title: Isolation and characterization of cold-adapted strains producing beta-galactosidase.
abstract: beta-Galactosidase is extensively employed in the manufacture of dairy products, including lactose-reduced milk. Here, we have isolated two gram-negative and rod-shaped coldadapted bacteria, BS 1 and HS 39. These strains were able to break down lactose at low temperatures. Although two isolates were found to grow well at 10 degrees , the BS 1 strain was unable to grow at 37 degrees . Another strain, HS-39, evidenced retarded growth at 37 degrees . The biochemical characteristics and the results of 16S rDNA sequencing identified the BS 1 isolate as Rahnella aquatilis, and showed that the HS 39 strain belonged to genus Buttiauxella. Whereas the R. aquatilis BS 1 strain generated maximal quantities of beta-galactosidase when incubated for 60 h at 10 degrees , Buttiauxella sp. HS-39 generated beta-galactosidase earlier, and at slightly lower levels, than R. aquatilis BS 1. The optimum temperature for beta-galactosidase was 30 degrees for R. aquatilis BS-1, and was 45 degrees for Buttiauxella sp. HS-39, thereby indicating that R. aquatilis BS-1 was able to generate a cold-adaptive enzyme. These two cold-adapted strains, and most notably the beta-galactosidase from each isolate, might prove useful in some biotechnological applications.
authors.affiliation: Division of Life Sciences, College of Natural Sciences and Biotechnology Research Institute, Chungbuk National University, Cheongju 361-763, Chungbuk, Republic of Korea.
authors.forename: Jeong-Won
authors.initials: JW
authors.lastname: Park
authors.forename: Yong-Sik
authors.initials: YS
authors.lastname: Oh
authors.forename: Jai-Yun
authors.initials: JY
authors.lastname: Lim
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Roh
mesh_terms: D003080:Cold Temperature; D004755:Enterobacteriaceae / Q000145:classification / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification*; D007785:Lactose / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D020638:Rahnella / Q000145:classification / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification*; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012336:RNA, Ribosomal, 16S; D001616:beta-Galactosidase; D007785:Lactose