Linked Life Data

10849797

Source:http://linkedlifedata.com/resource/pubmed/id/10849797

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
2000-9-26
pubmed:abstractText
This study examined the continuous cofermentation performance characteristics of a dilute-acid "prehydrolysate-adapted" recombinant Zymomonas 39676:pZB4L and builds on the pH-stat batch fermentations with this recombinant that we reported on last year. Substitution of yeast extract by 1% (w/v) corn steep liquor (CSL) (50% solids) and Mg (2 mM) did not alter the cofermentation performance. Using declared assumptions, the cost of using CSL and Mg was estimated to be 12.5 cents/gal of ethanol with a possibility of 50% cost reduction using fourfold less CSL with 0.1% diammonium phosphate. Because of competition for a common sugar transporter that exhibits a higher affinity for glucose, utilization of glucose was complete whereas xylose was always present in the chemostat effluent. The ethanol yield, based on sugar used, was 94% of theoretical maximum. Altering the sugar ratio of the synthetic dilute acid hardwood prehydrolysate did not appear to significantly change the pattern of xylose utilization. Using a criterion of 80% sugar utilization for determining the maximum dilution rate (Dmax), changing the composition of the feed from 4% xylose to 3%, and simultaneously increasing the glucose from 0.8 to 1.8% shifted Dmax from 0.07 to 0.08/h. With equal amounts of both sugars (2.5%), Dmax was 0.07/h. By comparison to a similar investigation with rec Zm CP4:pZB5 with a 4% equal mixture of xylose and glucose, we observed that at pH 5.0, the Dmax was 0.064/h and shifted to 0.084/h at pH 5.75. At a level of 0.4% (w/v) acetic acid in the CSL-based medium with 3% xylose and 1.8% glucose at pH 5.75, the Dmax for the adapted recombinant shifted from 0.08 to 0.048/h, and the corresponding maximum volumetric ethanol productivity decreased 45%, from 1.52 to 0.84 g/(L.h). Under these conditions of continuous culture, linear regression of a Pirt plot of the specific rate of sugar utilization vs D showed that 4 g/L of acetic acid did not affect the maximum growth yield (0.030 g dry cell mass/g sugar), but did increase the maintenance coefficient twofold, from 0.46 to 1.0 g of sugar/(g of cell.h).
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0273-2289
pubmed:author
pubmed:issnType
Print
pubmed:volume
84-86
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
295-310
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Continuous fermentation studies with xylos-utilizing recombinant Zymomonas mobilis.
pubmed:affiliation
Department of Biochemistry, University of Toronto, Ontario, Canada. hugh.lawford@utoronto.ca
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't