Both cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are nanoscale cellulose fibers that have shown reinforcing effects in polymer nanocomposites. CNCs and CNFs are different in shape, size and composition. This study systematically compared their morphologies, crystalline structure, dispersion properties in polyethylene oxide (PEO) matrix, interactions with matrix, and the resulting reinforcing effects on the matrix polymer. Transparent PEO/CNC and PEO/CNF nanocomposites comprising up to 10 wt % nanofibers were obtained via solution casting. Scanning electron microscopy (SEM), wide-angle X-ray diffraction (WXRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analyzer (DMA), and tensile testing were used to examine the above-mentioned properties of nanocellulose fibers and composites. At the same nanocellulose concentration, CNFs led to higher strength and modulus than did CNCs due to CNFs' larger aspect ratio and fiber entanglement, but lower strain-at-failure because of their relatively large fiber agglomerates. The Halpin-Kardos and Ouali models were used to simulate the modulus of the composites and good agreements were found between the predicted and experimental values. This type of systematic comparative study can help to develop the criteria for selecting proper nanocellulose as a biobased nano-reinforcement material in polymer nanocomposites.

Potato starch with anomalous stable (constant with time) paste viscosity has been proposed as a natural replacement for cross-linked starch, Embut its behavior and the influencing factors are not well understood. Starch from 44 samples of potato tubers representing 34 genotypes was analyzed for phosphorus, mean granule diameter, amylose, cal-600cium, magnesium, sodium, and potassium. Except for granule diame-> ter, sodium, and potassium, each of those properties correlated C significantly with one or more of five paste characteristics determined using the Brabender Visco-amylograph. Three samples had a stable > viscosity in 1 yr of the study, but their behavior was not associated with unusual values of the other measured properties. The stable vis-200cosity is probably a heritable trait influenced by cultural and climatic factors.

THERMAL and other physicochemical properties of starch from 42 potato genotypes were studied to find those with unique properties for food use, and to analyze relationships between thermal and other physicochemical properties. Onset and peak transition temperatures and gelatinization enthalpy intercorrelated. Transition temperatures intercorrelated with pasting temperature using a Brabender Visco-amylograph. Gelatinization entbalpy correlated with Brabender pasting temperature and peak paste viscosity, and onset temperature correlated with phosphorus content. Genotype E55-3.5 with highest onset and peak transition temperatures also had highest phosphorus and peak Brabender viscosity. DSC might be useful for rapidly screening samples of

Thiolase (acetyl-coenzyme A [CoAl acetyltransferase, E.C. 2.3.1.19) from Clostridium acetobutylicum ATCC 824 has been purified 70-fold to homogeneity. Unlike the thiolase in Clostridium pasteurianum, this thiolase has high relative activity throughout the physiological range of internal pH of 5.5 to 7.0, indicating that change in internal pH during acid production is not an important factor in the regulation of this thiolase. In the condensation direction, the thiolase is inhibited by micromolar levels of CoA, and this may be an important factor in modulating the net condensation of acetyl-CoA to acetoacetyl-CoA. Other cofactors and metabolites that were tested and shown to be inhibitors are ATP and butyryl-CoA. The native enzyme consists of four 44,000-molecular-weight subunits. The kinetic binding mechanism is ping-pong. The Km value for acetyl-CoA is 0.27 mM at 30°C and pH 7.4. The Kmn values for sulfhydryl-CoA and acetoacetyl-CoA are, respectively, 0.0048 and 0.032 mM at 30°C and pH 8.0. The active site apparently contains a sulfhydryl group, but unlike other thiolases, this thiolase is relatively stable in the presence of 5,5'-dithiobis(2-nitrobenzoic acid). Studies of thiolase specific activity under various types of continuous fermentations show that regulation of this enzyme at both the genetic and enzyme levels is important.

The cooking and drying conditions for oilseeds preparatory to screw pressing are some of the most important factors that influence screw-press performance. Screw-press oil recovery, residual oil, pressing rate, and oil sediment content were measured for uncooked crambe seed and crambe seed cooked at 100°C for 10 min, pressed at six moisture contents ranging from 9.2 to 3.6% dry basis. Oil recovery significantly increased (P ≤ 0.01) from 69 to 80.9% and 67.7 to 78.9% for cooked and uncooked seeds, respectively, as moisture content decreased. Residual oil significantly decreased (P ≤ 0.01) from 16.3 to 11.1% and 16.9 to 11.9%, respectively, as moisture content decreased. The reduced oil loss due to only drying the seed from 9.2 to 3.6% was 32% for cooked seed, whereas cooking contributed only 3.6 to 7% reduced oil loss. Pressing rate decreased from 5.81 to 5.17 kg/h and 6.09 to 5.19 kg/h for cooked and uncooked seeds, respectively, whereas sediment content increased from 0.9 to 7.8% and 1.1 to 5.4%, respectively, as moisture content decreased. The effects of moisture content on pressing rate and sediment content were significant at P ≤ 0.05. All relationships of screw-press performance to moisture content were fitted to a second-order polynomial.