Selection of Proteolytic Bacteria from the Digestive Tract of Vanname Shrimp (Litopenaeus vannamei)

Abstract

The feed consumed by shrimp is not all digestible but some are excreted in the form of waste in the form of feces and other metabolic waste such as urine and ammonia. The amount of feed released into feces depends on the suitability of feed components with enzymatic capabilities in the shrimp digestive tract or digestibility.  One of the efforts to maintain aquaculture water quality is by using probiotics that can be mixed with feed and applied directly to aquaculture medium. The study aimed to obtain proteolytic and probiotic candidate bacteria from the digestive tract of vanname shrimp. Bacterial screening was carried out by isolating bacteria from the digestive tract of shrimp obtained from pond farmers in the Suppa area of Pinrang Regency. The results of the isolation of probiotic candidate bacteria from the digestive tract of shrimp obtained a total of 20 isolates of proteolytic candidates for further selection, then five isolates with different morphological characteristics were selected. The five isolates were then tested for proteolytic activity. The results showed the greatest proteolytic activity was observed in the UM5 isolate with an activity value of 17 mm; followed by the UM1 isolate at 10 mm; UM2 at 9 mm, UM4 at 7 mm; and UM3 at 5 mm. Then tested for resistance to acidic and alkaline conditions (pH 2.5) and (pH 7.5), bacterial attachment test, and antagonistic test against Vibrio harveyi bacteria.  The five isolates can survive in acidic conditions (pH 2.5 and alkaline (pH 7.5)) for eight hours. Antagonistic tests showed that the five selected isolates (UM1, UM2, UM3, UM4, and UM5) can inhibit the growth of Vibrio harveyi bacteria by forming an inhibition zone around the isolate. The highest inhibition zone was found in the UM5 isolate at 19 mm, followed by the UM2 isolate at 16 mm, UM4 at 15.5 mm, and UM3 at 15 mm. While the smallest antagonistic was obtained in isolate UM1 at 12 mm. The bacterial population in the swab shows the ability to colonize or attach a bacterium so the greater the number of bacteria in the swab, the better the bacteria are in sticking.  The largest bacterial population was found in isolate UM5 which amounted to 2.53 x 107 Cfu/ml. isolate UM 4 amounted to 7.27 x 106 cfu/ml.  Furthermore, UM3 amounted to 6.78 x 106 Cfu/ml.  Then UM 2 amounted to 3.32 x 106 cfu/ml. the smallest population was shown by isolate UM1, which amounted to 4.5 x 105 cfu.ml.