Agri Kultuur January / January 2018 - Page 43

Findings: The team ascertained that precipitation of the cocktail at a pH of between one and two resulted in maximum recovery of the antifungal lipopeptides (78% for fengycin and 67% for iturin); it was marginally higher than at pH 3. However, optimal purity was obtained at pH 3 (64% for fengycin, and 3% for iturin), thus establishing pH 3 as the preferred condition. Dr Vivek Rangarajan adapted the method of thin layer chromatography (TLC) to the measurement of the lipopeptides fengycin, iturin and surfactin. Compared A LITTLE TLC GOES A LONG WAY to high performance liquid Dr Vivek Rangarajan adapted the method chromatography (HLCP) that of thin layer chromatography (TLC) to the takes two hours to process one measurement of the lipopeptides fengycin, iturin sample, Vivek’s TLC method and surfactin. Compared to high performance processes 20 samples only liquid chromatography (HLCP) that in takes two minutes. hours to process one sample, Vivek’s 45 It saves time and TLC method processes 20 samples in only 45 money, and delivers the desired minutes. It saves time and money, and delivers indicative results. the desired indicative results. Lipids Surfactin They found that among all the organic solvents that could remove lipid and protein impurities from the antifungal lipopeptides, methanol proved to be most efficient, showing 100% extraction and the highest percentage purity (74%) of antifungal lipopeptides. Figure 1: Bioproducts effective against pathogens Figure 1: Bioproducts effective against pathogens Antibacterial Surfactin Bacillus lipopeptides Antiviral Antitumoril Iturin A Antifungal Fengycin Antifungal About 100 homologues with combined broad spectrum activity AgriKultuur |AgriCulture CF-MeOH “Even if the lipopeptide cocktail is not pure, it can still be very effective,” says Prof. Clarke. “Cocktails of varying purities will have different applications. A less pure product could be applied to agricultural crops in general, while a purer product could be required for specific phytopathogens affecting fruit in post-harvest storage.” Fengycin To reduce the pH of the supernatant, acid (four pH levels) was added to the filtered Bacillus culture to trigger the precipitation of the lipopeptides. Eleven different solvents were also added to the filtered Bacillus culture to affect concentration and purification. A LITTLE TLC GOES A LONG WAY Identify and quantify appropriate antifungal lipopeptide concentration and purification procedures: Having determined how to produce the maximum yield, the team’s focus shifted to finding a way to improve the efficacy of the lipopeptide cocktail by concentrating and purifying the product through acid precipitation and solvent extraction. Evaluate the effectiveness of different lipopeptides in various grades of purity on target plant phytopathogens targeting the fruit industry: The team tested the efficacy of the partially purified and purified lipopeptide cocktails against various fungal phytopathogens. Findings: Some of the most aggressive and destructive plant pathogens, Botrytis cinerea, Alternaria brassicicola and Rhizopus stolonifer, Monilinia fructigena, Penicillium expansum and Aspergillus sclerotiorum affecting fruit post-harvest, were used to 43