Isolation and Screening of Lactic Acid Bacteria from the Gut of Blue Swimming Crab, P. pelagicus, an in vitro Inhibition Assay and Small Scale in vivo Model for Validation of Isolates as Probiotics

摘要

Blue swimming crab, Portunus pelagicus has not anchored the roots in aquaculture due to non availability of commercial seed production . Letdown of seed production is owing to microbial infections. To combat with microbes, study was aimed to isolate and screen probiotics from the gut of female crab for larviculture. Based on characteristics of inhibitory activity against pathogenic V. harveyi , V. parahaemolyticus and P. piscicida, bile, acid, salt tolerances and survival in sea water, isolates were identified as L. plantarum , L. salivarius , L. rhamnosus W. confusa and W. cibaria and evaluated for probiotics. A new model small scale in vivo validation was developed for conformity of the isolates as probiotics for P. pelagicus larviculture. The LAB isolates were administrated as water additive at concentrations 102, 104 and 106 cfu mL-1 for one day and five days in vivo validation experiments and positive control was inoculated with same concentrations of V. harveyi while negative control employed with larvae and no inoculation. Highest larval survival achieved at concentration 106 cfu mL-1 and L. plantarum, L. salivarius and L. rhamnosus did show significant larval survival. W. confusa and W. cibaria did not demonstrate as probiotics. L. plantarum showed highest survival 49.45±4.80% and 54.44±6.74% in both inoculations, respectively and no survival was observed in five days+ve control. Water quality degradation was not evident but improvement in pH was noticed. Based on results of small-scale in vivo test three LAB probiotics, L. plantarum , L. salivarius and L. rhamnosus were selected for larviculture of P. pelagicus .