Karen Kohlmann

Cellulose pretreatments of lignocellulosic substrates.

Cellulose in inedible plant materials, forestry residues, and municipal wastes must be pretreated to disrupt its physical structure, thereby making its hydrolysis to glucose practical. Developments since 1991 are summarized.

Assessment of ethanol production options for corn products

Abstract The production of ethanol from corn fiber has the potential to increase ethanol yields by a maximum of 0.3 gal/bushel in a wet-milling process. Incremental yields would be 0.13 gal/bushel from hexose, 0.1 from d -xylose and 0.07 from l -arabinose, at 100% hydrolysis and fermentation efficiency. At 80% efficiency for hexose hydrolysis and fermentation, and 70% for pentose, an incremental yield of 0.22 gallons/bushel of corn is expected. Of this total, 0.1 gal/bushel would be from hexoses, 0.07 from d -xylose, and 0.05 from l arabinose. A maximum practical incremental yield would probably fall between 0.22 and 0.3 gallons/bushel. These calculations are based on published compositional analyses of cellulose, starch, mono-saccharides, hemicellulose, protein and oil as distributed between the compartmentalized components of the corn kernel and published yield factors for hexose and pentose fermentations. Experimental yield factors for xylose (0.36 g ethanol/g xylose) and arabinose (0.34) fermenting microorganisms are lower than that for glucose (0.45–0.50), and significantly less than the theoretical yield of 0.51 g ethanol/g pentose. Nonetheless, we estimate that a wet-milling facility which currently produces 100 million gallons/year of ethanol from starch could generate an additional

Electrochromatographic separation of proteins

4–8 million of annual income if the fiber components were processed into ethanol. Hence, advances in fiber pretreatment and pentose fermentation are likely to have a major impact on enhancing productivity of corn ethanol plants. An engineering framework for assigning economic consequences of the additional utilization of fiber is presented.

Enzyme conversion of lignocellulosic plant materials for resource recovery in a Controlled Ecological Life Support System.

We have developed a modified electrochromatography system which minimizes Joule heating at electric field strengths up to 125 V/cm. A non-linear equilibrium model is described which incorporates electrophoretic mobility, hydrodynamic flow velocity, and an electrically induced concentration polarization at the surface of the stationary phase. This model is able to provide useful estimates of protein retention time and velocity in a column packed with Sephadex gel and subjected to an electric field. A correlation of electrophoretic mobility of peptide and proteins with respect to their charge, molecular mass, and asymmetry enables the selection of solute target molecules for electrochromatographic separations. Good separation of protein mixtures have been obtained.

Bioprocessing in space

A large amount of inedible plant material composed primarily of the carbohydrate materials cellulose, hemicellulose, and lignin is generated as a result of plant growth in a Controlled Ecological Life-Support System (CELSS). Cellulose is a linear homopolymer of glucose, which when properly processed will yield glucose, a valuable sugar because it can be added directly to human diets. Hemicellulose is a heteropolymer of hexoses and pentoses that can be treated to give a sugar mixture that is potentially a valuable fermentable carbon source. Such fermentations yield desirable supplements to the edible products from hydroponically-grown plants such as rapeseed, soybean, cowpea, or rice. Lignin is a three-dimensionally branched aromatic polymer, composed of phenyl propane units, which is susceptible to bioconversion through the growth of the white rot fungus, Pluerotus ostreatus. Processing conditions, that include both a hot water pretreatment and fungal growth and that lead to the facile conversion of plant polysaccharides to glucose, are presented.

Analysis of plant harvest indices for bioregenerative life support systems

Two approaches for biomass processing in Controlled Ecological Life Support Systems are compared in a literature survey. The approaches are based on (1) total oxidation of plant matter and (2) the potential of bioregenerative recovery.

Recombinant Human Insulin

Harvest indices, which are measures of the ratio of edible to total plant weight, are redefined to include edible sugars derived from enzymatic hydrolysis of the cellulose content of inedible plant components. Compositional analysis and carbohydrate contents of rapeseed, rice, soybeans, cowpea, wheat, sweet potato, white potato, and lettuce were analyzed to develop such generalized harvest indices. Cellulose conversion is shown to extend considerably the food available from plants otherwise grown for their oil and protein content in a bioregenerative life support system.