Sherald H. Gordon

Starch- polyvinyl alcohol crosslinked film— performance and biodegradation

Starch-PVOH cast films were prepared with and without crosslinking agent (hexamethoxymethylmelamine) in the absence of plasticizer. Moisture absorption in films without crosslinking agent at a low relative humidity was similar to that of PVOH and increased as the relative humidity increased. Films with crosslinking agent showed moisture absorption linearly proportional to the relative humidity. Significant improvement in resistance to water disintegration for crosslinked starch-PVOH films was observed. While the tensile strength decreased with increased relative humidity, crosslinking significantly improved the tensile strength. Increased PVOH content improved elongation of films even when the relative humidity was 80% or higher. Biodegradation studies revealed that the degradation rate was negatively correlated with the PVOH content in films and crosslinking generated more converged degradation curves.

Neural network pattern recognition of photoacoustic FTIR spectra and knowledge-based techniques for detection of mycotoxigenic fungi in food grains

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS), a highly sensitive probe of the surfaces of solid substrates, is used to detect toxigenic fungal contamination in corn. Kernels of corn infected with mycotoxigenic fungi, such as Aspergillus flavus, display FTIR-PAS spectra that differ significantly form spectra of uninfected kernels. Photoacoustic infrared spectral features were identified, and an artificial neural network was trained to distinguish contaminated form uncontaminated corn by pattern recognition. Work is in progress to integrate epidemiological information about cereal crop fungal disease into the pattern recognition program to produce a more knowledge-based, and hence more reliable and specific, technique. A model of a hierarchically organized expert system is proposed, using epidemiological factors such as corn variety, plant stress and susceptibility to infection, geographic location, weather, insect vectors, and handling and storage conditions, in addition to the analytical data, to predict Al. flavus and other kinds of toxigenic fungal contamination that might be present in food grains.

Solid state analysis of plant polymers by FTIR

Abstract Wheat straw, kenaf, oak, and pine were extracted to give samples with various contents of lignin, hemicellulose, and cellulose. Precise amounts of these samples were blended with KBr and pressed into discs, and their FTIR spectra were determined. Two-spectra subtraction, and combination of multiple spectra by matrix inversion and least squares matrix methods were used to give spectra of individual lignin, hemicellulose, and cellulose components in all 4 plant types. They are the most complete IR spectra available for lignin in plant matrices.

Pseudo-halogen sugar derivatives: Synthesis and hofmann-rearrangement reactions; 6-O-[2-(N,N-dichlorocarbamoyl)-ethyl]-1,2:3,4-di-O-isopropylidene-α-d-galactopyranose

6-O-[2-(N,N-Dichlorocarbamoyl)ethyl]-1,2:3,4-di- O-isopropylidene-α-d-galactopyranose, a highly reactive pseudo-halogen, was conveniently prepared in 97% yield by addition of sodium hypochlorite to an aqueous acidic (pH <2) solution of 6-O-(2-carbamoylethyl)-1,2:3,4-di-O-isopropylidene-α-d-galactopyranose. Mild, reductive dechlorination or alkaline hydrolysis readily converted the nonpolar N,N-di-chloroamide sugar derivative into the corresponding water-soluble N-monochloroamide form. Hofmann rearrangement of the N-chloroamide group provides a synthetic route to novel binary sugar-derivatives having carbamoyl, ureylene, and allophanoyl linkages. Structural proof for the pseudo-halogens and their Hofmann-rearrangement products was obtained from i.r., 1H-n.m.r., mass-spectral, and chemical data.

Identification and Measurement of Intermolecular Interaction in Polyester/Polystyrene Blends by FTIR-Photoacoustic Spectrometry

Fourier transform infrared photoacoustic spectrometry was used to reveal and identify n–π type intermolecular interaction formed in plastic comprising binary blends of polystyrene and a biodegradable polymer, either polylactic acid, polycaprolactone or poly(tetramethyleneadipate-co-terephthalate). This was the first reported direct and definitive experimental evidence of n–π type bond formation in thermoplastic blends of these polyesters with polystyrene. Also, an infrared method was devised that permits quantitative measurement of the degree of interaction between the two polymers at various concentrations in the blends. The method employs spectral deconvolution by least squares curve fitting of the polymer carbonyl band into its underlying peaks. In a new algorithm the method compares deconvoluted Gaussian/Lorentzian peaks of the polymer blends with deconvoluted peaks in the neat polymers and computes both the magnitude and direction of change in the n–π bond formation with change in polymer concentration. The results indicated that the degree of interaction was dependent on the type and concentration of the biodegradable polymer in the blend. These findings are supported by differential scanning calorimetry and thermogravimetric analyses. Unlike conventional spectral deconvolution methods, this technique with its new algorithm approximates infrared absorptivities of all the underlying peaks, and is thus a superior method that should be applicable to multicomponent polymer blends in general.

Osage Orange (Maclura pomifera L.) Seed Oil Poly(α-hydroxydibutylamine) Triglycerides: Synthesis and Characterization

Milled Osage orange seeds (Maclura pomifera (Raf.) Schneid) were Soxhlet extracted with hexane, and portions of the extract were treated with activated carbon before solvent removal. The crude oil was winterized and degummed by centrifugation at low temperature. Decantation of the centrifugate gave an admixture of the triglycerides and free fatty acids. The free fatty acid content of the oil was removed when portions of the admixture were diluted with hexane and shaken with cold aqueous ammonium hydroxide (0.1 M) solution. The desiccant-dried organic phase was concentrated under reduced pressure to give the cleaned Osage orange triglyceride after solvent removal by rotary evaporation at 67 °C. Epoxidation of the resulting cleaned triglyceride was effected by reaction with in situ generated peroxy performic acid in H2O2. The oxirane rings of the derivatized oil were then opened using N,N-dibutylamine catalyzed by anhydrous ZnCl2 to afford the poly(α-hydroxydibutylamine) triglyceride. The purpose of this work was to derivatize and thereby stabilize this highly unsaturated tree oil for its eventual use in lubrication applications.

Monitoring Solid-Substrate fermentations by Fourier Transform Infrared-Photoacoustic Spectroscopy

Fermentation systems that utilize insoluble substrates, such as cellulose, are difficult to monitor because few techniques are suitable to analyze solid-state samples. A new technique, photoacoustic spectroscopy (PAS), has been developed and provides information about the UV, visible and JR absorption spectra of solids, gels and other materials not suited for conventional optical analyses (Rosencwaig, 1980a, b; Gerson, Wong and Casper, 1984). PAS has the added advantages of requiring little sample preparation and being non-destructive to the sample. To obtain a PAS spectrum, the sample is placed in a closed cell containing a sensitive microphone. Light is admitted through a window to irradiate the sample. When the sample absorbs light, it becomes heated and warms the surrounding layer of air or gas. The warmed gas expands resulting in increased pressure within the cell. If the light is blocked off, the sample cools and the gas pressure in the cell returns to its original level. Periodically modulating or chopping the light produces gas pressure waves that can be detected as sound. The pitch of the sound corresponds to the modulation frequency, but the intensity depends on the amount of light absorbed by the sample. Light scattering properties of the .sample or optical opacity have virtually no effect in PAS because only absorbed light can produce an acoustic wave. Therefore, the photoacoustic spectrum of a given material is an accurate representation of the optical absorption spectrum of that material. Coincidental with the recent developments in PAS has been the development of Fourier transform (FT) technology, especially for analysis of the mid-JR region (Perkins, 1986). In FTIR, the form of the signal is an interferogram, which is subsequently transformed mathematically into a representative JR spectrum. This allows for rapid data acquisition and processing, which is necessary for application of PAS. Biological materials generally have rather complex chemical structures, which translate into distinct absorption patterns in the mid-IR spectral region. Therefore, FTIR-PAS is ideally suited for analysis of solid-substrate fermentations. Recent experimentation in our laboratory has shown that fungal growth on Solid cellulose discs may be quantitatively determined by monitoring protein absorption bands with FTIR-PAS (Greene, Freer and Gordon, 1988). Cellulose (Whatman #1 filter paper) discs which were impregnated with increasing dry weights of the fungus, Phanerochaete chrysosporikum, exhibited increasing absorbance at 1654 cm(superscript -1) (amide I region )and 1544 cm(superscript -1) (amide II region), These absorbances were attibuted to the peptide backbone of the fungal proteins. By monitoring amide I absorption relative to known quantities of fungal dry weight, it was possible to generate a standard curve. P. chrysosporium, which is cellulolytic, was then grown on filter paper discs. As expected, FTIR-PAS spectra of discs inoculated with a spore suspension exhibited significant increases in amide I and II absorption as a function of culture age. When ‘amide I absorption was converted into fungal dry weight by using the previously described standard curve, a growth curve was generated. The FTIR-PAS growth curve was remarkably similar to one generated by using a Lowry protein assay on the same samples after sonic disruption. FTIR-PAS is subject to instrumental artifacts that can result in data scattering. Lower levels of fungal biomass exhibit such scattering. Although this level of scattering is not of great concern when determining gross fungal biomass, it could introduce significant irreproducibility in attempts to measure lesser constituents, such as secondary metabolites. However, instrumental artifacts may be removed by normalizing to an appropriate internal standard. Ployacrylonitrile (PAN) was selected (Gordon, Greene, Freer and James, 1990).PAN exhibits a sharp absorption peak (2243 cm(superscript -1) far removed from absorptions of biological interest. PAN is easy to apply and uniformly distributes throughout the sample. The reproducibility of FTIR-PAS using PAN for quantitation of microbial biomass on solid surfaces was tested. Four proteins and four microorganisms, selected to cover a range of species and morphologies, were deposited on Millipore filters containing PAN. The use of PAN internal standard greatly enhanced the correlation of the FTIR-PAS assay, routinely enabling biomass measurements to be achieved with less than 10% error. With the degree of accuracy afforded by utilizing the PAN internal standard, it should be possible to measure secondary metabolite production with FTIR-PAS. Peniclillin was selected as a model system. Due to an ester carbonyl and a free carbonyl, the GTIR-PAS spectrum of penicillin exhibited two sharp peaks at 1700 cm(superscript -1) and 1775 cm(superscript -1) A distinct band at 3356 cm(superscript -1) was also observer which was attributed to an NH vibrational stretch. These bands were readily visible when 10-20% penicillin was added to a penicillin-free fungal culture (dry weight basis). In the near future, with the aid of mathematical models for multivariant calibration (a current project in .our laboratory), it should be possible to accurately determine penicillin production at the 1% level from an FTIR spectrum. These results demonstrate the potential ability of FTIR-PAS for analysis of biomass, and constitute a significant advance toward the goal of practical application of the new technique to solid-state assays for microorganisms used in the production of drugs, hormones and other biological agents. With further improvement in technology, FTIR-PAS is potentially a powerful tool for in situ analysis of biological systems.