| 1. |
- Akerberg, C, et al.
(författare)
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A kinetic model for enzymatic wheat starch saccharification
- 2000
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Ingår i: Journal of Chemical Technology and Biotechnology. - 0268-2575. ; 75:4, s. 306-314
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic model describing the enzymatic saccharification of wheat starch by a mixture of ol-amylase and amyloglucosidase has been developed. The model describes the influence of pH, glucose inhibition and starch and enzyme concentration, The results of experimental saccharification under different physical conditions, eg pH and temperature, were used to determine the parameters in the model. The dominant enzyme in the mixture was amyloglucosidase and the maximum rate of saccharification due to this enzyme was found to be optimal at pH 5, and increased Five-Fold when the temperature was increased from 30 to 55 degrees C, Saccharification due to the action of amyloglucosidase was inhibited by the glucose produced and simulation showed that the maximum rate of saccharification decreased by 58% at a starch concentration of 140gdm(-3) compared with a starch concentration much less than 110 gdm(-3) where the effect of glucose inhibition was negligible, (C) 2000 society of Chemical Industry.
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| 2. |
- Akerberg, C, et al.
(författare)
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An economic evaluation of the fermentative production of lactic acid from wheat flour
- 2000
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Ingår i: Bioresource Technology. - 1873-2976. ; 75:2, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- A process for the fermentative production of lactic acid from whole-wheat flour consisting of starch and bran containing nutrients is presented and an economical evaluation of the lactic acid production cost performed. Bottlenecks were identified and alternative processes were evaluated and compared. The costs of raw material, the sodium hydroxide in the fermentation step, and the conversion of lactate to lactic acid using electrodialysis were found to contribute considerably to the total production cost. Performing the fermentation step as a batchwise step was economically better than continuous fermentation. The lactic acid production cost can be reduced by lowering the pH and/or by recycling the sodium hydroxide produced by electrodialysis to the fermentor. Using higher wheat flour concentrations reduced the lactic acid production cost and numerical optimisation of the process, with respect to the wheat flour concentration, showed that the optimal concentration corresponded to 116 g glucose/l, which resulted in a production cost of 0.833 US$/kg product. A Monte Carlo simulation of the total production cost for this concentration when the investment and operational cost and the price of the raw material were varied showed that the probability that the production cost could be lower than 0.90 or 1.0 US$/kg was 61% or 91%, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Akerberg, C, et al.
(författare)
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Modelling the influence of pH, temperature, glucose and lactic acid concentrations on the kinetics of lactic acid production by Lactococcus lactis ssp. lactis ATCC 19435 in whole-wheat flour
- 1998
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 49:6, s. 682-690
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic model of the fermentative production of lactic acid from glucose by Lactococcus lactis ssp. lactis ATCC 19435 in whole-wheat flour has been developed. The model consists of terms for substrate and product inhibition as well as for the influence of pH and temperature. Experimental data from fermentation experiments under different physical conditions were used to fit and verify the model. Temperatures above 30 degrees C and pH levels below 6 enhanced the formation of byproducts and D-lactic acid. By-products were formed in the presence of maltose only, whereas D-lactic acid was formed independently of the presence of maltose although the amount formed was greater when maltose was present. The lactic acid productivity was highest between 33 degrees C and 35 degrees C and at pH 6. In the concentration interval studied (up to 180 g l(-1) glucose and 89 g l(-1) lactic acid) simulations showed that both substances were inhibiting. Glucose inhibition was small compared with the inhibition due to lactic acid.
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| 4. |
- Hofvendahl, Karin, et al.
(författare)
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Simultaneous enzymatic wheat starch saccharification and fermentation to lactic acid by Lactococcus lactis
- 1999
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 52:2, s. 163-169
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous saccharification of starch from whole-wheat flour and fermentation to lactic acid (SSF) was investigated. For saccharification the commercial enzyme mixture SAN Super 240 L, having alpha-amylase, amyloglucosidase and protease activity, was used, and Lactococcus lactis ssp. lactis ATCC 19435 was used for the fermentation. SSF was studied at flour concentrations corresponding to starch concentrations of 90 g/l and 180 g/l and SAN Super concentrations between 3 mu l/g and 8 mu l/g starch. Kinetic models, developed for the saccharification and fermentation, respectively, were used for simulation and data from SSF experiments were used for model verification. The model simulated SSF when sufficient amounts of nutrients were available during fermentation. This was achieved with high wheat hour concentrations or with addition of yeast extract or amino acids. Nutrient release was dependent on the level of enzyme activity.
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| 5. |
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| 6. |
- Torto, N, et al.
(författare)
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Monitoring of enzymatic hydrolysis of starch by microdialysis sampling coupled on-line to anion exchange chromatography and integrated pulsed electrochemical detection using post-column switching
- 1997
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Ingår i: Biotechnology and Bioengineering. - 1097-0290. ; 56:5, s. 546-554
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative evaluation of the hydrolysis of wheat starch using Termamyl, a thermostable alpha-amylase (endo-l,4-alpha-D-glucan, glucanohydrolase; EC 3.2.1.78), is reported. Data from the monitoring of the hydrolysis of wheat starch indicated that, after 1 h, glucose and maltooligosaccharides up to DP 7 were the main hydrolysis products and thus enabled optimization of a liquefication step during the production of L-lactic acid. The monitoring system used, both in the on- and off-line mode, was based on continuous flow microdialysis sampling (CFMS) coupled to anion exchange chromatography and integrated pulsed electrochemical detection (IPED). A microdialysis probe equipped with a 5-mm polysulfone (SPS 4005) membrane, with a molecular-weight cut-off of 5 kDa, was used to sample the hydrolysis products of native wheat starch at 90 degrees C. Characteristic fingerprint separations were achieved by anion exchange chromatography after enzymatic hydrolysis. Post-column switching improved the detection and, consequently, also quantification of the hydrolysates as fouling of the electrode could be reduced. Maltooligosaccharide standards were used for quantification and to verify the elution of the hydrolysates by spiking the off-line samples. (C) 1997 John Wiley & Sons, Inc.
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