Niwooti Whangchai

Bio: Niwooti Whangchai is an academic researcher from Maejo University. The author has contributed to research in topics: Tilapia & Fish farming. The author has an hindex of 12, co-authored 43 publications receiving 363 citations.

The immobilization of yeast for fermentation of macroalgae Rhizoclonium sp. for efficient conversion into bioethanol

Abstract: Macroalgae are considered to be one of the rich lignocellulosic biomass materials. Aquatic biomass has gained more attention to biofuels generation in recent years due to its renewable, abundant, and environmentally friendly aspects. Macroalgae are photosynthetic organisms that are found in both marine and freshwater environments. These are considered as a third-generation feedstock for the production of biofuels since they have the ability to synthesize a high amount of lipids, proteins, and carbohydrates. This research study aimed to evaluate the potential of bioethanol production from macroalgae (Rhizoclonium sp.) biomass. The fermentation process was applied in the research by two-way separate hydrolysis and fermentation (SHF). Algae biomass undergoes a pretreatment process to release necessary sugars for yeast digestion. The fermentation process was carried at 30 to 35 °C in the incubator. Finally, the percentage of ethanol was estimated by the ebulliometer. Fermentation was enhanced by immobilization of yeast, which showed the highest concentration of ethanol (65.43 ± 18.13 g/l) after 96 h of fermentation and can be reused for several times for fermentation. Moreover, these study results confirmed that freshwater macroalgae biomass is a suitable and susceptible raw material for bioethanol production.

Tilapia diseases and management in river-based cage aquaculture in northern Thailand

Abstract: A total of 662 farmers who rear tilapia in river-based cages in Northern Thailand were interviewed on their knowledge and perception on disease constraints and their control measures. Most farms (84%) had disease problems in the last two years. Exophthalmia ranked higher than other clinical signs. Most farmers noticed that the risk of disease problems was similar every month. Most (95%) believed that fish diseases were caused by bacterial pathogens. To treat perceived disease outbreaks, most farmers (96%) removed infected and dead fish and applied, usually inappropriately, antibiotics. As disease prevention through good management is better than treatment, farmers and fish disease experts could use these research findings as a tool to work together to develop better control strategies.

Relationships of Dissolved Oxygen with Chlorophyll-a and Phytoplankton Composition in Tilapia Ponds

Abstract: This study investigated the relationships among the parameters of dissolved oxygen, chlorophyll-a and phytoplankton composition in tilapia ponds. Each pond (a total of 18 ponds) was sampled once in the dry, winter season between January and March and again early in the rainy season between May and June. The data were analyzed by examining correlations among parameters as affected by season, altitude and culture system. Observations were made at sites located in 5 selected provinces of northern Thailand: Chiangrai, Chiangmai, Phayao, Lampang and Nakornsawan. Mean elevation of these areas range from 25 to 582 meters above sea level (masl) and were categorized into low ( 400 masl) elevation sites. Ponds were 0.8 - 2.0 m deep, 0.16 - 0.64 ha in area and could be further categorized into high and low input systems.Mean air temperature in winter ranged between 16.5°C - 35.8°C while mean water temperature ranged between 25.5°C - 27.1°C. In rainy season, air temperature ranged between 22.0°C - 37.3°C and water temperature ranged between 29.4°C - 31.8°C. The amount of chlorophyll-a in both seasons were comparable (p > 0.05), but chlorophyll-a in high input system was significantly higher (p < 0.05) than in low input ponds. Only weak correlation was found between chlorophyll-a, DOmax and DOmin. Multifactor-ANOVA was used to analyze the difference of total bacteria and filamentous cyanobacteria in ponds based upon elevation, culture systems and season. Result shows that there is a significant interaction observed between elevation, culture system and season (p < 0.05). Species diversity and composition of phytoplankton in fish ponds in 2 seasons revealed the presence of 90 genera of phytoplankton under all 7 divisions. Divisions Chlorophyta and Cyanophyta had the most number of genera identified in both seasons with Pediastrum spp., and Scendesmus spp., and Anabaena spp. as dominant genera/genus, respectively.

Perceptions of climate-related risks and awareness of climate change of fish cage farmers in northern Thailand

Abstract: How climate risks are understood and perceived by farmers is important because it can influence their management practices. Farmers in Northern Thailand who rear fish in floating cages in rivers can cope with modest fluctuations in water levels, but appear vulnerable to more extreme changes in flow. This study used in-depth interviews and a quantitative survey across many sites to explore how fish farmers perceive climate-related risks and understand climate change. Important climate-related risks – such as floods and droughts – vary by season, year and location, and are modified by water infrastructure. Recent experience of negative impacts increases levels of concern about risks. Risks from droughts were perceived to have significantly worsened. The overall level of awareness of climate change among fish farmers is high, suggesting that future work should focus on building on from how farmers manage risks under the current climate, to then take into account climate change. This study shows that a good understanding of risk perception is likely to be important in improving climate risk management, and thus adaptation to climate change.

Effect of water de-stratification on dissolved oxygen and ammonia in tilapia ponds in Northern Thailand

Abstract: Episodes of low concentrations of dissolved oxygen and high concentrations of ammonia are major causes of fish stress, which in turn, reduces growth and increases mortality rates in aquaculture ponds. This study measured the effects of water de-stratification on dissolved oxygen and ammonia concentrations in tilapia ponds in Northern Thailand. Fifteen ponds in five provinces in Northern Thailand were sampled on multiple dates in the hot, wet, and dry seasons. Thermal water stratification peaked around 14:00-16:00 h each day; wherein the differences between surface and lower water temperatures in the 0.8-2.0 m deep ponds reached 1.3-4.0 C. Thermal de-stratification in the hot season and dry season usually occurred late at night; in the wet season however, it occurred early in the evening due to the cooling effects of rain. The mixing of surface and bottom waters decreased dissolved oxygen levels in water near the surface, and, increased concentration levels in the bottom water layer. Mean DO concentrations of integrated and commercial ponds were lower than 1 mg/L from 02:00 to 06:00 h, in 68 % of the observations. Repeated measures ANOVA analysis showed that water depth and fish culture systems have significant effects on total ammonia nitrogen (TAN). TAN concentrations near the surface were lower than at the bottom, and increased after water de- stratification. TAN in the integrated culture system was significantly higher than in commercial and subsis- tence systems. Toxic, un-ionized ammonia (NH3) concentrations in all culture systems, however, were still lower than standard toxicity level for tilapia. The improved understanding of the seasonal and culture-system specific effects of de-stratification on pond water quality provided by this study, are useful for improving pond management practices to reduce the risks of exceeding DO thresholds. In particular, fish farmers should: (1) take care to avoid over-feeding and manage water and sediments to prevent excessive accumulation of organic matter and waste at the bottom of ponds, which can influence other water quality parameters; and, (2) use aeration and mechanical mixing interventions at critical times to reduce stress on fish from low DO con- centrations, and thus avoid risks of mass mortality events.

Ozone as a novel emerging technology for the dissipation of pesticide residues in foods–a review

Abstract: Background Consumption of fruits and vegetables is an indispensable component of human dietary preference, however; it is unfortunate that the enormous pesticide residues remain in the plant produces. Pesticides used to control the pests and diseases of the crops and livestock and its spill-over in the food production system has been an inevitable consequence. Researchers have been taking persistent efforts to eliminate pesticide residues in the food to make it safe for human consumption. Conventional techniques such as the washing of agricultural produces with chemicals, peeling, salting, and using different agents have not been an efficient means of pesticide removal. Scope and approach In recent times, the emergence of non-thermal technology such as the ozone to degrade the pesticide residues is of great utility in the food processing industries. It is also considered as a green technology because unlike other conventional methods ozone treatment leaves little residual traces. However, some of the discrepancies and challenges in using this technology require to be addressed to increase its efficiency. The objective of the current review is to provide a comprehensive and critical view of the use of ozone in pesticide residue dissipation in various food matrixes. Key findings and conclusion Analysis of the pros and cons of ozone treatment reveals it as a potential technique for the degradation of pesticide residues. The diversity and complexity of pesticides along with the inherent differences in their chemical structures and residue levels of pesticides in agro-products are the factors that require due consideration. Furthermore, processing and operating conditions of the ozone treatment are some of the other major determinants to improve the efficiency of ozone treatment for the degradation of pesticides.