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Characterization of an exo-inulinase from Arthrobacter: a novel NaCl-tolerant exo-inulinase with high molecular mass.

ABSTRACT: A glycoside hydrolase family 32 exo-inulinase gene was cloned from Arthrobacter sp. HJ7 isolated from saline soil located in Heijing town. The gene encodes an 892-residue polypeptide with a calculated mass of 95.1 kDa and a high total frequency of amino acid residues G, A, and V (30.0%). Escherichia coli BL21 (DE3) cells were used as hosts to express the exo-inulinase gene. The recombinant exo-inulinase (rInuAHJ7) showed an apparently maximal activity at pH 5.0-5.5 and 40-45°C. The addition of 1.0 and 10.0 mM Zn(2+) and Pb(2+) had little or no effect on the enzyme activity. rInuAHJ7 exhibited good salt tolerance, retaining more than 98% inulinase activity at a concentration of 3.0%-20.0% (w/v) NaCl. Fructose was the main product of inulin, levan, and Jerusalem artichoke tubers hydrolyzed by the enzyme. The present study is the first to report the identification and characterization of an Arthrobacter sp exo-inulinase showing a high molecular mass of 95.1 kDa and NaCl tolerance. These results suggest that the exo-inulinase might be an alternative material for potential applications in processing seafood and other foods with high saline contents, such as marine algae, pickles, and sauces.

SUBMITTER: Shen J

PROVIDER: S-EPMC4601504 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Characterization of an exo-inulinase from Arthrobacter: a novel NaCl-tolerant exo-inulinase with high molecular mass.

Shen Jidong J Zhang Rui R Li Junjun J Tang Xianghua X Li Ruixian R Wang Min M Huang Zunxi Z Zhou Junpei J

Bioengineered 20150101 2

A glycoside hydrolase family 32 exo-inulinase gene was cloned from Arthrobacter sp. HJ7 isolated from saline soil located in Heijing town. The gene encodes an 892-residue polypeptide with a calculated mass of 95.1 kDa and a high total frequency of amino acid residues G, A, and V (30.0%). Escherichia coli BL21 (DE3) cells were used as hosts to express the exo-inulinase gene. The recombinant exo-inulinase (rInuAHJ7) showed an apparently maximal activity at pH 5.0-5.5 and 40-45°C. The addition of 1 ...[more]

PMID: 25695343

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Project description:Probiotic gut bacteria employ specific metabolic pathways to degrade dietary carbohydrates beyond the capabilities of their human host. Here, we report how individual commercial probiotic strains degrade prebiotic (inulin type) fructans. First, a structural analysis of commercial fructose oligosaccharide-inulin samples was performed. These ?-(2-1)-fructans differ in termination by either glucose (GF) or fructose (FF) residues, with a broad variation in the degrees of polymerization (DPs). The growth of individual probiotic bacteria on short-chain inulin (sc-inulin) (Frutafit CLR), a ?-(2-1)-fructan (DP 2 to DP 40), was studied. Lactobacillus salivarius W57 and other bacteria grew relatively poorly on sc-inulin, with only fractions of DP 3 and DP 5 utilized, reflecting uptake via specific transport systems followed by intracellular metabolism. Lactobacillus paracasei subsp. paracasei W20 completely used all sc-inulin components, employing an extracellular exo-inulinase enzyme (glycoside hydrolase family GH32 [LpGH32], also found in other strains of this species); the purified enzyme converted high-DP compounds into fructose, sucrose, 1-kestose, and F2 (inulobiose). The cocultivation of L. salivarius W57 and L. paracasei W20 on sc-inulin resulted in cross-feeding of the former by the latter, supported by this extracellular exo-inulinase. The extent of cross-feeding depended on the type of fructan, i.e., the GF type (clearly stimulating) versus the FF type (relatively low stimulus), and on fructan chain length, since relatively low-DP ?-(2-1)-fructans contain a relatively high content of GF-type molecules, thus resulting in higher concentrations of GF-type DP 2 to DP 3 degradation products. The results provide an example of how in vivo cross-feeding on prebiotic ?-(2-1)-fructans may occur among probiotic lactobacilli.IMPORTANCE The human gut microbial community is associated strongly with host physiology and human diseases. This observation has prompted research on pre- and probiotics, two concepts enabling specific changes in the composition of the human gut microbiome that result in beneficial effects for the host. Here, we show how fructooligosaccharide-inulin prebiotics are fermented by commercial probiotic bacterial strains involving specific sets of enzymes and transporters. Cross-feeding strains such as Lactobacillus paracasei W20 may thus act as keystone strains in the degradation of prebiotic inulin in the human gut, and this strain-exo-inulinase combination may be used in commercial Lactobacillus-inulin synbiotics.

Dataset Information

Characterization of an exo-inulinase from Arthrobacter: a novel NaCl-tolerant exo-inulinase with high molecular mass.

Publications

Characterization of an exo-inulinase from Arthrobacter: a novel NaCl-tolerant exo-inulinase with high molecular mass.

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