Cloning, expression and characterization of novel fungal endoglucanases

Global energy consumption is projected to double between 1980 and 2020. Furthermore, about 65% of present energy consumption is derived by burning nonrenewable fossil fuels that increase atmospheric levels of CO2 , the major greenhouse gas implicated in global warming. It is therefore important that carbon neutral alternative energy sources be developed. For transportation fuels bioethanol derived from renewable energy sources is considered among the most attractive alternatives. Presently, most bioethanol is produced from corn kernels and sugar cane sucrose, with the United State and Brazil being the world's major producers. Cellulose is another possible feedstock that can be used to produce bioethanol. Compared with the currently used feedstocks, cellulose is very abundant in nature and its use for biofuels production would not compete with the food or animal feed industries. In order to use cellulose for bioethanol production, the cellulose must be converted into the fermentable sugar glucose. Currently, the high cost of converting the cellulose into glucose is a major impediment to using cellulose as a feedstock for the production of bioethanol. The goal of my research was to address this issue by discovering new fungal enzymes that could improve the cellulose hydrolyzing efficiency of existing commercial cellulase systems. In this study I identified, cloned, functionally expressed and characterized six endoglucanases, AfumEgl2010, AnidEgl2020, FgraEgl2010, FgraEgl1020, FgraEgl2020 and NcraEgl2010. Three of these endoglucanases, AfumEgl2010, AnidEgl2020, FgraEgl2010, were characterized in detail in this study. Only AfumEgl2010 harbours a carbohydrate-binding module (CBM). All three of the endoglucanases that were subject to detailed characterization show highest activity at pH 5.0. The temperature optima of these three endoglucanases were determined to be 40°C, 60°C and 70°C. All of them were stable during 30 minutes pre-incubation at 60°C. The kinetic parameters of these three endoglucanases and four other endoglucanases, the Trichoderma reesei (T. reesei ) Eg2/Cel5A and ApulSEQ15654, StheSEQ13822, GtraSEQ630 (previously identified by undergraduate student Christopher St-Francois) were determined at 37°C and the pH optima of each endoglucanase. The Km values ranged from 2.0 to 29 mg/ml. The Vmax values ranged from 5.7 to 41 omole/mg/min. The degree of synergism when these endoglucanases were combined with the T. reesei Cbh1/Ce17A was also determined

Bi-Deniable Public-Key Encryption

In CRYPTO 1997, Canetti \etal put forward the intruiging notion of \emph{deniable encryption}, which (informally) allows a sender and/or receiver, having already performed some encrypted communication, to produce `fake\u27 (but legitimate-looking) random coins that open the ciphertext to another message. Deniability is a powerful notion for both practice and theory: apart from its inherent utility for resisting coercion, a deniable scheme is also noncommitting (a useful property in constructing adaptively secure protocols) and secure under selective-opening attacks on whichever parties can equivocate. To date, however, known constructions have achieved only limited forms of deniability, requiring at least one party to withhold its randomness, and in some cases using an interactive protocol or external parties. In this work we construct \emph{bi-deniable} public-key cryptosystems, in which both the sender and receiver can simultaneously equivocate; we stress that the schemes are noninteractive and involve no third parties. One of our systems is based generically on ``simulatable encryption\u27\u27 as defined by Damgård and Nielsen (CRYPTO 2000), while the other is lattice-based and builds upon the results of Gentry, Peikert and Vaikuntanathan (STOC 2008) with techniques that may be of independent interest. Both schemes work in the so-called ``multi-distributional\u27\u27 model, in which the parties run alternative key-generation and encryption algorithms for equivocable communication, but claim under coercion to have run the prescribed algorithms. Although multi-distributional deniability has not attracted much attention, we argue that it is meaningful and useful because it provides credible coercion resistance in certain settings, and suffices for all of the related properties mentioned above

Undefined cellulase formulations hinder scientific reproducibility

In the shadow of a burgeoning biomass-to-fuels industry, biological conversion of lignocellulose to fermentable sugars in a cost-effective manner is key to the success of second-generation and advanced biofuel production. For the effective comparison of one cellulase preparation to another, cellulase assays are typically carried out with one or more engineered cellulase formulations or natural exoproteomes of known performance serving as positive controls. When these formulations have unknown composition, as is the case with several widely used commercial products, it becomes impossible to compare or reproduce work done today to work done in the future, where, for example, such preparations may not be available. Therefore, being a critical tenet of science publishing, experimental reproducibility is endangered by the continued use of these undisclosed products. We propose the introduction of standard procedures and materials to produce specific and reproducible cellulase formulations. These formulations are to serve as yardsticks to measure improvements and performance of new cellulase formulations