A tunable switch to regulate the synthesis of low and high molecular weight microbial polyesters.
The addition of poly(ethylene glycol) (Mn = 200 g/mol) (PEG-200) to the fermentation media of Alcaligenes eutrophus and Alcaligenes latus at various stages of growth resulted in the synthesis of poly(3-hydroxybutyrate) (PHB) with bimodal molecular weight distributions. The presence of 2% w/v-PEG-200 did not have deleterious effects on PHB volumetric yields and cell productivity. In general, the Mn values of the high (H) and low (L) fractions showed little variability as a function of the time at which PEG-200 was added to the cultures. By this approach, the H:L ratios (w/w) of the PHB synthesized by A. eutrophus and A. latus were varied from 9:91 to 76:24 and from 16:84 to 88:12, respectively. It is believed that the H fractions were formed prior to the addition of PEG-200 to the cultures. Also, once PEG-200 was made available to the cells, PEG-200 acted as a switch so that the reduced molecular weight fraction was formed. In addition, a necessary requirement for the above is that the frequency of transesterification reactions during polymer synthesis was small. The efficiency that PEG-200 reduced the molecular weight of the PHBs formed by both bacteria appears similar. Indirect evidence suggests that the PHB L fractions formed by A. latus subsequent to PEG-200 addition consist primarily of chains that have PEG terminal groups. This terminal chain structure was not observed for PHB formed by A. eutrophus.
Ashby
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RD
University of Massachusetts-Lowell, Department of Chemistry, 1 University Avenue, Lowell, Massachusetts 01854, USA.
Shi
F
F
Gross
R A
RA
D000421:Alcaligenes / Q000378:metabolism; D001704:Biopolymers / Q000096:biosynthesis* / Q000737:chemistry; D001709:Biotechnology; D005285:Fermentation; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry / Q000378:metabolism*; D011092:Polyethylene Glycols
D001704:Biopolymers; D011091:Polyesters; D011092:Polyethylene Glycols