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Yeo, In-Seok,Shim, Woo-Yong,Kim, Jung Hoe Elsevier 2018 Journal of biotechnology Vol.274 No.-
<P>For the biological production of L-ribulose, conversion by enzymes or resting cells has been investigated. However, expensive or concentrated substrates, an additional purification step to remove borate and the requirement for cell cultivation and harvest steps before utilization of resting cells make the production process complex and unfavorable. Microbial fermentation may help overcome these limitations. In this study, we constructed a genetically engineered Candida tropicalis strain to produce L-ribulose by fermentation with a glucose/L-arabinose mixture. For the uptake of L-arabinose as a substrate and conversion of L-arabinose to L-ribulose, two heterologous genes coding for L-arabinose transporter and L-arabinose isomerase, were constitutively expressed in C. tropicalis under the GAPDH promoter. The Arabidopsis thaliana-originated L-arabinose transporter gene (STP2)-expressing strain exhibited a high L-arabinose uptake rate of 0.103 g/g cell/h and the expression of L-arabinose isomerase from Lactobacillus sakei 23 K showed 30% of conversion (9 g/L) from 30 g/L of L-arabinose. This genetically engineered strain can be used for L-ribulose production by fermentation using mixed sugars of glucose and L-arabinose.</P>
Lee, Y.J.,Lee, S.J.,Kim, S.B.,Lee, S.J.,Lee, S.H.,Lee, D.W. North-Holland Pub ; Elsevier Science Ltd 2014 FEBS letters Vol.588 No.6
Structural genomics demonstrates that despite low levels of structural similarity of proteins comprising a metabolic pathway, their substrate binding regions are likely to be conserved. Herein based on the 3D-structures of the α/β-fold proteins involved in the ara operon, we attempted to predict the substrate binding residues of thermophilic Geobacillus stearothermophilusl-arabinose isomerase (GSAI) with no 3D-structure available. Comparison of the structures of l-arabinose catabolic enzymes revealed a conserved feature to form the substrate-binding modules, which can be extended to predict the substrate binding site of GSAI (i.e., D195, E261 and E333). Moreover, these data implicated that proteins in the l-arabinose metabolic pathway might retain their substrate binding niches as the modular structure through conserved molecular evolution even with totally different structural scaffolds.
Hong, Young-Ho,Lee, Dong-Woo,Pyun, Yu-Ryang,Lee, Sung Haeng American Chemical Society 2011 Journal of agricultural and food chemistry Vol.59 No.24
<P>Hyperthermophilic L-arabinose isomerases (AIs) are useful in the commercial production of D-tagatose as a low-calorie bulk sweetener. Their catalysis and thermostability are highly dependent on metals, which is a major drawback in food applications. To study the role of metal ions in the thermostability and catalysis of hyperthermophilic AI, four enzyme chimeras were generated by PCR-based hybridization to replace the variable N- and C-terminal regions of hyperthermophilic Thermotoga maritima AI (TMAI) and thermophilic Geobacillus stearothermophilus AT (GSAI) with those of the homologous mesophilic Bacillus halodurans AI (BHAI). Unlike Mn2+-dependent TMAI, the GSAI- and TMAI-based hybrids with the 72 C-terminal residues of BHAI were not metal-dependent for catalytic activity. By contrast, the catalytic activities of the TMAI- and GSAI-based hybrids containing the N-terminus (residues 1-89) of BHAI were significantly enhanced by metals, but their thermostabilities were poor even in the presence of Mn2+, indicating that the effects of metals on catalysis and thermostability involve different structural regions. Moreover, in contrast to the C-terminal truncate (Delta 20 residues) of GSAI, the N-terminal truncate (Delta 7 residues) exhibited no activity due to loss of its native structure. The data thus strongly suggest that the metal dependence of the catalysis and thermostability of hyperthermophilic Ails evolved separately to optimize their activity and thermostability at elevated temperatures. This may provide effective target regions for engineering, thereby meeting industrial demands for the production of D-tagatose.</P>
Kim, Ho Myeong,Song, Younho,Wi, Seung Gon,Bae, Hyeun-Jong Elsevier Science Publishers 2017 Journal of biotechnology Vol.260 No.-
<P>The rapid increase of agricultural waste is becoming a burgeoning problem and considerable efforts are being made by numerous researchers to convert it into a high-value resource material. Onion waste is one of the biggest issues in a world of dwindling resource. In this study, the potential of onion juice residue (OJR) for producing valuable rare sugar or bioethanol was evaluated. Purified Paenibacillus polymyxa L-arabinose isomerase (PPAI) has a molecular weight of approximately 53 kDa, and exhibits maximal activity at 30 degrees C and pH 7.5 in the presence of 0.8 mM Mn2+. PPAI can produce 0.99 g D-tagatose from 10 g OJR. In order to present another application for OJR, we produced 1.56 g bioethanol from 10 g OJR through a bioconversion and fermentation process. These results indicate that PPAI can be used for producing rare sugars in an industrial setting, and OJR can be converted to D-tagatose and bioethanol.</P>
ENHANCED STABILITY OF BACILLUS LICHENIFORMIS L-ARABINOSE ISOMERASE BY IMMOBILIZATION WITH ALGINATE
Zhang, Ye-Wang,Prabhu, Ponnandy,Lee, Jung-Kul,Kim, In-Won Taylor Francis 2009 PREPARATIVE BIOCHEMISTRY AND BIOTECHNOLOGY Vol.40 No.1
<P> Recombinant Escherichia coli whole cells harboring Bacillus licheniformis L-arabinose isomerase (BLAI) were harvested to prepare alginate-immobilized biocatalysts. The operational conditions for immobilization were optimized according to relative activity and the cell leakage of the immobilized cell. The optimal conditions are as follows: alginate concentration, Ca2+ concentration, cell mass loading, and curing time were 2% (w/v), 0.1 M, 50 g l-1, and 4 hours, respectively. After immobilization, cross-linking with 0.1% glutaraldehyde significantly reduced cell leakage. The immobilized whole cells harboring BLAI were very stable with 89% residual activity remaining after 33 days of incubation at 50°C and were much more stable than the free enzyme and cells. The results showed that immobilizing whole cells harboring BLAI is suitable for use as a biocatalyst in the production of L-ribulose, largely due to its high stability and low cost.</P>