Efficient synthesis of tyrosol from L-tyrosine via heterologous Ehrlich pathway in Escherichia coli

For the efficient conversion of L-tyrosine(L-Tyr)to tyrosol,which is an aromatic compound widely used in the pharmaceutical and chemical industries,a novel four-enzyme cascade pathway based on the Ehrlich pathway of Saccharomyces cerevisiae was designed and reconstructed in Escherichia coli.Then,the expression levels of the relevant enzymes were coordinated using a modular approach and gene duplication after the identification of the pyruvate decarboxylase from Candida tropicalis(CtPDC)as the rate-limiting enzymatic step.In situ product removal(ISPR)strategy with XAD4 resins was explored to avoid product inhibition and further improve tyrosol yield.As a result,the titer and conversion rate of tyrosol obtained were 35.7 g·L^(-1) and 93.6%,respectively,in a 3-L bioreactor.Results presented here provide a potential enzymatic process for industrial production of tyrosol from cheap amino acids.

Thermally removable in-situ formed ZnO template for synthesis of hierarchically porous N-doped carbon nanofibers for enhanced electrocatalysis

Rational design and simple synthesis of one-dimensional nanofibers with high specific surface areas and hierarchically porous structures are still challenging. In the present work, a novel strategy utilizing a thermally removable template was developed to synthesize hierarchically porous N-doped carbon nanofibers （HP-NCNFs） through the use of simple electrospinning technology coupled with subsequent pyrolysis. During the pyrolysis process, ZnO nanoparticles can be formed in situ and act as a thermally removable template due to their decomposition and sublimation under high-temperature conditions. The resulting HP-NCNFs have lengths of up to hundreds of micrometers with an average diameter of 300 nm and possess a hierarchically porous structure throughout. Such unique structures endow HP-NCNFs with a high specific surface area of up to 829.5 m2-g 1, which is 2.6 times higher than that （323.2 m2.g 1） of conventional N-doped carbon nanofibers （NCNFs）. Compared with conventional NCNFs, the HP-NCNF catalyst exhibited greatly enhanced catalytic performance and improved kinetics for the oxygen reduction reaction （ORR） in alkaline media. Moreover, the HP-NCNFs even showed better stability and stronger methanol crossover effect tolerance than the commerdal Pt-C catalyst. The optimized ORR performance can be attributed to the synergetic contribution of continuous and three-dimensional （3D） cross-linked structures, graphene-like structure on the edge of the HP- NCNFs, high specific surface area, and a hierarchically porous structure.

Optimization of L(+)-Lactic Acid Fermentation Without Neutralisation of Rhizopus Oryzae Mutant RK02 by Low-Energy Ion Implantation

In order to get an industrial strain which can yield a high concentration of lactic acid for ISPR （in situ product removal）, the original strain Rhizopus oryzae RE3303 was mutated by low-energy ion beam implantation. A mutant RK02 was screened, and the factors such as the substrate concentration, nitrogen source concentration, inoculum size, seed age, aeration and temperature that affect the production of lactic acid were studied in detail. Under optimal con- ditions, the maximum concentration of L（＋）-lactic acid reached 34.85 g/L after 30 h shake-flask cultivation without adding any neutralisation （5% Glucose added）, which was a 146% increase in lactic acid production after ion implantation compared with the original strain. It was also shown that RK02 can be used in ISPR to reduce the number of times of separation.