2. Materials and methods
2.1. Selection of salt resistant PNSB strains with potential use in saline
paddy fields
A total of 272 salt resistant PNSB isolates obtained from our
previous study (Nunkaew et al., 2012), were maintained in
glutamate-acetate (GA) medium, and used in this study. This
medium was used because acetate is a major available carbon
source in paddy fields: it is produced during the anaerobic
metabolism of organic matter (Conrad, 2007). Therefore, PNSB
intended for applications in paddy fields were grown in GA
medium, and their activities to produce ALA and reduce CH4 were
investigated. To prepare the inocula, one loopful of a pure culture
from a stab culture was inoculated into a screw cap test tube
(150 15 mm: 20 mL) containing 18 mL GA medium, leaving a
small headspace for microaerobic conditions. The test tubes were
incubated under light from tungsten bulbs (3500 200 lux) at
30 C for 48 h. Bacterial growth was measured as turbidity, using a
spectrophotometer at a wavelength of 660 nm, and then the
culture broth was adjusted to an optical density (OD) of 0.5 at
660 nm by dilution with GA broth, for use as an inoculum.