The accumulation of proline was estimated by spectrophotometric
analysis at 530 nm (Bates et al.,1973). The bacterial extracts
react with ninhydrin and glacial acetic acid during 1 h at 100 C.
The reaction stops by introducing the tubes in ice bath. The
reaction mixture is extracted with 2 mL of toluene, shaking
vigorously for 20 s. A standard curve was prepared with known
concentrations of proline