Catálogo de publicaciones - libros

The main objective of this work was to investigate the biotransformations of (−)β-pinene, (−)β-pinene, and (+) limonene by ATCC 9642. The culture conditions involved—concentration of cosolvent (EtOH), substrate applied, and sequential addition of substrates—were investigated. Adaptation of the precultures with small amounts of substrate was also studied. The experiments were performed in conical flasks with liquid cultures. This strain of was able to convert only (−)β-pinene into α-terpineol. An optimum conversion of (−)β-pinene into γ-terpineol of about 4% was obtained when the substrate was applied as a diluted solution in EtOH and sequential addition of substrate was used.

lipase was entrapped in silica sol-gel particles prepared by hydrolysis of methyltrimethoxysilane and assayed by p-nitrophenyl palmi-tate hydrolysis, as a function of pH and temperature, giving pH optima of 7.8 (free enzyme) and 5.0–8.0 (immobilized enzyme). The optimum temperature for the immobilized enzyme (50–55°C) was 19°C higher than for the free enzyme. Thermal, operational, and storage stability were determined with n-butanol and butyric acid, giving at 45°C a half-life 2.7 times greater for the immobilized enzyme; storage time was 21 d at room temperature. For ester synthesis, the optimum temperature was 47°C, and high esterification conversions were obtained under repeated batch cycles (half-life of 138 h).

A new acetic acid-producing microorganism, sp. RKY4, was isolated from Korean traditional persimmon vinegar, and we optimized the culture medium for acetic acid production from ethanol using the newly isolated sp. RKY4. The optimized culture medium for acetic acid production using this microorganism was found to be 40 g/L ethanol, 10 g/L glycerol, 10 g/L corn steep liquor, 0.5 g/L MgSO•7HO, and 1.0 g/L (NH)HPO. sp. RKY4 produced 47.1 g/L of acetic acid after 48 h of fermentation in a 250 mL Erlenmeyer flask containing 50 mL of the optimized medium.

Processes that produce only ethanol from lignocellulosics display poor economics. This is generally overcome by constructing large facilities having satisfactory economies of scale, thus making financing onerous and hindering the development of suitable technologies. Lignol Innovations has developed a biorefining technology that employs an ethanol-based organosolv step to separate lignin, hemicellulose components, and extractives from the cellulosic fraction of woody biomass. The resultant cellulosic fraction is highly susceptible to enzymatic hydrolysis, generating very high yields of glucose (>90% in 12–24 h) with typical enzyme loadings of 10–20 FPU (filter paper units)/g. This glucose is readily converted to ethanol, or possibly other sugar platform chemicals, either by sequential or simultaneous saccharification and fermentation. The liquor from the organosolv step is processed by well-established unit operations to recover lignin, furfural, xylose, acetic acid, and a lipophylic extractives fraction. The process ethanol is recovered and recycled back to the process. The resulting recycled process water is of a very high quality, low BOD and suitable for overall system process closure. Significant benefits can be attained in greenhouse gas (GHG) emission reductions, as per the Kyoto Protocol. Revenues from the multiple products, particularly the lignin, ethanol and xylose fractions, ensure excellent economics for the process even in plants as small as 100 mrpd (metric tonnes per day) dry woody biomass input—a scale suitable for processing wood residues produced by a single large sawmill.

This year’s session highlighted several exciting advances in the field of pretreatment and hydrolysis of lignocellulosic biomass. Iogen Corporation (Ottawa, Canada) announced the successful completion of their demonstration plant and first shipment of ethanol. The facility uses wheat straw as its feed source. Other highlights included the announcement by Dr. Guido Zacchl (Lund University, Sweden) that the ribbon will be cut this month at their new bioethanol pilot plant; the capacity will be 2 ton/day of feedstock (primarily softwood residue). Mr. Daniel Schell (National Renewable Energy Laboratory, CO, USA) detailed the production of high sugar streams from pretreating corn stover with dilute acid at the NREL pilot plant. Finally, Mr. David Gregg (University of British Columbia, Canada) and Dr. Henning Jorgensen (Royal Veterinary and Agricultural University, Denmark) also announced construction of new pilot plants for treatment of softwoods primarily by organosolv, and wheat straw possibly by alkali treatment, respectively. Several trends emerged from these presentations.

The application of Fenton’s reaction to enhance the fermentability of prehydrolysates obtained from steam explosion pretreatment of poplar biomass was studied. Reaction conditions of temperature and HO and Fe(II) concentrations were studied. The fermentability of prehydrolysate treated by Fenton’s reaction was tested by using different inoculum sizes of thermotol-erant strain CECT 10875. The highest percentages of toxic compound degradation (ranging from 71 to 93% removal) were obtained at the highest HO concentration tested (50 m). However, a negative effect on fermentability was observed at this HO concentration at the lower inoculum loading. An increase in inoculum size to 0.6 g/L resulted in an enhanced ethanol fermentation yield of 95% relative to control.

Both cellulase and cellobiase can be effectively recovered from hydrolyzed biomass using an ultrafiltration recovery method. Recovery of cellulase ranged from 60 to 66.6% and for cellobiase from 76.4 to 88%. Economic analysis shows that cost savings gained by enzyme recycling are sensitive to enzyme pricing and loading. At the demonstrated recovery of 60% and current loading of 15 Filter paper units of cellulase/g of glucan, enzyme recycling is expected to generate a cost savings of approx 15%. If recovery efficiency can be improved to 70%, the savings will increase to >25%, and at 90% recovery the savings will be 50%.

When dilute-acid hydrolysates from spruce are fermented to produce ethanol, detoxification is required to make the hydrolysates fermentable at reasonable rates. Treatment with alkali, usually by overtiming, is one of the most efficient approaches. Several nutrients, such as ammonium and phosphate, are added to the hydrolysates prior to fermentation. We investigated the use of NHOH for simultaneous detoxification and addition of nitrogen source. Treatment with NH4OH compared favorably with Ca(OH), Mg(OH), Ba(OH), and NaOH to improve fermentability using . Analysis of monosaccharides, furan aldehydes, phenols, and aliphatic acids was performed after the different treatments. The NHOH treatments, performed at pH 10.0, resulted in a substantial decrease in the concentrations of furfural and hydroxymethylfurfural. Under the conditions studied, NHOH treatments gave better results than Ca(OH) treatments. The addition of an extra nitrogen source in the form of NHC1 at pH 5.5 did not result in any improvement in fermentability that was comparable to NHOH treatments at alkaline conditions. The addition of CaCl or NHC1 at pH 5.5 after treatment with NHOH or Ca(OH) resulted in poorer fermentability, and the negative effects were attributed to salt stress. The results strongly suggest that the highly positive effects of NHOH treatments are owing to chemical conversions rather than stimulation of the yeast cells by ammonium ions during the fermentation.

A technique for the removal of acetic acid from an actual pretreated corn stover hydrolysate was investigated. A powdered form of activated carbon previously shown to be effective in the removal of acetic acid from a synthetic hydrolysate was utilized. The method proved to be effective at lowering acetic acid levels while exhibiting minimal adsorption of the desired sugars from the hydrolysate, although at a lower efficiency in the actual hydrolysate than in the synthetic hydrolysate. Results are obtained for temperatures between 25 and 35°C and agitation rates between 150 and 350 rpm in shake flasks. Adsorption isotherm and kinetic rate data are presented. Temperature differences over this range did not have an effect on adsorption characteristics. Five stages of detoxification were necessary to lower acetic acid concentration to the maximum 2 g/L desired for fermentation.

Computational fluid dynamics simulations were employed to compare performance of various designs of a pretreatment screw conveyor reactor. The reactor consisted of a vertical screw used to create cross flow between the upward conveying solids and the downward flow of acid. Simulations were performed with the original screw design and a modified design in which the upper flights of the screw were removed. Results of the simulations show visually that the modified design provided favorable plug flow behavior within the reactor. Pressure drop across the length of the reactor without the upper screws in place was predicted by the simulations to be 5 vs 40 kPa for the original design.