Comparing levels of perfluorinated compounds in processed marine products.

Perfluorinated compounds (PFCs) are widely distributed in nature and have many applications due to their unique chemical and physicochemical properties. While, PFCs are present in soil, water, and air, their pathway for entry into the human body is circumstantially via contaminated food. The demand for seafood has been increasing. In this study, we investigated via LC-MS/MS, the content of 19 different types of PFCs in 302 samples belonging to five different categories of the typical South Korean seafood. The highest levels of PFOA, PFTrDA, PFOS, and PFPeA were found in dried seafood, canned and salted seafood, processed fish food, and seasoned laver, respectively. The levels of PFOA and PFOS were compared on the basis of various criteria including the nomenclature, biological classification, and habitat of the source of seafood. High levels of PFOA and PFOS were detected in anchovy, sea squirt, and mackerel based on the nomenclature of raw seafood, in crustaceans based on the biological classification, and in demersal organisms based on the habitat. The human intake values of PFOA and PFOS from the processed marine products in South Korea were lower than the tolerable daily intake, indicating that the consumption of these processed seafood poses no immediate harm.

Molecular cloning and characterization of a bile salt hydrolase from Lactobacillus acidophilus PF01.

Phenotypic screening for bile salt hydrolase (BSH) activity was performed on Lactobacillus acidophilus PF01 isolated from piglet feces. A gene encoding BSH was identified and cloned from the genomic library of L. acidophilus PF01. The bsh gene and surrounding regions were characterized by nucleotide sequence analysis and were found to contain a single open reading frame (ORF) of 951 nucleotides encoding a 316 amino acid protein. The potential bsh promoter region was located upstream of the start codon. The protein deduced from the complete ORF had high similarity with other BSHs, and four amino acid motifs located around the active site, FGRNXD, AGLNF, VLTNXP, and GXGXGXXGXPGD, were highly conserved. The bsh gene was cloned into the pET21b expression vector and expressed in Escherichia coli BLR(DE3) by induction with 0.1mM of isopropylthiogalactopyranoside. The BSH enzyme was purified with apparent homogeneity using a Ni2+-NTA agarose column and characterized. The overexpressed recombinant BSH enzyme of L. acidophilus PF01 exhibited hydrolase activity against tauroconjugated bile salts, but not glycoconjugated bile salts. It showed the highest activity against taurocholic acid. The maximum BSH activity occurred at approximately 40oC. The enzyme maintained approximately 70% of its maximum activity even at 60 degrees , whereas its activity rapidly decreased at below 37 degrees . The optimum pH was 6, and BSH activity was rapidly inactivated below pH 5 and above pH 7.