Reactive oxygen species (ROS) are crucial molecules in cancer therapy. Unfortunately, the therapeutic efficiency of ROS is unsatisfactory in clinic, primarily due to their rigorous production conditions. By taking advantage of the intrinsic acidity and overproduction of H 2 O 2 in the tumor environment, we have reported an ROS nanoreactor based on core−shell-structured iron carbide (Fe 5 C 2 @Fe 3 O 4 ) nanoparticles (NPs) through the catalysis of the Fenton reaction. These NPs are able to release ferrous ions in acidic environments to disproportionate H 2 O 2 into • OH radicals, which effectively inhibits the proliferation of tumor cells both in vitro and in vivo. The high magnetization of Fe 5 C 2 @Fe 3 O 4 NPs is favorable for both magnetic targeting and T 2 -weighted magnetic resonance imaging (MRI). Ionization of these NPs simultaneously decreases the T 2 signal and enhances the T 1 signal in MRI, and this T 2 /T 1 switching process provides the visualization of ferrous ions release and ROS generation for the supervision of tumor curing. These Fe 5 C 2 @Fe 3 O 4 NPs show great potential in endogenous environment-excited cancer therapy with high efficiency and tumor specificity and can be guided further by MRI.

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High-fructose corn syrup (HFCS) is an agro-source product and has been the most commonly used substitute for sugar as sweetener in food industry due to its low price and high solution property. In this study, the F55 HFCS, rich in fructose and glucose, was first tested for biomass and docosahexaenoic acid productions as a mixed carbon source by a newly isolated Aurantiochytrium sp.YLH70. After the compositions of the HFCS media were optimized, the results showed that the HFCS with additions of metal ion and vitamin at low concentrations was suitable for biomass and docosahexaenoic acid productions and the metal ion and sea salt had the most significant effects on biomass production. During the 5-l fed-batch fermentation, total HFCS containing 180 g l(-1) reducing sugar was consumed and yields of biomass, lipid, and DHA could reach 78.5, 51, and 20.1 g l(-1), respectively, at 114 h. Meanwhile, the daily productivity and the reducing sugar conversion yield for docosahexaenoic acid were up to 4.23 g l(-1)day(-1) and 0.11 g g(-1). The fatty acid profile of Aurantiochytrium sp.YLH70 showed that 46.4% of total fatty acid was docosahexaenoic acid, suggesting that Aurantiochytrium sp.YLH70 was a promising DHA producer.

Rhodococcus erythropolis WZ010 was capable of producing optically pure (2S,3S)-2,3-butanediol in alcoholic fermentation. The gene encoding an acetoin(diacetyl) reductase from R. erythropolis WZ010 (ReADR) was cloned, overexpressed in Escherichia coli, and subsequently purified by Ni-affinity chromatography. ReADR in the native form appeared to be a homodimer with a calculated subunit size of 26,864, belonging to the family of the short-chain dehydrogenase/reductases. The enzyme accepted a broad range of substrates including aliphatic and aryl alcohols, aldehydes, and ketones. It exhibited remarkable tolerance to dimethyl sulfoxide (DMSO) and retained 53.6 % of the initial activity after 4 h incubation with 30 % (v/v) DMSO. The enzyme displayed absolute stereospecificity in the reduction of diacetyl to (2S,3S)-2,3-butanediol via (S)-acetoin. The optimal pH and temperature for diacetyl reduction were pH 7.0 and 30 °C, whereas those for (2S,3S)-2,3-butanediol oxidation were pH 9.5 and 25 °C. Under the optimized conditions, the activity of diacetyl reduction was 11.9-fold higher than that of (2S,3S)-2,3-butanediol oxidation. Kinetic parameters of the enzyme showed lower K(m) values and higher catalytic efficiency for diacetyl and NADH in comparison to those for (2S,3S)-2,3-butanediol and NAD⁺, suggesting its physiological role in favor of (2S,3S)-2,3-butanediol formation. Interestingly, the enzyme showed higher catalytic efficiency for (S)-1-phenylethanol oxidation than that for acetophenone reduction. ReADR-catalyzed asymmetric reduction of diacetyl was coupled with stereoselective oxidation of 1-phenylethanol, which simultaneously formed both (2S,3S)-2,3-butanediol and (R)-1-phenylethanol in great conversions and enantiomeric excess values.