Isolation and Characterization of Chitinase-ProducingBacillusandPaenibacillusStrains from Salted and Fermented Shrimp,Acetes japonicus

Abstract

Chitinases catalyze the conversion of chitin and are produced by a wide range of bacteria. The biological applications of these enzymes have been exploited in food and pharmaceutical industries. We isolated 2 halophilic chitinase-producing novel strains of bacteria-SCH-1 and SCH-2 from Saeu-jeot, a traditional Korean salted and fermented food made with shrimp (Acetes japonicus). The isolated strains- SCH-1 and SCH-2 were Gram-positive, rod-shaped, endospore-forming facultative anaerobes, with strain SCH-2 showing peritrichous flagella. Molecular characterization of the 16S rRNA gene identified the strains SCH-1 and SCH-2 as Bacillus sp. and Paenibacillus sp. respectively. Basic Local Alignment Search Tool and subsequent phylogenetic analysis of strain SCH-1 showed an identity of 97.83% with Bacillus cereus ATCC 14579 (NR_074540), whereas strain SCH-2 showed an identity of 99.16% with Paenibacillus lautus JCM 9073 (NR_040882). Furthermore, the SCH-1 strain could use glucose, N-acetyl glucosamine, esculin, and maltose as carbon source substrates. Cellular fatty acid analysis showed that iso-C15:0 and anteiso-C15:0 are the major acids in strain SCH-1 and SCH-2, respectively. The SCH-1 strain showed a higher chitinase activity at 15.71 unit/mg protein compared with SCH-2 strain. Chitinase isozymes of Bacillus sp. SCH-1was expressed as 2 bands having sizes of 41 and 50 kDa, and as 4 bands with sizes of 30, 37, 45.7, and 50 kDa in Paenibacillus sp. SCH-2. The rich chitinase activity with the isozyme profiles of the isolated Bacillus and Paenibacillus strains provide advancement in the study of fermentation and may play putative functions in the chitin bioconversion of sea crustacean foods.