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A tunable switch to regulate the synthesis of low and high molecular weight microbial polyesters
Author(s) -
Ashby Richard D.,
Shi Fengying,
Gross Richard A.
Publication year - 1999
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19990105)62:1<106::aid-bit12>3.0.co;2-x
Subject(s) - peg ratio , ethylene glycol , fermentation , polymer , chemistry , polyester , biochemistry , nuclear chemistry , polymer chemistry , organic chemistry , finance , economics
The addition of poly(ethylene glycol) ( M n = 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 M n 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. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 106–113, 1999.