Structural and Rheological Characteristics of Alginate from Sargassum cristaefolium Extracted by Twin Screw Extruder

This study aimed to investigate the effects of process extrusion on the characteristics of Sargassum cristaefolium sodium alginate (SCSA) extracted using twin-screw extruder. Box-Behnken Design (BBD) from response surface methodology (RSM) was established to understand the effects of temperature, screw speed, and pH on the multiple-responses of alginate characteristics including intrinsic viscosity, yield, and molecular weight. The results revealed that temperature, screw speed, and pH significantly affected (P < .05) all responses. The optimum extraction condition was found at temperature of 58.18°C, screw speed of 77.99 rpm, and pH 10.11. At this condition, the response of residence time distribution was 7.07 ± 0.029 min, yield of 34.01 ± 0.12%, intrinsic viscosity of 460.13 ± 14.75 mL/g, and molecular weight of 217.94 ± 7.14 × 10³ g/mol. This alginate had mannuronic acid to guluronic acid (M/G) ratio of 0.28, and the L-guluronic acid block was 0.78, which was higher than the D-mannuronic acid block. Rheological characterization of SCSA in aqueous solution was shear-thinning pseudoplastic, and alginate gel in 1 M CaCl₂ was more elastic than liquid.     

Assessment of the Nutritive,Biochemical, Antioxidant and Antibacterial Potential of Eight Tropical Macro algae Along Kachchh Coast,India as Human Food Supplements

Eight tropical marine macro algae were investigated for in-vitro antioxidant, antibacterial, and biochemical properties. The moisture content [% DW (dry weight)] ranged from 7.21 to 14.72%; ash, 24.92 to 47.04%; lipids, 0.73 to 2.67%; protein, 4.56 to 12.59%; and carbohydrate, 30.1 to 48.51%. The % sum of polyunsaturated fatty acids (PUFAs) ranged from 21.71 to 78.22%, while omega-6/omega-3 (ω6/ω3) ratio was from 0 to 2.08, which remained within the prescribed World Health Organization (WHO) standards (<10). The % sum of essential amino acids (EAAs) ranged from 86.18 to 204.66, and Na/K ratio ranged from 0.37 to 2.85. The extracts exhibited significant (P < 0.05) values for total phenol (7.25–16.0 µg PGE mg^–1 DW) and total flavonoid (4.06–15.63 µg QE mg^–1 DW) at 200 µg/ml. Antibacterial activity was tested against the selected food spoilage and pathogenic bacteria. The principal component analysis (PCA) confirmed a positive correlation between total phenolic content, 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging activities, and ferric reducing antioxidant power (FRAP), which supports the integration of seaweeds as ingredients in functional foods.     

Protein Hydrolysates from Shrimp (Metapenaeus dobsoni) Head Waste: Optimization of Extraction Conditions by Response Surface Methodology

Utilization of shrimp head waste from the processing industry offers a solution to environmental pollution and also produces valuable bioactive peptides. The present study was aimed to optimize the alcalase assisted extraction conditions by response surface methodology (RSM) to obtain protein hydrolysates from shrimp (Metapenaeus dobsoni) head waste with maximum antioxidant activity. Based on the models derived by RSM, the optimized conditions for maximum degree of hydrolysis (DH) were pH 8.2, temperature of 45.4°C, and enzyme/substrate (E/S) of 1.8%. Meanwhile, the optimized conditions for maximum antioxidant activity of protein hydrolysates as measured by 2, 2-diphenyl-1-picrylhydrozyl (DPPH) and ferric reducing antioxidant power (FRAP) assays were pH 8.2 and 8.1, temperatures of 49.7 and 59.4°C, and E/S of 2.1 and 2.7%, respectively. The maximum predicted values for DH, DPPH, and FRAP were 42.44%, 39.64% inhibition, and 8.3 μM Fe (II)/g wet wt. of sample, respectively. The extraction of protein hydrolysates at optimal conditions derived by these models resulted in DH, DPPH, and FRAPs of 40.31%, 38.93%, and 8.21 μM Fe (II)/g of sample, respectively, demonstrating the fitness of the models. The present study demonstrates the potential of Metapenaeus dobsoni head waste as a source of protein hydrolysates with prospective antioxidant activity.     

Optimization of Antioxidant Activity and Phenolic Compound Extraction Conditions from Red Seaweed (Laurencia obtuse)

ABSTRACT

Response surface methodology was used to investigate the effect of ultrasound-assisted extraction conditions including solvent:seaweed ratio (10:1–30:1), extraction temperature (30–50°C), and extraction time (30–60 min) on the total phenolic compounds and antioxidant activity of red seaweed (Laurencia obtuse) extracts. The optimum extraction parameters for maximum phenolic content were as follows: solvent:seaweed ratio, 30:1; extraction temperature, 50°C; and extraction time, 42.8 min. The experiment results showed that the solvent:seaweed ratio was the most significant parameter for the extraction. The optimum extraction conditions for maximum antioxidant activity were as follows: solvent:seaweed ratio, 24.3:1; extraction temperature, 45.3°C; and extraction time, 58 min. Under the above-mentioned conditions, the experimental total phenolic content and antioxidant activity value were 26.23 ± 0.75 mg GAE/g seaweed and 120.89 ± 0.81 TEAC, respectively, of seaweed tested, which are well compatible with the predicted contents.     

Antiviral activity of sulfated polysaccharides from Sargassum ilicifolium against fish Betanodavirus infection

Sulfated polysaccharides (SP) from seaweeds exhibit numerous biological activities and are less toxic than conventional antiviral drugs. However, little is known about their mode of action. This study aims at extracting the polysaccharides from brown seaweed Sargassum ilicifolium and then evaluating its antiviral activity against fish Betanodavirus. The extracted SP was characterized through FT-IR, ¹H NMR, and thermal gravimetric analysis (TGA). The antiviral activity of SP was tested on SGA cell line by syncytia reduction and the polysaccharide represented a prominent antiviral activity to Betanodavirus by reducing the cytopathic effect (CPE) formation in vitro. The study revealed that SP effectively blocked viral attachment and entry. Moreover, during the in vivo challenge experiment in Gambusia affinis, SP treatment showed a significant decrease in the viral titers. Hence, these results indicate that the polysaccharides obtained from S. ilicifolium exhibited the high antiviral potential to Betanodavirus infection in fishes both in vitro and in vivo.

     

Antioxidant Properties of Seven Cultivated and Natural Edible Seaweed Extracts from Taiwan

Seven species of cultivated and edible seaweeds found in Southern Taiwan—including Enteromorpha intestinalis, Monostorma nitidum, Ulva lactuca, Dictyopteris undulata, Sargassum hemiphyllum var. chinense, Laurencia intermedia, and Porphyra dentate—were used to determine their antioxidant activity by different extraction methods. All seaweeds were extracted using water at 90°C, sterilization at 121°C, homogenization, or enzymatic hydrolysis. Extracts were evaluated for their free radical-scavenging capacity using 1,1-diphenyl-2-pricrylhydrazyl (DPPH), their reducing power, and their superoxide anion scavenging activity. The DPPH-scavenging capacity of S. hemiphyllum var. chinense extracts produced by sterilization (98.59%), homogenization (94.72%), and carbohydrate-degrading enzyme treatment was higher than that of protease extracts, except for U. lactuca. The reducing power of S. hemiphyllum var. chinense water extracts and M. nitidum Viscozyme extracts was better than that of a commercial antioxidant. S. hemiphyllum var. chinense exhibited higher superoxide anion scavenging activity than the other species. The results demonstrate that different extracts of some of the seaweeds showed remarkable antioxidant activity in different assays. The results also provide important information for the marine food industry and suggest that seaweed might be a valuable source of natural antioxidants.     

Evaluation of the Antioxidant Activity In Vitro and in Hippocampal HT-22 Cells System of Protein Hydrolysates of Common Carp (Cyprinus carpio) By-Product

Fish processing by-products may become more than 50% of the starting material. If mismanaged, these large quantities of discarded fish can create serious pollution problems and can also generate cost associated with their disposal. Enzymatic hydrolysis is one of the techniques that is currently being developed in order to recover and add value to these biomolecules. There is an increasing interest in natural antioxidants that are safer for consumers compared with synthetic antioxidants. In this study, common carp by-product was hydrolyzed using the enzymes Alcalase (A) and Protamex (P) to reach degrees of hydrolysis (DH) of 10 and 15%, respectively. Antioxidant capacity against peroxyl radicals (ACAP); 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging; and the measurement of intracellular reactive oxygen species (ROS) concentration after exposure to common carp protein hydrolysates were investigated. The results revealed that the hydrolysate A15 exhibited significantly (p < 0.05) higher antioxidant activity against the DPPH radical. A15 showed the highest in vitro antioxidant competence against peroxyl radicals, whereas P15 showed the lowest activity against peroxyl radicals (p < 0.05). Hydrolysates having the highest and the lowest in vitro antioxidant activity (A15 and P15, respectively) were selected for the determination of antioxidant activity in the HT-22 cells system. Measurement of intracellular ROS concentration revealed that P15 at the concentration of 1.25 mg/mL significantly (p < 0.05) reduced the intracellular ROS concentration. These results showed that common carp by-product protein hydrolysates are a source of antioxidant peptides with a high potential for food and pharmaceutical industries to develop new nutraceuticals and functional foods.     

iTRAQ‐based quantitative proteomic analysis of Sargassum fusiforme in response to high temperature stress

Global warming increases seawater temperature, causing high temperature stress to marine organisms, including algae. This study aimed to explore the global proteomic response of Sargassum fusiforme under high temperature stress. Sargassum fusiforme seedlings were cultured in natural seawater for 24 hr and subjected to different temperatures (22°C, control group; 27°C and 32°C, high temperature stress group) for 1, 3, 5 and 7 days. Changes in their membrane lipid peroxidation after high temperature stress were investigated. Proteomic changes in the air bladders of S. fusiforme were analysed using isobaric tags for relative and absolute quantification, along with liquid chromatography–tandem mass spectrometry. Data were analysed using bioinformatics methods. Results showed that high temperature stress destroyed the cell membrane of the air bladders. Further, 28 and 53 differentially expressed proteins (DEPs) were found in the 27°C and 32°C treatment groups respectively. These DEPs were mainly involved in glycolysis, single‐organism catabolism, purine nucleoside diphosphate metabolism and carbohydrate catabolism. In addition, DEPs were significantly enriched in 10 pathways, such as glycolytic process, biosynthesis of antibiotics, ribosome, biosynthesis of secondary metabolites and biosynthesis of amino acids. Proteomics analyses indicated that proteins associated with synthesis, folding, degradation, photosynthesis and energy and carbohydrate metabolism are differentially expressed under high temperature stress and normal conditions.     

Evaluation of Antioxidant Activity of Marine Algae-Extracts From Korea

Among 51 marine algae distributed along the Korean coast, Sargassum muticum (Yendo) Fensholt, Ishige okamurae Yendo, Ecklonia cava Kjellman, Polysiphonia morrowii Harvey, Dictyopteris undulata Holmes, Sargassm micracanthum (Kutzing) Endlicher, and Sargassum macrocarpum C. Agarch were found to have potent antioxidant activity. Additionally, the reducing power of marine algae-extracts was consistent with diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity. Because little is known about Sargassum muticum (Yendo) Fensholt, Ishige okamurae Yendo, Ecklonia cava Kjellman, Polysiphonia morrowii Harvey, Dictyopteris undulata Holmes, Sargassm micracanthum (Kutzing) Endlicher, and Sargassum macrocarpum C. Agarch, these marine algae may act as candidates for potent antioxidant food materials and are expected to have functional activity for foods and pharmaceuticals for treating oxidative diseases.     

Evaluation of Plasticizing and Antioxidant Properties of Silver Carp Protein Hydrolysates in Fish Gelatin Film

Physico-mechanical and antioxidant properties of glycerol plasticized fish gelatin films were investigated at different levels of fish protein hydrolysates (FPH) from silver carp muscle (5, 10, 15, and 20 g FPH/100 g gelatin). The films supplemented with FPH, especially at higher concentration showed significant increase in 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 20-azinobis-(3-ethylbenzothiazoline-6-sulfnic acid) (ABTS) radical scavenging, and ferric reducing antioxidant power (FRAP), elongation at break, difference of color, water vapor permeability and opacity, while tensile strength, elastic modulus, L*, b*, and contact angle decreased markedly (p < 0.05). However, no significant differences were observed for a* and solubility of all samples (p > 0.05). Films prepared using 20% FPH had lower glass transition temperature and more homogeneous structure, compared with control film. Also, Fourier transform infrared (FTIR) spectroscopy confirmed the increase of free groups of hydrolysates and lower interaction between chains of film incorporated with the highest content of FPH. Thus, these results indicate that FPH enhanced the antioxidant activities and affected some characteristics due to less interaction between gelatin and FPH.     

Optimization of Antioxidant Peptides Production from the Mantle of Cuttlefish (Sepia pharaonis) Using RSM and Fractionation

Persian Gulf cuttlefish mantles were hydrolyzed (CPH) using alcalase, and the optimal hydrolysis parameters were obtained for the highest degree of hydrolysis (DH) and strongest antioxidant (based on their ability to quench 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals) activity using response surface methodology (RSM). The predicted optimal parameters of DH and quenching DPPH radicals was: pH of 7.88, 50.2°C, 150 min, and enzyme to substrate ratio of 1.5%. The reducing power (RP) and ability of optimized peptides to quench ABTS radicals in a gastro-intestinal track model system increased during the intestinal stage, while scavenging ability against DPPH radicals dropped (P < 0.05). The oxidation of lipid was retarded in a lecithin-liposome model added with optimized CPH in a concentration dependent response. Ultrafiltration of optimized CPH showed that the 3–10 KDa fraction had the greatest DPPH radical scavenging activity, the 10–30 KDa fraction had the highest reducing power, and the <3 KDa fraction had the greatest ABTS radical scavenging activity.     

鼠尾藻有性繁育及人工育苗技术的初步研究

对鼠尾藻有性繁育规律进行观察、研究。鼠尾藻雌、雄异株,在黄海北部其生殖季节是7月上中旬,高光照和升温可促进精卵成熟,鼠尾藻在海区和室内都可正常完成受精。干露1~2h能促进幼孢子体生长,幼孢子体在实验范围的光照强度(1000~4000lx)下,光照越强生长越快;在试验盐度(21~40)范围内均可正常生长。在此基础上建立起了鼠尾藻人工苗种繁育技术,并对鼠尾藻有性繁育技术中存在的问题及今后研究的方向进行了分析。     

Comparative analysis of total carotenoid content in tissues of purple and white inner-shell color pearl mussel,Hyriopsis cumingii

The freshwater pearl mussel Hyriopsis cumingii is the most important mussel species for freshwater pearl production in China. Mussel shell color is an important indicator of pearl quality. The objective of this study was to assess whether total carotenoid content (TCC) in H. cumingii is related to shell color. TCC of different tissues (gonad, gill, hepatopancreas, kidney, axe foot, mantle, and adductor muscle) of purple and white inner-shell H. cumingii was determined by UV–Vis spectrophotometry. The results revealed that TCC ranged from 12.91 ± 0.78 to 56.30 ± 0.74 μg/g. In general, TCC was higher in the hepatopancreas, followed by the mantle, gonad, gill, kidney, axe foot, and adductor muscle. TCC in gonad, gill, hepatopancreas, kidney, and mantle of purple mussels was significantly higher than that of white mussels. TCC in mussel tissues of H. cumingii was significantly different (P < 0.001) with respect to shell color. There were significant positive correlations between TCC in mussel mantle and shell color intensity. Future studies will assess the biological roles of carotenoids in shell color formation.     

Depletion of stored nutrients during fasting in Nile tilapia (Oreochromis niloticus) juveniles

We evaluated growth performance and metabolic responses in Nile tilapia (Oreochromic niloticus) juveniles (30.2 ± 0.9 g) subjected to 1 (F1), 2 (F2), or 3 weeks (F3) of fasting and then refed for 10 weeks (10WR) compared to controls (FC), which were fed for the full 13-week trial. Weight gain and specific growth rate (SGR) during fasting were lower in all treatments compared to the FC. However, during refeeding, feed intake/body mass and SGR increased in F1, F2, and F3, inducing partial compensatory growth. The hepatosomatic index (HSI), visceral fat index (VFI), liver glycogen (LG), and carcass lipid levels dropped in all fasted fish compared to FC (P < 0.05), showing a depletion of stored nutrients such as fat and LG. Along with LG, fat reserves were mobilized during fasting to maintain basal metabolism and survival, but these energy constituents returned to control levels at 10WR, at which time HSI was higher in all refed fish compared to FC. Additionally, the variables VFI, LG, and lipid in carcass increased in all refed fish, equaling those of FC at 10WR. The results showed that, in contrast with other protocols that used smaller tilapia juveniles, the feeding strategies utilized for Nile tilapia juveniles in this study (1 to 3 weeks of fasting and 10WR) were able to induce only partial compensatory growth. It can be concluded that in situations that require complete food restriction in juvenile Nile tilapia (30 g), an acceptable strategy is to limit the period of fasting to 1 week or less to minimize losses and to achieve partial compensatory growth.     

In vitro monoamine oxidase A and B inhibitory activity and molecular docking simulations of fucoxanthin

Fucoxanthin is the primary carotenoid found in edible seaweeds, such as Eisenia bicyclis, Undaria pinnatifida, and others. The aim of this study was to determine the effectiveness of fucoxanthin against Parkinson’s disease (PD) by inhibiting monoamine oxidase (MAO) A and B because MAO inhibitors are used in early management of PD. A sensitive enzyme-based chemiluminescent assay and kinetics methods were used to investigate the enzyme inhibitory activities and mode of inhibition. A molecular docking simulation was performed to clarify the binding characteristics of fucoxanthin to hMAO-A (2z5x) and hMAO-B (2v5z). Our results suggest that fucoxanthin shows significant inhibitory activity against hMAO-A and hMAO-B with IC₅₀ values of 197.41 ± 2.20 and 211.12 ± 1.17 μM, respectively. Selegiline was used as the positive control (IC₅₀: 10.54 ± 1.25 and 0.128 ± 0.01 μM for hMAO-A and hMAO-B, respectively). The enzyme-based kinetics results demonstrated that fucoxanthin inhibited both hMAOs in a reversible competitive manner. The molecular docking simulation predicted that fucoxanthin exhibits higher binding affinity towards hMAO-A and hMAO-B through hydrogen bonding and hydrophobic interactions. These findings suggest that fucoxanthin is a reversible competitive hMAO inhibitor that could be used to manage PD.     

Growth performance and feed utilization of Haliotis tuberculata coccinea (Reeve) juveniles from the Azores (north-eastern Atlantic Ocean): An assay of three mono algae diets

We assessed the dietary value of available seaweeds (Ulva lactuca, Ulva intestinalis, and Sargassum vulgare) as food for juvenile abalone Haliotis tuberculata coccinea. During the 6 weeks that the experiment lasted, initial shell length and weight increased from 13.95 ± 0.32 mm to 15.30 ± 0.30 mm and from 0.39 ± 0.02 g to 0.47 ± 0.03 g. Ulva lactuca diet resulted in higher shell growth rate (58.47 ± 16.76 μm day^?1), SGR (1.15 ± 0.47%.day^?1), weight gain (65.5% ± 33.3), and PER (1.56 ± 0.31), possibly thanks to its higher crude protein content. Both green algae (U. lactuca, U. intestinalis) prove to support the growth of H. tuberculata coccinea. However, they might not be appropriate for an optimal intensive aquaculture production; further research should be conducted to find more efficient diets for juvenile abalone.     

A Comparative Study on Some Functional and Antioxidant Properties of Kilka Meat,Fishmeal, and Stickwater Protein Hydrolysates

This study determined some antioxidative activities and functional properties of hydrolyzed proteins prepared from kilka (Clupeonella sp.) meat (KMH), kilka fishmeal (KFH), and stickwater (SWH). The highest degree of hydrolysis (DH) was 25.02% (p < 0.05) in SWH; however, the difference in DH between KMH and KFH was not significant. KFH had the highest protein content (85.69%) compared with other hydrolysis samples. The Fourier transform infrared spectra of KFH had the highest amide absorption picks (p < 0.05). Solubility at neutral pH was 84.09%, 86.00%, and 93.08% for KMH, KFH, and SWH, respectively. The highest fat absorption capacity was obtained with KFH (204 mg/50 mg). KFH also showed the best foaming properties with 25.66% foaming capacity and proper stability during 60 min (p < 0.05). The highest and lowest whiteness values were obtained in KMH (72.33%) and SWH (36.54%), respectively (p < 0.05). The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC₅₀ value of 1.99 mg/mL) and 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (IC₅₀ value of 2.00 mg/mL) radical scavenging activities were measured at the highest concentrations (40 mg/mL) in KFH (p < 0.05). KFH had the best functional and antioxidant properties, while SWH had a strong ability to inhibit lipid oxidation. Therefore, stickwater from fishmeal production factories is a potential resource for use in developing value-added products instead of being discarded.     

三十烷醇对铜藻生长及岩藻黄素含量的影响

为探讨三十烷醇对铜藻生长的影响，本研究采用不同浓度(0、0.1、 0.5、1.0 和2.0 mg/L)的三十烷醇连续施用20 d，或用三十烷醇浸泡处理24 h后，再恢复正常条件培养20 d，分别测定了铜藻的生长、生理生化指标(光合色素、可溶性蛋白、可溶性糖)以及岩藻黄素含量的变化情况。结果显示，连续施用5 d时，各组藻体的比生长速率(RGR)、叶绿素a(Chl.a)、类胡罗卜素(Car)、可溶性蛋白、可溶性糖的含量均显著高于对照组；15 d时，2.0 mg/L浓度组的铜藻生长受到抑制，各项生理指标均显著下降；20 d时，除了0.1 mg/L浓度组的铜藻生长仍有促进外，其他3个较高浓度的施用组均受到不同程度的抑制，且三十烷醇的浓度越高，抑制作用越明显。经三十烷醇浸泡处理的藻体恢复正常条件培养5 d时，各组藻体的RGR、Chl-a、Car、可溶性蛋白和可溶性糖的含量均显著上升；10 d时，0.5和1.0 mg/L浓度组的铜藻生长速率仍显著高于对照组，但15 d时已与对照组无显著差异，且综合各项生理生化指标，1.0 mg/L组的促进作用最为明显，这种促生长的作用能持续到处理后10 d左右。岩藻黄素的含量除连续施用2.0 mg/L组在实验20 d时低于对照组外，其余各实验组在培养20 d内均显著高于对照组，其中1.0 mg/L三十烷醇浸泡处理24 h恢复培养10 d，可使岩藻黄素的含量提高79.5%。研究表明，连续施用低浓度的三十烷醇(0.1 mg/L) 20 d或以1.0 mg/L三十烷醇每10 d浸泡处理24 h，对铜藻的生长和岩藻黄素的积累有显著的促进作用。     

Fish condensate as effective replacer of fish meal protein in diet for striped snakehead, <Emphasis Type="Italic">Channa striata</Emphasis> (Bloch)

The optimal protein replacement of fish meal (FM) by fish condensate (FC) was investigated in striped snakehead, Channa striata (Bloch) (1.78 ± 0.02 g initial weight). The FM-based diet (0FC) was replaced by substituting protein from FC for 100 (100FC), 200 (200FC), 300 (300FC), 400 (400FC), 500 (500FC) or 600 (600FC) g kg^?1 of the FM, and a commercial diet (CD) for carnivorous fish was included for comparison. The experiment was conducted indoors under completely randomized design (8 treatments × 3 replications × 60 fish per pond) over a 6-month trial. There were no significant differences in water quality during the experiment. The fish fed with 500FC had superior growth performance and feed utilization. This dietary treatment gave similar levels to all observed specific activities of digestive enzymes as did baseline 0FC. Survival, carcass composition, hematological parameters and liver histopathology were not negatively impacted by this protein replacement level. Economic analysis also supports the use of this by-product as a potent protein replacer in striped snakehead diet. Findings from the current study indicate that a 500 g kg^?1 protein replacement of FM by FC is near optimal for striped snakehead, and similar use of it in the aquafeed of other species appears worth further studies.     

Antioxidant and Angiotensin-Converting Enzyme Inhibitory Activities of Protein Hydrolysates Prepared from Threadfin Bream (Nemipterus spp.) Surimi By-products

Solid wastes from threadfin bream (Nemipterus spp.) surimi production composed of head and frame were hydrolyzed by various commercial proteases (Alcalase, Flavourzyme, Neutrase, Protamex, papain, and pepsin) to produce protein hydrolysates with bioactive properties. An Alcalase-hydrolyzed sample at 24.4% degree of hydrolysis (DH) displayed the highest antioxidant activity based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP) assay, and potassium ferricyanide method. In addition, it showed an inhibitory activity toward angiotensin-converting enzyme (ACE) of 25.5%. Antioxidant activity of threadfin bream by-product hydrolysates increased with hydrolysis time and reached the highest DPPH activity after 6 h, while that hydrolyzed for 3 h showed the highest reducing power based on FRAP and potassium ferricyanide assays. In addition, ACE inhibitory activity was found to be at an optimum after 3 h of hydrolysis. The hydrolysates (1 mg/mL) also retarded oxidation of a linoleic acid emulsion system to a similar extent as 0.1 mg/mL 3-tert-butyl-4-hydroxy anisole (BHA), indicating a potential use in the food system. Protein hydrolysates from threadfin bream surimi by-products could be tailor-made to possess both antioxidant and ACE inhibitory activity through controlling DH of Alcalase-catalyzed reactions.