The purpose of this study was to investigate lactic acid bacteria with antioxidative and probiotic activities isolated from Korean healthy infant feces and kimchi. Isolates A1, A2, S1, S2, and S3 were assigned to Lactobacillus sp. and isolates A3, A4, E1, E2, E3, and E4 were assigned to Leuconostoc sp. on the basis of their physiological properties and 16S ribosomal DNA sequence analysis. Most strains were confirmed as safe bioresources through nonhemolytic activities and non-production of harmful enzymes such as β-glucosidase, β- glucuronidase and tryptophanase. The 11 isolates showed different resistance to acid and bile acids. In addition, they exhibited antibacterial activity against foodborne bacteria, especially Bacillus cereus, Listeria monocytogenes, and Escherichia coli. Furthermore, all strains showed significantly high levels of hydrophobicity. The antioxidant effects of culture filtrates of the 11 strains included 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging capacity, 2.2'- azino-bis (2-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity, and superoxide dismutase activity. The results revealed that most of the culture filtrates have effective scavenging activity for DPPH and ABTS radicals. All strains appeared to have effective superoxide dismutase activity. In conclusion, the isolated strains A1, A3, S1, and S3 have significant probiotic activities applicable to the development of functional foods and health-related products. These strains might also contribute to preventing and controlling several diseases associated with oxidative stress, when used as probiotics.

Isoprenoid biosynthesis involves mostly head to tail addition of isopentenyl diphosphate (IPP), to its isomer dimethylallyl diphosphate (DMAPP) synthesizing geranyl diphosphate (GPP). Isopentenyl diphosphate (IPP) isomerase catalyses the interconversion of IPP to dimethylallyl diphosphate (DMAPP). In the present study, the gene coding for Isopentenyl‐diphosphate Isomerase (idi) was isolated from the marine bacterium, Kocuria gwangalliensis. The idi gene coding for IPP isomerase consists of 543 base pairs encoding 180 amino acids residues. The nucleotide sequence of the idi gene was analyzed and compared with that of other species, including K. rhizophila and S. keddieii, and it turned out to be well conserved during evolution. An expression plasmid containing the idi gene was constructed and expressed in E. coli, and produced a recombinant protein of approximately 20 kDa, corresponding to the molecular weight. In order to increase production of astaxanthin, pET‐44a(+)‐idi was co‐transformed into E. coli containing the pCR‐XL‐TOPO‐crt‐full carrying crtEBIYWZ genes required for astaxanthin biosynthesis. This engineered E.coli strain containing both idi gene and astaxanthin biosythesis gene cluster produced 900 ug/g DCW of astaxanthin, resulting 2‐fold increased production of astaxanthin.