A microfibril-generating factor from the cellulase of Trichoderma reesei

A combination of ionic strength reduction and diafiltration of Trichoderma reesei cellulate complex through a hollow fiber apparatus of 5000 molecular weight (MW) cutoff and subsequent passage of filtrate over a Spherogel-TSK 3000-SW column provided extracts that had the ability to generate microfibrils in filter paper and to disrupt filter paper and corn leaf tissue. Milligram quantities of material obtained from these extracts released small amounts of soluble carbohydrate from filter paper, required ferric iron for increased activity, and contained amino acids. Short fiber formation and disruption of filter paper during interaction with these extracts was enhanced by prior acid treatment and eliminated by prior base treatment. The amount of soluble carbohydrate hydrolyzed in 24 h from filter paper by whole cellulase complex was not changed by first disrupting the substrate with the extracts.     

Treatment of leachate from a solid waste landfill site using a two-stage anaerobic filter

Raw leachate was treated using a two-stage upflow anaerobic filter process. Leachate from a solid waste landfill site, which received both municipal and industrial wastes, contained high organic matter (17-21 g/L COD, 13-14 g/L BOD, and 3.5-4.6 g/L volatile acids), and low metal (Zn and Fe) concentrations. Depending on sampling time, leachate composition and characteristics varied considerably. At an organic loading up to 4 g COD/day(2) media area, the BOD and COD removal percentages were 98 and 91%, respectively. The biofilters were also effective for metal removal. However, the filter effluent contained a high concentration of ammonia. System overloading was characterized by the accumulation of large quantities of volatile acids and by a now ratio of alkalinity/volatile acids, resulting in low COD removal and reduced gas production. Once the first filter was upset, the second stage could only partially respond to the volatile acids accumulated in the effluent of first filter.     

Polyelectrolyte precipitation of proteins: II. Models of the particle size distributions

A population-balance model has been used to characterize continuous polyelectrolyte precipitation of egg white proteins. We have modeled the particle size distributions of aggregates formed under a range of mixing conditions. The models, accounting for aggregate growth (by both shear-driven and Brownian-like collisions), breakage (by hydrodynamic shear or aggregate-aggregate collisions), and birth (by the breakage of large aggregates), fit the data well. The kinetic constants show dependencies on shear rate and residence time that have not been previously theoretically predicted; these dependencies are due in part to aging effects on the aggregate. The model constants show a dominance of growth over breakage, supporting qualitative interpretations of the particle size distributions. A mechanism for growth-rate enhancement, caused by polymer extensions from the particle surfaces, produced improved model performance. A collisional breakage mechanism is supported.     

A numerical evaluation of a hollow fiber extractive fermentor process for the production of ethanol

The economics of a process for the production of ethanol employing a hollow fiber extractive fermentor have been investigated. A computer simulation of the process incorporating a mathematical model of the fermentor was used to calculate the mass and energy balances. The results of the process simulation were read into a computer spreadsheet programmed with the economic calculations from which a final ethanol product cost was obtained. The process was found to be as competitive as conventional fermentation processes even at the currently high cost--$4/sq ft--of hollow fibers. It was determined that the 1986 price of 46.2 cents/L of ethanol produced by the process would be reduced by 1.8 cents/L for every $1/sq foot drop in the price of hollow fibers. A comparison of this process with conventional fermentation processes indicates that its potential savings lie in its ability to use a concentrated sugar feed, and the fermentor's increased productivity and ability to produce a concentrated ethanol stream which is removed by the extracting solvent.     

Improved performance in viscous mycelial fermentations by agitator retrofitting

For viscous mycelial fermentations it was demonstrated at the pilot-plant scale that the replacement of standard radial flow Rushton turbines with larger diameter axial-flow Prochem hydrofoil impellers significantly improved oxygen transfer efficiency. It was also determined that the Streptomyces broth under evaluation is highly shear thinning. Separate experiments using a Norcardia broth with similar Theological properties demonstrated that the oxygen transfer coefficient, K(L)a, can be greatly increased by use of water additions to reduce broth viscosity. These observations are consistent with the hypothesis that the improvement in oxygen transfer by changing agitator types is primarily due to an improvement in bulk mixing. A model is presented, based on the concepts of Bajpai and Reuss, which explains this improvement in performance in terms of enlargement of the well mixed micromixer region for viscous mycelial broths.     

Biospecific adsorption in fixed and periodic countercurrent beds

A mathematical model that describes the adsorption and wash stages of biospecific adsorption (affinity chromatography) in a packed column is presented. The model expressions account for film and pre diffusion mass transfer as well as for different mechanisms of interaction between the adsorbate(s) and the ligand. The model equations may be applicable to single and multi-component biospecific adsorption systems involving both monovalent and multivalent adsorbates.The results obtained from model simulations show that the breakthrough time of the adsorbate is significantly influenced by the rate of the interaction step between the adsorbate and the ligand. The results indicate that when short beds are employed, then the choice of ligand with respect to its rate of interaction with the adsorbate may be of paramount importance. In certain systems involving bivalent adsorbates, the adsorbate may be displaced from the one-site complex, reenter the flowing fluid stream, and increase the effluent adsorbate concentration above its inlet value. It is also shown that when a single column is divided into two beds operating in a periodic counter current mode, the ligand utilization can be almost four times higher than that obtained in a column of the same length operating in the fixed bed mode.The studies on the wash stage indicate that the reduction of the concentration of the contaminant to a specified low level may be accomplished for certain systems in a shorter time, if the direction of flow in the wash stage is opposite to that used in the adsorption stage. However, a larger amount of product will be lost, in general, when the direction of flow of the washing medium is opposite to that employed during the adsorption stage.     

Improved pseudoanalytical solution for steady-state biofilm kinetics

Simple algebraic expressions for the flux of substrate into a steady-state biofilm are developed. This pseudoanalytical solution, which eliminates the need for repetitiously solving numerically a set of nonlinear differential equations, is based on an analysis of the numerical results from the numerical solution of the differential equations. The critical advantage of this new pseudoanalytical solution is that it is highly accurate for the entire range of substrate concentrations and kinetic parameters. The article also illustrates that previous pseudoanalytical solutions for steady-state biofilm kinetics are seriously inaccurate for certain ranges of substrate concentration and kinetic parameters.