Continuous production of indole-3-acetic acid by immobilized cells of Arthrobacter agilis

Abstract

Indole acetic acid (IAA) is a plant growth-promoting hormone used in agriculture; therefore, its continuous production is of paramount importance. IAA-producing eight bacteria were isolated from the rhizosphere of Verbascum vulcanicum. Among them, Arthrobacter agilis A17 gave maximum IAA production (75 mg/L) and this strain was used to immobilization studies. The A. agilis A17 cells were immobilized in calcium alginate for the production of IAA. Optimization of process parameters for IAA production was carried out to enhance IAA production using immobilized cells. The maximal production of IAA was 520 mg/L under the following optimal conditions: 1% mannitol, 30 °C, pH 8.0, and 24 h incubation. It was determined that the immobilized cells could be reused (13 times) for the production of IAA.

Keywords: Arthrobacter agilis; Fermentation; Immobilized cells; Indole acetic acid.

Fig. 1

Phylogenetic tree based on the 16s rDNA sequences of strain A17 and related species

Fig. 2

Effect of temperature on IAA production by Ca-alginate immobilized A. agilis A17. Reaction conditions: T pH 7.2, 150 rpm, 24 h,  %1 Glucose. An asterisk (*) denotes a value significantly greater than the other values (p < 0.05)

Fig. 3

Effect of initial pH on IAA production by Ca-alginate immobilized A. agilis A17. Reaction conditions: T 30 °C, 150 rpm, 24 h,  %1 Glucose. An asterisk (*) denotes a value significantly greater than the other values (p < 0.05)

Fig. 4

Effect of carbon sources on IAA production by Ca-alginate immobilized A. agilis A17. Reaction conditions: T 30 °C, pH 8, 150 rpm, 24 h. An asterisk (*) denotes a value significantly greater than the other value (p < 0.05)

Fig. 5

Effect of reaction time on the production of IAA by Ca-alginate immobilized A. agilis A17. Reaction conditions: T 30 °C, pH 8, 150 rpm, %1 mannitol. An asterisk (*) denotes a value significantly greater than the other values (p < 0.05)

Fig. 6

Reusability of the immobilized cells of A. agilis A17. A. agilis A17 cells were immobilized in 3.5% alginate gel and incubated in 100 mM Tris buffer containing %1 mannitol at 30 °C for 15  days, the buffer being changed daily