Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

greater dilution of the medium was prepared to allow very slow growth of bacteria for
better adaptation. On day 1, lmax of the compound was below 200 nm and thus could
not be recorded. However, the consortium was allowed to grow for a period of 11
days in the presence of LDPE as observed OD suggested a stationary phase 7th day
onward. For further confirmation of biodegradation of the polymers, FTIR spectra
and TGA of the degraded and undegraded compounds were carried out.
12.3.2.5 FTIR Spectroscopy
The FTIR spectrum of undegraded LDPE-g-PMMA was compared with that of the
polymer degraded by B. cereus. Formation of a graft copolymer of polymethyl methacrylate
with LDPE was confirmed as an additional absorption appeared corresponding
to C¼O stretching (1733.1 cm 1 ) in the undegraded sample [3]. Comparison of
FTIR spectrum of the undegraded polymer with that of its degraded counterpart
(acted upon by B. cereus) indicates a strong shift in the fingerprint region. Furthermore,
an overall decrease in percent transmittance of the degraded compound is also
observed from about 85% in the undegraded product to about 70% in the degraded
product (Figure 12.5).
The FTIR spectrum of undegraded LDPE-g-PMH was compared with that of the
polyamide degraded by B. pumilus. The formation of an amide linkage in the graft
was confirmed due to the absorption corresponding to CO NH stretching combined
with NH bending (1595 cm 1 ). Comparison of the FTIR spectrum of the
undegraded polymer with that of the B. pumilus treated sample indicates a shift in
the fingerprint region of B. pumilus degraded polymer at higher wavenumber without
the appearance of any additional absorption band. On the basis of these results, a
consortium of B. pumilus, B. cereus and other Bacillus species was used for further
studies, wherein one (PN15) was found to degrade LDPE-g-PMMA, another (S2)
LDPE-g-PMH and the third (PN13) degraded both (Figure 12.6).
The FTIR spectrum of LDPE showed characteristic absorption bands corresponding
to CH2 rocking (720.2 cm 1 ), CH3 bending (1362.6 cm 1 ), CH2 bending
(1465.2 cm 1 ), CH3 stretching (symmetrical, 2850.6 cm 1 ), CH3 stretching (asymmetrical,
2919.9 cm 1 ) and CH stretching (3426.6 cm 1 ). Comparison of the FTIR
Figure 12.5 FTIR spectrum of biodegraded LDPE-g-PMMA using
B. cereus against reference undegraded LDPE-g-PMMA.
12.3 Results and Discussionj241