Enzymes play a critical role in the conversion of lignocellulosic waste into fuels and chemicals, but the high cost of these enzymes presents a significant barrier to commercialization. In the simplest terms, the cost is a function of the large amount of enzyme protein required to break down polymeric sugars in cellulose and hemicellulose to fermentable monomers. In the past 6 years, significant effort has been expended to reduce the cost by focusing on improving the efficiency of known enzymes, identification of new, more active enzymes, creating enzyme mixes optimized for selected pretreated substrates, and minimization of enzyme production costs. Here we describe advances in enzyme technology for use in the production of biofuels and the challenges that remain.

Spo11, a type II topoisomerase, is likely to be required universally for initiation of meiotic recombination. However, a dichotomy exists between budding yeast and the animals Caenorhabditis elegans and Drosophila melanogaster with respect to additional roles of Spo11 in meiosis. In Saccharomyces cerevisiae, Spo11 is required for homolog pairing, as well as axial element (AE) and synaptonemal complex (SC) formation. All of these functions are Spo11 independent in C.elegans and D.melanogaster. We examined Spo11 function in a multicellular fungus, Coprinus cinereus. The C.cinereus spo11‐1 mutant shows high levels of homolog pairing and occasionally forms full‐length AEs, but no SC. In C.cinereus, Spo11 is also required for maintenance of meiotic chromosome condensation and proper spindle formation. Meiotic progression in spo11‐1 is aberrant; late in meiosis basidia undergo programmed cell death (PCD). To our knowledge, this is the first example of meiotic PCD outside the animal kingdom. Ionizing radiation can partially rescue spo11‐1 for both AE and SC formation and viable spore production, suggesting that the double‐strand break function of Spo11 is conserved and is required for these functions.

The interaction of 6-fluoroquinolones at the lipid-water interface is the primary step for the activity of membrane transporters involved in the generation of drug resistance. In this work the interaction of the antibiotic ciprofloxacin (CPX) and its N-4-butylpiperazinyl derivative (BCPX) with dipalmitoylphosphatidylcholine (DPPC) as a model membrane is described. BCPX forms a stable film at the air-water interface and induces a condensing effect of the DPPC monolayer. A basic thermodynamic analysis was performed which suggests a possible segregation of the drug at the lowest proportion studied. The temperature dependence of 3-(4-(6-phenyl)-1,3,5-hexatrienyl)phenylpropionic acid fluorescence anisotropy measurements shows that the incorporation of CPX or BCPX into bilayers does not greatly modify the DPPC lamellar gel state. In the liquid-crystalline phase, BCPX lowered the anisotropy values and both drugs lowered the main transition temperature (Tm) of pure DPPC by approximately 1 °C. On the other hand, significant changes in the cooperativity of the phospholipid transition were found only in the presence of BCPX. In 31 P-NMR experiments the presence of BCPX induced, both below and above the main transition, a strong line shape narrowing of the DPPC spectra that suggests an increase in the local mobility of the phosphate groups; that is, the interactions between DPPC headgroups are altered by the presence of BCPX. Although the incorporation of CPX also promotes a remarkable line shape narrowing in the fluid phase, it only slightly modifies the spectral parameters of DPPC in the gel phase. This suggests that CPX could be "squeezed out" or segregated from the lipid-water interface when the phospholipids are in this tight packed phase. The segregation is likely to occur to defects on the gel phase. Values of 1-anilino-8naphthalenesulfonate binding to the liposome surface were fitted to a Freundlich-like isotherm. The binding constant (K) and maximum concentration bound to liposomes (Cm) both are dependent on the structure of the drugs, which indicates a definite effect due to the drug hydrophobicity. K values in the presence and absence of drug were used to calculate the variation in the surface potential (∆Ψ) of the liposomes. All the results are consistent with an electrostatic interaction of 6-fluoroquinolones at the lipid-water interface. This interaction is favored by the presence of the N-4-butyl chain and could have important implications in the efflux of this drug from bacteria.

In this work, the interaction between the antibiotic ciprofloxacin (CPX) and liposomes formed with zwitterionic and acidic phospholipids was studied using fluorescence methods. Binding of 1-anilino-8-naphthalene sulfonate to the liposome surface was dependent on the presence of CPX and the lipid composition. The data were fitted to a Freundlich-like isotherm. The binding constant (K), maximum concentration bound to liposomes (C m), and cooperativity (b) were obtained. K values, in the presence and absence of CPX, were used to calculate the variation in the surface potential (ΔΨ) of the liposomes. Fluorescence quenching and anisotropy measurements suggest that the drug interacts with the headgroups of the phospholipids and does not penetrate deeper in the bilayer. No significant changes were observed in the cooperativity of the phospholipid transition. Hydrogen bonding with dipalmitoylphosphatidylethanolamine and electrostatic interactions with dipalmitoylphosphatidylglycerol and zwitterionic phospholipids such as dipalmitoylphosphatidylcholine appear to be involved in the interaction occurring in natural membranes.

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