Evaluation of dietary freeze-dried Chaetoceros calcitrans supplementation to control Vibrio harveyi infection on Penaeus monodon juvenile

Effects of supplementation of diets with freeze-dried Chaetoceros calcitrans to control Vibrio harveyi infection are evaluated through immune responses, and disease resistance of juvenile Penaeus monodon. Total lipid and fatty acid profile of Chaetoceros calcitrans is also analyzed. A challenge infection with 107 cfu/mL concentration of Vibrio harveyi is intramuscularly injected to juvenile Penaeus monodon after 45 days of feeding of diets supplemented with 15 g/kg and 30 g/kg dried Chaetoceros calcitrans. The use of dried Chaetoceros calcitrans is compared with that of ß-1,3 glucan Curdlan, a commercial immune enhancer. Incorporation of 30 g/kg Chaetoceros calcitrans in the diet enhances the immune system of shrimp as effected by high prophenoloxidase activity and plasma protein concentration and is better compared to the commercially available Curdlan. Chaetoceros calcitrans also contains polyunsaturated fatty acids (PUFAs) such as linolenic acid and eicosapentanoic acid (EPA) which are responsible for its antibacterial action against Vibrio harveyi. All these biological activities of Chaetoceros calcitrans add up to increase resistance of the juvenile Penaeus monodon to vibriosis as shown by its high survival rate from the challenge infection with Vibrio harveyi. Therefore, it is worthwhile to use Chaetoceros calcitrans as supplementary feed. Its effect in increasing the immune competence coupled with its antibacterial action, make the shrimp resistant to luminous vibriosis that continues to affect the industry, thereby augmenting aquaculture production

Antimicrobial activity screening of Lyngbya majuscula crude methanolic extract against selected aquaculture pathogens

Lyngbya majuscula crude methanolic extract (LMCME) was screened for antimicrobial properties in vitro. The Gram-negative Vibrio harveyi and Aeromonas hydrophila and the Gram-positive Staphylococcus aureus and Micrococcus luteus were used as reference test bacteria. The filamentous Lagenidium sp. was used as test fungus. LMCME showed a poor or weak antibacterial activity against the bacterial isolates. The activity against V. harveyi was observed at 1,000 mg/mL-1 while that against A. hydrophila was at 500 and 1,000 mg/mL-1 concentrations. These activities, however, were significantly lower (p-1 concentration and was comparable (p>0.05) with the positive control (malachite green). The minimum inhibitory concentration (MIC) of LMCME against Lagenidium sp. was at 50 mg/mL-1, and the minimum fungicidal (lethal) concentration (MFC) at 100 mg/mL-1. Phytochemical screening revealed the presence of alkaloids to which its antifungal activity may be attributed. Brine shrimp assay against the larvae of Artemia salina L each showed that the LMCME was not toxic even at the highest concentration (1,000 mg/mL-1). By and large, L. majuscula can be a potential source of secondary metabolites that can be used for the control and treatment of larval mycosis in the aquaculture industry

Antimicrobial activity screening of Lyngbya majuscula crude methanolic extract against selected aquaculture pathogens

Lyngbya majuscula crude methanolic extract (LMCME) was screened for antimicrobial properties in vitro. The Gram-negative Vibrio harveyi and Aeromonas hydrophila and the Gram-positive Staphylococcus aureus and Micrococcus luteus were used as reference test bacteria. The filamentous Lagenidium sp. was used as test fungus. LMCME showed a poor or weak antibacterial activity against the bacterial isolates. The activity against V. harveyi was observed at 1,000 mg/mL-1 while that against A. hydrophila was at 500 and 1,000 mg/mL-1 concentrations. These activities, however, were significantly lower (p-1 concentration and was comparable (p>0.05) with the positive control (malachite green). The minimum inhibitory concentration (MIC) of LMCME against Lagenidium sp. was at 50 mg/mL-1, and the minimum fungicidal (lethal) concentration (MFC) at 100 mg/mL-1. Phytochemical screening revealed the presence of alkaloids to which its antifungal activity may be attributed. Brine shrimp assay against the larvae of Artemia salina L each showed that the LMCME was not toxic even at the highest concentration (1,000 mg/mL-1). By and large, L. majuscula can be a potential source of secondary metabolites that can be used for the control and treatment of larval mycosis in the aquaculture industry

Antibacterial properties of the microalgae Chaetoceros calcitrans

The antibacterial properties of the microalgae Chaetoceros calcitrans were assessed. Samples of C. calcitrans were first extracted in methanol, and then in different organic solvents of increasing polarity, n-hexane (n-Hex), dichloromethane (DCM) and ethyl acetate (EA) by liquid-liquid extraction. Solvent extracts were screened for antibacterial activity against four species of bacteria: Gram positive, Staphylococcus aureus and Bacillus subtilis; and Gram negative, Escherichia coli and Vibrio harveyi, with Amoxicillin as positive control, N-Hex extract, with significantly lower antibacterial activity than Amoxicillin, showed significantly higher activity than DCM and EA extracts, and least in methanolic extract. High antibacterial activity of n-Hex extract against all the microorganisms indicates that the bioactive components could be non-polar since the activity decreased as the solvent became more polar like methanol, and finally lost in aqueous extract. Results also showed that the extracts have a broad spectrum activity. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of all solvent extracts on all microorganisms tested ranged from 125 to 500 μg.mL-1. Partial purification and characterisation of the extracts confirmed the antibacterial activity in the non-polar fraction, which could be terpenes. The results suggest a good prospect in using C. calcitrans against Vibrio and other bacterial species.We thank the University of the Philippines (UP) System Creative and Research Scholarship Program and UP Visayas In-house Research Fund for funding the project, and SEAFDEC-AQD, Tigbauan, Iloilo, Philippines for the use of their facilities

Characterization of the solar drying of Tetraselmis sp. for biofuel production using a laboratory-scale setup and statistical analysis

Microalgae is one of the most promising sources of biofuel, but its high initial moisture content remains a hindrance to efficient lipid extraction. According to Halim, et al. (2011), the lipid yield of dried microalgae is 33% higher than wet microalgae using hexane extraction. In this study, Tetraselmis sp. was dried using a laboratory-scale set up simulating a solar dryer. The direct radiation (Qr), air flow rate (V1) and convective heat input to the inlet air (Qci) were the control variables. Statistical analysis showed that Qr is limited by the chamber temperature, which is largely controlled by Qci. With regards to Vf, increasing its results to less energy-efficient drying. As a conclusion, it can be derived that the drying rate is best at high Qci and low Vf. Also, Qr significantly improves the drying rate. Finally, when modeling drying rate, it is best to describe it as a function of chamber temperature and mass flow rate instead of Vf and heat input