Cost analysis in laccase production.

In this paper the cost of producing the enzyme laccase by the white-rot fungus Trametes pubescens under both submerged (SmF) and solid-state fermentation (SSF) conditions was studied. The fungus was cultured using more than 45 culture medium compositions. The cost of production was estimated by analyzing the cost of the culture medium, the cost of equipment and the operating costs. The cost of the culture medium represented, in all cases, the highest contribution to the total cost, while, the cost of equipment was significantly low, representing less than 2% of the total costs. The cultivation under SSF conditions presented a final cost 50-fold lower than the one obtained when culturing under SmF conditions at flask scale. In addition, the laccase production under SSF conditions in tray bioreactors reduced the final cost 4-fold compared to the one obtained under SSF conditions at flask scale, obtaining a final price of 0.04 cent €/U.

Sunflower seed shells: a novel and effective low-cost adsorbent for the removal of the diazo dye Reactive Black 5 from aqueous solutions.

In this paper, the potential of two low-cost adsorbents such as sunflower seed shells (SS) and mandarin peelings (MP) in the removal of the synthetic anionic dye Reactive Black 5 (RB5) from aqueous solutions was investigated. SS led to a percentage of dye removal higher than MP (85% and 71% after 210min, respectively, for an initial RB5 concentration of 50mgL(-1) and an initial pH of 2.0). The rate of adsorption followed a pseudo-second-order kinetic model and the intra-particle diffusion was found to be the rate-controlling stage. In addition, the equilibrium data fitted well both the Freundlich and multilayer adsorption isotherm equations indicating the heterogeneity of the adsorbent surface. This was also corroborated by the SEM photographs. On the whole, the results in this study indicated that SS were very attractive materials for removing anionic dyes from dyed effluents.

A simple method for probing the mechanical unfolding pathway of proteins in detail.

Atomic force microscopy is an exciting new single-molecule technique to add to the toolbox of protein (un)folding methods. However, detailed analysis of the unfolding of proteins on application of force has, to date, relied on protein molecular dynamics simulations or a qualitative interpretation of mutant data. Here we describe how protein engineering Phi value analysis can be adapted to characterize the transition states for mechanical unfolding of proteins. Single-molecule studies also have an advantage over bulk experiments, in that partial Phi values arising from partial structure in the transition state can be clearly distinguished from those averaged over alternate pathways. We show that unfolding rate constants derived in the standard way by using Monte Carlo simulations are not reliable because of the errors involved. However, it is possible to circumvent these problems, providing the unfolding mechanism is not changed by mutation, either by a modification of the Monte Carlo procedure or by comparing mutant and wild-type data directly. The applicability of the method is tested on simulated data sets and experimental data for mutants of titin I27.