The potentials of secondary metabolites from Bacillus cereus SN7 and Vagococcus fluvialis CT21 against fish pathogenic bacteria.

One of the major factors that affect the total production of fisheries is the declining number of catches and aquaculture production due to the high pathogenicity in aquatic environment. This enforces the need to find anti-pathogenic agents that could solve the problem. In addition, the application of potential Bacillus cereus SN7 and Vagococcus fluvialis CT21 isolated and identified from the sea water of Siak, Riau, Indonesia need to be optimally exploited. The aim of this study, therefore, is to determine the component of bioactive compounds present in Bacillus cereus SN7 and Vagococcus fluvialis CT21, and also to explore their intrinsic potential as a biological control agent in fisheries, especially for inhibiting the growth of pathogenic bacteria (Vibrio alginolyticus, Aeromonas hydrophila and Pseudomonas aeruginosa). The method used was experimental, where the ethyl acetate crude extracts of both samples were analyzed for their phytochemical content, followed by thin layer chromatography analysis and Liquid Chromatography Mass Spectrometry. In addition, anti-pathogenic activity test was performed using the Kirby-Bauer method, minimum inhibitory and bactericidal concentration analysis. The results showed alkaloids, flavonoids, and saponins were the potential bioactive components in the crude extracts of Bacillus cereus SN7 and Vagococcus fluvialis CT21. Furthermore, the anti-pathogenic activity test demonstrated the ability for both bacteria to inhibit three types of pathogens with the following inhibitory zone values: Vibrio alginolyticus (10-11 mm), Aeromonas hydrophila (8-12 mm), and Pseudomonas aeruginosa (8-10 mm). In conclusion secondary metabolite compounds produced by Bacillus cereus SN7 and Vagococcus fluvialis CT21 possess the capacity to inhibit pathogenic bacteria. Hence, both samples are potential candidates for anti-pathogen development, especially in fisheries.

Use of chicken feather meal fermented with Bacillus subtilis in diets to increase the digestive enzymes activity and nutrient digestibility of silver pompano Trachinotus blochii (Lacepede, 1801).

Background: Feather has the potential to be used as a fish feed ingredient because it has high protein content (80-85%), and is rich in amino acids arginine, leucine, isoleucine and valine. However, the protein consists mainly of keratin, which is classified as fiber that is difficult to digest. Therefore, to improve digestibility, the keratin protein is degraded using microbial Bacillus subtilis. This study aimed to determine the digestibility of fermented feather meal (FFM) in silver pompano ( Trachinotus blochii) diets and to observe the histological structure of their intestines after digestion. Methods: The method used was a one factor experiment with five treatments and three replications each, which were: diet without FFM, diet containing 10% FFM, 20%, 30% and 40%. The diets were given to juvenile silver pompano (with average body weight of 8.56 ± 0.18 g) and stocked in 15 similar 20-L plastic jars with 10 fish per jar in a density of 100 L capacity container. The experimental diets were given three times daily at approximately 8.00 AM, 12.00 PM and 5.00 PM to apparent satiation for 60 days. Results: The results showed that the use of FFM increased the activity of digestive enzymes (protease and lipase), but reduced the amylase activity of silver pompano, which was significantly different between treatments (P <0.05). Meanwhile, the diet containing 20% FFM produced the highest feed and protein, which are 37.05% and 67.24%, respectively. This was significantly different from other treatments (P <0.05), and was effectively absorbed by fish intestines. Conclusion: The addition of chicken feather meal fermented with Bacillus subtilis could increase the activity of protease and lipase enzymes and nutrient digestibility of silver pompano but not amylase activity.

Antibacterial activity in secondary metabolite extracts of heterotrophic bacteria against Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas aeruginosa.

Background: Disease causing bacteria such as Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas aeruginosa present a problem for fish farming. Treatment to remove them are generally carried out using antibiotics which have side effects on fish, the environment and humans. However, the use of antibacterial compounds derived from heterotrophic bacteria serve as a good alternative for antibiotics. Therefore, this study aimed to explore antibacterial activity in the secondary metabolite extracts of heterotrophic bacteria against Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas aeruginosa. Methods: Heterotrophic bacteria namely Bacillus sp. JS04 MT102913.1, Bacillus toyonensis JS08 MT102920.1, Bacillus cereus JS10 MT102922.1, Bacillus sp. JS11 MT102923.1, Pseudoalteromonas sp. JS19 MT102924.1, Bacillus cereus JS22 MT102926.1, and Bacillus sp. strain JS25 MT102927.1 were used in this study. The sequences of these bacteria have been deposited and are available from NCBI GenBank. Each heterotrophic bacterium was cultured on 6L nutrient broth for 8 days, and extracts produced using ethyl acetate to obtain their secondary metabolites. These extracts were tested for their phytochemical contents using FT-IR and also tested for their inhibitory property in pathogenic bacteria by agar diffusion method. Results: Phytochemical test results showed that the seven heterotrophic bacterial isolates produced terpenoid compounds. Based on the inhibitory test, the secondary metabolite extracts from Bacillus sp strain JS04 had the highest inhibitory effect on the growth of pathogenic bacteria namely, V. alginolyticus (17.5 mm), A. hydrophila (16.8 mm), and P. aeruginosa (17.3 mm). Conclusion: It was concluded that the secondary metabolite extracts of heterotrophic bacteria inhibit the growth of V. alginolyticus, A. hydrophila, and P. aeruginosa.

Potential of bacteriocins produced by probiotic bacteria isolated from tiger shrimp and prawns as antibacterial to Vibrio, Pseudomonas, and Aeromonas species on fish.

Backgrounds: Bacteriocin has been used widely in industry as a biopreservative agent. The objective of the present study was to investigate the potency of Bacteriocin isolated from tiger prawn Penaeus monodon and freshwater shrimp Macrobrachium rosenbergii as an anti-bacterial on fish. Methods: A total of ten candidates of probiotic bacteria consisted of five isolates from tiger shrimps (H1, H2, H3, H4, H5) and five isolates from freshwater prawns (W1, W2, W3, W4, W5) were evaluated. Bacteriocin wasBacteriocin was produced by centrifugation at a speed of 150 rpm and at 37 °C for 24 hours. The bacteriocin extract was purified by adding sulphate ammonium salt {(NH4) 2SO4} at 80% of the saturation level. Bacteriocin activity was determined using a diffusion method against pathogenic bacteria Vibrio alginolyticus, Aeromonas hydrophillaAeromonas hydrophilla and Pseudomonas stutzeri. Bacteriocins were analyzed usinganalyzedusing High Performance Liquid Chromatography (HPLC) and Fourier Transform Infra-Red (FTIR). The data were subjected to analysis of variance (ANOVA) and followed with Duncans multiple range test. Results: Bacteriocins produced by bacteria isolate H4 from tiger prawn indicated the highest bacteriocin activity againstbacteriocin activity against Pseudomonas stutzeri at stutzeri at the diameter of inhibition zone of 887.10 ± 409.24 mm 2/mL. While isolate W2 from freshwater shrimp indicated inhibition zone of 1466.96 ± 127.62 mm 2/mL. Both bacteriocins were purified by chromatography column using Sephadex LH-20. Conclusions: This finding showed that bacterial isolates H4 and W2 have the potential to produce bacteriocins which inhibit the pathogenic bacteria. FTIR analysis showed an amide group at wave number 1652cm -1 contained in the bacteriocins of isolates H4 and W2.