Purification and identification of Bacillus subtilis SPB1 lipopeptide biosurfactant exhibiting antifungal activity against Rhizoctonia bataticola and Rhizoctonia solani

Abstract

This study reports the potential of a soil bacterium, Bacillus subtilis strain SPB1, to produce lipopeptide biosurfactants. Firstly, the crude lipopeptide mixture was tested for its inhibitory activity against phytopathogenic fungi. A minimal inhibitory concentration (MIC), an inhibitory concentration at 50% (IC50%), and an inhibitory concentration at 90% (IC90%) values were determined to be 0.04, 0.012, and 0.02 mg/ml, respectively, for Rhizoctonia bataticola with a fungistatic mode of action. For Rhizoctonia solani, a MIC, an IC50%, and IC90% values were determined to be 4, 0.25, and 3.3 mg/ml, respectively, with a fungicidal mode of action. For both of the fungi, a loss of sclerotial integrity, granulation and fragmentation of hyphal mycelia, followed by hyphal shriveling and cell lysis were observed with the treatment with SPB1 biosurfactant fraction. After extraction, separation, and purification, different lipopeptide compounds were identified in the culture filtrate of strain SPB1. Mass spectroscopic analysis confirmed the presence of different lipopeptide compounds consisting of surfactin isoforms with molecular weights of 1007, 1021, and 1035 Da; iturin isoforms with molecular weights of 1028, 1042, and 1056 Da; and fengycin isoforms with molecular weights of 1432 and 1446 Da. Two new clusters of lipopeptide isoforms with molecular weights of 1410 and 1424 Da and 973 and 987 Da, respectively, were also detected. This study reported the ability of a B. subtilis strain to co-produce lipopeptide isoforms with potential use as antifungal compounds.

Genomics-guided discovery and structure identification of cyclic lipopeptides from the Bacillus siamensis JFL15

“…Bacillus produces a distinguished class of cyclic lipopeptides (CLPs), which are known for their broad-spectrum antimicrobial activity, low toxicity, and high effectiveness under extreme conditions[1]. In contrast to conventional antibiotics, CLPs cause lethal effects on pathogenic bacteria by disrupting biological membranes through permeabilization; as a result, pathogenic bacteria experience greater difficulty in developing resistance to CLPs than to traditional antibiotics[2,3].…”

Potential application of Bacillus subtilis SPB1 lipopeptides in toothpaste formulation

“…As previously reported, the lipopeptide biosurfactants produced by the Bacillus subtilis SPB1 strain (HQ392822) revealed a wide spectrum of actions including antimicrobial activity towards multidrug resistant profiles microorganisms [18], antifungal activity against phytopathogenic fungi [19] and antidiabetic and antilipidemic properties in alloxan-induced diabetic rats [20]. This biosurfactant is able to reduce surface tension of the water from 70 mN/m to 34 mN/m [21] with a critical micellar concentration of 150 mg/L.…”

Preservation of Microbial Spoilage of Food by Biosurfactant-Based Coating

“…These reports greatly emphasize on the possible application of these biosurfactants in the development of various antimicrobial preparations. In past, biosurfactants have been reported to inhibit the growth of a variety of fungal species in various in vitro and vegetable-based in vivo models, thus suggesting its possible use in controlling the fungal spoilage in fruits and vegetables [6,7]. Therefore, this study was targeted to screen the bacterial biosurfactants for their potential to control fungal spoilage of vegetables.…”

“…The major classes of SAC are surfactin, fengycin, iturin, lichenysin, and rhamnolipid compounds with potent antimicrobial, antiadherent, anti-inflammatory, anticancer, antifebrin clot formation, antiviral, antimycoplasma, and hypocholesterolemic activities for a large spectrum of application in medical and pharmaceutical field [6]. They also have application in the field of agriculture as biocontrol, bioremediation, and metal sequestering, also in food processing industries of their emulsifying, foaming, and dispersing properties [7,8]. One of the widely studied biosurfactants over the years has been the rhamnolipids [9] and has also reported to show antimicrobial and antifungal properties [10].…”