ISSN:
0006-3592
Keywords:
poly-β-hydroxybutyrate
;
molcular weight distribution
;
Alcaligens eutrophus
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
The effect of magnesium and phosphate limitation on the molecular weight distribution of poly-β-hydroxybutyrate (PHB) in Alcaligens europhus in cotinuons culture has been stuied. Conditions of nitrogen limitation both with glucose excess (above ca. 20 g/L) and without excess were investigated Under N-limitation and glucose excess, Mw decreases when the magnesium content is decreased below 50% (19.7 mg/L) of the basal medium content; this also results in a broadenng of molecular weight distribution (Mw/Mn) from 2 to 5 and a decrease in Mw fron 2 × 106 to 0.9 × 106. Below 20% of the basal content of magnesium (7.9 mg/L) these two trends were reversed. This behaviour was not observed in the absence of glucose excess, phshate had virtually no effect on PHB Mw or its distribution, whereas wih no (or little) glucose excess Mw of the PHB decreased with phosphate concentrations below 50% of the basal level (0.705 g/L). Hence, in continuous or fed-batch cultures, in addition to nitrogen limitation to alklow for PHB accumulation, it is necesary to control both the addition of glucose (no excess) and also to maintain magnesium limitation (ca. 25% of basal medium level, 9.9 mg/L) and phosphate above 50% of he basal level (0.705 g/L). Thus, when broadening of molecular weight destribution (increase in Mw/Mn) is observed at the end of fed-batch culture it is probably caused by phosphate limitation and/or glucose excess. © 1995 John Wiley & Sons, Inc.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bit.260460514
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