Cs. Ryu et al., Interferometeric sensing of beta-galactosidase released by recombinant E-coli responding to an endocrine disruptor, tributyltin, BIOTECH LET, 23(9), 2001, pp. 653-659
A recombinant E. coli ACV1003 releasing beta -galactosidase by a SOS regulo
n system when it is exposed to a DNA-damaging compound, has been used to de
tect endocrine disruptors such as tributyltin (TBT) and triphenyltin (TPT).
Maximum response ratio by E. coli ACV 1003 (recA::lacZ) - indicating the m
aximum ratio of enzyme produced against an environmental toxicant to that p
roduced in the absence of a toxicant - was estimated as 6.3 with 1.0 mug TB
T ml(-1) at 37 degreesC, which was considerably higher than those with othe
r strains. Extracellular beta -galactosidase activity was 51 unit ml(-1), w
hich was 5% of that obtained by the conventional Miller's enzyme assay usin
g solvents. Such a low enzyme activity can be rapidly determined, not by th
e usual time-consuming and tedious enzyme assay, but by an alternative inte
rferometric biosensor. Heavily-doped porous silicon to apply to an interfer
ometer was fabricated by etching to produce a Fabry-Perot fringe pattern, w
hich caused the change in the refractive index of the medium including beta
-galactosidase. The change in the effective optical thickness versus beta
-galactosidase activity showed a sigmoid increase up to the concentration o
f 250 unit beta -galactosidase ml(-1).