Isolation of alginate lyase-producing bacteria and screening for their potential characteristics as abalone probionts

This study is aimed at the isolation and screening of alginate lyase-producing bacteria from the gastrointestinal tracts of hybrid abalone, Haliotis rubra x H. laevigata, as probiotic candidates. Six bacterial isolates were detected to produce alginate lyase. Of these, the isolate with the highest alginate-lyase activity was identified as Enterobacter ludwigii strain EN-119, displaying 99% similarity of 16S rDNA sequence. Further assays indicated that E. ludwigii showed good viability and stability when it was incorporated into manufactured pellets and stored at 4°C for 7 days. The isolate also had high tolerance of high salinity (35 mg/L), low pH in simulated stomach juice (5) and to simulated intestinal juice containing surfactants such as bile salts and gastric enzymes (pepsin and trypsin). Additionally, a short, preliminary study indicated that supplementation of E. ludwigii via manufactured pellets improved the total weight gain and specific growth rate of hybrid abalone. These results suggest that E. ludwigii is a potential probiont for shortening the culture period of hybrid abalone.