Whether to Abolish or Introduce Dual Regulation as Trade and Environmental Policy?

China,which has already introduced an environmental tax in an effort to decarbonize,has recently begun emissions trading and is using two environmental policies in tandem,but there are concerns about the impact on growth and trade.Trade and environmental policies affect firms'entry and exit,resulting in changes in aggregate productivity and pollution emissions.This study compares the impacts of single regulation and dual regulation on welfare,using a research-and-development based growth model with heterogeneous firms.Under single regulation,the cleansing effect of trade liberalization could be undermined.Under dual regulation,trade liberalization decreases pollution and improves average productivity whereas decreasing total permits reduces pollution.From the perspective of improving welfare it is desirable to choose dual regulation because trade liberalization can reduce total pollution emissions via the cleansing effect of trade liberalization.

Enhancing single-cell hyaluronic acid biosynthesis by microbial morphology engineering

Microbial morphology engineering is a novel approach for cell factory to improve the titer of target product in bio-manufacture.Hyaluronic acid(HA),a valuable glycosaminoglycan polymerized by HA synthase(HAS),a membrane protein,is particularly selected as the model product to improve its single-cell HA-producing capacity via morphology engineering.DivIVA and FtsZ,the cell-elongation and cell division related protein,respectively,were both down/up dual regulated in C.glutamicum via weak promoter substitution or plasmid overexpression.Different from the natural short-rod shape,varied morphologies of engineered cells,i.e.small-ellipsoid-like(DivIVA-reduced),bulb-like(DivIVA-enhanced),long-rod(FtsZ-reduced)and dumbbell-like(FtsZ-enhanced),were observed.Applying these morphology-changed cells as hosts for HA production,the reduced expression of both DivIVA and FtsZ seriously inhibited normal cell growth;meanwhile,overexpression of DivIVA didn't show morphology changes,but overexpression of FtsZ surprisingly change the cell-shape into long and thick rod with remarkably enlarged single-cell surface area(more than 5.2-fold-increase).And finally,the single-cell HA-producing capacity of the FtsZ-overexpressed C.glutamicum was immensely improved by 13.5-folds.Flow cytometry analyses verified that the single-cell HAS amount on membrane was enhanced by 2.1 folds.This work is pretty valuable for high titer synthesis of diverse metabolic products with microbial cell factory.