Evaluation of the Environmental Factors Modulating Indole-3-acetic Acid (IAA) Production by Trichoderma harzianum InaCC F88

Abstract

Indole-3-acetic acid (IAA) is one of the most common plant hormones that regulate many aspects of growth and development of plants. Trichoderma harzianum, a plant growth promoting fungus, has the ability to produce IAA. However, various environmental factors influence the formation of the hormone. The objective of this study was to optimize the environmental condition for the production of IAA by Trichoderma harzianum InaCC F88 strain. The effects of L-tryptophan concentration, temperature, pH, salinity, and incubation time on IAA production and biomass were studied. The in vitro evaluations were carried out in the axenic condition of Luria-Bertani Medium. Supplementation of 1% L-tryptophan in the medium gives maximum IAA production. The most favourable initial pH and temperature for IAA production are 6.0 and 27°C, respectively. In the salinity test, the medium containing 1% NaCl yielded maximum IAA formation. After 4 days of incubation, the concentration of IAA reached equilibrium. Hence, optimum IAA production in liquid fermentation could be achieved by manipulating those factors.

Optimization of Culture Condition for Iaa Roduction by Bacillus Sp. Isolated From Cassava Field of Vietnam

“…About 1.0 % concentration of L-tryptophan was found to be optimum for IAA production by strains Serratia marcescens AL2-16 and then decreased at a higher concentration of tryptophan [7]. Diazotrophic B. subtilis DR2, isolated from the rhizosphere of Eragrostis cynosuroides produced maximum IAA (168.09 µg/mL) at tryptophan concentration of 1.2 g/L [16]. The report of Napitupulu et al [17].…”

“…The maximum amount of IAA (448.5 mg/L) was observed at 10 days of incubation (for Enterobacter sp.) and 96 h (for B. subtilis DR2) and then declined gradually [16,17]. Our studied strains need only 84 h of incubation for maximum IAA production.…”

“…Maximum IAA concentration (370 mg/L) was obtained at an initial pH of 8.0, but no statistically significant difference between pH 8.0 and pH 9.0 of immobilized Arthrobacter agilis A17 cells [15]. In the investigation of Kumari et al [16] maximum (158.79 µg/mL) indole production was observed at pH7 in Trp+ media and high acidic and alkaline pH was not suitable for IAA production. Interestingly, endophytic bacteria isolated from P.nigrum had the maximum production of IAA at pH 4, and IAA production by these selected isolates reduced dramatically with increasing pH to alkaline level.…”

“…The carbon sources provide energy and improve co-factor recycling in the cells, and are used in the production of secondary metabolites, so they have a profound effect on the overall efficiency of biosynthesis. Thus, carbon sources contribute to the overall efficiency of IAA biosynthesis by microorganisms [16,1]. In this study, four different sugars (sucrose, fructose, lactose, and glucose) were added externally to the production medium in order to evaluate their effect on IAA production of DTAN1-M5 strain.…”

“…But IAA-producing bacterial isolates CA1001, CA2003, and CA2004 from plant root preferred dextrose for their IAA production, with 104 µg/mL of IAA for CA1001 and 50 µg/mL of IAA for CA2003 [1]. For B. subtilis DR2 using the mannitol carbon source in the synthetic culture medium, the maximum yield was achieved at 160.85 µg/mL [16]. Other studies also optimized IAA production by different carbon sources as well as their combinations, such as mannitol in B.subtilis-W2 [15,16] and Arthrobacter agilis [25].…”