Development of xylose-fermenting yeasts for ethanol production at high acetic acid concentrations

Mutants resistant to comparatively high levels of acetic acid were isolated from the xylose-fermenting yeastsCandida shehatae andPichia stipitis by adapting these cultures to increasing concentrations of acetic acid grown in shake-flask cultures. These mutants were tested for their ability to ferment xylose in presence of high acetic acid concentrations, in acid hydrolysates of wood, and in hardwood spent sulfite liquor, and compared with their wild-type counterparts and between themselves. TheP. stipitis mutant exhibited faster fermentation times, better tolerance to acid hydrolysates, and tolerance to lower pH.     

Bond Prices Under Information Asymmetry and a Short Rate with Instantaneous Feedback

Methodology and Computing in Applied Probability - We study an information asymmetry problem in a bond market. Especially we derive bond price dynamics of traders with different levels of...     

Three-particle interactions in a quark-gluon plasma

We explore the influence of three-particle interactions, in either the initial or final state, on the collision rate in a high temperature plasma, and on the rate of quark and anti-quark pair (flavor) production. When the interactions are taken to be screened at the Debye wave numberq dT, three-particle interactions contribute significantly to the collision rate, but only marginally enhance flavor production over that from two-particle interactions. The magnitudes of the rates are, however, sensitive to the infra-red thresholds, which emphasizes the need for a reliable analysis of this issue. Our results also highlight the importance of treating many-particle processes adequately in the space-time evolution of quarks and gluons produced in ultrarelativistic heavy-ion collisions.We thank members of the Theoretical Physics Institute and the School of Physics and Astronomy at the University of Minnesota for their kind hospitality. Special thanks are due to J.I. Kapusta for stimulating discussions. The stay of P. L. at the University of Minnesota was supported by the U.S. Department of Energy under grant No. DOE/DE-FG02-87ER-40328; travel expenses were borne by the grant MM SR 01/35. Research support for M. P. by the U.S. Department of Energy under grant No. DE-FG02-88ER-40388 is acknowledged. The paper was written in its final form at the Institute of Theoretical Physics, Santa Barbara, during the research program Strong Interactions at Finite Temperatures. The authors express gratitude for the warm hospitality extended there and acknowledge the support of the National Science Foundation under Grant No. PHY89-04035.