Managing water scarcity at a river basin scale with economic instruments

This paper presents a conceptual framework for both assessing the role of economic instruments, and reshaping them in order to enhance their contribution to the goals of managing water scarcity. Water management problems stem from the mismatch between a multitude of individual decisions, on the one hand, and the current and projected status of water resources on the other. Economics can provide valuable incentives that drive individual decisions, and can design efficient instruments to address water governance problems in a context of conflicting interests and relevant transaction costs. Yet, instruments such as water pricing or trading are mostly based on general principles of welfare economics that are not readily applicable to assets as complex as water. A flaw in welfare economic approaches lies in the presumption that economic instruments may be good orbad on their own (e.g., finding the "right" price). This vision changes radically when we focus on the problem, instead of the instrument. In this paper, we examine how economic instruments to achieve welfare-enhancing water resource outcomes can realize their full potential in basin-scale management contexts. We follow a political economy perspective that views conflicts between public and private interest as the main instrumental challenge of water management. Our analysis allows us to better understand the critical importance of economic instruments for reconciling individual actions towards collective ambitions of water efficiency, equity and sustainability with lessons for later-adopting jurisdictions. Rather than providing panaceas, the successful design and implementation of economic instruments as key river basin management arrangements involves high transaction costs, wide institutional changes and collective action at different levels

The Alcohol Dehydrogenase System in the Xylose-Fermenting Yeast Candida maltosa

The alcohol dehydrogenase (ADH) system plays a critical role in sugar metabolism involving in not only ethanol formation and consumption but also the general "cofactor balance" mechanism. Candida maltosa is able to ferment glucose as well as xylose to produce a significant amount of ethanol. Here we report the ADH system in C. maltosa composed of three microbial group I ADH genes (CmADH1, CmADH2A and CmADH2B), mainly focusing on its metabolic regulation and physiological function.Genetic analysis indicated that CmADH2A and CmADH2B tandemly located on the chromosome could be derived from tandem gene duplication. In vitro characterization of enzymatic properties revealed that all the three CmADHs had broad substrate specificities. Homo- and heterotetramers of CmADH1 and CmADH2A were demonstrated by zymogram analysis, and their expression profiles and physiological functions were different with respect to carbon sources and growth phases. Fermentation studies of ADH2A-deficient mutant showed that CmADH2A was directly related to NAD regeneration during xylose metabolism since CmADH2A deficiency resulted in a significant accumulation of glycerol.Our results revealed that CmADH1 was responsible for ethanol formation during glucose metabolism, whereas CmADH2A was glucose-repressed and functioned to convert the accumulated ethanol to acetaldehyde. To our knowledge, this is the first demonstration of function separation and glucose repression of ADH genes in xylose-fermenting yeasts. On the other hand, CmADH1 and CmADH2A were both involved in ethanol formation with NAD regeneration to maintain NADH/NAD ratio in favor of producing xylitol from xylose. In contrast, CmADH2B was expressed at a much lower level than the other two CmADH genes, and its function is to be further confirmed

The political nexus between water and economics in Brazil:A critique of recent policy reforms

The reform of water policies in Brazil has involved a combination of regulatory norms and economic-incentive instruments. Nonetheless, contrary to its formal objectives, the process has largely failed to prevent widespread environmental impacts and growing spatial and sectoral conflicts. The main reason for such failures is the perverse influence of market rationality, which is particularly evident in the reorganization of the public sector, the quantification of the monetary value of water, and the payment for environmental services

Triose Phosphate Isomerase Deficiency Is Caused by Altered Dimerization–Not Catalytic Inactivity–of the Mutant Enzymes

Triosephosphate isomerase (TPI) deficiency is an autosomal recessive disorder caused by various mutations in the gene encoding the key glycolytic enzyme TPI. A drastic decrease in TPI activity and an increased level of its substrate, dihydroxyacetone phosphate, have been measured in unpurified cell extracts of affected individuals. These observations allowed concluding that the different mutations in the TPI alleles result in catalytically inactive enzymes. However, despite a high occurrence of TPI null alleles within several human populations, the frequency of this disorder is exceptionally rare. In order to address this apparent discrepancy, we generated a yeast model allowing us to perform comparative in vivo analyses of the enzymatic and functional properties of the different enzyme variants. We discovered that the majority of these variants exhibit no reduced catalytic activity per se. Instead, we observed, the dimerization behavior of TPI is influenced by the particular mutations investigated, and by the use of a potential alternative translation initiation site in the TPI gene. Additionally, we demonstrated that the overexpression of the most frequent TPI variant, Glu104Asp, which displays altered dimerization features, results in diminished endogenous TPI levels in mammalian cells. Thus, our results reveal that enzyme deregulation attributable to aberrant dimerization of TPI, rather than direct catalytic inactivation of the enzyme, underlies the pathogenesis of TPI deficiency. Finally, we discovered that yeast cells expressing a TPI variant exhibiting reduced catalytic activity are more resistant against oxidative stress caused by the thiol-oxidizing reagent diamide. This observed advantage might serve to explain the high allelic frequency of TPI null alleles detected among human populations