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Enantiopure alcohols have received much attention due to their widespread use as pharmaceutical intermediates. In the asymmetric biosynthesis of enantiopure alcohols, the excellent performance of carbonyl reductase makes it be the best choice as the biocatalysts. In this work, an alkali-tolerant carbonyl reductase (BsCR, encoded by yueD) from Bacillus subtilis (strain 168) was obtained through gene mining, and successfully heterologously expressed in Escherichia coli with pET-32a. BsCR showed excellent alkali resistance and even can keep more than 70% of its peak activity after incubation in Tris–HCl buffer at pH 9.0 for 40 h. The Michaelis constants and maximal velocity of the BsCR to NADPH (A) and ethyl 4-chloroacetoacetate (B) are K m A = 5.390 × 10−2 mmol/L, K m B = 1.855 mmol/L, and V max = 147.3 μmol·min−1·mg−1, respectively. Applying the E. coli BL21(DE3)/pET-32a-yueD to catalyze asymmetric reduction of ethyl 4-chloroacetoacetate and acetophenone, the yield of S-CHBE reached 89.9% and S-1-phenyl ethanol reached 66.7%, and e.e. of both products reached more than 99%. This work provides a novel CR for asymmetric reduction. A carbonyl reductase (BsCR) and its gene were identified through gene mining, and overexpressed in Escherichia coli BL21(DE3) for whole-cell biocatalytic asymmetric reduction [ABSTRACT FROM AUTHOR]

Carbonyl reductase, as biocatalyst, is very important to chiral alcohols production through asymmetric reduction of carbonyl compound. A novel thermal stable carbonyl reductase from Bacillus cereus (BcCR) dependant on NADPH was obtained through a new genome mining strategy proposed in this work. By analyzing its amino acid sequence and structure, the BcCR should be a thermal stability and wide pH tolerance carbonyl reductase. Its gene was cloned by PCR with B. cereus genomic DNA as template. Its heterologous expression system, E. coli BL21 (DE3) plysS/pET28a-bccr, was constructed, and BcCR was successfully expressed. Enzymatic properties show that at 57.5 °C and pH 7.0 it can reach maximum reaction rate. Its Km and Vmax to ethyl 4-chloroacetoacetate is 1.85 mmol/L and 0.22 µmol/(min·mgprotein), respectively. It can catalyze the asymmetric reduction of the β-carbonyl compound, such as ethyl 4-chloroacetoacetate to ethyl S-4-chloro-3-hydroxybutyrate. This paper proposes a practical method for discovery of new carbonyl reductases, and provides a novel enzyme as biocatalyst for asymmetric reduction of β-carbonyl compound. [ABSTRACT FROM AUTHOR]

Sulfonated graphene nanosheet/gold nanoparticle (SGN/Au) hybrid was synthesized by electrostatic self-assembly of anionic SGN and positively charged gold nanoparticles. Due to the well-dispersivity of SGN in aqueous solution and its adequate negative charge, Au nanoparticles were assembled uniformly on graphene surface with high distribution. With the advantages of both graphene and Au nanoparticles, SGN/Au hybrid showed enhanced electrocatalytic activity towards O reduction. Furthermore, it provided a conductive and favorable microenvironment for the glucose oxidase (GOD) immobilization and thus promoted its direct electron transfer at the glassy carbon electrode. Based on the consumption of O caused by glucose at the interface of GOD electrode modified with SGN/Au hybrid, the modified electrode displayed satisfactory analytical performance, including high sensitivity (14.55 μA mM cm), low detection limit (0.2 mM), an acceptable linear range from 2 to 16 mM, and also the prevention from the interference of some species. These results indicated that the prepared SGN/Au hybrid is a promising candidate material for high-performance glucose biosensor. [ABSTRACT FROM AUTHOR]

We describe a highly sensitive and selective amperometric sensor for the determination of nitrite. A glassy carbon electrode was modified with a composite made from gold nanoparticles (AuNPs) and sulfonated graphene (SG). The modified electrode displays excellent electrocatalytic activity in terms of nitrite oxidation by giving much higher peak currents (at even lower oxidation overpotential) than those found for the bare electrode, the AuNPs-modified electrode, and the SG-modified electrode. The sensor has a linear response in the 10 μM to 3.96 mM concentration range, a very good detection sensitivity (45.44 μA mM), and a lower detection limit of 0.2 μM of nitrite. Most common ions and many environmental organic pollutants do not interfere. The sensor was successfully applied to the determination of nitrite in water samples, and the results were found to be consistent with the values obtained by spectrophotometry. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In order to reasonably utilize the abundant resources of high-phosphorus iron ore and ilmenite in China, the technology of top-blown smelting reduction with oxygen enrichment was used to smelt the mixed ore of high-phosphorus iron and ilmenite. The effect, which is related to basicity, reduction temperature, carbon-oxygen ratio and time of ventilated oxygen to iron recovery, dephosphorization rate, content of iron, phosphorus, sulfur and titanium in pig iron, was investigated in the experiment. The results show that an ideal outcome can be gained in condition of 6:4 ration on Mengqiao concentrate and Huimin iron ore, temperature of 1 500 °C, basicity of 1.3, 1.0 on molar ration of carbon to oxygen, time of 10 min on blowing-oxygen. The outcome is that there is no foamy slag in generation, a good separation of slag and iron, iron recovery with 91.41%, content of phosphorus with 0.27% and tilanium content less than 0.001%. The atmosphere of strong oxidizing in the upper of reduction container and high potential of oxygen in the composition of slag in this technique bring phosphorus, titanium and silicon into slag, which ensures less content of impurity in pig iron. [ABSTRACT FROM AUTHOR]