Microbial production of cis,cis-muconic acid from aromatic compounds in engineered Pseudomonas

Industrial expansion has led to environmental pollution by xenobiotic compounds like polycyclic aromatic hydrocarbons and monoaromatic hydrocarbons.Pseudomonas spp.have broad metabolic potential for degrading aromatic compounds.The objective of this study was to develop a“biological funneling”strategy based on genetic modification to convert complex aromatic compounds into cis,cis-muconate(ccMA)using Pseudomonas putida B6-2 and P.brassicacearum MPDS as biocatalysts.The engineered strains B6-2(B6-2ΔcatBΔsalC)and MPDS(MPDSΔsalC(pUCP18k-catA))thrived with biphenyl or naphthalene as the sole carbon source and produced ccMA,attaining molar conversions of 95.3%(ccMA/biphenyl)and 100%(ccMA/naphthalene).Under mixed substrates,B6-2ΔcatBΔsalC grew on biphenyl as a carbon source and transformed ccMA from non-growth substrates benzoate or salicylate to obtain higher product concentration.Inserting exogenous clusters like bedDC1C2AB and xylCMAB allowed B6-2 recombinant strains to convert benzene and toluene to ccMA.In mixed substrates,constructed consortia of engineered strains B6-2 and MPDS specialized in catabolism of biphenyl and naphthalene;the highest molar conversion rate of ccMA from mixed substrates was 85.2%when B6-2ΔcatBΔsalC was added after 24 h of MPDSΔsalC(pUCP18k-catA)incubation with biphenyl and naphthalene.This study provides worthwhile insights into efficient production of ccMA from aromatic hydrocarbons by reusing complex pollutants.

Physiological effects of weightlessness: countermeasure system development for a long-term Chinese manned spaceflight

The Chinese space station will be built around 2020. As a national space laboratory, it will offer unique opportunities for studying the physiological effects of weightlessness and the efficacy of the countermeasures against such effects. In this paper, we described the development of countermeasure systems in the Chinese space program. To emphasize the need of the Chinese space program to implement its own program for developing countermeasures, we reviewed the literature on the negative physiological effects of weightlessness, the challenges of completing missions, the development of countermeasure devices, the establishment of countermeasure programs, and the efficacy of the countermeasure techniques in American and Russian manned spaceflights. In addition, a brief overview was provided on the Chinese research and development on countermeasures to discuss the current status and goals of the development of countermeasures against physiological problems associated with weightlessness.