Conversion of gamma-butyrobetaine to L-carnitine by Achromobacter cycloclast.
L-Carnitine is an ubiquitous substance that plays a major role in the transportation of long-chain fatty acids. We investigated crucial factors that influence microbial conversion of gamma-butyrobetaine to L-carnitine using an Achromobacter cycloclast strain. Two-stage culture results showed that gamma-butyrobetaine induced enzymes essential for the conversion, which suggests that the precursor should be present in the initial cell growth stage. The addition of yeast extract enhanced L-carnitine production whereas inorganic nitrogen sources inhibited it. Under nitrogen-limiting conditions, the cells accumulated poly-beta-hydroxybutyrate instead of L-carnitine. Among the trace elements tested, nickel addition enhanced L-carnitine production by almost twice that of the control and copper strongly inhibited the conversion. L-Carnitine production was reduced when the medium contained inorganic salts of sodium, potassium, and calcium at a concentration greater than 2 g l(-1). A higher L-carnitine yield was achieved when cells were incubated in a lower culture volume. The optimal pH for L-carnitine production was 5 to 5.5, whereas that of growth was 7.0, indicating that a pH shift was required. Under optimal conditions, L-carnitine concentrations as high as 15 g l(-1) were obtained in 62 h with a 45% molar conversion yield.
Naidu
G S
GS
Microbial and Bioprocess Engineering Laboratory, Korea Research Institute of Bioscience and Biotechnology, P.O. Box 115, Yusong, Taejon 305-600, South Korea.
Lee
I Y
IY
Cho
O K
OK
Park
Y H
YH
D000421:Alcaligenes / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D001622:Betaine / Q000031:analogs & derivatives* / Q000378:metabolism*; D002331:Carnitine / Q000096:biosynthesis / Q000378:metabolism*; D002455:Cell Division; D003470:Culture Media; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D013997:Time Factors; D014131:Trace Elements / Q000494:pharmacology
D003470:Culture Media; D014131:Trace Elements; D001622:Betaine; C002889:gamma-butyrobetaine; D009584:Nitrogen; D002331:Carnitine; D010100:Oxygen