Nano-Porous Light-Emitting Silicon Chip as a Potential Biosensor Platform

Nano-porous silicon (PS) offers a potential platform for biosensors with benefits both in terms of light emission and the large functional surface area. A light emitting PS chip with a stable and functional surface was fabricated in our laboratory. When protein was deposited on it, the light emission was reduced in proportion to the protein concentration. Based on this property, we developed a rudimentary demonstration of a label-free sensor to detect bovine serum albumin (BSA). A serial concentration of BSA was applied to the light chip and the reduction in light emission was measured. The reduction of the light intensity was linearly related to the concentration of the BSA at concentrations below 10-5 M. The detection limit was 8×10-9 M

Co-immobilization multienzyme nanoreactor with co-factor regeneration for conversion of CO2

Multienzymatic conversion of carbon dioxide (CO2) into chemicals has been extensively studied. However, regeneration and reuse of co-factor are still the main problems for the efficient conversion of CO2. In this study, a nanoscale multienzyme reactor was constructed by encapsulating simultaneously carbonic anhydrase (CA), formate dehydrogenase (FateDH), co-factor (NADH), and glutamate dehydrogenases (GDH) into ZIF-8. In the multienzyme reactors, cationic polyelectrolyte (polyethyleneimine, PEI) was doped in the ZIF-8 by dissolving it in the precursors of ZIF-8. Co-factor (NADH) was anchored in ZIF-8 by ion exchange between PEI (positive charge) and co-factor (negative charge), and regenerated through GDH embedded in the ZIF-8, thus keeping high activity of FateDH. Activity recovery of FateDH in the multienzyme reactors reached 50%. Furthermore, the dissolution of CO2 in the reaction solution was increased significantly by the combination of CA and ZIF-8. As a result, the nanoscale multienzyme reactor exhibited superior capacity for conversion of CO2 to formate. Compared with free multienzyme system, formate yield was increased 4.6-fold by using the nanoscale multienzyme reactor. Furthermore, the nanoscale multienzyme reactor still retained 50% of its original productivity after 8 cycles, indicating excellent reusability

Bimetal based inorganic-carbonic anhydrase hybrid hydrogel membrane for CO2 capture

In this study, we synthesized for the first time a bimetal-based inorganic-carbonic anhydrase (CA) hybrid nanoflower to immobilize CA using Cu2+ and Zn2+ instead of single metal ion. Subsequently, the synthesized bimetallic hybrid nanoflowers (CANF) were embedded into the poly(vinyl alcohol) (PVA)-chitosan (CS) hydrogel networks to obtain PVA/CS@CANF hydrogel membrane. The CANF exhibited a significantly higher activity recovery of 70 % compared with 35 % with CA/Zn3(PO4)2 hybrid nanoflowers and 10 % with CA/Cu3(PO4)2 hybrid nanoflowers. The PVA/CS@CANF hydrogel membrane possessed excellent mechanical strength, high catalytic activity, and were easy to flow out without centrifugation or filtration. At the same time, the PVA/CS@CANF displayed higher thermostability, storage stability, and pH stability than free CA and CANF, and superior reusability and CO2 capture capacity. The hydrogel membrane maintained more than 75 % of its original activity after 8 cycles. However, CANF only maintained 12 % of its original activity. Furthermore, the amount of CaCO3 produced by PVA/CS@CANF membrane was 9.0-fold and 2.0-fold compared with free CA and CANF, respectively. Therefore, This approach to synthesizing bimetallic-based protein hybrid hydrogel membrane could have a bright future in CO2 capture

Genome Assembly and Annotation of a High-Polymalic Acid (PMLA) Producing Strain Aureobasidium melanogenum CGMCC18996 and Analysis of Its Key Proteins Related to PMLA Synthesis

In this study, we applied PacBio Sequel II and Illumina NovaSeq 6000 sequencing platforms to sequence the genome of a high-polymalic acid (PMLA)-producing strain, Aureobasidium melanogenum CGMCC18996, and used different assemblers to obtain a high-quality genome assembly, which was then annotated using transcriptomic data. The results indicated a total of 6 202 genes were found in the A. melanogenum genome, mainly involved in carbohydrate transport and metabolism, amino acid transport and metabolism, post-translational modification, RNA processing and modification. Meanwhile, functional annotation revealed that most genes in the genome were related to peroxisome in the strain. Transmission electron microscopy (TEM) indicated the existence of a circular peroxisome-like (glyoxysome) structure in the cells, demonstrating the ability to malic acid through the glyoxylate cycle. Finally, we predicted the protein structures of two enzymes related to PMLA biosynthesis, phosphoenolpyruvate carboxykinase (PCKA) and malate synthase (MASY). It was found that the enzymes could have the ability to synthesize malic acid. This study could provide a reference for metabolism regulation in A. melanogenum for improved PMLA production, and the assembled genome has been uploaded to the database, which could provide the basis for the future development and utilization of A. melanogenum CGMCC18996

Self-assembly of activated lipase hybrid nanoflowers with superior activity and enhanced stability

Lipase-inorganic hybrid nanoflowers were prepared using Ca3(PO4)2 as the inorganic component and lipase from Aspergillus oryzae (A. oryzae) as the organic component. The influences of metal ions with different valence, various additives (surfactant), and synthesis conditions on the activity of the lipase hybrid nanoflowers were systematically investigated. Results revealed that the valence state of metal ions played an important role on the shape and activity of lipase hybrid nanoflowers. The synthesized lipase hybrid nanoflowers using bivalence metal ions (Ca2+, Mn2+, and Zn2+) as the inorganic components exhibited relative high activity. However, very low activities were observed in the lipase hybrid nanoflowers using univalent metal ions (Ag+) or trivalent metal ions (Al3+, Fe3+). More importantly, Ca2+ not only induced self-assemble of lipase hybrid nanoflowers, but also activated the enzyme activity by inducing conformational changes in lipase from A. oryzae. As a result, lipase/Ca3(PO4)2 hybrid nanoflowers (hNF-lipase) exhibited the high activity. The hNF-lipase displayed 9, 12, and 61 folds higher activity than lipase/Ag3PO4 hybrid nanoflowers, lipase/AlPO4 hybrid nanoflowers, and lipase/FePO4 nanoflowers, respectively. Compared with free lipase, the hNF-lipase displayed 172 % increase in activities by using 0.15 mM Tween-80 as an activity inducer (activated hNF-lipase). Furthermore, the hNF-lipase and activated hNF-lipase exhibited increased stability against high temperature and denaturant, and had good storage stability and reusability

ICEberg: a web-based resource for integrative and conjugative elements found in Bacteria

ICEberg (http://db-mml.sjtu.edu.cn/ICEberg/) is an integrated database that provides comprehensive information about integrative and conjugative elements (ICEs) found in bacteria. ICEs are conjugative self-transmissible elements that can integrate into and excise from a host chromosome. An ICE contains three typical modules, integration and excision, conjugation, and regulation modules, that collectively promote vertical inheritance and periodic lateral gene flow. Many ICEs carry likely virulence determinants, antibiotic-resistant factors and/or genes coding for other beneficial traits. ICEberg offers a unique, highly organized, readily explorable archive of both predicted and experimentally supported ICE-relevant data. It currently contains details of 428 ICEs found in representatives of 124 bacterial species, and a collection of >400 directly related references. A broad range of similarity search, sequence alignment, genome context browser, phylogenetic and other functional analysis tools are readily accessible via ICEberg. We propose that ICEberg will facilitate efficient, multi-disciplinary and innovative exploration of bacterial ICEs and be of particular interest to researchers in the broad fields of prokaryotic evolution, pathogenesis, biotechnology and metabolism. The ICEberg database will be maintained, updated and improved regularly to ensure its ongoing maximum utility to the research community

Engineering allosteric inhibition of homoserine dehydrogenase by semi-rational saturation mutagenesis screening

Allosteric regulation by pathway products plays a vital role in amino acid metabolism. Homoserine dehydrogenase (HSD), the key enzyme for the biosynthesis of various aspartate family amino acids, is subject to feedback inhibition by l-threonine and l-isoleucine. The desensitized mutants with the potential for amino acid production remain limited. Herein, a semi-rational approach was proposed to relieve the feedback inhibition. HSD from Corynebacterium glutamicum (CgHSD) was first characterized as a homotetramer, and nine conservative sites at the tetramer interface were selected for saturation mutagenesis by structural simulations and sequence analysis. Then, we established a high-throughput screening (HTS) method based on resistance to l-threonine analog and successfully acquired two dominant mutants (I397V and A384D). Compared with the best-ever reported desensitized mutant G378E, both new mutants qualified the engineered strains with higher production of CgHSD-dependent amino acids. The mutant and wild-type enzymes were purified and assessed in the presence or absence of inhibitors. Both purified mutants maintained >90% activity with 10 mM l-threonine or 25 mM l-isoleucine. Moreover, they showed >50% higher specific activities than G378E without inhibitors. This work provides two competitive alternatives for constructing cell factories of CgHSD-related amino acids and derivatives. Moreover, the proposed approach can be applied to engineering other allosteric enzymes in the amino acid synthesis pathway

The Role of Lactic Acid Adsorption by Ion Exchange Chromatography

Background: The polyacrylic resin Amberlite IRA-67 is a promising adsorbent for lactic acid extraction from aqueous solution, but little systematic research has been devoted to the separation efficiency of lactic acid under different operating conditions. Methodology/Principal Findings: In this paper, we investigated the effects of temperature, resin dose and lactic acid loading concentration on the adsorption of lactic acid by Amberlite IRA-67 in batch kinetic experiments. The obtained kinetic data followed the pseudo-second order model well and both the equilibrium and ultimate adsorption slightly decreased with the increase of the temperature at 293–323K and 42.5 g/liter lactic acid loading concentration. The adsorption was a chemically heterogeneous process with a mean free energy value of 12.18 kJ/mol. According to the Boyd _ plot, the lactic acid uptake process was primarily found to be an intraparticle diffusion at a lower concentration (,50 g/liter) but a film diffusion at a higher concentration (.70 g/liter). The values of effective diffusion coefficient D i increased with temperature. By using our Equation (21), the negative values of DGu and DHu revealed that the adsorption process was spontaneous and exothermic. Moreover, the negative value of DSu reflected the decrease of solid-liquid interface randomness at the solid-liquid interface when adsorbing lactic acid on IRA-67. Conclusions/Significance: With the weakly basic resin IRA-67, in situ product removal of lactic acid can be accomplishe