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  • Articles  (22,737)
  • Springer  (22,737)
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  • Articles  (22,737)
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  • 1
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    The Geneva risk and insurance review 20 (1995), S. 7-8 
    ISSN: 1554-9658
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
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  • 2
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    The Geneva risk and insurance review 20 (1995), S. 5-5 
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    Topics: Economics
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  • 3
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    The Geneva risk and insurance review 20 (1995), S. 9-50 
    ISSN: 1554-9658
    Keywords: insurance ; risk sharing ; non-expected utility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper uses the tools and techniques of generalized expected utility analysis to explore the robustness of some of the classical basic results in insurance theory to departures from the expected utility hypothesis on agents' risk preferences. The areas explored consist of individual demand for coinsurance and deductible insurance, the structure of Pareto-efficient bilateral insurance contracts, the structure of Pareto-efficient multilateral risk-sharing agreements, and self-insurance and self-protection. Most, though not all, of the basic results in this area are found to be quite robust to dropping the expected utility hypothesis.
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  • 4
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    The Geneva risk and insurance review 20 (1995), S. 51-56 
    ISSN: 1554-9658
    Keywords: non-expected utility ; insurance economics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper discusses some aspects of the robustness of the classical insurance paradigm with respect to departures from the independence axiom of expected utility theory. The discussion focuses on the significance of the distinction between risk aversion and outcome convexity and the role of smoothness of the preferences in non-expected-utility analysis of insurance.
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  • 5
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    The Geneva risk and insurance review 20 (1995), S. 57-72 
    ISSN: 1554-9658
    Keywords: deductible insurance ; non-expected utility theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper identifies comparative statics results for insurance contracts that distinguish between various models of decision making under risk—specifically, expected utility, rank-dependent expected utility, and weighted utility. Insurance contracts offer full coverage above a deductible. Firms offer premium schedules that give the premium charged as a function of the deductible; households choose both an insurance company and a deductible to maximize utility. A competitive equilibrium requires zero expected profit for firms. We identify changes in the distribution of losses such that the optimal deductible increases for utility representations in a particular class but decreases for some representations outside that class. We give results both for the demand for insurance, as well as for the equilibrium contract.
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  • 6
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    The Geneva risk and insurance review 20 (1995), S. 73-91 
    ISSN: 1554-9658
    Keywords: increasing risk ; risk aversion ; non-expected utility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract The non-expected-utility theories of decision under risk have favored the appearance of new notions of increasing risk like monotone increasing risk (based on the notion of comonotonic random variables) or new notions of risk aversion like aversion to monotone increasing risk, in better agreement with these new theories. After a survey of all the possible notions of increasing risk and of risk aversion and their intrinsic definitions, we show that contrary to expected-utility theory where all the notions of risk aversion have the same characterization (u concave), in the framework of rank-dependent expected utility (one of the most well known of the non-expectedutility models), the characterizations of all these notions of risk aversion are different. Moreover, we show that, even in the expected-utility framework, the new notion of monotone increasing risk can give better answers to some problems of comparative statics such as in portfolio choice or in partial insurance. This new notion also can suggest more intuitive approaches to inequalities measurement.
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  • 7
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    The Geneva risk and insurance review 20 (1995), S. 93-110 
    ISSN: 1554-9658
    Keywords: risk perception ; insurance ; moral hazard ; information
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Biases in risk perception potentially have a large effect on insurance and risk-related behavior. The government can alter these perceptions either through informational programs or controlling the risk. Policies that convey a higher risk level generally have the expected effects on insurance and protective actions, whereas efforts that increase the precision of either the government risk information or private beliefs typically have ambiguous effects. In some cases, the structure of how government policies enter the risk-belief function is consequential. Ascertaining the magnitude of the effects, not simply the direction, also is an important issue. For example, misperceptions have a dramatic effect on the tradeoffs between compensating differentials and the size of the loss but a negligible effect on the tradeoff between compensating differentials and the magnitude of the probability.
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  • 8
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    The Geneva risk and insurance review 20 (1995), S. 111-133 
    ISSN: 1554-9658
    Keywords: expected utility ; non-expected-utility ; experiments ; pairwise choice ; complete ranking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper extends the literature on the estimation of expected utility and non-expected-utility preference functionals (and the consequent exploration of the superiority of non-expected-utility over expected utility preference functionals) to a comparison of two different ways (pairwise choice and complete ranking) of experimentally obtaining data on such preferences. What is revealed is that the magnitude of the subject error is clearly conditional on the elicitation method used and, rather alarmingly, that the preference functional apparently employed by the subject may also be conditional on the elicitation method.
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  • 9
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    The Geneva risk and insurance review 20 (1995), S. 135-150 
    ISSN: 1554-9658
    Keywords: non-expected utility ; gambling ; insurance ; functional form problems ; risky activities in the national accounts ; state contingent commodities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Defining the outputs of the property insurance and gambling sectors of an economy has proved to be a difficult problem for national income accountants. It is well known that the traditional expected-utility model is not consistent with economic agents fully insuring their property. Thus the present paper adapts existing non-expected-utility theories to yield useful measures of output for the property insurance and gambling sectors.
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  • 10
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    The Geneva risk and insurance review 20 (1995), S. 157-175 
    ISSN: 1554-9658
    Keywords: catastrophe ; insurance ; moral hazard ; copayment ; experience rating ; distribution distortion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Catastrophes provide a principal justification for insurance. Traditional conceptions of catastrophes miss three critical elements. (1) Many catastrophes-the liability revolution in the United States, for example-are not bolts from the blue. Rather, they develop over many years and result from human activity. (2) Conventional, experiencedbased models for assessing losses often smudge the distinction, so critical for catastrophes, between probability and magnitude of loss. (3) Normal insurance contracts, with heavy copayments for small losses but little charge at the margin for large ones, perform poorly when the insured can tradeoff probability and size of loss-a phenomenon we label distribution distortion. The structures of optimal insurance contracts are assessed.
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  • 11
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    The Geneva risk and insurance review 20 (1995), S. 185-187 
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    Topics: Economics
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  • 12
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    The Geneva risk and insurance review 20 (1995), S. 189-190 
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    Topics: Economics
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  • 13
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    The Geneva risk and insurance review 20 (1995), S. 177-184 
    ISSN: 1554-9658
    Keywords: catastrophes ; torts ; asbestos ; insurance ; liability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Insurance catastrophes are increasingly the result of actions by human beings rather than nature. Chief among these insurance changes has been the surge in tort liability insurance costs. Unfortunately, the courts have misunderstood the mechanisms for transmitting these costs throughout the economy. A principal deficiency is that the structure of liability has been inconsistent with the courts' assumption that the losses could be borne by consumers or parties other than the insurer.
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  • 14
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    The Geneva risk and insurance review 20 (1995), S. 191-202 
    ISSN: 1554-9658
    Keywords: demand for insurance ; risk aversion ; first-degree and second-degree stochastic dominance shifts ; copula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract A risk-averse agent does not necessarily decrease the optimal insurance whenever a beneficial change in the distribution of final wealth occurs. This paper provides sufficient conditions to guarantee such a decrease. Beneficial changes can be induced by either a beneficial loss-distribution shift, by a modification of the dependence structure between the randomness sources, or by both of these. Conditions for each case are stated. Hadar-Seo and Meyer results turn out as special cases.
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  • 15
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    The Geneva risk and insurance review 21 (1996), S. 5-6 
    ISSN: 1554-9658
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    Topics: Economics
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  • 16
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    The Geneva risk and insurance review 20 (1995), S. 213-216 
    ISSN: 1554-9658
    Keywords: demand for insurance ; loss probability ; FSD shifts ; symmetric information
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract It is shown that the effect of increased probability of loss on the demand for insurance depends on whether both insured and insurer are aware of the change. When both insurer and insured share the same beliefs about the probability of loss (symmetric information), an increase in the loss probability may lead risk-averse agents to demandless insurance.
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  • 17
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    The Geneva risk and insurance review 20 (1995), S. 203-211 
    ISSN: 1554-9658
    Keywords: insurance ; insurable assets ; expected utility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper takes an additional step toward analyzing the demand for insurance in the context of a portfolio model. An investor is endowed with a portfolio containing a risky and riskless asset that can be augmented by purchasing insurance. Here, insurance is paid for by reducing the quantity of the risky insurable asset, holding the quantity of the riskless asset fixed. In the standard insurance demand model, insurance is paid for by reducing the amount of the riskless asset. This distinction leads to a different insurance demand function because the opportunity cost of purchasing insurance is now random.
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  • 18
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    The Geneva risk and insurance review 21 (1996), S. 29-33 
    ISSN: 1554-9658
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    Topics: Economics
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  • 19
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    The Geneva risk and insurance review 21 (1996), S. 7-28 
    ISSN: 1554-9658
    Keywords: term structure ; interest rates ; contingent claims valuation ; Black-Scholes model ; mean-reversion ; no-arbitrage condition ; preference-free pricing ; general equilibrium ; equivalent martingale measure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract One of the most active areas of research in financial economics has been the modeling of the term structure of interest rates and its relationship to the pricing of contingent claims. There is a vast array of issues in the area, as well as a variety of perspectives, ranging from theoretical to practical. This article provides a general framework for the analysis of issues in the modeling of the term structure. Specifically, this article provides an overview of the conceptual issues and the empirical evidence in the area, based on an examination of five seminal models by Black, Scholes, and Merton; Vasicek; Cox, Ingersoll, and Ross; Ho and Lee; and Heath, Jarrow, and Morton. The article provides a synthesis of the area and suggests directions for future research.
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  • 20
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    The Geneva risk and insurance review 21 (1996), S. 35-63 
    ISSN: 1554-9658
    Keywords: unit-linked life insurance ; exotic contracts ; equivalent martingale measures ; financial risk ; insurance premiums
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This article integrates aspects of traditional insurance with advances in financial economics, yielding proper valuation and premium assessments of insurance benefits linked to various financial assets. Several new types of unit-linked life insurance contracts are discussed, with substantial potential for real-life applications. Compared to usual unit-linked products, these contracts offer added flexibility and/or altered exposure to financial risk for the insured and/or the insurer. The single premiums of these policies are calculated as expectations under a risk-adjusted probability measure (equivalent martingale measure), satisfying no-arbitrage conditions in financial markets.
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  • 21
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    The Geneva risk and insurance review 21 (1996), S. 65-102 
    ISSN: 1554-9658
    Keywords: Asian option ; forward risk adjusted measure ; life insurance ; Monte Carlo simulation ; stochastic interest rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract An equity-linked life insurance contract combines an endowment life insurance and an investment strategy with a minimum guarantee. The benefit of this contract is determined by the guaranteed amount plus a bonus equal to a call on the portfolio. This bonus is similar to an Asian option. This article analyzes the relationship between the periodic insurance premium and its proportional share invested into the portfolio. For a general model of the financial risks we show the existence and uniqueness of an insurance premium. Furthermore the premium is strictly increasing and convex as a function of the share invested.
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  • 22
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    The Geneva risk and insurance review 21 (1996), S. 103-122 
    ISSN: 1554-9658
    Keywords: hedging ; incomplete markets ; use of futures ; wealth constraint ; exponential utility ; logarithmic utility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This article derives optimal hedging demands for futures contracts from an investor who cannot freely trade his portfolio of primitive assets in the context of either a CARA or a logarithmic utility function. Existing futures contracts are not numerous enough to complete the market. In addition, in the case of CARA, the nonnegativity constraint on wealth is binding, and the optimal hedging demands are not identical to those that would be derived if the constraint were ignored. Fictitiously completing the market, we can characterize the optimal hedging demands for futures contracts. Closed-form solutions exist in the logarithmic case but not in the CARA case, since then a put (insurance) written on his wealth is implicitly bought by the investor. Although solutions are formally similar to those that obtain under complete markets, incompleteness leads in fact to second-best optima.
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  • 23
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    The Geneva risk and insurance review 21 (1996), S. 123-141 
    ISSN: 1554-9658
    Keywords: deposit insurance ; incentive compatibility
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    Topics: Economics
    Notes: Abstract This article provides incentive compatible regulations that support fairly priced deposit insurance in a competitive banking industry. If informational asymmetry exists between the regulator and banks regarding loan quality, but the regulator can observe actual loan rates charged, then imposing a capital requirement schedule that leads market loan rates to decrease in loan quality is shown to be incentive compatible. Competition in the loan market induces banks to be indifferent to all loans that satisfy a minimum acceptable quality and reject all riskier loans. The regulator could reduce the banking industry's riskiness by imposing stricter capital requirements that increase this minimum quality.
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  • 24
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    The Geneva risk and insurance review 21 (1996), S. 147-158 
    ISSN: 1554-9658
    Keywords: stochastic dominance ; mean preserving dominance ; MLR-dominance ; capital budgeting ; comparative statics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract The value of an insurance company mainly depends on the premiums received in each underwriting period, the probability distribution of the accumulated claims against the company, the equity capital, and the risk-adjusted rate of return determined by the market. We analyze how the value of the company is affected by marginal changes in the underlying determinants, when there is a regulatory requirement on equity capital. The major factor we are interested in is the claims against the company in each underwriting period, which we represent by a stationary stochastic process. The existing orders for partially ranking risks do not suffice for our purpose, and new conditions are found on the risks facing the companies, for the successful ranking of the company values.
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  • 25
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    The Geneva risk and insurance review 21 (1996), S. 159-177 
    ISSN: 1554-9658
    Keywords: expected utility theory ; state-dependent preferences ; risk aversion ; non-expected utility theory ; rank-dependent probabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We extend the analysis of risk aversion with state-dependent preferences to the rank-dependent expected utility theory. We find that in this extended theory, for two preference relations to be comparable in risk aversion not only do their reference sets need to coincide (a condition first introduced by Karni [1983, 1985] in the original expected utility framework), but they must also rank the prospective state-dependent outcomes in the same manner. We formalize this additional condition by introducing the concept of certainty sets. Under our condition of comparability, various results and characterizations of interpersonal comparison of risk aversion are obtained. The implications for a specific insurance problem are also discussed.
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  • 26
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    The Geneva risk and insurance review 21 (1996), S. 179-189 
    ISSN: 1554-9658
    Keywords: uncertainty ; investment ; newsboy problem ; increase in risk ; optimal capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract In this article we study the effect of uncertainty on an entrepreneur who must choose the capacity of his business before knowing the demand for his product. The unit profit of operation is known with certainty, but there is no flexibility in our one-period framework. We show how the introduction of global uncertainty reduces the investment of the risk-neutral entrepreneur and, even more, that of the risk-averse one. We also show how marginal increases in risk reduce the optimal capacity of both the risk-neutral and the risk-averse entrepreneur, without any restriction on the concave utility function and with limited restrictions on the definition of a mean preserving spread. These general results are explained by the fact that the newsboy has a piecewise-linear, and concave, monetary payoff with a kink endogenously determined at the level of optimal capacity. Our results are compared with those in the two literatures on price uncertainty and demand uncertainty, and particularly, with the recent contributions of Eeckhoudt, Gollier, and Schlesinger [1991, 1995].
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  • 27
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    The Geneva risk and insurance review 21 (1996), S. 191-210 
    ISSN: 1554-9658
    Keywords: adverse selection ; hidden information ; informational equilibrium ; learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Standard models of adverse selection in insurance markets assume policyholders know their loss distributions. This study examines the nature of equilibrium and the equilibrium value of information in competitive insurance markets where consumers lack complete information regarding their loss probabilities. We show that additional private information is privately and socially valuable. When the equilibrium policies separate types, policyholders can deduce the underlying probabilities from the contracts, so it is information on risk type, rather than loss probability per se, that is valuable. We show that the equilibrium is “as if” policyholders were endowed with complete knowledge if, and only if, information is noiseless and costless. If information is noisy, the equilibrium depends on policyholders' prior beliefs and the amount of noise in the information they acquire.
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  • 28
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    The Geneva risk and insurance review 22 (1997), S. 5-19 
    ISSN: 1554-9658
    Keywords: infinite dimensional problem ; angular norm ; coinsurance ; deductible ; increasing costs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This article deals with the optimal design of insurance contracts when the insurer faces administrative costs. If the literature provides many analyses of risk sharing with such costs, it is often assumed that these costs are linear. Furthermore, mathematical tools or initial conditions differ from one paper to another. We propose here a unified framework in which the problem is presented and solved as an infinite dimensional optimization program on a functional vector space equipped with an original norm. This general approach leads to the optimality of contracts lying on the frontier of the indemnity functions set. This frontier includes, in particular, contracts with a deductible, with total insurance and the null vector. Hence, we unify the existing results and point out some extensions.
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  • 29
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    The Geneva risk and insurance review 22 (1997), S. 21-42 
    ISSN: 1554-9658
    Keywords: prudence ; risk aversion ; dual theory ; nonexpected utility ; background risk ; monopoly ; piecewise linear payoff function ; profits tax
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We identify two motives, prudence and risk aversion, which give rise to precautionary behavior for a quantity- or price-setting monopolist facing demand uncertainty who has dual theoretic preferences. We also analyze a piecewise linear profit function due to a tax on profits that varies with the profit level. We show that the comparative statics of greater risk (mean-preserving spread and mean-utility preserving spread) can be totally or partially determined by the Diamond-Stiglitz and Kihlstrom-Mirman single-crossing property. For example, for a prudent risk-averse quantity-setting dual theoretic monopolist, a mean-preserving spread will have the same impact on output under uncertainty as a fall in the state of demand under certainty. Finally, we find that, in contrast to expected utility, a stochastically larger state of demand (first-order stochastic dominance) will raise output even if background risk is present.
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    The Geneva risk and insurance review 22 (1997), S. 71-71 
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    Topics: Economics
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  • 31
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    The Geneva risk and insurance review 22 (1997), S. 59-65 
    ISSN: 1554-9658
    Keywords: principal-agent contracts ; first-order approach ; wage-action interactions ; action-risk interactions ; nonseparable utility
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    Topics: Economics
    Notes: Abstract The first-order approach (FOA) to principal agent problems is very convenient and mathematically tractable. However, existing results show that the FOA is valid only for additively separable utility functions. This is somewhat limiting. In this article sufficient conditions are identified that extend the validity of the FOA to nonseparable cases. The additional conditions involve restrictions on the agent's preferences, particularly interactions between action and the wage contract. These conditions imply that leisure is normal and the agent's absolute risk aversion increases with action. Comparative static results regarding the wage contract and its gradient are also discussed.
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    The Geneva risk and insurance review 22 (1997), S. 43-58 
    ISSN: 1554-9658
    Keywords: trade financing costs ; export credit insurance ; credit risk ; insurance premia ; option pricing ; non-parametric regressions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This article investigates the relationship between a debtor country's external financial indicators and the costs associated with the insurance of export credits to that country. For this purpose a stylized model of export credit insurance (ECI) is developed, the central idea being that ECI is similar to a contingent claim such as a European put option. Thus, tools from option pricing theory were used to calculate the price of ECI, implying that not only the current financial position but also the volatility of the changes in that position determine such costs. The empirical results of a statistical analysis of the premium rates for ECI, applied by a private export credit insurer to seventy-seven developing countries during 1993, provide some support for these hypotheses. In particular, the reserves-over-imports ratio of a debtor country and the volatility of the rates of change of this ratio appear to contribute significantly to the premium rates that apply to that country. Thus, the article provides evidence that option pricing parameters do play role in practical insurance pricing, even if this pricing is not explicitly based on these parameters. Premium rates are set as if an underlying option market operated. Thus, the trade of countries with volatile external financial positions is saddled with higher costs than that of countries with more stable positions.
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    The Geneva risk and insurance review 22 (1997), S. 81-101 
    ISSN: 1554-9658
    Keywords: insurance ; adverse selection ; multidimensional screening ; multiple risks ; bundling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This article extends the standard adverse-selection model for competitive insurance markets, which assumes a single source of risk, to the case where individuals are subject to multiple risks. We compare the following market situations—the case where insurers can offer comprehensive policies against all sources or risks (complete contracts) and the case where different risks are covered by separate policies (incomplete contracts). In the latter case, we consider whether the insurer of a particular risk has perfect information regarding an individual's coverage against other sources of risks. The analysis emphasizes the informational role of bundling in multidimensional screening. When the market situation allows bundling, it is shown that in equilibrium the low-risk type with respect to a particular source of risk does not necessarily obtain partial coverage against that particular risk.
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    The Geneva risk and insurance review 22 (1997), S. 73-79 
    ISSN: 1554-9658
    Keywords: insurance ; adverse selection ; competitive outcomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We are honored to address the European Group of Risk and Insurance Economists and will take the opportunity to make some reflections on the rather uneasy relationship between insurance and competition. Economists generally prescribe competition as a solution for markets that do not work well. Competition allocates resources efficiently and encourages innovation and attention to what customers want. Insurance markets differ from most other markets because in insurance markets competition can destroy the market rather than make it work better. One of the dimensions along which insurance companies compete is underwriting—trying to ensure that the risks covered are “good” risks or that if a high risk is insured, the premium charged is at least commensurate with the potential cost. The resulting partitioning of risk limits the amount of insurance that potential insurance customers can buy. In the extreme case, such competitive behavior will destroy the insurance market altogether. A simple model illustrates.
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    The Geneva risk and insurance review 22 (1997), S. 121-134 
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    Topics: Economics
    Notes: Abstract In this article, we show that common insurance policy provisions—namely, deductibles, coinsurance, and maximum limits–can arise as a result of adverse selection in a competitive insurance market. Research on adverse selection typically builds on the assumption that different risk types suffer the same size loss and differ only in their probability of loss. In this study, we allow the severity of the insurance loss to be random and, thus, generalize the results of Rothschild and Stiglitz [1976] and Wilson [1977]. We characterize the separating equilibrium contracts in a Rothschild-Stiglitz competitive market. By further assuming a Wilson competitive market, we show that an anticipatory equilibrium might be achieved by pooling, and we characterize the optimal pooling contract.
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    The Geneva risk and insurance review 22 (1997), S. 103-120 
    ISSN: 1554-9658
    Keywords: adverse selection ; insurance markets ; marketing costs ; pooling equilibria ; separating equilibria
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    Topics: Economics
    Notes: Abstract In the Rothschild-Stiglitz [1976] model of a competitive insurance market with adverse selection, pooling equilibria cannot exist. However in practice, pooling contracts are frequent, notably in health insurance and life insurance. This is due to the fact that distribution costs are nonnegligible and increase rapidly when more contracts are offered. We modify accordingly the Rothschild-Stiglitz model by introducing such distribution costs. We find that, however small these costs may be, they entail possible existence of pooling equilibria. Moreover, in these pooling equilibria, it is the high-risk individuals who are rationed, in the sense that they would be willing to buy more insurance at the current premium/insurance ratio.
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    The Geneva risk and insurance review 23 (1998), S. 5-5 
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    Topics: Economics
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    The Geneva risk and insurance review 22 (1997), S. 135-150 
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    Keywords: insurance ; adverse-selection ; Bayesian learning
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    Topics: Economics
    Notes: Abstract In the classic Rothschild-Stiglitz model of adverse selection in a competitive environment, we analyse a “no-claims bonus” type contract (bonus-malus). We show that, under full insurance coverage, if the insurance company applies Bayes's rule to learn about client probability types over time and uses this information in premium calculations for contract renewals, then there exist conditions under which all client types strictly prefer the Bayesian updating contract to the classic Rothschild-Stiglitz separating equilibrium.
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    The Geneva risk and insurance review 22 (1997), S. 151-168 
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    Keywords: regulation ; health care ; principal-agent ; hospital ; agency
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    Topics: Economics
    Notes: Abstract This article addresses the combined problem of imperfect agency and asymmetric information in the regulation of hospitals by modeling the physician as a utility maximizer with both the utility of patients and profit of the hospital as arguments in his or her utility function. The article concludes that optimal regulation of hospitals is based on three important factors: the doctor's marginal rate of substitution between profit of the hospital and utility of the patients, moral hazard in the relationship between the regulator and the hospital, and adverse selection in the same relation.
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    The Geneva risk and insurance review 23 (1998), S. 7-27 
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    Keywords: insurance ; background risk ; prudence
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    Topics: Economics
    Notes: Abstract Theory suggests that people facing higher uninsurable background risk buy more insurance against other risks that are insurable. This proposition is supported by Italian cross-sectional data. It is shown that the probability of purchasing casualty insurance increases with earnings uncertainty. This finding is consistent with consumer preferences being characterized by decreasing absolute prudence.
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    The Geneva risk and insurance review 23 (1998), S. 41-48 
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    Keywords: insurance ; oligopoly ; imperfect competition
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    Topics: Economics
    Notes: Abstract This article analyzes the behavior of an oligopoly of risk-averse insurers that insure many consumers facing identical independent risks; however, the probability of a loss is ex ante not known with certainty. It is shown that there is a continuum of equilibria in the Bertrand game. The most plausible equilibrium can be obtained by requiring that all insurers are content with the number of policies they sell given the equilibrium premium.
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    The Geneva risk and insurance review 23 (1998), S. 29-40 
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    Keywords: background risk ; stochastic dominance ; coinsurance ; deductibles
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    Topics: Economics
    Notes: Abstract The demand for insurance against loss from a particular risky asset is likely to depend on other risks the decision-maker faces. For independently distributed other risks, referred to as background risk, Eeckhoudt and Kimball [1992] determine the effect on insurance demand of introducing background risk. Recently, Eeckhoudt, Gollier, and Schlesinger [1996] determine conditions on preferences such that first- and second-degree stochastic deteriorations in background risk lead to a decrease in the decision-maker's willingness to accept other risks. These results, although formulated in a general decision model, also apply to insurance demand. This article continues analysis of this question by determining the effect on insurance demand of several other general changes in background risk.
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    The Geneva risk and insurance review 23 (1998), S. 49-61 
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    Keywords: long-term care insurance ; life insurance
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    Topics: Economics
    Notes: Abstract This article investigates the interaction between life insurance and long-term care insurance markets on the demand side. In the model utility depends on both consumption and bequest, and utility from consumption is contingent on the state of health. While the demand for life insurance increases both with decreasing income and with a rising degree of altruism, the influences of these two parameters on the demand for long-term care insurance are ambiguous. If the utility shock arising from disability declines, both insurance demands will rise.
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  • 44
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    The Geneva risk and insurance review 23 (1998), S. 63-82 
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    Keywords: fuzzy inference ; risk classification ; life insurance ; imprecise information
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    Topics: Economics
    Notes: Abstract Traditionally, policyholders in life insurance are classified in simple mortality tables, most often according to only a few risk characteristics. Instead of a risk classification according to the numerical rating system, this article describes how to classify by using a fuzzy inference methodology. By defining risk factors as fuzzy sets, it is shown that an insurer can utilize multiple prognostic factors that are imprecise and vague. The presented fuzzy risk classification provides a more realistic way of modeling mortality risks since it allows for compensations and interactions between multiple risk factors.
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    The Geneva risk and insurance review 23 (1998), S. 89-117 
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    Keywords: inequality ; risk ; utility
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    Topics: Economics
    Notes: Abstract Recalling the class of risk measures introduced by Stone [1973], the authors survey measures from different academic disciplines—including psychology, operations research, management science, economics, and finance—that have been introduced since 1973. We introduce a general class of risk measures that extends Stone's class to include these new measures. Finally, we give four axioms that describe necessary attributes of a good financial risk measure and show which of the measures surveyed satisfy these. We demonstrate that all measures that satisfy our axioms, as well as those that do not but are commonly used in finance, belong to our new generalized class.
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  • 46
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    The Geneva risk and insurance review 23 (1998), S. 119-125 
    ISSN: 1554-9658
    Keywords: social security ; privatization ; overlapping generations model ; endogenous growth
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    Topics: Economics
    Notes: Abstract It is generally accepted that moving from an unfunded to a funded social security system implies a welfare loss for the transition generation—that is, the generation that has to pay twice: first, saving for its own retirement and, second, contributing to the pensions of the then retired generation. This article shows that in a setting of endogenous growth with positive externality such a transition can be Pareto improving. But it argues also that social security reform is more a pretext than a requirement for internalizing such a positive externality.
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  • 47
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    The Geneva risk and insurance review 23 (1998), S. 127-137 
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    Keywords: asset preferences ; utility functions ; moment orderings ; Von Neumann-Morgenstern rationality
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    Topics: Economics
    Notes: Abstract This article examines the relationship between risk, return, skewness, and utility-based preferences. Examples are constructed showing that, for any commonly used utility function, it is possible to have two continuous unimodal random variables X and Y with positive and equal means, X having a larger variance and lower positive skewness than Y, and yet X has larger expected utility than Y, contrary to persistent folklore concerning U″′ 〉 0 implying skewness preference for risk averters. In additon, it is shown that ceteris paribus analysis of preferences and moments, as occasionally used in the literature, is impossible since equality of higher-order central moments implies the total equality of the distributions involved.
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    The Geneva risk and insurance review 23 (1998), S. 139-149 
    ISSN: 1554-9658
    Keywords: deposit insurance ; bank runs ; diamond dybuig model ; market failure
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    Topics: Economics
    Notes: Abstract The apparent banking market failure modeled by Diamond and Dybvig [1983] rests on their inconsistently applying their “sequential servicing constraint” to private banks but not to their government deposit insurance agency. Without this inconsistency, banks can provide optimal risk-sharing without tax-based deposit insurance, even when the number of “type 1” agents is stochastic, by employing a “contingent bonus contract.” The threat of disintermediation noted by Jacklin [1987] in the nonstochastic case is still present but can be blocked by contractual trading restrictions. This article complements Wallace [1988], who considers an alternative resolution of this inconsistency.
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  • 49
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    The Geneva risk and insurance review 23 (1998), S. 151-165 
    ISSN: 1554-9658
    Keywords: environmental management ; uncertainty ; public goods ; voluntary contributions ; precaution ; risk
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    Topics: Economics
    Notes: Abstract This article presents a model in which production causes pollution that diminishes the welfare of its agents. Each agent is concerned with the quality of its environment and may voluntary contribute to improve it by financing depollution technology. The effectiveness of this technology on the quality of the environment is uncertain. We show that if an agent is sufficiently risk averse, voluntary contribution is a decreasing function of the average efficiency of depollution technology. If, on the contrary, the pollution effect is weaker than the substitution effect, the opposite holds. We show that precaution about environmental quality has two possible consequences that depend on agents' risk aversion. Therefore, the implications of a precautionary attitude lead us to consider the agents' risk-aversion characterization, which implies knowledge about prudent attitude.
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    The Geneva risk and insurance review 24 (1999), S. 5-17 
    ISSN: 1554-9658
    Keywords: adverse selection ; coalition proof ; insurance
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    Topics: Economics
    Notes: Abstract We reexamine the canonical adverse selection insurance economy first studied by Rothschild and Stiglitz [1976]. We define blocking in a way that takes private information into account and define a coalition-proof correspondence as a mapping from coalitions to allocations with the property that allocations are in the correspondence, if and only if, they are not blocked by any other allocations in the correspondence for any subcoalition. We prove that the Miyazaki allocation—the Pareto-optimal allocation (possibly cross-subsidized) most preferred by low-risk agents—is coalition-proof.
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    The Geneva risk and insurance review 24 (1999), S. 19-28 
    ISSN: 1554-9658
    Keywords: self-insurance ; self-protection ; comparative statics
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    Topics: Economics
    Notes: Abstract Consider an agent facing a risky distribution of losses who can change this distribution by exerting some effort. Should he exert more effort when he becomes more risk-averse? For instance, should we expect more risk-averse drivers to drive more cautiously? In this article, we give sufficient conditions under which the answer is positive, using results presented in Jewitt (1989). We first extend the standard models of self-insurance and self-protection and show that the comparative statics depends only on the effect of effort on the net loss. We then present conditions for the continuous case with applications.
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    The Geneva risk and insurance review 24 (1999), S. 29-54 
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    Keywords: insurance ; auditing ; risk aversion
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    Topics: Economics
    Notes: Abstract We provide a characterization of an optimal insurance contract (coverage schedule and audit policy) when the monitoring procedure is random. When the policyholder exhibits constant absolute risk aversion, the optimal contract involves a positive indemnity payment with a deductible when the magnitude of damages exceeds a threshold. In such a case, marginal damages are fully covered if the claim is verified. Otherwise, there is an additional deductible that disappears when the damages become infinitely large. Under decreasing absolute risk aversion, providing a positive indemnity payment for small claims with a nonmonotonic coverage schedule may be optimal.
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    The Geneva risk and insurance review 24 (1999), S. 55-68 
    ISSN: 1554-9658
    Keywords: insurance regulation ; information ; insolvency
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    Topics: Economics
    Notes: Abstract There have been major changes in the way European insurance markets are regulated, and there is still considerable debate about what the form and scope of regulation should be. This article examines the arguments for solvency regulation when consumers are fully informed of the insurer's insolvency risk. It is shown firms always provide enough capital to ensure solvency, unless there are restrictions on the composition of their asset portfolios. The conclusion holds even when competition means that only normal profits can be earned. This suggests that the role of regulation in insurance markets should be confined to providing consumers with information about the default risk of insurers.
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    The Geneva risk and insurance review 24 (1999), S. 69-96 
    ISSN: 1554-9658
    Keywords: insurance futures ; futures derivatives ; claims processes ; reinsurance
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    Topics: Economics
    Notes: Abstract This article presents a valuation model of futures contracts and derivatives on such contracts, when the underlying delivery value is an insurance index, which follows a stochastic process containing jumps of random claim sizes at random time points of accident occurrence. Applications are made on insurance futures and spreads, a relatively new class of instruments for risk management launched by the Chicago Board of Trade in 1993, anticipated to start in Europe and perhaps also in other parts of the world in the future. The article treats the problem of pricing catastrophe risk, which is priced in the model and not treated as unsystematic risk. Several closed pricing formulas are derived, both for futures contracts and for futures derivatives, such as caps, call options, and spreads. The framework is that of partial equilibrium theory under uncertainty.
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    The Geneva risk and insurance review 24 (1999), S. 119-137 
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    Keywords: risk classification ; adverse selection ; moral hazard ; Poisson-gamma model ; bonus-malus
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    Topics: Economics
    Notes: Abstract We present in this article some questions related to risk classification. These are discussed depending on the information used—either data on conditional characteristics or also including data on claim histories or on endogenous insurance demand by the agents.
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    The Geneva risk and insurance review 24 (1999), S. 97-114 
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    Keywords: adverse selection ; moral hazard ; automobile insurance contracts ; risk of accident ; econometrics
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    Topics: Economics
    Notes: Abstract Insurance has for a long time been perceived as a way of transferring responsibility from insured agents to insurers and thus as potentially influencing insured agents' behavior. Two particular opportunistic behaviors have been analyzed. First, the theory of adverse selection predicts that high-risk agents are likely to demand more insurance than are low-risk agents. Second, the theory of moral hazard predicts that the wider the insurance coverage, the less agents will try to prevent accidents. Both theories thus conclude that agents who are totally insured should have a higher probability of accident than those with only partial insurance, ceteris paribus. Nevertheless, one of the aims of insurance rating systems is to control for these opportunistic behaviors. In this article, we use individual data to see if the French automobile insurance rating system has achieved this aim. We do this using a two-step maximum-likelihood method. First, we compute a probit model to estimate the probability of taking out comprehensive versus third-party insurance. We then calculate the generalized residual, which is included as an independent variable in a negative binomial model estimating the probability of having an accident. The coefficient of this variable is argued to represent adverse selection and ex-ante moral-hazard behavior.
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    The Geneva risk and insurance review 24 (1999), S. 173-192 
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    Keywords: distribution systems ; price dispersion ; consumer search behavior ; long-run equilibrium ; uninformed consumers
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    Topics: Economics
    Notes: Abstract We attempt to explain the coexistence of two distribution systems when consumers are poorly informed about price distribution. The interaction of price dispersion and consumer search behavior is shown to affect the choice of marketing systems. We provide a necessary and sufficient condition for the coexistence as a long-run equilibrium. The market may observe the coexistence of the two agency systems regardless of the relative efficiency of agency types, or the domination by the less efficient agency system offering higher average price.
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    The Geneva risk and insurance review 24 (1999), S. 159-171 
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    Keywords: crop insurance ; yield options contracts ; incomplete markets ; systemic risk
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    Topics: Economics
    Notes: Abstract This article focuses on the design of a crop insurance contract when the indemnity is based on the aggregate yield of a surrounding geographical area. Coinsurance under a critical yield often provides an efficient sharing of systemic risk. Under a linear relationship between individual yield and aggregate yield, the optimal form depends on the individual beta coefficient, which measures the sensitivity of individual yield to aggregate yield. The optimal hedging position of the producer on the yield options market is to buy put options or call options depending upon whether his beta coefficient is positive or negative.
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    The Geneva risk and insurance review 24 (1999), S. 139-158 
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    Keywords: self-selection ; screening ; information asymmetry ; insurance markets
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    Topics: Economics
    Notes: Abstract A major characteristic of insurance markets is information asymmetry that may lead to phenomena such as adverse selection and moral hazard. Another aspect of markets with asymmetric information is self-selection, which refers to the pattern of choices that individuals with different personal characteristics make when facing a menu of contracts or options. To combat problems of asymmetric information, insurance firms can use screening. That is, they can offer the clients a menu of choices and infer their characteristics from their choices. This article reports the results of several studies that examined the degree to which people behave according to the notions of self-selection and screening. Subjects played the role of either insurance buyers or sellers. The results of these studies provide partial support for the hypothesis that subjects use self-selection and screening in insurance markets. Our study also points at the importance of learning in experimental studies. In one-stage experiments where subjects did not get feedback, screening was not detected. When multistage experiments were conducted, and the subjects learned from experience and were also taught the relevant theories, their decisions were more aligned with screening.
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    The Geneva risk and insurance review 24 (1999), S. 193-207 
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    Keywords: corporate insurance ; business insurance ; agency problems
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    Topics: Economics
    Notes: Abstract Existing literature argues that corporate insurance is purchased because the insurance company produces risk management information for publicly held corporations. In this article, we address a fundamental question as to why other financial intermediaries cannot perform the same information production function as the insurance company. We argue that when the risk manager of the firm performs multiple tasks and needs consulting and investigation services from an outside agent for efficient risk management, the optimal contract with the agent has to be in the form of an insurance contract. Other types of contracts, such as flat-fee contracts, cannot be optimal. Therefore, the insurance company is ideally suited to provides these services.
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 328-332 
    ISSN: 1476-5535
    Keywords: Keywords: lipase; enzymatic synthesis; aromatic polyester; diacid; diol; polyesterification
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymatic synthesis of aromatic polyesters by direct polyesterification between a diacid and a diol is described. The effects of the type of substrate, type and quantities of lipase, temperature, vacuum, and reaction time on the synthesis of aromatic polyesters were studied in detail. Among three lipases investigated, only Novozym 435 worked well for aromatic polyester synthesis. Temperature and vacuum played an important role in obtaining a high molar mass of the aromatic polyesters. Furthermore, with isophthalic acid and 1,6-hexanediol as substrates, the mass average molar mass of the polyester obtained increased with an increase in the lipase quantity up to 0.375 g (11.7%, w/w of total reactor contents). The mass average molar mass of the polyester was as high as 50000 g mol−1 in 168 h, with a polydispersity of PD ≈ 1.4.
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 344-353 
    ISSN: 1476-5535
    Keywords: Keywords: Acremonium chrysogenum; cephalosporin C; deacetoxycephalosporin C; 7-ACA; 7-ADCA; expandase/ hydroxylase
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deacetoxycephalosporin C (DAOC) is produced by Acremonium chrysogenum as an intermediate compound in the cephalosporin C biosynthetic pathway, and is present in small quantities in cephalosporin C fermentation broth. This compound forms an undesirable impurity, 7-aminodeacetoxycephalosporanic acid (7-ADCA), when the cephalosporin C is converted chemically or enzymatically to 7-aminocephalosporanic acid (7-ACA). In the cephalosporin C biosynthetic pathway of A. chrysogenum, the bifunctional expandase/hydroxylase enzyme catalyzes the conversion of penicillin N to DAOC and subsequently deacetylcephalosporin C (DAC). By genetically engineering strains for increased copy number of the expandase/hydroxylase gene, we were able to reduce the level of DAOC present in the fermentation broth to 50% of the control. CHEF gel electrophoresis and Southern analysis of DNA from two of the transformants revealed that one copy of the transforming plasmid had integrated into chromosome VIII (ie a heterologous site from the host expandase/hydroxylase gene situated on chromosome II). Northern analysis indicated that the amount of transcribed expandase/hydroxylase mRNA in one of the transformants is increased approximately two-fold over that in the untransformed host.
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 323-327 
    ISSN: 1476-5535
    Keywords: Keywords: thermotolerance; process development; novel yeast
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fermentation characteristics of the novel, thermotolerant, isolate Kluyveromyces marxianus var marxianus were determined to evaluate its aptitude for use in an ethanol production process. Sustainable growth was not observed under anaerobic conditions, even in the presence of unsaturated fatty acid and sterol. A maximum ethanol concentration of 40 g L−1 was produced at 45°C, with an initial specific ethanol production rate of 1.7 g g−1 h−1. This was observed at ethanol concentrations below 8 g L−1 and under oxygen-limited conditions. The low ethanol tolerance and low growth under oxygen-limited conditions required for ethanol production implied that a simple continuous process was not feasible with this yeast strain. Improved productivity was achieved through recycling biomass into the fermenter, indicating that utilising an effective cell retention method such as cell recycle or immobilisation, could lead to the development of a viable industrial process using this novel yeast strain.
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  • 64
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    Keywords: Keywords: carbon concentration; Colletotrichum coccodes; conidiation; C:N ratio; mycoherbicide
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of carbon concentration and carbon-to-nitrogen ratio (C:N) as well as their interaction on Colletotrichum coccodes growth and sporulation in submerged flask culture were evaluated. When C:N ratios were held constant, both mycelial dry biomass and spore yield increased with increasing carbon concentration. The specific spore yields (spore yield g−1 carbon), however, were not significantly different for the same C:N ratio in most cases. The highest spore yields (1.3 × 108 spores per ml) were obtained from media containing 20 g per liter carbon with C:N ratios ranging from 5:1 to 10:1. When the C:N ratio was greater than 15:1, spore yields were significantly decreased with increasing C:N ratios. High carbon concentration (20 g L−1) combined with high C:N ratios (above 15:1) reduced both mycelial growth and sporulation, and increased spore matrix production. Spores produced in medium containing 10 g L−1 carbon with C:N ratios from 10:1 to 15:1 had 90% germination on potato dextrose agar after 12 h and caused extensive shoot dry weight reduction on the target weed, velvetleaf. These results suggest that C:N ratios from 10:1 to 15:1 are optimal for C. coccodes spore production.
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 275-280 
    ISSN: 1476-5535
    Keywords: Keywords: microbial biofilms; modified Robbins device (MRD); antifouling paint; tributyltin (TBT); copper
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of biofilms of Pseudomonas aeruginosa PAO-1 was studied using modified Robbins devices. Biofilm development was measured using viable counts, acridine orange direct counts (AODC), and a colorimetric method for exopolysaccharide (EPS). Biofilms reached their maximum population 24–72 h after inoculation on coupons with no paint or on coupons coated with marine paint VC-18 without additives. Biofilms on stainless steel contained higher numbers of total cells and of viable cells than biofilms on fiberglass or aluminum. Coating the surfaces with marine paint VC-18 resulted in decreased numbers of cells on stainless steel but had little effect on numbers of cells on fiberglass or aluminum. Addition to the paint of Cu or tributyltin (TBT), the active components in two types of antifouling paints, inhibited the initial development of biofilms. However, by 72–96 h, most biofilms contained the same number of cells as surfaces without additives as shown by both viable counts and AODC. Biofilms that formed on surfaces coated with Cu- or TBT-containing paint did not synthesize more EPS, suggesting that P. aeruginosa PAO-1 does not respond to these compounds by synthesizing more EPS, which could bind the metal and protect the cells. Rather, these biofilms may contain Cu- or TBT-resistant cells. TBT-resistant cells made up 1–10% of the viable counts in biofilms on uncoated stainless steel, but in biofilms on stainless steel coated with marine paint containing TBT, TBT-resistant cells made up as much as 50% of the population. For non-coated stainless steel surfaces, Cu-resistant cells initially made up the majority of the population, but after 48 h they made up less than 1% of the population. On Cu-coated stainless steel, Cu-resistant cells predominated through 48 h, but after 48 h they comprised less than 10% of the population. These results suggest that the growth of TBT-resistant and Cu-resistant cells contributes to biofilms of P. aeruginosa PAO-1 at early stages of development but not at later stages.
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 339-343 
    ISSN: 1476-5535
    Keywords: Keywords: chemostat; Candida shehatae; mixed sugars; D-xylose; Monod kinetics; pH
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of biomass formation, D-xylose utilization, and mixed substrate utilization were determined in a chemostat using the yeast Candida shehatae. The maximum growth rate of C. shehatae grown aerobically on D-xylose was 0.42 h−1 and the Monod constant, K s, was 0.06 g L−1. The biomass yield, Y {X/S}, ranged from 0.40 to 0.50 g g−1 over a dilution rate range of 0.2–0.3 h−1, when C. shehatae was grown on pure D-xylose. Mixtures of D-xylose and glucose (∼1 : 1) were simultaneously utilized over a dilution rate from 0.15 to 0.35 h−1 at pH 3.5 and 4.5, but pH 3.5 reduced μmax and reduced the dilution rate range over which D-xylose was utilized in the presence of glucose. At pH 4.5, μmax was not reduced with the mixed sugar feed and the overall or lumped K s value was not significantly increased (0.058 g L−1 vs 0.06 g L−1), when compared to a pure D-xylose feed. Kinetic data indicate that C. shehatae is an excellent candidate for chemostat production of value added products from renewable carbon sources, since simultaneous mixed substrate utilization was observed over a wide range of growth rates on a 1 : 1 mixture of glucose and D-xylose.
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  • 67
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 373-375 
    ISSN: 1476-5535
    Keywords: Keywords: Actinomadura; compactin; hydroxylase; microbial transformation; pravastatin
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hydroxylase in cell-free extracts of Actinomadura sp strain 2966 converts compactin to pravastatin. It requires NADPH as coenzyme and Mg2+ as cofactor; Mn2+ can partially replace Mg2+. In contrast with the inducible cytochrome P-450 system of Streptomyces carbophilus which catalyzes the same overall reaction, this constitutive hydroxylase is stimulated by ATP and ascorbic acid and is not inactivated by CO.
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  • 68
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 377-378 
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  • 69
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    Keywords: Keywords: hirudin; Hansenula polymorpha; methylotrophic yeast; methanol oxidase; autonomously replicating sequence
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    Notes: Various recombinant Hansenula polymorpha strains were developed and compared for their level of expression of the anticoagulant hirudin. H. polymorpha DL1-57 harboring an autonomously replicating sequence, HARS36, efficiently expressed the gene for recombinant hirudin. The effect of methanol oxidase (MOX) on the expression of the hirudin gene in H. polymorpha DL1-57 was studied, and the fermentation strategies coupled with the MOX activity and an antioxidant, tocopherol, were also examined.
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  • 70
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 19-21 
    ISSN: 1476-5535
    Keywords: Keywords: yogurt; Lactobacillus bulgaricus; Streptococcus thermophilus; Lactobacillus acidophilus; Bifidobacterium spp
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    Notes: The microbiological quality of four brands of natural yogurts and two probiotic yogurts available in the Portuguese market, was evaluated during the shelf-life period. Although the specific flora decreased during storage it was always within the range of recommended values. No coliforms and an insignificant number of fungi were detected.
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  • 71
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 6-10 
    ISSN: 1476-5535
    Keywords: Keywords: cytoplasmic membrane; biocides; potassium leakage; Escherichia coli; Pseudomonas aeruginosa; Pseudomonas-gap
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    Notes: Many antimicrobial compounds exhibit bacterial cell membrane activity as either potassium ion leakage and/or leakage of material that absorbs at 260 nm from the cell. In this experiment a potassium ion selective electrode and spectophotometric observation of 260-nm leakage were used in order to examine cell membrane effects in a selection of common biocides upon both Escherichia coli NCIMB 10000 and Pseudomonas aeruginosa NCIMB 10548. The observation of potassium ion leakage for pyrithione biocides yielded results which were initially difficult to interpret, but are thought to suggest a species-dependent combination of potassium ion leakage from affected membranes and chelation of those leaked ions in the bathing suspension. Such a result is not, however, supported by the 260-nm material leakage results, which indicate very similar levels of membrane active effects for both species of bacteria.
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  • 72
    ISSN: 1476-5535
    Keywords: Keywords: Alcaligenes eutrophus; biodegradable plastics; poly(β-hydroxybutyrate); vegetable oil; Vernonia galamensis; vernolic acid
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    Notes: Saponified vernonia oil was converted exclusively to poly(β-hydroxybutyrate) (PHB) by Alcaligenes eutrophus in a single-stage batch culture. After harvesting, centrifugation followed by lyophilization, the resulting dried cells contained up to 42.8 wt% PHB having a peak molecular mass of 381 863 Da, weight-average molecular mass of 308 390 Da, and a polydispersity of 1.1. The PHB had a melting point (Tm) range of 163–174°C with a maximum at 172°C (lit. Tm, 175°C), and heat of fusion of 18.43 cal g−1. Fermentation performed under varying conditions of nitrogen limitation indicated that there was no significant effect of nitrogen concentration on the molecular mass of PHB produced from vernonia oil by A. eutrophus.
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  • 73
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 37-45 
    ISSN: 1476-5535
    Keywords: Keywords: glucosyltransferase; dextransucrase; alternansucrase; Leuconostoc mesenteroides; mutant; glucan; dextran; polysaccharide
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    Notes: A mutant strain (R1510) of Leuconostoc mesenteroides B-1355 was isolated which synthesized primarily an insoluble polysaccharide and little soluble polysaccharide when grown in sucrose-containing medium. Glucose or sucrose cultures of this strain produced a single intense band of GTF-1 activity of 240 kDa on SDS gels, and a number of faint, smaller bands. Oligosaccharides synthesized by strain R1510 from methyl-α-D-glucoside and sucrose included a trisaccharide whose structure contained an α(1→2) glucosidic linkage. This type of linkage has not been seen before in any products from strain B-1355 or its mutant derivatives. The structure of the purified trisaccharide was confirmed by 13C-nuclear magnetic resonance. The insoluble polysaccharide also contained α(1→2) branch linkages, as determined by methylation analysis, showing that synthesis of the linkages was not peculiar to methyl-α-D-glucoside. GTF-1, which had been excised with a razor blade from an SDS gel of a culture of the parent strain B-1355, produced the same trisaccharides as strain R1510, showing that GTF-1 from the wild-type strain was the same as GTF-1 from strain R1510. Mutant strains resembling strain R1510, but producing a single intense band of alternansucrase (200 kDa) instead of GTF-1 were also isolated, suggesting that mutations may be generated which diminished the activities for any two of the three GTFs of strain B1355 relative to the third. Strain R1554 produced a soluble form of alternansucrase, while strain R1588 produced a cell-associated form. The mechanism(s) by which specific GTFs become associated with the cells of L. mesenteroides was not explored.
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  • 74
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 75-80 
    ISSN: 1476-5535
    Keywords: Keywords: lipase; Pseudomonas aeruginosa; wastewater treatment
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipase from Pseudomonas aeruginosa LP602, a bacterial strain isolated from a domestic wastewater sample, was preliminarily characterized. The enzyme exhibited maximum lipolytic activity at pH 8.0 where it was also stably maintained. At 55°C, the lipase had the highest activity but not stability. The enzyme was insensitive to EDTA and to many ions tested except Zn2+. It was sensitive to SDS but not to Tween-20, Tween-80 or Triton X-100. The enzyme was active towards a number of commercial food grade fats and oils. A suitable medium formula for lipase production was MMP containing 6.25% whey as a carbon source, 1% soybean oil as inducer and 0.5% yeast extract supplement. The culture was fed with glucose to a final concentration of 0.1% at the 15th hour of incubation. Lipase production under this condition was 3.5 U ml−1. Both P. aeruginosa LP602 cells and the lipase were shown to be usable for lipid-rich wastewater treatment.
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  • 75
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 92-98 
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    Keywords: Keywords: immunomagnetic separation; bovine feces; carcass wash water; apple cider; ground beef
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Contamination of foods with pathogens such as Escherichia coli O157:H7 and Salmonella is a major concern worldwide and rapid, sensitive, and reliable methods are needed for detection of these organisms. Since these pathogens can contaminate similar foods and other types of samples, a multiplex polymerase chain reduction (PCR) was designed to allow simultaneous detection of both E. coli O157:H7 and Salmonella spp directly from enrichment cultures. Samples of apple cider, beef carcass wash water, ground beef, and bovine feces were inoculated with both E. coli O157:H7 and S. typhimurium at various bacterial levels. Following enrichment culturing for 20–24 h at 37°C in modified EC broth or buffered peptone water both containing novobiocin, the samples were subjected to a DNA extraction technique or to immunomagnetic separation then tested by the multiplex PCR assay. Four pairs of primers were employed in the PCR: primers for amplification of E. coli O157:H7 eaeA, stx 1/2 and plasmid sequences and for amplification of a portion of the Salmonella invA gene. Four fragments of the expected sizes were amplified in a single reaction and visualized following agarose gel electrophoresis in all the samples inoculated with ≤ 1 CFU g−1 or ml−1. Results can be obtained in approximately 30 h. The multiplex PCR is a potentially powerful technique for rapid and sensitive co-detection of both pathogens in foods and other types of samples.
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  • 76
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 150-166 
    ISSN: 1476-5535
    Keywords: Keywords: Cryptosporidium parvum; detection; PCR; environmental samples; water; food
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    Notes: Since 1991 more than 30 PCR protocols have been published, which show a potential to replace the current microscopic detection method for Cryptosporidium parvum in environmental samples and food. This review provides a synoptic comparison of these protocols with respect to the following features: isolation and purification of oocysts from tested matrices, elimination of free DNA, viability and infectivity assessment, release of nucleic acids, nucleic acid extraction, type of PCR (PCR, RT-PCR, internal-standard-PCR, in situ PCR, TaqMan-PCR), primary product detection, additional specificity control, secondary product detection, reported sensitivity, cross-reaction with other Cryptosporidium species, and target and sequence information such as amplicon length, primer sequences, multiple copy target, presence of strain-specific differences in the amplicon, GenBank accession numbers and gene function. The results demonstrate that problems like PCR inhibition, viability assessment, and the requirement of an extreme sensitivity have been solved. PCR assays would be most valuable to control presence-absence standards in defined matrix volumes, and the setup of such standards would very much contribute to a rapid introduction of this awaited technology into routine monitoring of environmental, water and food samples, and to a further standardization of the various protocols. It can be expected that satisfactory solutions for quantification will be found for a growing number of PCR-based assays. Systematic field evaluation and interlaboratory studies will complement our present knowledge of these methods in the near future.
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  • 77
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 141-144 
    ISSN: 1476-5535
    Keywords: Keywords: Salmonella; pigs; ERIC PCR; epidemiology
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    Notes: The purpose of this study was to test a protocol for a standardized ERIC PCR for its capability of genotyping Salmonella, isolated from pigs and their environment, in an epidemiologic approach. To test repeatability, four different Salmonella isolates were subjected to PCR three times. Furthermore, it was tested if the profiles on gel differed when a higher annealing temperature was used. Four Salmonella isolates were subjected to four different annealing temperatures (36, 40, 48 and 55°C). Moreover it was tested if the differentiation of Salmonella isolates, based on the genotypes, differed when a higher annealing temperature was used. Eight Salmonella isolates were tested at normal (36°C) and high (55°C) annealing temperatures. The results showed that this standardized ERIC PCR protocol was an efficient tool for typing many Salmonella isolates within a short period of time. The profiles were repeatable within one PCR reaction, but some profiles differed when they were compared between reactions. A higher annealing temperature resulted in profiles that contained more or fewer bands. The differentiation between isolates, when comparing profiles, remained the same. It was concluded that the standardized ERIC PCR protocol is useful for genotyping Salmonella.
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  • 78
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 175-177 
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    Keywords: Keywords: plasminogen activator inhibitor-2; baculovirus; expression vector; secretion
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    Notes: Using pSXIVVI+X3 as an expressing vector, an occluded recombinant Trichoplusia ni nuclear polyhedrosis virus carrying the cDNA encoding plasminogen activators inhibitor-2 (PAI-2) under the control of the Syn and XIV promoters, has been constructed. SDS-PAGE and immunoblot analysis revealed that the virus-mediated PAI-2, with a molecular weight of ∼45 kDa, was synthesized in the Sf cells at a level of ∼16% of total intracellular protein and in the supernatant phase at a level of ∼64% of total extracellular protein secreted into the hemolymph of infected larvae. The expressed protein was similar to its authentic counterpart in terms of immunoreactivity and bioactivity.
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  • 79
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 187-191 
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    Keywords: Keywords: Clostridium beijerinckii; butanol; solvent production; corn steep water
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    Notes: Corn steep water (CSW) medium (1.6% solids plus 6% glucose) was evaluated for growth and butanol production by Clostridium beijerinckii NCIMB 8052 wild-type and hyper-amylolytic, hyper-butanol-producing mutant strain BA101. CSW alone was not a suitable substrate, whereas addition of glucose supported growth and butanol production by both strains. In a batch-scale fermentation using an optimized 6% glucose-1.6% solids CSW medium, C. beijerinckii NCIMB 8052 and strain BA101 produced 10.7 g L−1 and 14.5 g L−1 of butanol, respectively. The total solvents (acetone, butanol, and ethanol) produced by C. beijerinckii NCIMB 8052 and strain BA101 were 14 g L−1 and 20 g L−1, respectively. Initial fermentation in small-scale flasks containing 6% maltodextrin-1.6% solids concentration CSW medium resulted in 6 g L−1 and 12.6 g L−1 of butanol production by C. beijerinckii NCIMB 8052 and strain BA101, respectively. CSW can serve as an economic source of nitrogen, vitamins, amino acids, minerals, and other nutrients. Thus, it is feasible to use 6% glucose-1.6% solids CSW medium in place of semi-defined P2 medium.
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  • 80
    ISSN: 1476-5535
    Keywords: Keywords: human epidermal growth factor; Bacillus brevis recombinants; expanded bed adsorption; fermentation
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    Notes: Recombinant Bacillus brevis which carried an expression plasmid encoding the human epidermal growth factor (EGF) gene on a cryptic high-copy number plasmid, pHT926, extracellularly produced EGF in its biologically active form at a concentration of over 1.5 g L−1 in the culture broth in a 30-L jar fermenter. The culture broth also contained some other EGF compounds, which mainly consisted of oligomeric and polymeric forms with disulfide bonds. We developed a simple purification method for EGF, without prior cell removal from the culture broth, comprising cation exchange expanded bed adsorption followed by ultrafiltration with UF 10 000 and 3000 membranes. The EGF compounds were efficiently separated from the EGF in its native form in the expanded bed adsorption step. With this purification method, only EGF in its native form was recovered from the culture broth, with a yield of nearly 80%, and 90% purity. This efficient and economic system has made it possible to use EGF as a pharmaceutical in the livestock industry.
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  • 81
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 225-227 
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    Keywords: Keywords: azaarenes; biotransformation; fungi; heterocyclic compounds; N-oxidation
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    Notes: Cultures of the fungi Cunninghamella elegans and Aspergillus niger were grown in fluid Sabouraud medium at 28°C for 3 days and then dosed with cinnoline (1,2-diazanaphthalene). After 3 more days, metabolites were extracted from the cultures with ethyl acetate, separated by high-performance liquid chromatography, and identified by mass spectrometry and proton nuclear magnetic resonance spectroscopy. Both fungi oxidized 2–10% of the added cinnoline to mixtures of cinnoline 2-oxide and cinnoline 1-oxide.
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  • 82
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 242-246 
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    Keywords: Keywords: xanthan; agricultural wastes; Xanthomonas campestris
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    Notes: Four different acid-hydrolyzed wastes, from melon, watermelon, cucumber and tomato were compared for xanthan production. Growth of Xanthomonas campestris, xanthan biosynthesis, kinetics and chemical composition were investigated. Both growth and xanthan production were dependent on the acid hydrolysate concentrations and available nitrogen. Melon acid hydrolyzed waste was the best substrate for xanthan production. Exopolysaccharide obtained throughout this study was compared to commercial xanthan, showing a very similar chemical composition. Acid hydrolyzed wastes are proposed as a new carbon source for xanthan production.
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  • 83
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 289-291 
    ISSN: 1476-5535
    Keywords: Keywords: hNGF; Luc; PCR; baculovirus system; transfer vector; gene expression
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Human nerve growth factor (hNGF) gene was proliferated with human leucocyte DNA as template by PCR. Then a fusion gene coding hNGF and luciferase (Luc) cDNAs was inserted into transfer vector pSXIVVI+X3/3 with the control of Syn XIV promoter. Luc and hNGF were simultaneously synthesized in Spodoptera larvae upon infection with a recombinant baculovirus, TnNPV-Luc-NGF-OCC+. Densitometric scanning of SDS-PAGE revealed that ∼18% of the total Coomassie blue-stainable protein of the infected larvae was represented by Luc protein, while the hNGF level was ∼8%. Both proteins were similar to their authentic counterparts in terms of immunoreactivity.
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  • 84
    ISSN: 1476-5535
    Keywords: Keywords: Fab antibody expression; E. coli fermentation; immobilized metal affinity chromatography (IMAC); proteases; botulinum toxin; temperature sensitivity
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    Notes: Recombinant E. coli clones expressing a 50-kDa poly-histidine tail tagged antibody fragment against botulinum toxin (bt-Fab) were initially screened for yield and binding affinity. One clone was selected for bioprocess development. The selected bt-Fab vector was induced by addition of IPTG and the protein was targeted to the periplasm by inclusion of a pelB leader sequence. A histidine6 affinity ligand at the heavy chain C-terminus facilitated single-step purification by immobilized metal-affinity chromatography (IMAC). Notably, the effects of post-induction temperature on bt-Fab expression and downstream purification were evaluated. Our results demonstrated that fermentation conditions interfered with purification on the IMAC column at 37°C. Protease analysis by gelatin polyacrylamide gel electrophoresis (GPAGE) indicated the presence of a membrane-bound ∼39 kDa protease activity shortly after induction. The appearance of the protease activity was inversely correlated with the bt-Fab yield. The protease was purified and was shown to degrade bt-Fab. A simple kinetic model was developed describing temporal regulation of protease and bt-Fab degradation. Partially degraded bt-Fab was unrecoverable by IMAC, presumably due to the loss of the His6 affinity ligand. The amount of purified bt-Fab obtained per liter of fermentation broth was typically ∼1 mg.
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  • 85
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 261-274 
    ISSN: 1476-5535
    Keywords: Keywords: biofilms; stainless steel; Baltic Sea; ennoblement; CLSM; in situ hybridization; fluorescent beads
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    Notes: ca 400 mV), the biofilm on the steel surface was characterized using confocal laser scanning microscopy (CLSM) in combination with functional and phylogenetic stains. The biofilm consisted of microbial cell clusters covering 10–20% of the surface. The clusters were loaf-formed, with a basal diameter of 20–150 μm, 5–20 per mm−2, each holding 〉104 cells in a density of 1–5 × 107 cells mm−3. The typical cluster contained mainly small Gram-negative bacteria (binding the EUB338 probe when hybridized in situ on the steel surface), and often carried one to three spherical colonies, either homogeneously composed of large Gram-negative cocci or more often small bacterial rods in high density, 108–109 cells mm−3. The clusters in live biofilms contained no pores, and clusters over 25 μm in diameter had a core nonpenetrable to fluorescent nucleic acid stains and ConA lectin stain. Fluorescently-tagged ConA stained cells at a depth of 〈5 μm, indicating the presence of cells with α-d-mannosyl and α-d-glucosyl residues on surfaces. ethidium bromide (log K ow −0.38) penetrated deeper (17 μm in 15 min, corresponding to 〉10 cells in a stack) into the cluster than did the less polar dyes SYTO 16 (log K ow 1.48) and acridine orange (log K ow 1.24), which stained five cells in a stack. Fluorescent hydrophobic and hydrophilic latex beads (diameter 0.02, 0.1 or 1.0 μm) coated patchwise the cluster surface facing the water, but penetrated only to depths of ⩽2 μm indicating a permeability barrier. About 1/3 of the stainable cells hybridized in situ with Alf1b, while fewer than 1/7 hybridized to GAM42, probes targeted towards α- and γ-Proteobacteria, respectively. Our results represent a microscopic description of an ennobling biofilm, where the ennoblement could follow the sequence of redox events as suggested by the model of Dickinson and Lewandowski (1996) for the structure of corrosive biofilms on a steel surface.
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  • 86
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 331-331 
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  • 87
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    Keywords: Keywords: bacterial inoculum; consortium; crude oil biodegradation; oil spill bioremediation agents; petroleum
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    Notes: Six crude oil-degrading bacterial strains isolated from different soil and water environments were combined to create a defined consortium for use in standardized efficacy testing of commercial oil spill bioremediation agents (OSBA). The isolates were cryopreserved in individual aliquots at pre-determined cell densities, stored at −70°C, and thawed for use as standardized inocula as needed. Aliquots were prepared with precision (typically within 10% of the mean) ensuring reproducible inoculation. Five of the six strains displayed no appreciable loss of viability during cryopreservation exceeding 2.5 years, and five isolates demonstrated stable hydrocarbon-degrading phenotypes during inoculum preparation and storage. When resuscitated, the defined consortium reproducibly biodegraded Alberta Sweet Mixed Blend crude oil (typically ± 7% of the mean of triplicate cultures), as determined by quantitative gas chromatography–mass spectrometry of various analyte classes. Reproducible biodegradation was observed within a batch of inoculum in trials spanning 2.5 years, and among three batches of inoculum prepared more than 2 years apart. Biodegradation was comparable after incubation for 28 days at 10°C or 14 days at 22°C, illustrating the temperature tolerance of the bacterial consortium. The results support the use of the synthetic consortium as a reproducible, predictable inoculum to achieve standardized efficacy tests for evaluating commercial OSBA.
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  • 88
    ISSN: 1476-5535
    Keywords: Keywords: Bacillus subtilis; riboflavin; 3,4-dihydroxy-2-butanone 4-phosphate synthase; GTP cyclohydrolase II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the proteins encoded by the riboflavin operon of Bacillus subtilis, RibA, was identified as the rate limiting enzyme in an industrial riboflavin producing strain. An additional single copy of the ribA gene was introduced into the sacB locus of the riboflavin production strain and was expressed constitutively from the medium strength vegI promoter. This led to improved riboflavin titers and yields of riboflavin on glucose of up to 25%. Both enzymatic activities of RibA, the 3,4-dihydroxy-2-butanone 4-phosphate synthase activity located in the N-terminal half of the protein and the GTP cyclohydrolase II activity of the C-terminal domain, are necessary for the improved riboflavin productivity.
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  • 89
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 39-43 
    ISSN: 1476-5535
    Keywords: Keywords: murein; cell wall hydrolase; phage lysin; thymol-triggered lysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effective disruption of Escherichia coli cells is achieved by the intracellularly accumulated recombinant murein hydrolase (Lactobacillus bacteriophage LL-H muramidase) after the addition of 5 mM thymol. Thymol destroys the integrity and electric potential of the cytoplasmic membrane, and as a consequence the muramidase can access and hydrolyze the cell wall murein leading to cell lysis. Lysis occurred within 5 min after the addition of thymol and seemed to be efficient at high culture densities. This lysis method does not require cell harvesting or addition of other cell wall weakening substances or exogenous enzymes. As a cell disruption method, thymol-triggered lysis is as efficient as sonication in the presence of 1% Triton. Furthermore, thymol did not interfere with the purification steps of Mur by expanded bed adsorption chromatography (EBA), suggesting that the lysis method presented here is well suited for large-scale production and purification of intracellular proteins of E. coli.
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  • 90
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 52-57 
    ISSN: 1476-5535
    Keywords: Keywords: nitro-PAHs; metabolism; Cunninghamella elegans; biotransformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biotransformation of 1-nitrobenzo[e]pyrene (1-nitro-BeP), an environmental pollutant derived from the nitration of a non-carcinogen, benzo[e]pyrene, was studied using the fungus Cunninghamella elegans ATCC 36112. After 72 h incubation, 89% of 1-nitro-[3H]BeP added had been metabolized to two major metabolites. These metabolites were separated by reversed-phase high performance liquid chromatography and identified by 1H NMR, UV-visible, and mass spectral techniques as 1-nitro-6-benzo[e]pyrenylsulfate and 1-nitrobenzo[e]pyrene 6-O-β-glucopyranoside. Comparison of the fungal metabolism patterns of 1-nitro-BeP and BeP indicates that the nitro group at the C-1 position of BeP altered the regioselectivity of metabolism.
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  • 91
    ISSN: 1476-5535
    Keywords: Keywords: recombinant Bacillus subtilis; riboflavin produced by fermentation; down-stream processing; analytics; registration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel process for riboflavin production using a recombinant Bacillus subtilis strain has been developed. Here we describe a down-stream processing procedure to obtain riboflavin qualities having a minimal content of 96% (‘feed-grade’) and 98% (‘food/pharma-grade’) riboflavin, respectively. Compared to riboflavin produced by chemical synthesis, products with improved chemical purity were obtained. All compounds representing more than 0.1% of the final products were identified. Feed-grade riboflavin material ex fermentation contained small amounts of amino acids and amino sugars and the biosynthetic riboflavin precursor dimethyl-ribityl-lumazine. All other side products found were derived from riboflavin, resulted from the purification procedure and were also found in riboflavin obtained by chemical synthesis. The Bacillus-produced riboflavin does not contain DNA. The data presented here were used to obtain product approval for the commercial application in the USA, Japan and the UK.
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  • 92
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 80-87 
    ISSN: 1476-5535
    Keywords: Keywords: airborne bacteria; phospholipid fatty acids; human health
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exposure to airborne biocontaminants may result in a multitude of health effects and is related to a pronounced increase in adult-onset asthma. Established culture-based procedures for quantifying microbial biomass from airborne environments have severe limitations. Assay of the phospholipid fatty acid (PLFA) components of airborne microorganisms provides a quantitative method to define biomass, community composition and nutritional/physiological activity of the microbial community. By collecting airborne particulate matter from a high volume via filtration, we collected sufficient biomass for quantitative PLFA analysis. Comparing high (filtration) and low (impaction) volume air sampling techniques at 26 locations within the Eastern United States, we determined that PLFA analysis provided a viable alternative to the established but flawed culture-based techniques for measuring airborne microbial biomass and community composition. Compared to the PLFA analysis, the culture techniques underestimated the actual viable airborne biomass present by between one to three orders of magnitude. A case study of a manufacturing plant at which there had been complaints regarding the indoor air quality is presented. Phospholipid fatty acid characterization of the biomass enabled contamination point source determination. In comparison with samples taken outdoors, increases in the relative proportion of trans PLFA, reflecting shifts in the physiological status of viable airborne Gram-negative bacteria, were detected in the indoor air samples at a majority of sampling sites.
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  • 93
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 96-99 
    ISSN: 1476-5535
    Keywords: Keywords: Streptomyces sp; α-amylase; thermostability; structure-function; dimerisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The amylolytic system of Streptomyces sp IMD 2679 is composed of three α-amylases, amylase I, II and III, with temperature maxima of 60, 60–65 and 65°C, respectively. Although each α-amylase displayed higher stability in the pH range 6.0–8.5 than at pH 5.0–5.5, differences in their thermostabilities were more evident as the pH increased from pH 6.0 to 8.5. There was a 14-min difference in half-lives between amylase III, the most thermostable enzyme and amylase II at pH 6.0, and a 46-min difference in the half-lives of amylase III and the least thermostable enzyme, amylase I at pH 6.5. In addition, the α-amylases underwent a pH-dependent monomer-dimer transformation. Increased thermostability of the α-amylases was reflected in the variable contents of amino acids (Arg, His, Ser) responsible for electrostatic interactions, and in the levels of aliphatic and bulky hydrophobic amino acids. There was a two-fold reduction in Cys levels in amylase III relative to amylase I and II.
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  • 94
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 121-126 
    ISSN: 1476-5535
    Keywords: Keywords: biodegradation; phenol; Pseudomonas putida; immobilized
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alginate concentrations between 2 and 4% had little effect on the degradation rate of phenol by alginate-immobilized Pseudomonas putida. Ten-degree shifts from 25°C resulted in approximately 30% slower degradation. Maximal degradation rates were favored at pH 5.5–6.0. The response of degradation rate to increased air flow in the bubble column used was almost linear and an optimal higher than 16 vol vol−1 was indicated, although free cells appeared in the reaction medium above 12 vol vol−1. When the initial phenol concentration was raised, degradation rate was not significantly affected until levels higher than 1200 mg ml−1 where performance was markedly reduced. Increasing the ratio of total bead volume to medium volume gave progressively smaller increases in degradation rate. At a medium volume to total bead volume ratio of 5:1, the maximum degradation rate was 250 mg L−1 h−1.
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  • 95
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 160-163 
    ISSN: 1476-5535
    Keywords: Keywords: β-glucosidase; cellobiase; cellobiose-hydrolysis; Aureobasidium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: β-Glucosidase hydrolyzing cellobiose was extracted from Aureobasidium sp ATCC 20524 and purified to homogeneity. The molecular mass was estimated to be about 331 kDa. The enzyme contained 26.5% (w/w) carbohydrate. The optimum pH and temperature for the enzyme reaction were pH 4 and 80°C, respectively. The enzyme was stable at a wide range of pH, 2.2–9.8, after 3 h and at 75°C for 15 min. The kinetic parameters were determined. The enzyme was relatively stable against typical organic enzyme inhibitors. The enzyme also hydrolyzed gentiobiose, p-nitrophenyl-β-glucoside and salicin.
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  • 96
    ISSN: 1476-5535
    Keywords: Keywords: umami; L-glutamic acid, glutaminase; Cryptococcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An anamorphic basidiomycetous yeast, which produced a salt-tolerant and thermostable glutaminase, was isolated from soil in Japan and classified in the genus Cryptococcus. Its substrate specificity suggests that this enzyme is an L-glutaminase asparaginase (EC 3.5.1.38). The strain, G60, resembles Cryptococcus laurentii in the taxonomic criteria traditionally employed for yeasts, however it can be distinguished as a separate species based on DNA–DNA reassociation experiments and sequence analysis of the large sub-unit rDNA. Phenotypically, the isolate can be differentiated from C. laurentii by the inability to utilize arbutin as a sole source of carbon. Based on sequence analysis, the strain is related to a group of hymenomycetous yeasts including Bulleromyces albus, Bullera unica, C. laurentii and C. skinneri. The strain, which is formally described as Cryptococcus nodaensis, is industrially important for the formation of the umami taste during production of proteolytic seasonings.
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  • 97
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 216-224 
    ISSN: 1476-5535
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 98
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 167-175 
    ISSN: 1476-5535
    Keywords: Keywords: engineered biofilms; biocorrosion; sulfate-reducing bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To identify novel, less-toxic compounds capable of inhibiting sulfate-reducing bacteria (SRB), Desulfovibrio vulgaris and Desulfovibrio gigas in suspension cultures were exposed to several antimicrobial peptides. The bacterial peptide antimicrobials gramicidin S, gramicidin D, and polymyxin B as well as the cationic peptides indolicidin and bactenecin from bovine neutrophils decreased the viability of both SRB by 90% after a 1-h exposure at concentrations of 25–100 μg ml−1. To reduce corrosion by inhibiting SRB in biofilms, the genes for indolicidin and bactenecin were expressed in Bacillus subtilisBE1500 and B. subtilis WB600 under the control of the constitutive alkaline protease (apr) promoter, and the antimicrobials were secreted into the culture medium using the apr signal sequence. Bactenecin was also synthesized and expressed as a fusion to the pro-region of barnase from Bacillus amyloliquefaciens. Concentrated culture supernatants of B. subtilis BE1500 expressing bactenecin at 3 μg ml−1 decreased the viability of Escherichia coli BK6 by 90% and the reference SRB D. vulgaris by 83% in suspension cultures. B. subtilis BE1500 and B. subtilis WB600 expressing bactenecin in biofilms also inhibited the SRB-induced corrosion of 304 stainless steel six to 12-fold in continuous reactors as evidenced by the lack of change in the impedance spectra (resistance polarization) upon addition of SRB and by the reduction in hydrogen sulfide and iron sulfide in batch fermentations with mild steel. A 36-fold decrease in the population of D. vulgaris in a B. subtilis BE1500 biofilm expressing bactenecin was also observed. This is the first report of an antimicrobial produced in a biofilm for in vivo applications and represents the first application of a beneficial, genetically-engineered biofilm for combating corrosion.
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  • 99
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 225-240 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 100
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    Journal of industrial microbiology and biotechnology 22 (1999), S. 259-269 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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