Czarena Crofcheck

Effect of anatomical fractionation on the enzymatic hydrolysis of acid and alkaline pretreated corn stover

Due to concerns with biomass collection systems and soil sustainability there are opportunities to investigate the optimal plant fractions to collect for conversion. An ideal feedstock would require a low severity pretreatment to release a maximum amount of sugar during enzymatic hydrolysis. Corn stover fractions were separated manually and analyzed for glucan, xylan, acid soluble lignin, acid insoluble lignin, and ash composition. The stover fractions were also pretreated with either 0%, 0.4%, or 0.8% NaOH for 2 h at room temperature, washed, autoclaved and saccharified. In addition, dilute sulfuric acid pretreated samples underwent simultaneous saccharification and fermentation (SSF) to ethanol. In general, the two pretreatments produced similar trends with cobs, husks, and leaves responding best to the pretreatments, the tops of stalks responding slightly less, and the bottom of the stalks responding the least. For example, corn husks pretreated with 0.8% NaOH released over 90% (standard error of 3.8%) of the available glucan, while only 45% (standard error of 1.1%) of the glucan was produced from identically treated stalk bottoms. Estimates of the theoretical ethanol yield using acid pretreatment followed by SSF were 65% (standard error of 15.9%) for husks and 29% (standard error of 1.8%) for stalk bottoms. This suggests that integration of biomass collection systems to remove sustainable feedstocks could be integrated with the processes within a biorefinery to minimize overall ethanol production costs.

EFFECT OF STOVER FRACTION ON GLUCOSE PRODUCTION USING ENZYMATIC HYDROLYSIS

Corn stover was fractionated into three fractions: cobs, stalks, and leaves and husks. The fractions were dried and ground through a 2 mm screen. Samples of the three fractions and whole corn stover with and without NaOH pretreatment were subjected to enzymatic hydrolysis in order to determine the effect of fractionation on glucose production. The average amounts of glucose released after 60 h of hydrolysis from pretreated cobs, leaves and husks, stalks, and whole stover were 0.50, 0.36, 0.28, and 0.36 g/g dry biomass, respectively. The average amounts of glucose released after 60 h of hydrolysis from nonpretreated cobs, leaves and husks, stalks, and whole stover were 0.32, 0.23, 0.17, and 0.20 g/g dry biomass, respectively. Pretreatment resulted in an average increase of 60% in glucose production for all fractions and whole stover. The effect of stover fraction type on glucose production was significant with and without pretreatment. By collecting the fractions of the corn stover with the highest glucose potential (all the cobs and 74% of the leaves and husks) and leaving the remaining fraction (26% of the leaves and husks, and all the stalks) in the field for erosion control, the glucose potential of the collected biomass would increase by 21%. This could represent a decrease of up to 17% in the cost of ethanol production. This indicates that fractionation and collection of the biomass with the highest glucose potential may produce a higher quality feedstock for glucose production.

Histidine tagged protein recovery from tobacco extract by foam fractionation

Tobacco plants have the potential to be used for the production of proteins for pharmaceutical applications. This work describes a novel protein recovery strategy where the protein of interest is “tagged” with a histidine sequence, which forms a complex with cobalt ions and surfactant possessing a chelating functionality, such that the protein is recovered in the foamate of a foam fractionation step. His‐gus, a histidine‐tagged enzyme, was chosen as a model protein to study the feasibility of this strategy. The His‐gus is recovered from spiked prefoamed tobacco extract by foam fractionation in the presence of surfactant and cobalt ions with an enrichment of 1.29 and a recovery of 21.5% in terms of an adjusted activity.

Characterization of milk properties with a radiative transfer model

To characterize milk through light-scattering measurements, a semianalytical radiative transfer model was used to simulate the backscatter of light in milk having homogenized fat levels from 0.05 to 3.2 wt. %. The input parameters to the model include the incident wavelength, refractive index of particles and medium, and particle number densities. By varying the wavelength, we can obtain a reasonable fit between experimental data and the model for lower fat milks. Results indicate that the model is most sensitive to the particle diameter and size distribution and less sensitive to the number and index of refraction of the particles.

Spatially selective melting and evaporation of nanosized gold particles

We have developed an atomic force microscope-tip-based concept to pattern metallic nanoparticles on substrates. This new process has the potential to control the assembly of nanometer sized particles by combining their unique optical and thermophysical properties and is a flexible and low energy method of patterning at the nanoscale. The proof of concept is detailed by preliminary experimental work showing selective melting and evaporation of groups of 50 and 100 nm gold spherical particles.

Evaluation of Foam Fractionation Column Scale-Up for Recovering Bovine Serum Albumin

Foam fractionation is an adsorptive-bubble separation method that, according to researchers, is a feasible technique for the separation and/or concentration of proteins. The foam fractionation of bovine serum albumin (BSA) in laboratory -scale foam fractionation columns (750 and 1250 mL) and the relationship between the two laboratory-scale columns and a pilot-scale column (5000 mL) were investigated. Recovery, enrichment, and performance factor values were experimentally determined with three different column volumes with varying pore sizes, gas superficial velocities, and, in the case of the 750 mL column, foam column height. As the pore size decreased, the amount of protein recovered from the dilute protein solution increased and the enrichment decreased. As the flow rate of the gas increased, the effect of the pore size decreased. For the three column volumes, the optimal column conditions were achieved with the largest pore size (145- 174 .m) and an intermediate superficial gas velocity (7 mm/s). Increasing the foam column height increased the enrichment without sacrificing the recovery of the target protein. In the case of the largest pore size, the linear relationships between the recovery and the ratio of gas volume to initial liquid volume are parallel, such that the recovery in a pilot-scale column (5000 mL) can be predicted with the recovery found with a laboratory-scale column (750 or 1250 mL).

PREDICTING THE CUTTING TIME OF COTTAGE CHEESE USING LIGHT BACKSCATTER MEASUREMENTS

An automated system for monitoring culture growth and determining coagulum cutting time is needed for cottage cheese manufacturing. A light backscatter measurement system was designed and installed in a local cottage cheese manufacturing plant. A cutting time prediction algorithm was developed using parameters generated from the backscatter profile. The cutting time prediction algorithm, Tcut = Tmax + â2 S, used two time-based parameters generated from the backscatter profile (Tmax and S) and one operator selected parameter, â2, to predict the coagulum cutting time, Tcut. The standard error of prediction for the algorithm was 6.4 min and was an improvement over the standard error of 8.7 min previously reported (Payne et al., 1998). The algorithm is more robust than that used by Payne et al. (1998) because it predicts cutting time based on a measure of coagulation kinetics, S, and eliminates the uncertainty of the culture starting time from the algorithm. In addition, a method was proposed for continuous monitoring of culture growth during the first 210 min of the process.

Chapter 2:Energy Crops for the Production of Biofuels

Numerous options are available to supply biomass to biorefineries. Potential feedstocks include short rotation woody crops, herbaceous energy crops, and residues (forestry and agricultural). Each feedstock has unique chemical and physical properties that will influence the products and profitability from a biorefinery. For example, herbaceous feedstocks will have higher ash contents on average than woody products. Herbaceous feedstocks typically will have a lower lignin content and as a result a lower heating value than woody crops. Feedstock selection should consider the availability of equipment to establish, maintain, and harvest energy crops. In most cases, the equipment required is available to produce energy crops within the forestry and agricultural industries but is not optimized for energy crop production. Deciding which feedstock to produce will depend on site-specific considerations (soil type, temperature, and rainfall) that will influence the cost, yield, and composition of energy crops. Collection, storage, and transportation of energy crops is expensive relative to current fossil fuels, although biomass energy crops have lower greenhouse gas emissions than fossil fuels.

EFFECT OF FAT AND CASEIN PARTICLES IN MILK ON THE SCATTERING OF ELLIPTICALLY POLARIZED LIGHT

In this article, we present an experimental approach to determine the milk fat content using scattered light intensity profiles. The elements of the scattering (Mueller) matrix have been shown to provide valuable information about variation of the optical properties of scattering particles. The scattering behavior of fat and casein in terms of the scattering matrix elements was experimentally determined for milk with varying fat levels ranging from 0.05 wt% (skim) to 3.20 wt% (whole). Three of the scattering Mueller matrix elements, specifically S11, S12/S11, and S33/S11, were found to be sensitive to the number of fat particles in milk. These results indicate that it should be possible to develop a reliable sensor based on the measurement of these scattering elements, which will allow for the development of a robust, in-line sensor to be used in food processing. In addition, an attempt was made to model the phenomena using a relatively simple approach based on single scattering with a size distribution. The disagreement between the model and experiments suggests that a more comprehensive model is needed which can account for multiple scattering.

LIGHT BACKSCATTER OF MILK PRODUCTS FOR TRANSITION SENSING USING OPTICAL FIBERS

Transition sensors are needed, particularly in the dairy industry, for detecting transitions in pipe flow systems from product-to-water or product-to-product (such as from chocolate to vanilla ice cream mix). Transition information is used to automatically sequence valves to minimize product waste. Optical fibers were used to measure light backscatter between 400 and 950 nm as a function of milk concentration in water and milkfat concentration in milk. The normalized response (100% for product and 0% for water) as a function of product concentration in water was approximately logarithmic for skim milk between 400 and 900 nm and approximately linear for milk containing 1, 2, and 3.2% milkfat. The backscatter ratio (response relative to that for skim milk) as a function of milkfat in milk was wavelength dependent with longer wavelengths being more sensitive. The backscatter ratio at 900 nm for milk containing 3.2% homogenized fat was nearly four times that for skim milk. Backscatter ratio saturated (minimal response with increased milkfat) at 8% milkfat for homogenized cream and 16% milkfat for unhomogenized cream. Light backscatter for near infrared wavelengths around 900 nm was found ideally suited for transition sensing of dairy products and was found particularly sensitive to milkfat content. Light backscatter was found less suitable for discriminating between high milkfat products.