Environmental Engineering Reference
In-Depth Information
Growth of the recombinant RHA1 in 4-CBA
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Figure 6.9 Growth of RHA1(fcb) on 4-CBA.
plasmid pRHD34, and showed that the E. coli lac promoter contained in pRT1
enhanced expression of the fcb genes in both Rhodococcus strains NY05 and
RHA1. Although the parent RHA1 did not oxidize 4-CBA, its recombinant
derivative RHA1(pRHD34) grew exponentially in medium containing
4-CBA as the sole carbon source, concomitantly releasing stoichiometric
amounts of chloride (Figure 6.9). The fcb operon in strain RHA1 appeared
to be stable under nonselective conditions, as verified by polymerase chain
reaction (PCR) amplification using fcbA - and fcbB -specific primers (Rod-
rigues et al., 2001).
6.4.1.4 Degradative capabilities of the recombinant RHA1( fcb )
Similar to VP44, Rhodococcus strain RHA1(pRHD34:: fcb ) grew on and com-
pletely mineralized 4-CB, releasing nearly stoichiometric amounts of chloride.
The molar growth yield of the recombinant strain on biphenyl and 4-CB was
177 ± 6 and 189 ± 9 g dry weight of cells/mol of substrate, respectively, which
is similar to the theoretical value of 173 g dry weight of cells/mol for complete
4-CB oxidation. No transient formation of 4-CBA was detected during the
growth, and only slight transient formation of HOPDA was detected in the
log growth phase. We noted that the 4-CBA-grown RHA1(pRHD34) inoculum
was imperative for growth on 4-CB, possibly due to the rapid turnover of 4-CB
with accumulation of intermediate compounds such as HOPDA when the BP
 
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