2,5-Furandicarboxylic
acid (FDCA) is a promising biobased building
block for the synthesis of polymers. In this work, a novel whole-cell
biocatalyst was constructed by coexpressing vanillin dehydrogenase
(VDH1) and HMF/furfural oxidoreductase (HmfH) in Escherichia
coli for cascade catalytic oxidation of 5-hydroxymethylfurfural
(HMF) to FDCA under sacrificial substrate-free conditions. HMF was
rapidly transformed to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA)
by VDH1, followed by subsequent oxidation to 5-formyl-2-furancarboxylic
acid (FFCA) by HmfH, and finally, FFCA was converted to FDCA by VDH1
and/or HmfH. Under pH-controlled conditions, the biocatalyst enabled
efficient synthesis of FDCA from 150 mM HMF in a 96% yield. Besides,
FDCA was prepared in the gram scale with a productivity of around
0.4 g/L h.
Furan carboxylic acids are useful chemicals in various industries. In this work, biocatalytic production of furan carboxylic acids was reported with high productivities by cofactor‐engineered Escherichia coli cells. NADH oxidase (NOX) was introduced into E. coli harboring aldehyde dehydrogenases (ALDHs) to promote intracellular NAD+ regeneration, thus significantly enhancing ALDH‐catalyzed oxidation. These engineered biocatalysts were capable of efficient aerobic oxidation of a variety of aromatic aldehydes. More importantly, they exhibited high substrate tolerance toward toxic furans. E. coli co‐expressing vanillin dehydrogenase and NOX (E. coli_CtVDH1_NOX) enabled efficient oxidation of 250 mM of 5‐hydroxymethylfurfural (HMF) to 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA), providing a productivity of 3.7 g/L h. With E. coli_CtVDH2_NOX as catalyst, up to 240 mM of furfural and 5‐methoxymethylfurfural (MMF) could be smoothly oxidized. 2‐Furoic acid (FCA, 227 mM) and 5‐methoxymethyl‐2‐furancarboxylic acid (MMFCA, 287 mM) were produced in fed‐batch synthesis, providing the productivities of 2.0 and 5.6 g/L h, respectively.
TiO (Degussa P25) photocatalysts harboring abundant oxygen vacancies (Vacuum P25) were manufactured using a simple and economic Vacuum deoxidation process. Control experiments showed that temperature and time of vacuum deoxidation had a significant effect on Vacuum P25 photocatalytic activity. After 240 min of visible light illumination, the optimal Vacuum P25 photocatalysts (vacuum deoxidation treated at 330 °C for 3 h) reach as high as 94% and 88% of photodegradation efficiency for rhodamine B (RhB) and tetracycline, respectively, which are around 4.5 and 4.9 times as that of pristine P25. The XPS, PL and EPR analyses indicated that the oxygen vacancies were produced in the Vacuum P25 during the vacuum deoxidation process. The oxygen vacancy states can produce vacancy energy level located below the conduction band minimum, which resulting in the bandgap narrowing, thus extending the photoresponse wavelength range of Vacuum P25. The positron annihilation analysis indicated that the concentrations ratio of bulk and surface oxygen vacancies could be adjusted by changing the vacuum deoxidation temperature and time. Decreasing the ratio of bulk and surface oxygen vacancies was shown to improve photogenerated electron-hole pair separation efficiency, which leads to an obvious enhancement of the visible photocatalytic activities of Vacuum P25.
A stretchable fluorescent optical
fiber provides a flexible platform
for wearable functional devices due to its stretchability and immunity
to electromagnetic interference. However, for wearable applications,
stretchable fiber sensors suffer from severe body movement-induced
strain interference. Here, we report a stretchable optical sensor
with strain-decoupling ability. The stretchable core-clad structured
optical fiber is prepared with fluorescent nanoparticles and silicone-based
elastomers that enable both efficient excitation light delivery and
fluorescence collection. The excitation light loss and fluorescence
intensity exhibit a linear response to the sensing variables and strain
change, which have been utilized as the sensing parameters to decouple
the strain from the sensing variables. Our strain-decoupled scheme
is widely applicable to other stretchable fluorescent optical fiber
sensors that are simultaneously subject to strain. In the experiment
described here, the temperature-sensitive fluorescent nanoparticle-doped
stretchable fluorescent optical fiber exhibits stable temperature-sensing
in the range −10 to 60 °C, with an uncertainty as low
as ±0.23 °C and a relative sensitivity of 1.3% °C–1, even when it is subjected to large strain up to
40%. We demonstrate sensor-integrated wearable masks and gloves, which
can simultaneously measure physiological thermal changes and the movement
of the wrist joint. Our sensor shows great promise as a technology
for wearable health monitoring.
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