Michael C. Flickinger

Conversion of hemicellulose carbohydrates

Hemicellulose can be converted to a variety of useful products. There are two approaches to hemicellulose bioconversion; hemicellulose can be directly converted, or the hemicellulose-derived carbohydrates can be used as the substrate. The major problem in the bioconversion of hemicellulose carbohydrates is that suitable organisms which convert pentoses efficiently have not been developed. The advantage of bacterial processes is that a diverse range of products can be formed. The advantages of the yeast process is that specific products such as ethanol and polyols can be produced in high yields. The understanding of metabolic pathways and metabolic regulation is important for the improvement of existing microbial strains or the development of new strains. The use of yeasts to produce ethanol from d-xylose through isomerization of d-xylose to d-xylulose and the prospects for future developments in biomass conversion are discussed.

Ethanol production from pentoses by immobilized microorganisms

Abstract The capabilities of immobilized Fusarium oxysporum f. sp. lini, Mucor sp., and Saccharomyces cerevisiae in fermenting pentose to ethanol have been compared. S. cerevisiae was found to have the best fermentation rate on d -xylulose of 0.3 g l −1 h −1 . By using a separate isomerase column for converting d -xylose to d -xylulose and a yeast column for converting d -xylulose to ethanol, an ethanol concentration of 32 g l −1 was obtained from 10% d -xylose. The ethanol yield was calculated to be 64% of the theoretical yield .

Fermentation Substrates from Cellulosic Materials: Fermentation Products from Cellulosic Materials

Publisher Summary This chapter discusses the fermentation products from cellulosic materials. The substitution of fermentation derived fuels, chemical feedstocks, and protein supplements for those currently derived from nonrenewable resources is now possible because of the low-cost quantitative recovery of hexoses and pentoses from any cellulosic material. This chapter discusses the potential for cellulosic-derived fermentation substrates for those industrial fermentations that benefit the most from such an inexpensive renewable substrate source. Fermentation products solely derived from microbial metabolism, such as the enzyme and antibiotic industries, will gain little advantage. However, those fermentation products that directly compete with a current synthetic process based on a nonrenewable raw material will definitely gain an advantage by switching to a cellulose-derived substrate. The solvent pretreatment cellulose process may not immediately solve but will significantly alleviate the fossil-fuel dependency of the chemical industry. Cellulose will remain the largest renewable resource and the most logical raw material to base the future chemical needs.

A MODEL FOR THE GROWTH AND PRODUCT KINETICS OF FACULTATIVE ANAEROBES BASED ON ATP SYNTHESIS AND CONSUMPTION

ABSTRACT A mathematical model based on the production and consumption of ATP is presented which attempts to simulate the batch fermentation kinetics of Klebsiella pneumoniae. The chief utility of the model is its apparent ability to predict the non-linear way the product yields vary during oxygen limited growth when two different energy producing pathways are active.