Ethanol fermentation of various pretreated and hydrolyzed substrates at low initial pH.

Lignocellulosic materials represent an abundant feedstock for bioethanol production. Because of their complex structure pretreatment is necessary to make it accessible for enzymatic attack. Steam pretreatment with or without acid catalysts seems to be one of the most promising techniques, which has already been applied for large variety of lignocellulosics in order to improve enzymatic digestibility.

Heat extraction of corn fiber hemicellulose.

Water-soluble hemicellulose was extracted from corn fiber with microwave-assisted heat treatment. The effects of treatment temperature and initial pH of the aqueous extraction media were investigated regarding hemicellulose recovery and molecular mass of the isolated polysaccharides. In treatments carried out at neutral pH (simple water extraction), it has been demonstrated that hemicellulose recovery could be increased by applying higher treatment temperatures.

Thermoascus aurantiacus CBHI/Cel7A production in Trichoderma reesei on alternative carbon sources.

To develop functional enzymes in cellulose hydrolysis at or above 70 degrees C the cellobiohydrolase (CBHI/Cel7A) of Thermoascus aurantiacus was cloned and expressed in Trichoderma reesei Rut-C30 under the strong cbh1 promoter. Cellulase production of the parental strain and the novel strain (RF6026) was examined in submerged fermentation experiments using various carbon sources, which were lactose, Solka Floc 200 cellulose powder, and steam pretreated corn stover. An industrially feasible production medium was used containing only distiller's spent grain, KH(2)PO(4), and (NH(4))(2)SO(4).

Yields from glucose, xylose, and paper sludge hydrolysate during hydrogen production by the extreme thermophile Caldicellulosiruptor saccharolyticus.

This study addressed the utilization of an industrial waste stream, paper sludge, as a renewable cheap feedstock for the fermentative production of hydrogen by the extreme thermophile Caldicellulosiruptor saccharolyticus. Hydrogen, acetate, and lactate were produced in medium in which paper sludge hydrolysate was added as the sole carbon and energy source and in control medium with the same concentration of analytical grade glucose and xylose. The hydrogen yield was dependent on lactate formation and varied between 50 and 94% of the theoretical maximum.

Effect of pH on cellulase production of Trichoderma reesei RUT C30.

Currently, the high market price of cellulases prohibits commercialization of the lignocellulosics-to-fuel ethanol process, which utilizes enzymes for saccharification of cellulose. For this reason research aimed at understanding and improving cellulase production is still a hot topic in cellulase research. Trichoderma reesei RUT C30 is known to be one of the best hyper producing cellulolytic fungi, which makes it an ideal test organism for research.

Dynamics of cellulase production by glucose grown cultures of Trichoderma reesei Rut-C30 as a response to addition of cellulose.

An economic process for the enzymatic hydrolysis of cellulose would allow utilization of cellulosic biomass for the production of easily fermentable low-cost sugars. New and more efficient fermentation processes are emerging to convert this biologic currency to a variety of commodity products with a special emphasis on fuel ethanol production. Since the cost of cellulase production currently accounts for a large fraction of the estimated total production costs of bioethanol, a significantly less expensive process for cellulase enzyme production is needed.

Hydrogen production from paper sludge hydrolysate.

The main objective of this study was to develop a system for the production of "renewable" hydrogen. Paper sludge is a solid industrial waste yielding mainly cellulose, which can be used, after hydrolysis, as a feedstock in anaerobic fermentation by (hyper)thermophilic organisms, such as Thermotoga elfii and Caldicellulosiruptor saccharolyticus. Tests on different medium compositions showed that both bacteria were able to produce hydrogen from paper sludge hydrolysate, but the amount of produced hydrogen and the requirement for other components differed.

Chemical pretreatments of corn stover for enhancing enzymatic digestibility.

Corn stover, the most abundant agricultural residue in Hungary, is a potential raw material for the production of fuel ethanol as a result of its high content of carbohydrates, but a pretreatment is required for its efficient hydrolysis. In this article, we describe the results using various chemicals such as dilute H2SO4, HCl, and NaOH separately as well as consecutively under relative mild conditions (120 degrees C, 1 h). Pretreatment with 5% H2SO4 or 5% HCl solubilized 85% of the hemicellulose fraction, but the enzymatic conversion of pretreated materials increased only two times compared to the untreated corn stover.