The antimicrobial test was carried out according to the method
developed by Seydim and Sarikus (Seydim & Sarikus, 2006), with
some modifications. The zone of inhibition assay on solid media
was used for determination of the antimicrobial effects of the films
against E. coli, B. subtilis and A. niger. The starch/e-PL films were cut
into a disc (diameter 7.21 mm) with a punch. During tests, the film
disks were placed carefully into petri dishes containing LB agar or
PDA solid medium, which had been previously inoculated by
0.1 ml of inoculums containing the indicator microorganisms in
the range of 108–109 CFU/ml (E. coli and B. subtilis) or 104–105
spores/ml (A. niger). The petri dishes were left at 4 C for 1 h to
allow agar surface to dry. Then these plates were incubated at
37 C for 24 h (for bacterial) or 28 C for 48 h (for fungi) in the
appropriate incubation chamber. The plates were examined to
determine the ‘zone of inhibition’ of the film discs, and the diameter
of the zone was measured with a sliding caliper in triplicate.
The area of the whole zone was calculated then subtracted from
the film disc area and the difference in area was reported as the
‘zone of inhibition’.