Carotenoid biosynthesis and overproduction in Corynebacterium glutamicum

Heider S, Peters-Wendisch P, Wendisch VF. Carotenoid biosynthesis and overproduction in Corynebacterium glutamicum. BMC Microbiology. 2012;12(1): 198.Background Corynebacterium glutamicum contains the glycosylated C50 carotenoid decaprenoxanthin as yellow pigment. Starting from isopentenyl pyrophosphate, which is generated in the non-mevalonate pathway, decaprenoxanthin is synthesized via the intermediates farnesyl pyrophosphate, geranylgeranyl pyrophosphate, lycopene and flavuxanthin. Results Here, we showed that the genes of the carotenoid gene cluster crtE-cg0722-crtBIYeYfEb are co-transcribed and characterized defined gene deletion mutants. Gene deletion analysis revealed that crtI, crtEb, and crtYeYf, respectively, code for the only phytoene desaturase, lycopene elongase, and carotenoid C45/C50 epsilon-cyclase, respectively. However, the genome of C. glutamicum also encodes a second carotenoid gene cluster comprising crtB2I2-1/2 shown to be co-transcribed, as well. Ectopic expression of crtB2 could compensate for the lack of phytoene synthase CrtB in C. glutamicum DeltacrtB, thus, C. glutamicum possesses two functional phytoene synthases, namely CrtB and CrtB2. Genetic evidence for a crtI2-1/2 encoded phytoene desaturase could not be obtained since plasmid-borne expression of crtI2-1/2 did not compensate for the lack of phytoene desaturase CrtI in C. glutamicum DeltacrtI. The potential of C. glutamicum to overproduce carotenoids was estimated with lycopene as example. Deletion of the gene crtEb prevented conversion of lycopene to decaprenoxanthin and entailed accumulation of lycopene to 0.03 +/- 0.01 mg/g cell dry weight (CDW). When the genes crtE, crtB and crtI for conversion of geranylgeranyl pyrophosphate to lycopene were overexpressed in C. glutamicum DeltacrtEb intensely red-pigmented cells and an 80 fold increased lycopene content of 2.4 +/- 0.3 mg/g CDW were obtained. Conclusion C. glutamicum possesses a certain degree of redundancy in the biosynthesis of the C50 carotenoid decaprenoxanthin as it possesses two functional phytoene synthase genes. Already metabolic engineering of only the terminal reactions leading to lycopene resulted in considerable lycopene production indicating that C. glutamicum may serve as a potential host for carotenoid production

New Keynesian versus old Keynesian government spending multipliers

Renewed interest in fiscal policy has increased the use of quantitative models to evaluate policy. Because of modeling uncertainty, it is essential that policy evaluations be robust to alternative assumptions. We find that models currently being used in practice to evaluate fiscal policy stimulus proposals are not robust. Government spending multipliers in an alternative empirically-estimated and widely-cited new Keynesian model are much smaller than in these old Keynesian models; the estimated stimulus is extremely small with GDP and employment effects only one-sixth as large

Fiscal consolidation strategy: An update for the budget reform proposal of march 2013

Recently, we evaluated a fiscal consolidation strategy for the United States that would bring the government budget into balance by gradually reducing government spending relative to GDP to the ratio that prevailed prior to the crisis (Cogan et al, JEDC 2013). Specifically, we published an analysis of the macroeconomic consequences of the 2013 Budget Resolution that was passed by the U.S. House of Representatives in March 2012. In this note, we provide an update of our research that evaluates this year’s budget reform proposal that is to be discussed and voted on in the House of Representative in March 2013. Contrary to the views voiced by critics of fiscal consolidation, we show that such a reduction in government purchases and transfer payments can increase GDP immediately and permanently relative to a policy without spending restraint. Our research makes use of a modern structural model of the economy that incorporates the long-standing essential features of economics: opportunity costs, efficiency, foresight and incentives. GDP rises because households take into account that spending restraint helps avoid future increases in tax rates. Lower taxes imply less distorted incentives for work, investment and production relative to a scenario without fiscal consolidation and lead to higher growth

Fiscal consolidation strategy : [Version 21 September 2012]

In the aftermath of the global financial crisis and great recession, many countries face substantial deficits and growing debts. In the United States, federal government outlays as a ratio to GDP rose substantially from about 19.5 percent before the crisis to over 24 percent after the crisis. In this paper we consider a fiscal consolidation strategy that brings the budget to balance by gradually reducing this spending ratio over time to the level that prevailed prior to the crisis. A crucial issue is the impact of such a consolidation strategy on the economy. We use structural macroeconomic models to estimate this impact focussing primarily on a dynamic stochastic general equilibrium model with price and wage rigidities and adjustment costs. We separate out the impact of reductions in government purchases and transfers, and we allow for a reduction in both distortionary taxes and government debt relative to the baseline of no consolidation. According to the model simulations GDP rises in the short run upon announcement and implementation of this fiscal consolidation strategy and remains higher than the baseline in the long run. We explore the role of the mix of expenditure cuts and tax reductions as well as gradualism in achieving this policy outcome. Finally, we conduct sensitivity studies regarding the type of model used and its parameterization

Fiscal consolidation strategy

In the aftermath of the global financial crisis and great recession, many countries face substantial deficits and growing debts. In the United States, federal government outlays as a ratio to GDP rose substantially from about 19.5 percent before the crisis to over 24 percent after the crisis. In this paper we consider a fiscal consolidation strategy that brings the budget to balance by gradually reducing this spending ratio over time to the level that prevailed prior to the crisis. A crucial issue is the impact of such a consolidation strategy on the economy. We use structural macroeconomic models to estimate this impact focussing primarily on a dynamic stochastic general equilibrium model with price and wage rigidities and adjustment costs. We separate out the impact of reductions in government purchases and transfers, and we allow for a reduction in both distortionary taxes and government debt relative to the baseline of no consolidation. According to the model simulations GDP rises in the short run upon announcement and implementation of this fiscal consolidation strategy and remains higher than the baseline in the long run. We explore the role of the mix of expenditure cuts and tax reductions as well as gradualism in achieving this policy outcome. Finally, we conduct sensitivity studies regarding the type of model used and its parameterization