Comparative study on methyl orange removal by growing cells and washed cell suspensions of Lactobacillus casei TISTR 1500
Lactobacillus casei TISTR 1500 possesses cytoplasmic azoreductase, and converts methyl orange to N,N-dimethyl-p-phenylenediamine and 4-aminobenzenesulfonic acid. In culture growth, the strain completely degraded methyl orange at 200mg/l,
even though the pH value was lower than 4. The decolorization was inhibited in the growing culture with 800mg of the dye/l
after incubation for 12h. The percentage of decolorization and specific decolorization rate with 400 and 800mg/l were 66
and 15%, and 14.2, and 8.7mg/gCell/h, respectively. Additionally, a growing culture is more tolerant to a high initial dye
concentration than when using washed cell suspensions supplied with only sucrose. Moreover, incubation of a low cell density
in 600μM of Na+ and 20mM of sucrose increased the specific decolorization rate from 2.34mg/gCell/h (without Na+) to 4.32mg/gCell/h. However, Na+ had no effect on the enhancement of azoreductase activity in the reaction mixture.