CTU Journal of Innovation and Sustainable Development

Giant freshwater prawn (Macrobrachium rosenbergii de Man, 1879) is one of important aquaculture species in Vietnam, especially the Mekong Delta. Farming of giant freshwater prawn has been so far very well-known in the freshwater area with some important systems, typically the alternative rice-prawn farming system. However, this industry has recently expanded rapidly and largely to the brackish water area. Currently, there is 15,270 ha of prawn culture in the Mekong Delta with total production of 5,306 tons, of which coastal provinces cover for 90.1% of total culture area and 64.8% of total production. Two important systems for prawn culture in the brackish water area are (1) Prawn and rice farming alternatively with tiger shrimp culture on the rice field; and (2) Prawn culture in pond alternatively with tiger shrimp culture. The survey on 108 households in Bac Lieu and Tra Vinh provinces found that while the system (1) is in extensive management with average yields 110 kg/ha/crop and net income of 11.5 millions VND/ha/crop, the system (2) is considered the semi-intensive farming system with average yield and net income of 886 kg/ha/crop and 68 million VND/ha/crop, respectively. A trial on prawn culture in 9 brackish water ponds in Tra Vinh province was also carried out which improved the yield up to 988-1342kg/ha/crop. Prawn culture contributed significantly to the total income of the farming systems. The success of these new farming systems together with a large area of brackish water surface in the Mekong Delta gives the industry a great potential for further development.Key words:

This study aimed to assess the chemical composition of essential oils of Elsholtzia blanda (Benth.) Benth. in Lam Dong Province, Viet Nam, and evaluate their biological activities. Essential oils obtained by hydro-distillation of the aerial parts of E. blanda were analyzed by gas chromatography-mass spectrometry (GC-MS). Thirty-one constituents were identified in the oil, and the essential oil was predominantly monoterpenoid, with camphor (25.14%), camphene (22.64%), a-Pinene (11.53%), and cineole (9.89%) as the four most abundant constituents. The evaluation of antimicrobial activity using the agar wells diffusion method showed that the essential oil in all concentrations was active against the Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and pathogenic yeast (Candida albicans), they are most sensitive and resistant to S. aureus strain.

The objective of this study was to determine the suitable C:N ratio  for growth and survival of spotted scat (Scatophagus argus) cultured in the biofloc system. The experiment was designed randomly with four treatments in different ratios of C:N such as (i) control treatment (without adding molasses); (ii) C:N=10:1; (iii) C:N=15:1; (iv) C:N=20:1, each treatment was triplicated. Spotted scat with average initial weight of 3.59 g were stocked in the 0.5m3 tanks at a density of 40 fish/m3 and cultured at salinity of 5 ppt. Molasses was used to create  and maintain biofloc formation in each treatment. After 4 months of culture, the spotted scat in the C:N=15:1 treatment had an average weight of 34.9 g and was the highest growth, highest survival rate, highest biomass, lower feed conversion ratio, and were significantly different (p<0.05)  from the other treatments. The lowest survival rate and the yield were found out in the control treatment. Thus, the spotted scat were cultured in the biofloc system with supplementation of molasses (C:N=15: 1) could be suitable for this species.

In this study, we examined the effect of lightintensity and light cycle on the growth of hydroponic leaf lettuce. Four light intensity treatment were using included 1 LED light NCM 3000K – purple LED: 75% red, 25% blue (48 μmol.m-2.s-1 PPFD - Photosynthetic photon flux  density); 2 LED lights NCM 3000K – purple LED: 75% red, 25% blue (80 μmol.m-2.s-1  PPFD); 3 LED lights D NCM01 L/30W – White LED (60 μmol.m-2.s-1 PPFD) and 3 LED lights NCM 3000K – purple LED: 75% red, 25% blue (115 μmol·.m-2.s-1  PPFD), with a combination of fivelight cycles 6/18, 9/15, 12/12, 18/6, 24/0 (light/dark). The result showed thatthe combination of 80-24/0 (2 purple LEDs – 24 hours light /0 hour dark) resulted highest fresh weight (34.93 g) and the seconds highest in the 60-24/0 (3 whiteLEDs -24 hours light /0 hour dark) and 80-18/6 (2 purple LEDs – 18 hours light /6 hour dark) treatment (28.95 and 27.22 g), while control 2 treatment (grown under sunlight) was 11.62 g. The main stem was highest at combined of 3 white LEDs with 24/0 and 18/6 treatments (26.18 and 20.04, respectively), while the numer of leaves (17.60 and 16.38 leaves), leaf length (10.31 and 10.97 cm) and leaf width (9.91 and 7.36 cm)at combined treatment of 2 purple LEDs with 18/6  and 24/0 were higher than most of anothers.The combination of 18/6 and 24/0 with 2 and 3 purple LEDs showed highest Chlorophyll value (3.92-4.75 µg/g), lowest at combination of 6/18 with four different light intensity (1.25-1.40 µg/g).

In the present study, viscozyme L pre-treatment for aerial parts of Rosmarinus officinalis L. (rosemary), grown in Lam Dong province, was performed to evaluate the effective extraction of essential oils by hydro-distillation. Enzymatic pre-treatment with 1 g viscozyme L enzyme mixed with 5 mL sodium chloride 15% at 50oC for 1 hour, followed by hydro-distillation, was seen to slightly increase the yield of rosemary essential oils from 0.96% to 1.08%. GC/MS analysis showed the presence of 32 compounds in rosemary essential oils, of which the major components were α-pinene (29.71 - 32.17%) and cineol (17.55 - 18.74%) in both the control and the enzymatically treated samples. The results also revealed that rosemary essential oils obtained from both the control and the enzymatically treated samples exhibited moderate antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans in all tested concentrations.

A newly recorded Lithocarpus (Fagaceae) species for the flora of Vietnam, namely Lithocarpus encleisocarpus (Korth.) A.Camus was reported in this study. This species is most morphologically similar to L. dahuoaiensis Ngoc & L.V. Dung in having a completely entire leaf margin, solitary cupule, long stalks of fruits, deeply cup-shaped or turbinate cupules, with several horizontal filiform lines, but it differs from the latter by having cupules almost completely covering the nut, surface of the cupule densely fulvous tomentose by stellate hairs, secondary veins 8-10 pairs. This study provides the phylogenetic relationship of L. encleisocarpus with its close species based on genome-wide SNPs. Taxonomic treatment, photographs, information on distribution and habitat, and the GenBank accession number for DNA barcodes of the species are also provided.

This study aims to determine suitable photoperiod for growth of white leg shrimp in supper-intensive tank culture system applying biofloc technology. The experiment was randomly designed indoor with different photoperiod treatments, including (i) 24 hours Dark; (ii) 6 hours Light: 18 hours Dark; (iii) 12 hours Light: 12 hours Dark; (iv) 18 hours Light: 6 hours Dark and  (v) 24 hours Light. The lighting treatments, it was set with a 55w compact fluorescent (light intensity ~ 6000 lux). Shrimp with initial weight at 0.84g and 4.45cm of body length were cultured at density of 150 inds/m3 in Biofloc system (C:N=15:1), with 300L of water volume, 15‰ of salinity. Results showed that after 90 days of culture, water quality were in suitable range for shrimp growth. Body weight (BW) of shrimp among treatments were from 18.28 to 22.96 g. In which, BW of shrimp in completely dark condition was the lowest and significantly different compared to the others (p3), not significantly different compared to 18 hours Light (2,23kg/m3 ) but significantly different compared to the others. Besides, shrimp in the treatments with Light showed stronger color compared to shrimp in completetly dark condition.