1.Lyotropic Liquid Crystalline Cubic Phases as Versatile Host Matrices for Membrane-Bound Enzymes.
Sun W1, Vallooran JJ1, Fong WK1,2, Mezzenga R1. J Phys Chem Lett. 2016 Apr 8:1507-1512. [Epub ahead of print]
Lyotropic liquid crystalline cubic mesophases can function as host matrices for enzymes because of their biomimetic structural characteristics, optical transparency, and capability to coexist with water. This study demonstrates that the in meso immobilized membrane-bound enzyme d-fructose dehydrogenase (FDH) preserves its full activity, follows ideal Michaelis-Menten kinetics, and shows improved stability compared to its behavior in solution. Even after 5 days, the immobilized FDH retained its full activity in meso, whereas a model hydrophilic enzyme, horseradish peroxidase, maintained only 21% of its original activity. We reason that the lipidic bilayers in the three-dimensional structures of cubic mesophases provide an ideal environment for the reconstitution of a membrane-bound enzyme. The preserved activity, long-term stability, and reusability demonstrate that these hybrid nanomaterials are ideal matrices for biosensing and biocatalytic fuel cell applications.
2.Analysis and optimization of triacylglycerol synthesis in novel oleaginous Rhodococcus and Streptomyces strains isolated from desert soil.
Röttig A1, Hauschild P1, Madkour MH2, Al-Ansari AM2, Almakishah NH2, Steinbüchel A3. J Biotechnol. 2016 May 10;225:48-56. doi: 10.1016/j.jbiotec.2016.03.040. Epub 2016 Mar 23.
As oleaginous microorganisms represent an upcoming novel feedstock for the biotechnological production of lipids or lipid-derived biofuels, we searched for novel, lipid-producing strains in desert soil. This was encouraged by the hypothesis that neutral lipids represent an ideal storage compound, especially under arid conditions, as several animals are known to outlast long periods in absence of drinking water by metabolizing their body fat. Ten lipid-accumulating bacterial strains, affiliated to the genera Bacillus, Cupriavidus, Nocardia, Rhodococcus and Streptomyces, were isolated from arid desert soil due to their ability to synthesize poly(β-hydroxybutyrate), triacylglycerols or wax esters. Particularly two Streptomyces sp. strains and one Rhodococcus sp. strain accumulate significant amounts of TAG under storage conditions under optimized cultivation conditions. Rhodococcus sp. A27 and Streptomyces sp. G49 synthesized approx. 30% (w/w) fatty acids from fructose or cellobiose, respectively, while Streptomyces isolate G25 reached a cellular fatty acid content of nearly 50% (w/w) when cultivated with cellobiose.
3.T-to-R switch of muscle fructose-1,6-bisphosphatase involves fundamental changes of secondary and quaternary structure.
Barciszewski J1, Wisniewski J2, Kolodziejczyk R3, Jaskolski M1, Rakus D2, Dzugaj A4. Acta Crystallogr D Struct Biol. 2016 Apr 1;72(Pt 4):536-50. doi: 10.1107/S2059798316001765. Epub 2016 Mar 30.
Fructose-1,6-bisphosphatase (FBPase) catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and is a key enzyme of gluconeogenesis and glyconeogenesis and, more generally, of the control of energy metabolism and glucose homeostasis. Vertebrates, and notably Homo sapiens, express two FBPase isoforms. The liver isozyme is expressed mainly in gluconeogenic organs, where it functions as a regulator of glucose synthesis. The muscle isoform is expressed in all cells, and recent studies have demonstrated that its role goes far beyond the enzymatic function, as it can interact with various nuclear and mitochondrial proteins. Even in its enzymatic function, the muscle enzyme is different from the liver isoform, as it is 100-fold more susceptible to allosteric inhibition by AMP and this effect can be abrogated by complex formation with aldolase. All FBPases are homotetramers composed of two intimate dimers: the upper dimer and the lower dimer.
4.Construction of a Food Grade Recombinant Bacillus subtilis Based on Replicative Plasmids with an Auxotrophic Marker for Biotransformation of d-Fructose to d-Allulose.
He W1, Mu W1, Jiang B1, Yan X2, Zhang T1. J Agric Food Chem. 2016 Apr 14. [Epub ahead of print]
A food grade recombinant Bacillus subtilis that produces d-psicose 3-epimerase (DPEase; EC 22.214.171.124) was constructed by transforming a replicative multicopy plasmid with a d-alanine racemase gene marker into B. subtilis 1A751 with the d-alanine racemase gene knocked out. The DPEase was expressed in B. subtilis without antibiotic resistance genes and without adding antibiotics during fermentation. Whole cells of the food grade recombinant B. subtilis were used to biotransform d-fructose to d-allulose. The two tandem promoters, including the HpaII and P43 promoters, increased expression levels compared to the use of one promoter, HpaII. For large-scale d-allulose production, the optimal enzyme dose was 40 enzyme activity units of dry cells per gram of d-fructose, which produced a 28.5% turnover yield in 60 min. The recombinant plasmid exhibited stability over 100 generations. This food grade recombinant B. subtilis may be used for large-scale d-allulose production in the food industry.