Mb. Kellerhals et al., Development of a closed-loop control system for production of medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHAs) from bacteria, MACRO SYMP, 144, 1999, pp. 385-389
Large scale availability of bacterial polyhydroxyalkanoates (PHAs) is still
limited to a few types of short-chain-length PHAs, namely poly(3-hydroxybu
tyrate) (PHB) and its copolymer Biopol(TM), consisting of 3-hydroxybutyrate
and 3-hydroxyvalerate repeating units. In order to increase the number of
available medium-chain-length PHA (mcl-PHA) copolymers a flexible high-cell
-density fed-batch process was developed. Continuous process monitoring and
substrate control were achieved by coupling on-line gaschromatography (on-
line GC) to a software-based Proportional Integral (PI) substrate controlle
r. System development time and continuous system upgrading were considerabl
y shortened by using LABView(TM), a powerful graphical programming environm
ent. The control of octanoic acid and 10-undecenoic acid at 1.5 and 0.5 gL(
-1) respectively, enabled the production of high levels of biomass (30 gL(-
1)) and mcl-PHA (10.5 gL(-1)) by avoiding substrate limitations or toxiciti
es. The resulting mcl-PHA was an amorphous copolyester consisting of 37 mol
% unsaturated monomers. The present system represents a valuable tool for t
he production of tailor-made mcl-PHAs, where the desired monomer compositio
n is determined by the ratio of added cosubstrates.