Medium optimization of antifungal lipopeptide, iturin A, production by Bacillus subtilis in solid-state fermentation by response surface methodology

Abstract

Iturin A, a lipopeptide antibiotic produced by Bacillus subtilis RB14-CS, suppresses the growth of various plant pathogens. Here, enhancement of iturin A production in solid-state fermentation (SSF) on okara, a soybean curd residue produced during tofu manufacturing, was accomplished using statistical experimental design. Primary experiments showed that the concentrations of carbon and nitrogen sources were the main factors capable of enhancing iturin A production, whereas initial pH, initial water content, temperature, relative humidity, and volume of inoculum were only minor factors. Glucose and soybean meal were the most effective among tested carbon and nitrogen sources, respectively. Based on these preliminary findings, response surface methodology was applied to predict the optimum amounts of the carbon and nitrogen sources in the medium. The maximum iturin A concentration was 5,591 mug/g initial wet okara under optimized condition. Subsequent experiments confirmed that iturin A production was significantly improved under the predicted optimal medium conditions. The SSF product generated under the optimized conditions exhibited significantly higher suppressive effect on the damping-off of tomato caused by Rhizoctonia solani K-1 compared with the product generated under the non-optimized conditions.

Effects of critical medium components on the production of antifungal lipopeptides from Bacillus amyloliquefaciens Q-426 exhibiting excellent biosurfactant properties

“…Finally, the optimum pH 11.0 (OXOID) and 10.0 (AoBoXing) of lipopeptide production, as well as good growth of OD 600 [2.0 in this range (data not shown), suggested that this strain belonged to alkali-resistant bacteria, which could maintain the competitive advantage in alkaline conditions. This observation was in contrast to previous observation of B. subtilis BS5, MZ-7 and RB14-CS that produced the maximum activity of surfactin or iturin A in a pH range of 6.0-9.0 (Abdel-Mawgoud et al 2008;Al-Ajlani et al 2007;Mizumoto and Shoda 2007).…”

“…Nihorimbere et al (2012) reported that in all of the tested carbon sources, organic acids (citrate and malate) led to maximum surfactin production, whereas sugars (glucose, fructose and maltose) were most effective in promoting iturin and fengycin production. Several earlier studies showed that NH 4 NO 3 was the best nitrogen source for surfactin production, while organic nitrogen sources were the best substrates for iturin biosynthesis (Al-Ajlani et al 2007;Mizumoto and Shoda 2007). Fengycin production was proved to be repressed by ammonium salts (Vanittanakom et al 1986).…”

Optimization of worm-bed leachate for culturing of tomato (Lycopersicon esculentum Mill) inoculated with Glomus fasciculatum and Pseudomonas fluorescens

“…It has been used to optimize the medium for lipopeptide iturin production (Mizumoto and Shoda, 2007), to enhance acetoin production , and to optimize inactivation of endospores of Bacillus cereus (Huang et al 2007). RSM includes different statistical techniques related to experimental design, model development, and evaluation of factors, identifying optimum conditions and also to study interactions between variables (Lin et al 2007;Liu and Wang, 2007).…”

Isolation and identification of antifungal compounds produced by Bacillus Y-IVI for suppressing Fusarium wilt of muskmelon

“…A broad spectrum of active compounds such as active lipopeptides (iturins, surfactins, fengycins) are produced by Bacillus species (Ongena & Jacques 2008;Ma & Hu 2014). These lipopeptides are synthesised ribosomally in the early growth cycle or non-ribosomally after growth has ceased (Mizumoto & Shoda 2007). The iturin groups include iturin A, C, D, and E, bacillomycin D, F, and L, bacillopeptin, doi: 10.17221/70/2015-PPS and mycosubtilin (Peypoux et al 1986;Besson & Michel 1987;Kajimura et al 1995).…”