Recombinant thermostable cycloinulo-oligosaccharide fructanotransferase produced by Saccharomyces cerevisiae

Production of a single cyclic type of fructooligosaccharide structure by inulin-degrading Paenibacillus sp. LX16 newly isolated from Jerusalem artichoke root

A novel inulin‐degrading bacterium was isolated from a soil sample collected on Jerusalem artichoke roots. It is a Gram‐positive, aerobic, motile and central endospore‐forming straight rod, and exhibits phenotypic properties being consistent with its classification in the genus Paenibacillus. The predominant cellular fatty acids were anteiso‐C15:0, C16:0 and anteiso‐C17:0. This strain represents a novel species of the genus Paenibacillus on the basis of phenotypic data together with phylogenetic analysis, and it is here designated as LX16 and deposited in China centre for type collection, China (= CCTCC 2015256). Strain LX16 could produce a cyclofructooligosaccharide fructanotransferase catalysing the formation of one type of fructooligosaccharide (FOS) from inulin. The FOS was identified as a cyclofructooligosaccharide with a degree of polymerization of 6. Such homology in inulin degradation products may be beneficial for the functional FOS production.

Development of new HPLC chiral stationary phases based on native and derivatized cyclofructans

An unusual class of chiral selectors, cyclofructans, is introduced for the first time as bonded chiral stationary phases. Compared to native cyclofructans (CFs), which have rather limited capabilities as chiral selectors, aliphatic- and aromatic-functionalized CF6s possess unique and very different enantiomeric selectivities. Indeed, they are shown to separate a very broad range of racemic compounds. In particular, aliphatic-derivatized CF6s with a low substitution degree baseline separate all tested chiral primary amines. It appears that partial derivatization on the CF6 molecule disrupts the molecular internal hydrogen bonding, thereby making the core of the molecule more accessible. In contrast, highly aromatic-functionalized CF6 stationary phases lose most of the enantioselective capabilities toward primary amines, however they gain broad selectivity for most other types of analytes. This class of stationary phases also demonstrates high "loadability" and therefore has great potential for preparative separations. The variations in enantiomeric selectivity often can be correlated with distinct structural features of the selector. The separations occur predominantly in the presence of organic solvents.

Role of the N-Terminal Domain of Endoinulinase from Arthrobacter sp. S37 in Regulation of Enzyme Catalysis

Endoinulinase from Arthrobacter sp. S37 (EnIA), a member of the glycoside hydrolase family 32, is unique in that, unlike other members of the family, it contains a 250-residue N-terminal domain including a "laminin-G like jelly-roll" fold. This unique N-terminal domain is here suggested to be involved in dimerization and catalysis. The essentially inactive nature of enzymes produced by N-terminal truncation (Delta15, Delta45, Delta70, and Delta250) supported the pivotal role of this unique domain in catalysis and the need for its structural integrity. Significant reductions in the enzyme efficiency (kcat/Km) were observed when mutations were introduced at highly conserved tryptophan residues (Trp75 and Trp141) in the laminin-G like jelly-roll fold, implying their involvement in catalysis. Results from size-exclusion chromatography of the native and chimeric enzymes in the presence and absence of the domain suggested that the N-terminal domain could mediate dimerization.

Molecular characterization of cycloinulooligosaccharide fructanotransferase from Bacillus macerans

Cycloinulooligosaccharide fructanotransferase (CFTase) converts inulin into cyclooligosaccharides of beta-(2-->1)-linked D-fructofuranose by catalyzing an intramolecular transfructosylation reaction. The CFTase gene was cloned and characterized from Bacillus macerans CFC1. The CFTase gene encoded a polypeptide of 1,333 amino acids with a calculated Mr of 149,563. Western blot and zymography analyses revealed that the CFTase with a molecular mass of 150 kDa (CFT150) was processed (between Ser389 and Phe390 residue) to form a 107-kDa protein (CFT107) in the B. macerans CFC1 cells. The processed CFT107 was similar in its mass to the previously purified CFTase from B. macerans CFC1. The CFT107 enzyme was produced by B. macerans CFC1 but was not detected from the recombinant Escherichia coli cells, indicating that the processing event occurred in a host-specific manner. The two CFTases (CFT150 and CFT107) exhibited the same enzymatic properties, such as influences of pH and temperature on the enzyme activity, the intermolecular transfructosylation ability, and the ability of hydrolysis of cycloinulooligosaccharides produced by the cyclization reaction. However, the thermal stability of CFT107 was slightly higher than that of CFT150. The most striking difference between the two enzymes was observed in their Km values; the value for CFT150 (1.56 mM) was threefold lower than that for CFT107 (4.76 mM). Thus, the specificity constant (kcat/Km) of CFT150 was about fourfold higher than that of CFT107. These results indicated that the N-terminal 358-residue region of CFT150 played a role in increasing the enzyme's binding affinity to the inulin substrate.

Expression of an Aspergillus niger phytase gene (phyA) in Saccharomyces cerevisiae

Phytase improves the bioavailability of phytate phosphorus in plant foods to humans and animals and reduces phosphorus pollution of animal waste. Our objectives were to express an Aspergillus niger phytase gene (phyA) in Saccharomyces cerevisiae and to determine the effects of glycosylation on the phytase's activity and thermostability. A 1.4-kb DNA fragment containing the coding region of the phyA gene was inserted into the expression vector pYES2 and was expressed in S. cerevisiae as an active, extracellular phytase. The yield of total extracellular phytase activity was affected by the signal peptide and the medium composition. The expressed phytase had two pH optima (2 to 2.5 and 5 to 5.5) and a temperature optimum between 55 and 60 degrees C, and it cross-reacted with a rabbit polyclonal antibody against the wild-type enzyme. Due to the heavy glycosylation, the expressed phytase had a molecular size of approximately 120 kDa and appeared to be more thermostable than the commercial enzyme. Deglycosylation of the phytase resulted in losses of 9% of its activity and 40% of its thermostability. The recombinant phytase was effective in hydrolyzing phytate phosphorus from corn or soybean meal in vitro. In conclusion, the phyA gene was expressed as an active, extracellular phytase in S. cerevisiae, and its thermostability was affected by glycosylation.