| 1. |
- Eklund, R, et al.
(författare)
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Two-stage steam pretreatment of willow for increased pentose yield
- 1988
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Ingår i: Journal of Wood Chemistry and Technology. - : Informa UK Limited. - 0277-3813 .- 1532-2319. ; 8:3, s. 379-392
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Tidskriftsartikel (refereegranskat)abstract
- A two-stage procedure for pretreatment of fast-growing willow with steam has been investigated. The first stage was performed at temperatures in the range 180°C to 220°C for times between 6 and 10 minutes while the second stage was performed at 220°C for 10 minutes. The fibrous material was washed between the two stages to remove the pentosans and thus increase the pentose yield. The pretreatment was assessed in terms of glucose yield and xylose yield in the subsequent enzymatic hydrolysis. The maximum yields, around 70% for both glucose and xylose, were obtained for a pretreatment temperature of 200°C in the first stage. The major part of the xylose was found in the first rinsing water while almost all the glucose was recovered from the final fibrous material. The glucose yield was increased to above 80% when wet material (30% ODM) was used in the first stage. This required a modification of the steam pretreatment unit, allowing for condensate removal during steaming. The results are very promising but further investigations are needed to optimize the process.
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| 2. |
- Hahn-Hägerdal, Bärbel, et al.
(författare)
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Production of ethanol from lignocellulosic materials
- 1988
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Ingår i: Animal Feed Science and Technology. - : Elsevier BV. - 0377-8401. ; 21:2-4, s. 175-182
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Tidskriftsartikel (refereegranskat)abstract
- In the bioconversion of lignocellulosic materials to ethanol, the cost of the raw material and the cost of the enzymes have been identified as the major costs for the product. In addition, many lignocellulosic materials contain considerable amounts of five-carbon sugars which are not easily fermented to ethanol. The possibility of improving the cost-intensive steps was investigated. The steam pre-treatment of a fast-growing species of Salix (Q082) was optimized with respect to treatment time and temperature, to give the best glucose yield after enzymatic hydrolysis. It was found that the semi-continuous production of cellulolytic enzymes with Trichoderem reesei Rutgers C30 in an aqueous two-phase system (an extractive fermentation system) increased the amount of recoverable enzyme activity compared with a batch process. It was also found that the enzyme consumption in the hydrolysis of cellulolytic materials, in filter paper units (FPU) g−1 reducing sugars (RS), could be considerably reduced by recirculating the cellulolytic enzymes in an aqueous two-phase system combined with an ultra-filtration unit. For the fermentation of pentoses, it was found that the combination of the commercial enzyme glucose isomerase and regular bakers' yeast, Saccharomyces cerevisiae, was superior to xylose fermenting yeasts. Yields and productivities comparable to those obtained in hexose fermentation could be achieved.
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| 3. |
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| 4. |
- Zacchi, Guido, et al.
(författare)
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Economic evaluation of enzymatic hydrolysis of phenol-pretreated wheat straw
- 1988
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 32:4, s. 460-466
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data from the enzymatic hydrolysis of phenol-pretreated Swedish wheat straw have been used to evaluate the cost fractions of capital and utility, enzyme, and raw material. Two different raw material prices and varying enzyme prices have been used. The evaluation is based on an empirical model for the enzymatic hydrolysis and a computer program where utility and equipment, enzyme, and raw material prices can be varied. The optimal residence time for the enzymatic hydrolysis is in the range of 70–110 h. A fed-batch procedure with substrate concentrations higher than 10% oven-dried material (ODM) and enzyme concentrations in the range (6–10) · 106 FPU/ton ODM should be used.
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| 5. |
- Zacchi, Guido, et al.
(författare)
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Economic evaluation of preconcentration in production of ethanol from dilute sugar solutions
- 1989
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 34:2, s. 223-233
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Tidskriftsartikel (refereegranskat)abstract
- The economic feasibility of preconcentrating dilute sugar solutions prior to fermentation is investigated. Two methods, evaporation and reverse osmosis, are compared. A computer program to determine the optimal preconcentration conditions for glucose solutions of 1.5–16 wt% has been developed. It was used to compute the fractional cost for labor and maintenance, preconcentration, fermentation, and distillation. Preconcentration with evaporation resulted in a higher total cost, compared with no preconcentration, for all cases studied, although a six-effect unit was used. Reverse osmosis was found to be economically feasible for preconcentration to about 5–10 wt % depending on the concentration of the feed.
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