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The freezing–thawing method had been reported to be the best phycobiliprotein extraction technique. However, optimum parameters of this extraction method for Arthrospira sp. (one of the major phycobiliprotein sources) still remained unclear. Hence, this study aimed to optimize the freezing–thawing parameters of phycobiliprotein extraction in Arthrospira sp. (UPMC-A0087). The optimization of the freezing–thawing method was conducted using different solvents, biomass/solvent ratios, temperatures, time intervals and freezing–thawing cycles. The extracted phycobiliproteins were quantified using a spectrophotometric assay. Double distilled water (pH 7) with a 0.50% w/v biomass/solvent ratio was the most efficient solvent in extracting high concentrations and purity of phycobiliproteins from Arthrospira sp. In addition, the combination of freezing at −80 °C (2 h) and thawing at 25 °C (24 h) appeared to be the optimum temperature and extraction time to obtain the highest amount of phycobiliproteins. A minimum of one cycle of freezing and thawing was sufficient for extracting high concentrations of phycobiliproteins. The findings from this study could reduce the cost and labor needed for extracting high quality phycobiliproteins. It also allowed the harvesting of large amounts of valuable phycobiliproteins.

The responses of two species of microalgae, Chlorella sorokiniana and Chlorella zofingiensis , were compared regarding their morphological and biochemical properties under photoautotrophic and mixotrophic conditions. These microalgae were cultured under both conditions, and their crude ethanolic extracts were examined for their pigment and total phenolic contents. In addition, the microalgae’s antioxidant activities were determined using a DPPH radical scavenging assay and a ferric reducing antioxidant power (FRAP) assay. Both strains showed increases in cell size due to the accumulation of lipid bodies and other cell contents, especially carotenoids, under the mixotrophic condition. Notably, reductions in phenolic and chlorophyll contents were observed to be associated with lower antioxidant activity. C. zofingiensis compared with C. sorokiniana , demonstrated higher antioxidant activity and carotenoid content. This study showed that different species of microalgae responded differently to varying conditions by producing different types of metabolites, as evidenced by the production of higher levels of phenolic compounds under the photoautotrophic condition and the production of the same levels of carotenoids under both photoautotrophic and mixotrophic conditions.

Nitrogen cycling in freshwater ecosystems is critical for maintaining water quality, and understanding the processes of nitrification and denitrification is essential for effective nitrogen management, particularly in areas with diverse pollution sources. This study investigated the nitrification and denitrification processes in three tributaries of the Jinjing River—Tuojia (agricultural), Jinjing (residential), and Guanjia (woodland)—during both the wet and dry seasons. The potential nitrification rates (PNRs) and potential denitrification rates (PDNRs) were measured across these sites. The highest rates were observed in Tuojia during the wet season, with the PNR reaching 39.7 μg·kg−1 h−1 and the PDNR reaching 3.25 mg·kg−1·h−1, while the rates were considerably lower in Jinjing and Guanjia. The ammonia-oxidizing archaea (AOA) abundance was higher than the ammonia-oxidizing bacteria (AOB) abundance at all sites, with Tuojia exhibiting the highest AOA abundance (5.9 × 10⁷ copies·g−1) during the wet season. The nitrate-nitrogen (NO₃−-N) content was a key factor influencing denitrification, and the AOA abundance was significantly correlated with nitrification rates (r = 0.69; p < 0.05). These findings highlight the spatial and seasonal variability in nitrogen cycling and emphasize the importance of developing targeted nitrogen management strategies in regions with mixed land uses and pollution sources.

Chlorella can produce an unusually wide range of metabolites under various nutrient availability, carbon source, and light availability. Glucose, an essential molecule for the growth of microorganisms, also contributes significantly to the metabolism of various metabolic compounds produced by Chlorella . In addition, manipulation of light intensity also induces the formation of secondary metabolites such as pigments, and carotenoids in Chlorella . This study will focus on the effect of glucose addition, and moderate light on the regulation of carotenoid, lipid, starch, and other key metabolic pathways in Chlorella sorokiniana . To gain knowledge about this, we performed transcriptome profiling on C. sorokiniana strain NIES-2168 in response to moderate light stress supplemented with glucose under mixotrophic conditions. A total of 60,982,352 raw paired-end (PE) reads 100 bp in length was obtained from both normal, and mixotrophic samples of C. sorokiniana . After pre-processing, 93.63% high-quality PE reads were obtained, and 18,310 predicted full-length transcripts were assembled. Differential gene expression showed that a total of 937, and 1124 genes were upregulated, and downregulated in mixotrophic samples, respectively. Transcriptome analysis revealed that the mixotrophic condition caused upregulation of genes involved in carotenoids production (specifically lutein biosynthesis), fatty acid biosynthesis, TAG accumulation, and the majority of the carbon fixation pathways. Conversely, starch biosynthesis, sucrose biosynthesis, and isoprenoid biosynthesis were downregulated. Novel insights into the pathways that link the enhanced production of valuable metabolites (such as carotenoids in C. sorokiniana ) grown under mixotrophic conditions is presented.

The concentration profile, distribution and risk assessment of pharmaceutically active compounds (PhACs) in the coastal surface water from the Klang River estuary were measured. Surface coastal water samples were extracted using offline solid phase, applying polymeric C18 cartridges as extraction sorbent and measuring with liquid chromatography mass spectrometry–mass spectrometry (LC MS–MS) technique. Extraction method was optimized for its recovery, sensitivity and linearity. Excellent recoveries were obtained from the optimized method with percentage of recoveries ranging from 73 to 126%. The optimized analytical method achieved good sensitivity with limit of detection ranging from 0.05 to 0.15 ng L−1, while linearity of targeted compounds in the LC MS–MS system was more than 0.990. The results showed that amoxicillin has the highest concentration (102.31 ng L−1) followed by diclofenac (10.80 ng L−1) and primidone (7.74 ng L−1). The percentage of contribution (% of total concentration) for the targeted PhACs is in the following order; amoxicillin (92.90%) > diclofenac (3.95%) > primidone (1.23%) > dexamethasone (0.75%) > testosterone (0.70%) > sulfamethoxazole (0.33%) > progesterone (0.14%). Environmental risk assessment calculated based on deterministic approach (the RQ method), showed no present risk from the presence of PhACs in the coastal water of Klang River estuary. Nonetheless, this baseline assessment can be used for better understanding on PhACs pollution profile and distribution in the tropical coastal and estuarine ecosystem as well as for future comparative studies.

Recent limnological investigations conducted on the large lakes of Indonesia provide valuable physical and ecological data for future environmental and developmental programmes, yet few studies have focused on zooplankton taxonomy. Here we describe Eucyclops troposperatus Alekseev et Yusoff n. sp. from a pond in Sumatra, and Mesocyclops jakartensis Alekseev n. sp. from a city pond in Jakarta, Java. In the pelagic zone of the lakes of Sulawesi we found only few copepod species. For the endemic cyclopoid Tropocyclops matanoensis Defaye, 2007, we propose a new subgenus, Defayeicyclops n. subg., and provide more data on the morphology as well as scanning electron microscopy and confocal laser scanning images of Tropocyclops (Defayeicyclops) matanoensis. Two other cyclopoid species were possibly introduced to Sulawesi: Mesocyclops aequatorialis similis Van de Velde, 1984 from Africa and Thermocyclops crassus (Fischer, 1853) from Eurasia. A new subspecies, Phyllodiaptomus praedictus sulawesensis Alekseev et Vaillant n. ssp. (Calanoida, Diaptomidae), is described from the plankton of lake Tondano, North Sulawesi, Indonesia. The new subspecies resembles P. blanci (de Guerne et Richard, 1896) and P. wellekensae Dumont et Reddy, 1992. Phyllodiaptomus praedictus sulawesensis appears to be endemic to Sulawesi island. The form matanensis formerly treated as a subspecies of Eodiaptomus wolterecki Brehm, 1933 is here elevated to species rank, E. matanensis Brehm, 1933. A preliminary list of the copepod species found in Sulawesi and other large islands of Indonesia now includes more than 60 species. An updated key to the Southeast Asian species of the genus Eucyclops is provided.

The emerging aquaculture industry is in need of non-antibiotic-based disease control approaches to minimize the risk of antibiotic-resistant bacteria. Bacterial infections mainly caused by Vibrio spp. have caused mass mortalities of fish especially during the larval stages. The objectives of this study were to verify the potential of symbiotic probiont strains, isolated from microalgae (Amphora, Chlorella, and Spirulina) for suppressing the growth of Vibrio spp. and at the same time ascertain their abilities to enhance microalgal biomass by mutualistic interactions through microalgae–bacteria symbiosis. In addition, in vivo studies on Artemia bioencapsulated with probiont strains (single strain and mix strains) and microalgae were evaluated. The selected potential probionts were identified as Lysinibacillus fusiformis strain A-1 (LFA-1), Bacillus sp. strain A-2 (BA-2), Lysinibacillus fusiformis strain Cl-3 (LFCl-3), and Bacillus pocheonensis strain S-2 (BPS-2) using 16s rRNA. The cell densities of Amphora culture supplemented with BA-2 and Chlorella culture supplemented with LFCl-3 were higher than those of the controls. Artemia bioencapsulated with mix strains (LFA-1 + BA-2 + LFCl-3 + BPS-2) and Amphora demonstrated the highest survival rate compared to the controls, after being challenged with V. harveyi (60 ± 4%) and V. parahaemolyticus (78 ± 2%). Our study postulated that BA-2 and LFCl-3 were found to be good promoting bacteria for microalgal growth and microalgae serve as a vector to transport probiotic into Artemia. Moreover, mixture of potential probionts is beneficial for Artemia supplementation in conferring protection to Artemia nauplii against pathogenic Vibrios.

This study investigated the effects of effective microorganism (EM) in reducing the cyanobacterial density and improving the water quality and phytoplankton diversity. Four thousand litre of EM was sprayed over an area of 0.7 ha in a semi-enclosed area of the Putrajaya Lake. Sampling and analysis of water quality and phytoplankton were carried out at three locations over a period of 50 days. The results of the study showed that EM treatment temporarily reduced the cyanobacterial density from 3909.5 to 2200.9 cells/ml after 18 days, but the density began to increase again soon after. Similarly, mean phytoplankton density showed similar pattern to the cyanobacterial trend of decreasing density after application but started to increase 3 weeks afterwards. Cyanobacteria was the dominant phytoplankton group before and during EM treatment. Cyanobacterial dominance decreased 55.2% after EM application resulting in more balanced phytoplankton assemblages 18 days after treatment before regaining its dominance 3 week after EM application. Nostoc sp. was the main cyanobacterial species before-, during and after EM treatment. Only pH significantly differed after the EM treatment; while, other parameters such as dissolved oxygen, chlorophyll- a , transparency showed no significant changes before and after EM application. This study illustrated that EM application did not provide sustained microalgae reduction nor water quality improvement throughout the experiment.

Chlorella is a popular microalga with robust physiological and biochemical characteristics, which can be cultured under various conditions. The exploration of the small RNA content of Chlorella could improve strategies for the enhancement of metabolite production from this microalga. In this study, stress was introduced to the Chlorella sorokiniana culture to produce high-value metabolites such as carotenoids and phenolic content. The small RNA transcriptome of C. sorokiniana was sequenced, focusing on microRNA (miRNA) content. From the analysis, 98 miRNAs were identified in cultures subjected to normal and stress conditions. The functional analysis result showed that the miRNA targets found were most often involved in the biosynthesis of secondary metabolites, followed by protein metabolism, cell cycle, and porphyrin and chlorophyll metabolism. Furthermore, the biosynthesis of secondary metabolites such as carotenoids, terpenoids, and lipids was found mostly in stress conditions. These results may help to improve our understanding of regulatory mechanisms of miRNA in the biological and metabolic process of Chlorella species. It is important and timely to determine the true potential of this microalga species and to support the potential for genetic engineering of microalgae as they receive increasing focus for their development as an alternative source of biofuel, food, and health supplements.

The study was conducted in the six major rivers (Padma, Meghna, Jamuna, Brahmaputra Surma and Andermanik) of Bangladesh to evaluate the abundance and distribution of juvenile hilsa, Tenualosa ilisha from February to April 2017. Fish samples are collected by using monofilament gill net. The total length and depth of the gill net was 100 m and 4.5 m respectively. The mesh size of first 25 m net was 2.5 cm; second 25 m was 3.5 cm; third 25 m was 4.5 cm and the last 25 m was 5.5 cm. Daytime sampling was done at all the sites on a monthly basis and the Catch per Unit Effort (CPUE), total length (cm) and weight (g) were recorded and analyzed. The result showed that the highest CPUE of juvenile T. ilisha was observed at Ramgati station which was 72 individuals/100 m gill net/30 minutes. The second and third highest CPUE was found in Nalchira (58 individuals/100 m net/30 min) and Charking (46 individuals/100m net/30 min), those stations are located in lower Meghna region. There was a significance variation (P<0.05) of CPUE among the 18 stations. It is clear that the high abundance of juvenile T. ilisha in the lower Meghna River while the low abundance in upper part of the rivers. The abundance of juvenile T. ilisha was the highest in March (19 individuals/100 m net/30 min) and the lowest was in April (14 individuals/100 m net/30 min), while there was no significant difference among the months. The study indicated that T. ilisha juvenile are distributed all over the months from lower to upper of the rivers. The average length of juvenile in February, March and April was 9.18±0.10 cm, 15.94±0.17 cm and 22.11±0.18 cm respectively. It was also observed that the average weight of juveniles in February was 9.88±0.25 g while it was 41.16±1.48 g in March and 100.94±1.29 g in April respectively. During the study period there no T. ilisha juveniles was found in the upper areas of Padma, Jamuna and Surma rivers. It may be concluded that major nursery grounds are between Chandpur and Hatya of Meghna River.