Pham Thi Dung, Nguyen Thi Thu, Pham Thi Thu Trang, Nguyen Xuan Canh

Received: 14-06-2021 / Accepted: 16-02-2022
This study was carried out to identify lactic bacteria producing bacteriocin potentially as supplement in the aquaculture feeds to replace the antibiotics. Combining methods of spreading and observing morphological characteristics of the colony on MRS medium, 16 strains of lactic acid bacteria were isolated from 18 fish gut samples collected at different locations. Among these, 8 strains were able to produce bacteriocin showing antibacterial activity against Salmonellasp. and Escherichia coli. The strain HN1 isolated from Tilapiagut samples collected in Hanoi had the most vital bacteriocin - producing ability and exhibited strong antibacterial activity simultaneously against Salmonellasp. and Escherichia coliwith antibacterial ring diameters of 16mm and 15mm, respectively. On MRS medium supplemented with 3% glucose as a carbon source and 3% yeast extract as a nitrogen source, the strain HN1 was able to grow and produce the highest amount of bacteriocin. The combination of morphological, physiological, biochemical characteristics and analysis of molecular biological sequences has identified the strain HN1 as Enterococcus faecium.
HUMAN MILK OLIGOSACCHARIDES: CHEMICAL STRUCTURE, FUNCTIONS AND ENZYMATIC SYNTHESIS

Hoang Anh Nguyen, Thu-Ha Nguyen, Dietmar Haltrich

Received: 25-05-2012 / Accepted: 21-08-2012
Human milk is considered as the best form of nutrition for the first few months of human life. The part that contributes to the important function of human milk contains oligosaccharides which are not found in infant formulas. Human milk oligosaccharides (HMOs) are the third most abundant molecular species in human milk after lactose and fat and its amount approximates15 g/L. To date, about 200HMOs have been purified and theirstructures have been determined. Basic core structure of HMOs is lactose at the reducing end elongated by fucose, N-acetylglucosamine and sialic acid. HMOs are considered to be one of the most important growth factors for intestinal bifidobacteria, beneficial bacteria dominated in gastrointestinal tract of breast-fed infants, andpotential inhibitors of adhesion of pathogenic bacteria to epithelial surfaces. For this reason, there is a continuous interest in finding structures as well as synthesis of HMOs by enzymatic method that can be applied for infant foods and drugs. This review focuses on structure and functions of HMOs, and enzymatic synthesis of some well known HMOs.
Evaluation the Quality and Microbial Flora of King Grass Silage

Nguyen Thi Tuyet Le, Bui Quang Tuan

Received: 26-04-2016 / Accepted: 22-10-2016
The aim of this study was to evaluate the quality and the microbial population of king grass (Pennisetum purpureophoides) silage. The experiment was carried out in a completely randomized design consisting of four treatments with three replications, namely control: traditional king grass silage without additive as a control; CT1: king grass silage with 5% salt; CT2: king grass silage with 5% molasses and CT4: king grass silage with 5% salt and 5% molasses. All silages were prepared using plastic jars (5kg) and incubated at room temperature (25 - 30oC) for 90 days. Silages were analyzed for fermentation characteristics and microbial diversity. The result confirmed that king grass ensilaged with molasses (CT2, CT3) had good fermentation characteristics compared with control and CT1 group. The silage (CT2 & CT3) showed golden yellow color, pleasant and acidic smell, no viscosity, and no mold growth with pH value below 4,2 (3.98 - 4.18). DM and crude protein were reduced by 1.15 % and 0.35% respectively. The highest content of lactic acid (1.30 - 1.58%) and the lowest ratio of ammonia nitrogen to the total nitrogen (5.11 -7.03%) were observed in CT2 and CT3. The microbial diversity in silages indicated that there was a highest population of lactic acid bacteria in CT2 and CT3 (194.17x106 - 316.33x106 CFU/g). The number of Bacillus sp. and Clostridium sp. mold and yeast were highest in control and CT1 (P < 0,05).

26 - 50 of 80 items << < 1 2 3 4 > >>

Search

Advanced filters

Search Results