Microbial synthesis of N, P co-doped carbon supported PtCu catalysts for oxygen reduction reaction

Developing highly efficient and stable platinum-based electrocatalyst for oxygen reduction reaction(ORR) is critical to expediting commercialization of fuel cells.Herein,several PtCu alloy nanocatalysts supported on N,P co-doped carbon(PtCu/NPC) were prepared by microbial-sorption and carbonization-reduction.Among them,PtCu/NPC-700 ℃ exhibits excellent catalytic performance for ORR with a mass activity of 0.895 A mg_(pt)^(-1)(@0.9 V) which is 8.29 folds of commercial Pt/C.Additionally,the ECSA and MA of PtCu/NPC-700℃ only decrease by 14.2% and 18.7% respectively,while Pt/C decreases by 35.2% and 52.8% after 10,000 cycles of ADT test.Moreover,the PtCu/NPC-700℃ catalyst emanates a maximum power density of 715 mW cm^(-2) and only 11.1% loss of maximum power density after 10,000 ADTs in single-cell test,indicating PtCu/NPC-700℃ also manifests higher activity and durability in actual single-cell operation than Pt/C.This research provides an easy and novel strategy for developing highly active and durable Pt-based alloy catalyst.

Development of Biotechnology for Microbial Synthesis of Gold and Silver Nanoparticles

Several bacterial strains of Actinomycetes belonging to Streptomyces and Arthrobacter genera for the first time were used to study the biotechnology of synthesis of gold and silver nanoparticles. The experimental conditions of gold and silver nanoparticles production by the cells of studied strains in aqueous chloroauric acid （HAuCIq） and in silver nitrate （AgNO3） solutions, respectively, were determined. Concentration and time-dependences of nanoparticle formation were investigated. The complex of optical and analytical methods was used for testing the gold and silver nanoparticles in the bacterial biomass. The TEM （Transmission Electron Microscopy） and XRD （X-ray Diffraction） data in all cases demonstrated the presence of crystals with fcc （face centered cubic） structure. The results obtained show that the Actinomycetes are capable of producing gold and silver nanoparticles of spherical shape extracellularly when exposed to suitable compounds. The particle size distribution shows that the sizes of nanoparticles are in the range of 5 nm to 80 nm. The biomass obtained may be used for industrial as well as medical and pharmaceutical purposes.

Enzyme engineering in microbial biosynthesis of terpenoids:progress and perspectives

Terpenoids,known for their structural and functional diversity,are highly valued,especially in food,cosmetics,and cleaning products.Microbial biosynthesis has emerged as a sustainable and environmentally friendly approach for the production of terpenoids.However,the natural enzymes involved in the synthesis of terpenoids have problems such as low activity,poor specificity,and insufficient stability,which limit the biosynthesis efficiency.Enzyme engineering plays a pivotal role in the microbial synthesis of terpenoids.By modifying the structures and functions of key enzymes,researchers have significantly improved the catalytic activity,specificity,and stability of enzymes related to terpenoid synthesis,providing strong support for the sustainable production of terpenoids.This article reviews the strategies for the modification of key enzymes in microbial synthesis of terpenoids,including improving enzyme activity and stability,changing specificity,and promoting mass transfer through multi-enzyme collaboration.Additionally,this article looks forward to the challenges and development directions of enzyme engineering in the microbial synthesis of terpenoids.

Complete biosynthesis of the phenylethanoid glycoside verbascoside

Verbascoside,which was first discovered in 1963,is a well-known phenylethanoid glycoside(PhG)that exhibits antioxidant,anti-inflammatory,antimicrobial,and neuroprotective activities and contributes to the therapeutic effects of many medicinal plants.However,the biosynthetic pathway of verbascoside remains to be fully elucidated.Here,we report the identification of two missing enzymes in the verbascoside biosynthesis pathway by transcriptome mining and in vitro enzymatic assays.Specifically,a BAHD acyltransferase(hydroxycinnamoyl-CoA:salidroside hydroxycinnamoyltransferase[SHCT])was shown to catalyze the regioselective acylation of salidroside to form osmanthuside A,and a CYP98 hydroxylase(osmanthuside B 3,30-hydroxylase[OBH])was shown to catalyze meta-hydroxylations of the p-coumaroyl and tyrosol moieties of osmanthuside B to complete the biosynthesis of verbascoside.Because SHCTs and OBHs are found in many Lamiales species that produce verbascoside,this pathway may be general.The findings from the study provide novel insights into the formation of caffeoyl and hydroxytyrosol moieties in natural product biosynthetic pathways.In addition,with the newly acquired enzymes,we achieved heterologous production of osmanthuside B,verbascoside,and ligupurpuroside B in Escherichia coli;this work lays a foundation for sustainable production of verbascoside and other PhGs in micro-organisms.

A microbially based approach for the asymmetric synthesis of both enantiomers of R-and S-fluoxetine

Both enantiomers of fluoxetine were synthesized in five steps from ethyl benzoylacetate (1)using microbial-chemical approach with overall yields of 59% and 62% respectively.(S)-Enan- tiomer can be obtained in >99% e.e.by resting cell of baker's yeast and the R form was produced in 81 % e.e.by immobilized Geotrichum sp.G 38.

Oligo(p-phenylenevinylene)-rhodium complex as intracellular catalyst for enhancing biosynthesis of polyhydroxybutyrate biomaterials

Microbial synthesis utilizes sustainable resources to produce valuable chemicals,as a potential alternative to petroleum-based chemical industry.Although metabolic engineering is an efficient method to enhance the biosynthesis efficacy of microorganisms,it requires complicated biological procedures.Herein,we report a facile intracellular catalysis system for augmenting the production of bio-based material in microorganism.Covalent linking of oligo(p-phenylenevinylene)(OPV)and cyclopentadienyl rhodium(Ⅲ)bipyridine offers intracellular metal catalyst(OPV-Rh).The OPV-Rh complex displayed certain resistance to toxic biomolecules,which guaranteed its catalytic activity in complicated biological systems.With uptake by Gramnegative bacterium Ralstonia eutropha H16(R.eutropha H16),the OPV-Rh complex promotes the transformation of intracellular NADP+to NADPH,which further enhances the biosynthesis of polyhydroxybutyrate(PHB)by this microorganism.This work demonstrates that synthetic metal catalyst can be employed for regulating microbial biosynthesis intracellularly.

Biosynthesis, property comparison, and hemocompatibility of bacterial and haloarchaeal poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polyhydroxyalkanoates （PHAs） are a class of natural biopolyesters accumulated intracellularly by many microorganisms. These polymers have attracted particular attention as green plastic in biomedical and industrial applications due to their good biodegradability and bio- compatibility. Poly（3-hydroxybutyrate-co-3-hydroxyvaler- ate） （PHBV） is one of the most common members of PHAs. However, there is no report comparing the properties of PHBV from different groups of producers, e.g., bacteria and haloarchaea. In this study, two types of PHBV copolymers were synthesized in Halogranum amylolyticum and Ralstonia eutropha, respectively, by feeding different carbon sources. They possessed a similar concentration of 3HV monomers （21 tool%） and were named PHBV-H （produced by H. arnylolyticum） and PHBV-B （produced by R. eutropha） based on their source. Interestingly, they exhibited different behaviors especially in thermal stabil- ity, melting temperature, crystallinity percentage, and mechanical properties. Furthermore, the films of PHBV-Hand PHBV-B possessed different surface properties, such as surface roughness, wettability, and surface free energy. The value of hemolysis on the PHBV-H film was lower in comparison with the PHBV-B film, although both values were within the limit of 5 % permissible for biomaterials. Notably, few inactivated platelets adhered to the surface of the PHBV-H film, whereas numerous activated platelets were seen on film PHBV-B. These results indicated that PHBV-H was a better potential component of blood-contact biomaterials than PHBV-B. Our study clearly revealed that the properties of PHAs are source dependent and haloarchaeal species provide a new opportunity for the production of desired PHAs.