Journal of Tropical Science and Engineering

OPTIMIZATION OF CRISPR/CAS12A TRANS-CLEAVAGE REACTION FOR DETECTION OF THE STAPHYLOCOCCUS AUREUS NUCA GENE

2025-08-19T10:20:43+00:00

Staphylococcus aureus (S. aureus) is the most prevalent pathogen within the staphylococcal group, classified as a gram-positive bacterium responsible for severe infections affecting the skin, bloodstream, organs, and gastrointestinal tract. Consequently, the development of early and accurate detection tools is a research priority. Recently, CRISPR/Cas technology, particularly Cas12a, has emerged as a promising diagnostic tool due to its ability to trans-cleave single-stranded DNA (ssDNA) following the specific cleavage of double-stranded DNA (dsDNA) targets. In this study, we optimized a CRISPR/Cas12a trans-cleavage reaction for detecting the nucA gene, a specific marker of S. aureus. To enhance enzyme activity, four crRNAs (crRNA1–4) were designed and tested, each exhibiting different effects on the reaction. However, a mixture of three crRNAs demonstrated higher efficiency than reactions using a single crRNA. Additionally, key reaction parameters, including enzyme concentration, additives, probe sequence, and incubation temperature, were systematically evaluated. The optimized reaction conditions included 6.25 nM LbCas12a combined with the mixture of three crRNAs (crRNA1–3) in a reaction containing 10 mM dithiothreitol (DTT) and 1 µM TA5C ssDNA FAM-BHQ1 probe. The assay was incubated at 39°C for 30 minutes, achieving a detection limit of 284.8 amol or 1.72 × 10⁸ copies of the nucA gene. Fluorescent signals were detectable under a standard UV transilluminator. This study provides valuable insights for the development of CRISPR-based diagnostic kits for S. aureus detection. http://doi.org/10.58334/vrtc.jtst.n38.01

EFFECT OF FLY ASH AND GRANULATED BLAST FURNACE SLAG ON THE PHYSICAL PROPERTIES OF GEOPOLYMER CONCRETE USE CORAL SAND AND SEAWATER

2025-08-19T11:17:59+00:00

Geopolymer concrete is an eco-friendly material that possesses properties comparable to those of traditional Portland cement concrete. This study aimed to explore how the ratio of fly ash to blast furnace slag impacts the mechanical properties of geopolymer concrete using coral sand and seawater. Fly ash and blast furnace slag were used as binders alongside alkaline activators such as liquid glass and sodium hydroxide solution. The characteristics were assessed based on measurements of bulk density, water absorption, workability, compressive strength, and flexural strength. The compressive and flexural strengths of the samples increased gradually with the rising ratio of fly ash to blast furnace slag. Moreover, no significant differences were observed when comparing geopolymer concrete's flexural and compressive strengths using coral sand and seawater with those using river sand and freshwater. On the other hand, the FTIR analysis results indicate that the characteristic Si-O-Si(Al) bond of the geopolymerization reaction in the wavenumber range 950 to 1005 cm-1 is present in both types of concrete, with no significant difference observed. These findings suggest that river sand and freshwater in geopolymer concrete production can replace coral sand and seawater for geopolymer concrete. http://doi.org/10.58334/vrtc.jtst.n38.07

ASSESSMENT OF WATER ENVIRONMENT QUALITY IN HINH RIVER BASIN, PHU YEN PROVINCE

2025-08-20T00:17:09+00:00

The Hinh River basin is one of the regions with abundant surface water resources in Phu Yen Province, encompassing a diverse system of rivers, streams, ponds, and reservoirs. The water quality of a river describes its biological and physicochemical characteristics. In this study, 22 water sampling points were monitored during the dry season. The water quality in the river basin was evaluated based on parameters such as pH, DO, COD, total nitrogen, total phosphorus, As, Cd, Pb, Cu, Zn, Hg, coliform, and E. coli at each specific location according to the QCVN 08:2023 standard and the VN_WQI index. The research results show that the VN_WQI ranges from 60 to 99, with 20 out of 22 monitoring locations having a VN_WQI value ≥ 76, indicating good to very good water quality that meets the requirements for irrigation and waterway transportation. Some points meet the water quality standards for domestic use after appropriate treatment. When assessing water quality by individual parameters, only the TSS parameter consistently reached level A, indicating good water quality at all sampling points. However, the results also indicate signs of localized pollution in the Hinh River basin at some monitoring locations based on the total nitrogen, COD, coliform, and E. coli parameters. The cause is waste from agricultural and livestock farming activities of people living along the Hinh River basin. This study provides additional data on surface water quality, serving as a basis for developing management measures, rational use, and protection of water quality in the Hinh River basin. http://doi.org/10.58334/vrtc.jtst.n38.08

LENGTH-WEIGHT RELATIONSHIP AND CONDITIONAL FACTOR OF 16 IMPORTANT FISH SPECIES IN THE MEKONG DELTA, VIETNAM

2025-08-20T00:24:38+00:00

The length-weight relationship (LWR) constitutes a fundamental analytical tool in ichthyological research, facilitating the assessment of growth dynamics, health status, and morphometric variations within fish communities. The present investigation was conducted to analyze the LWRs of economically and ecologically important fish species, which are predominantly exploited by small-scale fisheries within the Mekong Delta, Vietnam. Between January 2019 and March 2020, a total of 1,546 specimens, encompassing 16 species across 11 taxonomic families, were systematically collected. Morphometric data, specifically total length (TL) and body weight (W), were meticulously recorded for each individual, and sex was identified wherever feasible to enhance biological interpretation. The length-weight relationship was estimated using the equation W=a*TLb, where a and b represent species-specific constants. To enable statistical inference, a logarithmic transformation was applied, yielding a linear form: log(W) = log(a) + b*log(TL), which was subsequently analyzed using least-squares linear regression. All length-weight relationships deviations fell within the range of 2.72 to 3.28, of which eight species exhibited positive allometry (b > 3), seven species demonstrated negative allometry (b < 3), and one species showed isometric growth (b = 3). In addition, Fulton’s condition factor (K) was utilized as an indicator of fish health status. With the exception of two species from the genus Coilia, all estimated fish species showed comparatively high K-values, suggesting a generally favorable physiological condition among the studied fish populations. Collectively, these results highlight the overall health resilience and adaptive potential of fish communities inhabiting the dynamic aquatic habitats of the Mekong Delta. http://doi.org/10.58334/vrtc.jtst.n38.09

CHECKLIST OF THE LARGE CENTIPEDES (CHILOPODA: SCOLOPENDROMORPHA) FROM LO GO - XA MAT NATIONAL PARK, TAY NINH PROVINCE, VIETNAM

2025-08-20T01:16:24+00:00

A study on the large centipede fauna (Chilopoda: Scolopendromorpha) was conducted in Lo Go - Xa Mat National Park (Tay Ninh Province, southern Vietnam) through two field surveys in March and July 2024. The primary aim of the study was to provide a species checklist for the national park and to update taxonomic and distributional data of scolopendromorph centipedes in a tropical region that remains poorly explored. Specimens were collected using standard soil fauna sampling techniques, including quadrat digging, soil sieving, pitfall trapping, and random sampling along forest transects. All specimens were preserved in ethanol and examined morphologically under stereomicroscopes for taxonomic identification. A total of eleven species and subspecies belonging to five genera and three families within the order Scolopendromorpha were identified, including: Alluropus calcaratus, Cryptops (Cryptops) tahitianus, Cryptops (Paracryptops) indicus, Otostigmus aculeatus, Otostigmus multidens, Otostigmus politus, Otostigmus scaber, Scolopendra dehaani, Scolopendra gracillima sternostriata, Scolopendra morsitans, and Scolopendra subspinipes. Among these, nine species and subspecies represent new records for the area. Although Scolopendra morsitans had been previously reported from the park, it was not encountered in the present study. This study provides an updated checklist of scolopendromorph species in Lò Gò - Xa Mát National Park, together with details of the specimen collection sites and species distributions in Vietnam and globally. The results highlight the high species richness and ecological significance of the park for invertebrate conservation. Moreover, the findings contribute to the national taxonomic database and serve as a scientific basis for biodiversity monitoring, conservation planning, and ecological management in Vietnam. http://doi.org/10.58334/vrtc.jtst.n38.10

SPECIES COMPOSITION AND DISTRIBUTION OF ACROPORA CORALS IN NHA TRANG BAY AND ADJACENT WATERS

2025-08-20T01:23:22+00:00

Nha Trang Bay (Khanh Hoa, Vietnam) is widely recognized for its rich and diverse coral reef ecosystems, where Acropora corals play a foundational role in reef construction and ecological function. Nevertheless, these ecosystems are increasingly threatened by the combined effects of climate change and human-induced disturbances. This study shows the species composition and distribution of the coral genus Acropora in Nha Trang Bay and adjacent waters. A total of 10 sites were surveyed using SCUBA-based Reef Check methodology, focusing on coral identification through morphological and skeletal characteristics. The 29 species of Acropora recorded with significant species richness found at Hon Bac Island, Hon Chong–Dang Tat, and Dam Bay sites. However, degradation of the coral reef is also recorded at multiple sites, with Acropora species experiencing dramatic declines due to the global coral bleaching event of 2024. Despite these pressures, some areas like Dam Bay show potential for coral restoration. Among the surveyed sites, Hon Bac Island and the nearshore waters north of Hon Chong stand out as ecologically valuable areas due to their exceptional live coral cover and biodiversity. In particular, Dam Bay, a designated coral gene pool preservation site - plays a vital role in ongoing conservation efforts. In addition to providing baseline ecological data, the study offers key recommendations for conserving and restoring Acropora reefs in Nha Trang Bay, including the establishment of marine protected zones in biodiversity hotspots, implementation of targeted coral restoration programs, enhancement of long-term monitoring and early-warning systems, and promotion of science-based, community-supported conservation strategies in areas showing signs of natural recovery. The findings provide crucial baseline data for conservation planning, restoration strategies, and genetic resource preservation of Acropora in Southern Vietnam. http://doi.org/10.58334/vrtc.jtst.n38.12